TAI LIEU HUONG DAN VUON UOM CAY NGAP MAN.pdf

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B NNG NGHIP V PHT TRIN NNG THN TRUNG TM KHUYN NNG QUC GIA

PGS.TS. NG NH QU PGS.TS. V I HI

XY DNG RNG PHNG H NGP MN VEN BIN

THC TRNG V GII PHP

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M U

Vit Nam l nc c kh hu nhit i gi ma, nng m v ma nhiu. Vi c im t nc ta di c hnh ch S v gip vi bin ng nn ng b bin ca Vit Nam rt di vi tng chiu di b bin ti hn 3000 km tri di t Bc vo Nam. Hng nm chng ta phi hng chu hng chc cn bo, lc t bin ng vo gy thit hi nghim trng c v ngi v ca. Chnh v vy, vai tr phng h mi trng ca di rng ngp mn phng h ven bin c mt ngha v cng quan trng. Vai tr ca di rng ny khng ch dng li vic gim tc hi ca gi, bo bin ti con ngi, ti sn xut, gim chi ph tu sa bin, m n cn c mt vai tr rt quan trng i vi s pht trin kinh t - x hi, to sinh k cho ngi dn vng bin nc ta, bn cnh hng nm rng ngp mn gip nc ta ln ra bin nhiu ch ti hng trm mt to iu kin m rng din tch ca t nc. S phn b v pht trin rng ngp mn ven bin ca nc ta cng c s khc bit rt r rt c v mc a dng loi, sinh trng v pht trin ca cy ngp mn n ph thuc vo c im a hnh ven bin, iu kin kh hu, mn, th nn, khu vc cc tnh pha Nam rng ngp mn phn b, sinh trng v pht trin tt hn khu vc pha Bc. Mc d vai tr ca rng ngp mn l v cng quan trng nh vy, nhng nhng nm qua din tch rng ngp mn khng ngng b suy gim, nu nh nm 1943 chng ta c khong 408.500ha rng ngp mn th ti nm 2006 con s ny ch cn khong 209.741ha. Nguyn nhn ch yu dn ti s suy gim din tch rng ngp mn l do tc ng cht ph ca con ngi nhm cc mc ch: ly ci, ly g v c bit l chuyn i din tch nui tm, nui thy sn khc. S suy gim din tch rng ngp mn gy ra nhng hu qu nghim trng c v kinh t, x hi v mi trng c bit l trong bi cnh m bin i kh hu ang rt phc tp. Vit Nam l 1 trong 5 nc c nh gi l chu nh hng nng n nht do bin i kh hu gy ra. Nhn thc c vai tr , trong mt vi nm gn y ng v Nh nc ta c nhiu ch trng, chnh sch nhm khi phc v pht trin rng ngp mn, c bit chng ta thnh lp c n phc hi v pht trin rng ngp

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mn ven bin giai on 2008 - 2015. Hin nay, ngun ti liu c lin quan ti rng ngp mn nc ta vn cn rt t v tng i tn mn, do vy vic bin son cun sch Xy dng rng phng h ngp mn ven bin, Thc trng v gii php l rt cn thit.

Cun sch gm 5 chng:

- Chng 1: Khi qut h sinh thi rng ngp mn Vit Nam.

- Chng 2: Thc trng rng ngp mn ven bin Vit Nam.

- Chng 3: Cc quy nh v xy dng rng ngp mn.

- Chng 4: C ch chnh sch lin quan ti khi phc v pht trin rng ngp mn Vit Nam.

- Chng 5: Hng dn k thut trng mt s loi cy rng ngp mn.

Trong qu trnh bin son, nhm tc gi nhn c s quan tm, gip ca Trung tm Khuyn Nng Quc gia, Nh xut bn Nng nghip, cc tc gi xin chn thnh cm n v s hp tc, gip .

Mc d c nhiu c gng nhng do hn ch v t liu v thi gian nn chc chn s khng trnh khi nhng thiu st cn phi b sung v sa cha. Cc tc gi rt mong nhn c s gp , ph bnh ca cc cc nh khoa hc, qun l, ngi sn xut, v cc bn ng nghip ni dung, hnh thc quyn sch c phong ph hn, phc v tt hn cho cng tc khuyn lm v sn xut lm nghip.

Cc tc gi

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MC LC

Chng 1: KHI QUT H SINH THI RNG NGP MN VIT NAM ..............................................................................................11

1.1. c im chung v rng ngp mn ............................................................... 11

1.2. c im t nhin rng ngp mn Vit Nam ................................................ 12 1.3. Qu trnh din th t nhin ca cc loi rng ngp mn Vit Nam ............. 18

1.3.1. Qu trnh din th t nhin ca cc loi rng ngp mn vng ven bin ng Bc Vit Nam (Tnh Qung Ninh) .......................................................... 19

1.3.2. Qu trnh din th t nhin ca cc loi rng ngp mn khu vc ca sng Hng (ng bng Bc B) .............................................................................. 21

1.3.3. Qu trnh din th t nhin ca cc loi rng ngp mn ti bn o C Mau (BSCL) ............................................................................................ 19

1.3.4. Qu trnh din th t nhin ca cc loi rng ngp mn khu vc ca sng Cu Long (ng bng Nam B) ...................................................................... 22

1.4. Cc dch v v gi tr ca rng ngp mn ..................................................... 24 1.4.1. Rng ngp mn bo v vng ven bin chng sng, xi l b bin, hn ch gi v thc y qu trnh bi t ph sa ............................................................. 25 1.4.2. Rng ngp mn l ngun dinh dng ca rt nhiu loi sinh vt vng ca sng ven bin ............................................................................................ 27 1.4.3. Cung cp nhiu sn phm trc tip cho ngi dn a phng ............... 28

1.4.4. L ni du lch, gii tr v nghin cu khoa hc ....................................... 29 1.4.5. Bo tn cc gi tr vn ha v cc gi tr ca thin nhin ........................ 30

1.4.6. Tc dng ca rng ngp mn khi mc nc bin dng cao ..................... 30 1.4.7. nh lng cc gi tr ca rng ngp mn .............................................. 33

1.5. nh hng ca iu kin t nhin v kinh t - x hi n phn b rng ngp mn ............................................................................................................. 34

Chng 2: THC TRNG RNG NGP MN VEN BIN VIT NAM ..............................................................................................39

2.1. Hin trng rng ngp mn ............................................................................ 39

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2.1.1. Din tch v phn b rng ngp mn ...................................................... 39

2.1.2 Din bin rng ngp mn ........................................................................ 46 2.2. nh gi khi qut vic qun l v pht trin rng ngp mn thi gian qua... 50

2.3. T chc qun l rng - mt s kt qu sn xut lm nghip trn a bn cc tnh c rng ngp mn khu vc pha Bc ............................................................. 52

2.3.1. V t chc qun l rng ......................................................................... 52 2.3.2. Cng tc trng rng ............................................................................... 53

2.3.3. Tnh hnh giao khon bo v rng kt hp nui trng thy sn ............... 54 2.3.4. Cc hot ng khc ................................................................................ 56

2.4. Nhng im mnh, im yu, c hi v thch thc trong bo v pht trin rng ngp mn .................................................................................................... 57

2.5. Nhng nguyn tc bo v, qun l v s dng tng hp rng ngp mn........ 60

Chng 3: CC QUY NH V XY DNG RNG PHNG H NGP MN VEN BIN .........................................................................67

3.1. Nhng quy nh chung ................................................................................. 67 3.1.1. Mc ch, yu cu .................................................................................. 67

3.1.2. Phm vi p dng .................................................................................... 67 3.2. i tng v phm vi xy dng rng phng h ngp mn ............................ 67

3.2.1. i tng xy dng rng phng h ngp mn........................................ 67 3.2.2. Phm vi xy dng .................................................................................. 68

3.3. K thut ci to rng ngp mn cht lng km thnh rng phng h .......... 68 3.3.1. iu kin ci to t rng ngp mn cht lng km sang rng phng h .................................................................................................................... 68 3.3.2. K thut ci to rng ngp mn cht lng km .................................... 68

3.4. K thut xy dng rng phng h ngp mn ................................................. 69 3.4.1. Cc iu kin xy dng rng phng h ngp mn .............................. 69

3.4.2. Chiu rng v c ly cc di rng ngp mn ............................................ 70 3.4.3. Phng thc trng rng phng h ngp mn .......................................... 70

3.4.4. Kt cu loi cy trong trng rng ngp mn ........................................... 71 3.4.5. Thit k cc ai rng phng h ngp mn .............................................. 74

3.5. Bin php k thut nui dng v khai thc cho rng ngp mn phng h.... 74

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3.5.1. i tng tc ng ................................................................................ 74

3.5.3. K thut khai thc .................................................................................. 75 3.6. Tiu chun kinh doanh kt hp trong rng phng h ngp mn .................... 75

3.6.1. i tng c php kinh doanh kt hp ............................................... 75 3.6.2. iu kin kt hp .............................................................................. 75

3.6.3. Quy nh v cc bin php kt hp ......................................................... 75

Chng 4: C CH CHNH SCH LIN QUAN TI KHI PHC V PHT TRIN RNG NGP MN VIT NAM ......................77

4.1. Cc chnh sch c lin quan p dng v giao rng, khon rng, quyn hng li, sn xut nng nghip kt hp, u t, ............................................. 77

4.1.1. Cc vn bn php quy c ban hnh ................................................ 77 4.1.2. Vic thc hin chnh sch, vn bn ti cc a phng ........................... 79

4.2. Thc trng c ch chnh sch lin quan n khi phc v pht trin rng ngp mn ..................................................................................................................... 83

4.2.1. Quy hoch s dng t rng ngp mn .................................................. 83 4.2.2. Giao t, khon rng .............................................................................. 84

4.2.3. u t .................................................................................................... 88 4.2.4. Khoa hc cng ngh............................................................................... 90

4.2.5. H thng t chc qun l v s phi hp lin ngnh .............................. 92 4.3. xut c ch chnh sch pht trin bn vng rng ngp mn...................... 94

4.3.1. nh hng chung v c ch chnh sch i vi vng rng ngp mn .... 94 4.3.2. xut c ch chnh sch v gii php c th ........................................ 95

Chng 5: HNG DN K THUT TRNG MT S LOI CY RNG NGP MN .............................................................................. 106

5.1. Bn chua (Sonneratia caseolaris (L.) Engler) ............................................. 106 5.1.1. c im sinh hc................................................................................ 106 5.1.2. K thut to cy con ............................................................................ 106

5.1.3. iu kin gy trng .............................................................................. 109 5.1.4. Trng rng ........................................................................................... 110

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5.1.5. Chm sc v bo v rng ..................................................................... 110

5.2. Trang (Kandelia candel (L.) Drues) ............................................................ 112 5.2.1. c im sinh hc................................................................................ 112

5.2.2. K thut to cy con ............................................................................ 113 5.2.3. iu kin gy trng .............................................................................. 116

5.2.4. Trng rng ........................................................................................... 116 5.2.5. Chm sc v bo v rng ..................................................................... 117

5.3. c vi (Rhizophora stylosa Guff) ........................................................... 118 5.3.1. c im sinh hc................................................................................ 118

5.3.2. K thut to cy con ............................................................................ 119 5.3.2.2. Ging ................................................................................................ 119

5.3.2.3. To bu ............................................................................................. 120 5.3.3. iu kin gy trng .............................................................................. 121


5.4. c i (Rhizophora apiculata B.L) ......................................................... 123 5.4.1. c im sinh hc................................................................................ 123



5.5. Vt d (Bruguiera gymnorrhiza (L.) Lam.) ................................................. 129 5.5.1. c im sinh hc................................................................................ 129



5.6. Mm bin (Avicennia marina) .................................................................... 134 5.6.1. c im sinh hc................................................................................ 134


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5.6.4. Trng rng ........................................................................................... 137

5.6.5. Chm sc v bo v rng ..................................................................... 138 5.7. S (Aegiceras corniculata (L.) Blanco) ....................................................... 139

5.7.1. c im sinh hc................................................................................ 139 5.7.2. K thut to cy con ............................................................................ 139


5.7.5. Chm sc v bo v rng ..................................................................... 142 5.8. Da nc (Nypa Fruticans) ........................................................................ 143



5.8.5. Chm sc v bo v rng ..................................................................... 147 5.9. D vi (Ceriop tagal CB. Robinson - 1908) ................................................ 148



5.9.5. Chm sc v bo v rng trng ............................................................ 154 5.10. Vt tch (Bruguiera parviflora (Roxb.) W. et A. ex Griff.) ....................... 156

5.10.1. c im sinh hc .............................................................................. 156 5.10.2. K thut to cy con .......................................................................... 157

5.10.3. iu kin gy trng ............................................................................ 157 5.10.4. Trng rng ......................................................................................... 158

5.10.5. Chm sc v bo v rng trng .......................................................... 159 5.11. Su Mekong (Xylocarpus Mekongensis Piere - 1987) ................................. 162

5.11.1. c im sinh hc .............................................................................. 162 5.11.2. K thut to cy con .......................................................................... 163

5.11.3. iu kin gy trng ............................................................................ 165 5.11.4. Trng rng ......................................................................................... 166

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5.11.5. Chm sc v bo v rng trng .......................................................... 167

5.12. Mm trng (Avicennia alba Blume - 1826) ............................................... 169 5.12.1. c im sinh hc .............................................................................. 169

5.12.2. K thut to cy con .......................................................................... 170 5.12.3. iu kin gy trng, khoanh nui xc tin ti sinh t nhin ................ 170

5.12.4. Trng rng ......................................................................................... 171 5.12.5. Chm sc v bo v rng trng, khoanh nui xc tin ti sinh t nhin ......................................................................................................... 173

TI LIU THAM KHO .................................................................... 177

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Chng 1

KHI QUT H SINH THI RNG NGP MN VIT NAM

1.1. c im chung v rng ngp mn

Rng ngp mn l nhng qun x thc vt hnh thnh vng ven bin v ca sng nhng ni b tc ng ca thy triu vng nhit i v nhit i. Trn th gii c nhiu tn gi khc nhau v rng ngp mn nh rng ven bin, rng vng thy triu v rng ngp mn (FAO, 1994). Vit Nam, hu ht cc nh khoa hc u thng nht tn gi chung l Rng ngp mn.

c im tng qut l loi rng ny thng phn b vng ca sng hoc ven bin, b ngp bi thy triu ln trong ngy hoc trong thng, t mn v bo ha nc. Trong iu kin nh vy, cc loi cy rng ngp mn thng c cu to v hnh thi thch nghi vi iu kin ngp nc: Thng c r kh sinh pht trin, l dy c nhiu tuyn mui, ht thng ny mm trn cy trc khi qu rng.

Ty theo kh nng thch nghi vi cc mc ngp thy triu, mn ca nc, thun thc ca t m hnh thnh cc ai rng ngp mn khc nhau. vng ca sng, ni c s giao thoa gia ngun nc ngt t sng ra bin, ngp thy triu ln trung bnh trong ngy cc loi cy in hnh vng ny thng gp l Bn chua (Sonneratia caseolaris) hoc Bn ng (S. alba), c (Rhizophora apiculata). Da nc (Nypa frutican) cng l mt i din vng ca sng, nhng chng thng ng su hn v pha t lin, pha sau ai rng Bn.

ni xa ca sng, mn ca nc thng nh hn so vi vng ven bin gn ca sng thng gp cc loi Mm trng (Avicennia alba) hoc Mm en (Avicennia officinalis). Trn nhng vng t cao, t mn, ch b ngp khi thy triu ln cao trong thng hoc trong nm xut hin cc loi Cc (Lumnitzera racemosa) hoc Tra (Hibiscus tiliaceus). Xa v bn trong trn nhng vng cao

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hn, t rng tng i kh, cc thc vt rng ngp mn b loi Trm (Melaleuca) thay th, hnh thnh h sinh thi rng Trm trn t phn.

Qu trnh hnh thnh v pht trin ca rng ngp mn lun lun c quan h mt thit vi cc iu kin mi trng, trong qu trnh ngp triu, s lu thng ca thy triu, s bi t ph sa l nhng yu t chi phi mnh m nht i vi i sng ca cc loi cy rng ngp mn.

Do nhng c im c bit ca mi trng nn ch c mt s lng rt t cc loi cy c th chu c v pht trin bnh thng trong iu kin ngp thy triu, t bn ly, mn, khc hn so vi nhng loi rng pht trin trn t kh, cao khc. Trn th gii, thnh phn cc loi cy ca rng ngp mn c FAO (1994) lit k gm 84 loi, trong c 66 loi cy g, 13 loi cy bi, 2 loi cy h Cau da, v 3 loi cy dng x.

Vit Nam, nh Sm v cc cng s (nm 2005) lit k 37 loi cy l nhng loi thc th l cy rng ngp mn. Cn Gi (thnh ph H Ch Minh) l a phng c s loi cy rng ngp mn nhiu nht (33 loi), C Mau c 32 loi. Kho st ti vng ca sng, ven bin tnh Sc Trng xc nh c 24 loi cy.

Theo L Vn K (1970), vo khong trc nm 1970, Vit Nam c khong 300.000ha rng ngp mn phn b tp trung cc vng B Ra - Vng Tu, Bn Tre, Tr Vinh, C Mau, Rch Gi, Qung Ninh, Ngh An, Thanh Ha. H thc vt rng ngp mn Vit Nam bao gm 15 - 20 h, ch yu c cc chi: c (Rhizophora), Vt (Bruguiera), D (Ceriops), S (Carapa), Cc (Lumnitzera), Bn (Sonneratia), Mm (Avicennia), Gi (Exoecaria), Tr (Aegiceras). n nay theo s liu ca Vin iu tra Quy hoch rng v B Ti nguyn & Mi trng (2006), din tch rng ngp mn c nc ch cn 209.741ha trong rng t nhin ch cn 57.610ha, trong ch yu tp trung khu vc pha Nam chim 81%. Thin tai, nn ph rng, m rng din tch nui trng thy sn v nhiu nguyn nhn khc lm st gim rng ngp mn bnh qun 5.000 - 6.000ha/nm trong vng 40 nm qua.

1.2. c im t nhin rng ngp mn Vit Nam

Nc ta c 30 tnh v thnh ph c rng v t ngp mn ven bin chy sut t Mng Ci n H Tin, trong :

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- Vng ven bin Bc B c 5 tnh: Qung Ninh, Hi Phng, Thi Bnh, Nam nh, Ninh Bnh.

- Vng ven bin Trung B c 14 tnh ri rc t Thanh Ho cho n Bnh Thun.

- Vng ven bin ng Nam B v Nam B c 11 tnh: B Ra - Vng Tu, ng Nai, TP.H Ch Minh, Long An, Bn Tre, Tin Giang, Tr Vinh, Sc Trng, Bc Liu, C Mau v Kin Giang.

Nhn chung, cc vng ven bin Vit Nam u mang c im kh hu nhit i m vi nhit trung bnh hng nm 22,2oC (Tin Yn - Qung Ninh) n 26,5oC (C Mau) v lng ma trung bnh 1.500 - 2.000 mm/nm. Mt s ni c lng ma hng nm kh cao t ti 2.749 mm/nm (Mng Ci), 2.929 mm/nm (K Anh - H Tnh), 2.867 mm/nm (Hu). Ngc li, mt s ni li c lng ma qu thp 794 mm/nm Nha H (Phan Rang), 1.152 mm/nm Phan Thit.

nhng ni c lng ma thp di 1.200 mm/nm thng khng c rng ngp mn phn b t nhin. Tng lng ma hng nm trn ton lnh th Vit Nam t 630km3 nc.

Min Bc Vit Nam do nm v tr chuyn tip gia hai i kh hu nhit i v nhit i, li chu nh hng ca gi ma ng Bc mang khi khng kh lnh xung tng t, tr thnh min kh hu nhit i m, bin tnh c ma ng lnh. Trong ma ng, c nhiu ngy nhit khng kh xung thp di 20oC v nh hn 15oC lm cho nhit nc bin ven b nhiu ni thp hn 20oC, c nh hng trc tip n sinh trng v phn b ca cc loi rng ngp mn.

Mng li sng ngi Vit Nam kh dy, nu ch tnh ring cc sng ngi di hn 10 km, th c nc c ti 2.500 con sng ln nh. Mt li sng thay i t 0,5 - 2km/km2. Lng dng chy ca sng ngi Vit Nam ra bin ng hng nm vo khong 800 - 900km3 nc. Nu khng tnh lng dng chy t ngoi vo th lng dng chy sinh ra trn lnh th Vit Nam vo khong 300km3 nc (Nguyn Vit Ph, 1984). Vit Nam c hai con sng ln nht l sng Cu Long v sng Hng, vi lng dng chy chim ti 70% tng lng dng chy ca cc sng ngi trong ton quc. Sng Cu Long v sng Hng hng nm a ra bin khong 200 triu tn ph sa. Do , cc vng ca sng Hng, sng Cu Long v mi nm ln ra bin ng 40 - 100m

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(VM. Fridland, 1964; Nguyn Vit Ph, 1978). Trn cc bi bi bn long cn pha nhiu nc bin, d t d nc, cn nng v qu trnh a cht hn l qu trnh hnh thnh t, xut hin cc rng ngp mn tin phong c nh bi bi.

Da vo s khc nhau v cc iu kin a l t nhin c th phn chia thm thc vt rng ngp mn v t ngp mn ven bin nc ta theo 3 min Bc B, Trung B, Nam B thnh 6 vng v 12 tiu vng.

Bng 1.1: Phn vng rng ngp mn v t ngp mn ven bin Vit Nam

Min Vng Tiu vng Ghi ch

A. Ven bin

Bc B

I. ng Bc (Qung

Ninh)

1. Mng Ci Ca ng

2. Ca ng Ca Lc

3. Ca Lc Sn

II. ng bng Bc B 4. Sn Vn c

5. Vn c Lch Trng

H sng Thi Bnh

H sng Hng

B. Ven bin

Trung B

III. Bc Trung B 6. Lch Trng Rn

7. Rn Hi Vn

IV. Nam Trung B 8. Hi Vn Vng Tu

C. Ven bin

Nam B

V, ng Nam B 9. Vng Tu Soi Rp Ba N 586km Vng Tu

- TP HCM

VI. ng bng Nam

B

10. Soi Rp M Thnh

11. M Thnh Bn Hp (mi

C Mau)

12. Bn Hp H Tin

(M Nai )

ng bng sng Cu Long,

Ty Nam bn o C Mau

Ty bn o C Mau

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Ngun: Phan Nguyn Hng

Kt qu nghin cu v c im t nhin vng ven bin ca 2 min c trnh by tm tt hai bng 1.2 v 1.3.

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Bng 1.2: c im t nhin vng ven bin min Bc Vit Nam

Vng ng Bc (Qung Ninh ) Vng ng bng Bc B

Tiu vng I

Mng Ci n Ca

ng

Tiu vng II

Ca ng n Ca

Lc

Tiu vng III

Ca Lc n

Sn

Tiu vng I

Sn n Vn c

Tiu vng II

Vn c n Lch

Trng

* Kh hu:

- Nhit i gi ma c ma ng lnh

- C 4 thng tO < 20OC

- Ma: > 2000 - 2400mm

- to nc bin m hn

2 vng trn.

- 1800-

2000mm

- tO TB: 23 23,7OC

50 - 60 ngy tO < 20OC

Ven b tO ma ng 18,3-18,5OC

Ma: 1287 - 1865mm

* Thu vn:

Sng sui nh, ngn,

dc: Sng Kalong,

Tin Yn, Ba Ch

Sng sui ngn,

nh, t ph sa

nh hng nc sng

Bch ng, sng

Kinh Thy, sng

Chanh

- Nc thng ngun

khng ln ca sng

rng hnh phu, nh

hng xm thc mnh

- Nc thng ngun

sng Hng v sng

Thi Bnh cha nhiu

ph sa

* Sn phm bi t:

Lp bi t, mng v,

cui, si, ct

Mng, nhiu

ct, si,

Dy, nhiu bn st

(st 50 - 60%) t

ct

- Sn phm phong

ho giu xt st,

nhm, ngho cation

kim th

Bi t mnh, giu cation

kim th, P2O5. Tc

ln bin nhanh 80 -

120m/nm

* Thu triu:

- Ch nht triu

- mn n nh: 15

- 24

- Nht triu

15 - 25

Nht triu

4 - 20 (ma

kh )

9 - 15 (ma

ma )

- Nht triu

4 - 20 (ma

kh )

9 - 15 (ma ma

)

Nht triu bin ng

Ngp 1 - 2m, ti a

3m

*c im t:

- t ngp mn phn

tim tng

t ngp mn

phn tim tng

Ct pha ln si

- t ngp mn

- t ngp mn phn

tim tng

- t ngp mn

- Tht pha st (29 -

35% st )

t ngp mn khng c

phn tim tng

Tht nh n nng

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- Ct pha tht

Cht hu c thp

*c im

thc vt

Mm bin, S, Vt

d, c vi, Gi

- Ngho, sinh

trng km, ch

yu: S

- Rng tt

- c vi: 30%

- S: 40 - 50%

- Bn chua; 8m

Ri rc

Bn chua + S

Bn chua + Trang

Bn chua v S

Bng 1.3: c im t nhin vng ven bin cc tnh ng bng sng Cu Long

Tiu vng I:

T Vng Tu

n Soi Rp

Tiu vng II:

T Soi Rp

n M Thnh

Tiu vng III:

T M Thnh

n mi C Mau

Tiu vng IV:

T mi C Mau

n H Tin

Kh hu:

- Nhit i m, khng c

ma ng.

- Nhit trung bnh

27,2oC.

- Lng ma

1.345mm/nm

- Nhit i m, khng c

ma ng

- Nhit trung bnh

26,8oC

- Lng ma 1.467-

1.859mm/nm

- Nhit i m, khng c

ma ng

- Nhit trung bnh

26,7oC

- Lng ma 1.883-

2.366mm/nm

- Nhit i m, khng c

ma ng

- Nhit TB 27,6oC

Lng ma 2.057-

2.400mm/nm

Thu vn:

- nh hng trc tip nc

thng ngun ca sng ng

Nai

- Lu lng nc nh

532m3/s.

- Ca sng hnh phu

- nh hng trc tip nc

thng ngun sng Cu

Long

- Lu lng nc rt ln

3.400m3/s

- t chu nh hng trc tip

ca thng ngun sng Cu

Long

- Nm xa cc vng ca sng

Tin v sng Hu.

- t chu nh hng trc tip

ca thng ngun sng Cu

Long

- Nm xa cc vng ca sng

Sn phm bi t: - Giu ct phn v st, hm - Giu ht st, l ni bi t - Giu ht ct

18

- Sn phm phong ha

nhit i giu xit Fe v Al,

giu ht st.

- Kiu bi t bin-sng

lng ct tng i cao.

- Kiu bi t sng-bin.

ph sa din ra mnh nht.

Bi bi rng, ln bin

- Kiu bi t m ly-bin

- Kiu bi t bo mn b

bin (do hot ng ca thu

triu)

c im thu triu:

- Ch bn nht triu.

- Bin triu 2m.

- mn ca nc bin

ng khng ln.

- Ch bn nht triu

- Bin triu 2,5-3m

- mn ca nc vng

ca sng bin ng ln 3-

17o/oo.

- Ch bn nht triu

- Bin triu TB 1,9m

- mn nc tng i

cao, bin ng khng nhiu

trong nm 20,7-

28,7o/oo

- Ch nht triu vnh Thi

Lan

- Bin triu thp 60-

70cm

- mn tng i cao, bin

ng khng nhiu trong nm

c im t:

- t ngp mn

- t ngp mn phn tim

tng

- Hm lng cht hu c

kh

- Giu ht st

- t ngp mn khng c

phn tim tng.

- Hm lng mn trung

bnh

- Thnh phn c gii bin

ng ln t ct pha n st

pha nng.

- t ngp mn

- t ngp mn phn tim

tng (loi t c din tch rng

nht)

- t ngp mn than bn

phn tim tng (din tch nh

nht)

- t giu cht hu c v

ht st

- t ngp mn phn tim

tng (chim din tch rng

nht)

- t giu ht ct

- Hm lng cht hu c cao

- C ni hnh thnh t ngp

mn than bn phn tim tng

c im thc vt:

- C phong ph cc rng

Mm, sau n rng

Bn, rng c t nhin c

din tch khng rng

- Ni phn b t nhin

phong ph ca cc loi rng

Bn v rng Mm. Hu

nh khng c rng c

phn b t nhin, nu c th

din tch rt nh

- Ni phn b rng ri ca

cc loi cy h c. Rng

c t nhin c din tch

rng nht, sau n Mm

trng v Mm en.

- L ni rng sinh trng tt

nht

- Rng ngp mn y t

phong ph v sinh trng

khng tt, ch yu l rng

c v rng Mm

1.3. Qu trnh din th t nhin ca cc loi rng ngp mn Vit Nam

Khc vi cc h sinh thi rng i ni, h sinh thi rng ngp mn ven bin

19

l mt h sinh thi khng khp kn (h sinh thi m). Trong qu trnh di chuyn ln xung hng ngy ca nc triu vng ven bin, c bit nhng ni c bin triu ln (t 3 - 4,5m) mang ra khi rng ngp mn t 20 - 40% tng sn phm hu c ca rng tr li cho t hng nm qua cnh l ri rng.

c bit cc yu t mi trng vt l ca rng nh ch ngp nc, cao ca t, thnh thc ca t lun thay i theo thi gian, bi bi v rng ngp mn lun pht trin theo hng tin dn ra bin v li sau lng n l cc dng t bi ven bin cao hn, ngp nc triu t hn. Cc cy ngp mn sinh trng cn ci v cng xu hn. Cui cng t thot khi nh hng ngp ca nc triu v tr thnh loi t ph sa khng b ngp mn thng xuyn, thch hp cho sn xut nng nghip.

1.3.1. Qu trnh din th t nhin ca cc loi rng ngp mn vng ven bin ng Bc Vit Nam (Tnh Qung Ninh)

bi bi mi c hnh thnh, nc ngp su, khi triu thp xut hin rng tin phong c nh bi bi: rng Mm bin hoc rng S. Di tc dng ca rng Mm bin v rng S, tc bi lng ph sa di rng c nhanh hn, t ngy cng cht hn, thnh thc ca t tng dn, to iu kin cho rng c vi nhy vo thay th dn rng Mm bin v rng S. Cng theo quy lut tng t nh vy, rng Trang s thay th rng c vi v rng Vt d s thay th cho rng Trang. Cui cng, trn dng t cao, t c ngp triu, ngp nc nng, t tng i cht (t thnh thc) th rng Cc, rng Gi s xut hin thay th cho rng Vt. Kt qu din th t nhin c tng hp khi qut qua bng 1.4.

Bng 1.4. Qu trnh din th t nhin ca cc loi rng ngp mn ti Qung Ninh (ng Bc Vit Nam)

Loi rng ngp

mn

Cha xut hin

rng ngp mn

Rng Mm

bin + rng

S

Rng

c vi

Rng

Trang Rng Vt

Rng Gi - Rng

Cc

Ch ngp triu

Ngp khi

nc triu rt

thp

Ngp khi nc triu thp Ngp khi nc triu cao

trung bnh

Ngp khi nc triu

cao v cao bt thng

trong nm

20

S ngy ngp

triu trong thng 30 29 - 25

24 -

20 19 - 15 14 - 10 9

Loi t t ngp mn phn tim tng, mng lp, ct pha

21

1.3.2. Qu trnh din th t nhin ca cc loi rng ngp mn khu vc ca sng Hng (ng bng Bc B)

Trn cc bi bi mi hnh thnh, bn long, ngp nc su, khi triu cng xut hin rng Bn chua tin phong c nh bi bi hoc rng Bn chua v S. Sau rng Bn chua hoc rng Bn chua v S l rng ngp mn hn loi: Bn chua xen Trang, sau rng Bn chua xen Trang l rng Trang v S, sau rng Trang v S l rng Gi trn t cao, cht, t thnh thc t c ngp triu trong nm. Qu trnh din th t nhin cc loi rng ngp mn khu vc ny c tng hp bng 1.5.

Bng 1.5. Qu trnh din th t nhin cc loi rng ngp mn khu vc sng Hng (ng bng Bc B)

Loi rng ngp mn Cha xut hin

rng ngp mn

Rng Bn chua

Rng Bn chua v

S

Rng Bn

chua v Trang

Rng

Trang v

S

Rng Gi

Ch ngp nc triu

Ngp khi

nc triu rt

thp

Ngp khi nc triu

thp

Ngp khi nc triu cao trung

bnh

Ngp khi nc

triu cao

S ngy ngp triu

trong thng 30 29 - 20 19 - 10 9

Loi t t ngp mn (khng c phn tim tng)

thnh thc ca t

(n) > 2,5 2,5 - 1,5 1,4 - 0,7 0,6

1.3.3. Qu trnh din th t nhin ca cc loi rng ngp mn ti bn o C Mau (BSCL)

Cng tng t nh quy lut din th t nhin ca cc loi rng ngp mn trn cc bi bi ven bin vng ng Bc (Qung Ninh), y rng Mm trng l loi rng ngp mn tin phong c nh cc bi bi mi hnh thnh, dng bn long. Sau rng Mm trng l rng c, sau rng c l rng Vt, sau rng Vt l

22

rng D, sau rng D l rng Gi v rng Cc. Qu trnh din th c tng hp bng 1.6.

Bng 1.6. Qu trnh din th t nhin ca cc loi rng ngp mn ti bn o C Mau (BSCL)

Loi rng

ngp mn

Cha xut

hin rng

ngp mn

Rng

Mm trng

(rng tin

phong c

nh bi bi)

Rng

Mm

trng +

c

Rng

c Rng Vt Rng D

Rng Gi

- Rng Cc

Ch

ngp nc

triu

Ngp khi

nc triu

thp

Ngp khi nc triu thp Ngp khi nc triu cao

trung bnh

Ngp khi

nc triu

cao

Ngp khi

nc triu cao

v cao bt

thng trong

nm

Loi t t ngp mn t ngp mn phn tim tng

Dng t

ai

Bn rt

long Bn long Bn St mm St St cht St rn chc

thnh

thc ca t 2,5 2,4 - 1,5 1,4 - 1,0

0,9 -

0,7

0,6 -

0,4 < 0,4

cc vng nc l ca sng, mn ca nc khng cao, di 20 v mc bin thin v mn ca nc trong nm rt ln, t 3 - 20, xut hin cc loi rng ngp mn gm cc cy rung mui.

1.3.4. Qu trnh din th t nhin ca cc loi rng ngp mn khu vc ca sng Cu Long (ng bng Nam B)

Qu trnh din th y cng nh quy lut din th t nhin ca sng Hng, nhng do kh hu rt thun li cho cc cy rng ngp mn phn b v sinh trng nn cc loi rng ngp mn y rt phong ph.

23

Trn cc bi bi mi hnh thnh, dng bn long ca sng chng ta gp cc loi rng Bn gm c Bn chua, Bn ng, Bn i; sau rng bn l cc loi rng Mm bao gm Mm trng, Mm en, Mm bin; sau rng mm l rng Da nc; sau rng Da nc l rng Cc v rng Gi. Qu trnh din th t nhin khu vc ca sng Cu Long c tng hp bng 1.7.

Bng 1.7. Qu trnh din th t nhin cc loi rng ngp mn khu vc ca sng Cu Long (ng bng Nam B)

Loi rng ngp mn Cha xut hin

rng ngp mn

R.Bn chua

R.Bn ng

R.Bn i

R.Mm trng

R.Mm bin

R.Mm en

Rng Da

nc

Rng Cc

- Rng Gi

Ch ngp nc

triu

Ngp khi nc

triu rt thp

Ngp khi nc

triu thp Ngp khi nc triu cao trung bnh

Ngp khi nc

triu cao

S ngy ngp triu

trong thng 30 29 - 20 19 - 10 9

Loi t t ngp mn t ngp mn tim tng su (yu)

thnh thc ca

t > 2,5 2,5 - 1,9 1,4 - 0,7 < 0,6

Qu trnh din th t nhin cc loi rng ngp mn khu vc ng bng sng Cu Long cho thy s phn b ca cc loi rng Bn chua v rng Mm ph thuc vo mn v bin mn ca nc v n lin quan n v tr gn hay xa ca sng.

Rng Bn chua thng phn b st ca sng ni mn ca nc t 3 n 20. Rng Bn ng thng xut hin xa ca sng hn, ni c mn ca nc bin ng t 7 n 25. Rng Mm trng thng sng bi bi xa ca sng, vi mn ca nc dao ng t 20 n 29. Rng Mm bin thng phn b bi bi c mn ca nc t 7 - 30. Rng Mm en thng sng cc bi bi ven sng v knh rch, ni c mn ca nc t 4 - 30.

24

1.4. Cc dch v v gi tr ca rng ngp mn

H sinh thi rng ngp mn c bit n l ni cung cp mt lng ln hng ho v dch v cho con ngi, l ni lu gi nhng ngun gen cho tng lai, ni cung cp thc n v ch sinh sn cho rt nhiu loi ng vt c gi tr sinh thi v mi trng cao (Macnae, 1974). ng thi, rng ngp mn cng l trm dng chn v l ni c tr ca rt nhiu loi chim nc di c. Rng ngp mn bo v cc ngun nc ngt chng li s nhim mn, bo v t ai khi s xi mn bi sng v gi (Semesi, 1998) v gp phn n nh b bin. Rng ngp mn c th c coi l tm barie t nhin bo v cho ti sn v cuc sng ca cc cng ng dn c ven bin trc bo gi v lc xoy.

Mc d c nhiu cng trnh nghin cu v cu trc, nng sut, li ch ca rng ngp mn, nhng nhiu dch v mi trng m rng ngp mn cung cp cha c xem xt v nh gi tha ng dn n vic qun l rng ngp mn cn nhiu bt cp. Chnh v vy, trong nhng nm qua, vic thu hp din tch rng ngp mn pht trin kinh t, c s h tng, th din ra rng khp nhiu a phng. Tuy nhin, thc t chng minh, nhng ni qu ch trng vo vic pht trin kinh t trc mt bng cch thu hp din tch rng ngp mn v ang gnh chu nhng tn tht rt ln v kinh t do suy thoi v chc nng sinh thi ca rng ngp mn.

Nghin cu lng gi kinh t cc dch v sinh thi do rng ngp mn cung cp l mt trong nhng t liu quan trng, h tr cho cc nh qun l trong qu trnh hoch nh cc chnh sch qun l rng ngp mn ni ring v cc chnh sch pht trin kinh t - x hi mt cch bn vng ti a phng ni chung. Lng gi kinh t l s xc nh cc gi tr c tnh nh lng cho cc hng ho v dch v m h sinh thi cung cp khi cc hng ha v dch v ny khng c th trng.

Cc nghin cu khoa hc cho thy rng ngp mn c kh nng lm gim nng lng sng t 50 - 70% ty thuc vo chiu rng ca ai rng v nh m n c tc dng to ln trong vic phng h ven bin. Thc t cho thy nhng h thng bin c ai rng phng h rng th nhng thit hi v bin l rt thp. nh gi bc u v thit hi do bo gy ra trong nhng nm qua cho thy, nhng ni bin c rng ngp mn phng h th hu nh bin khng b st l v do vy cc chi ph tu sa bin hng nm gim i hng t ng.
BINH KUTEHighlight

25

Sau y chng ta s ln lt xem xt lm r mt s gi tr dch v t rng ngp mn phng h ven bin.

1.4.1. Rng ngp mn bo v vng ven bin chng sng, xi l b bin, hn ch gi v thc y qu trnh bi t ph sa

Nh c h r pht trin n su xung t, lm cho nn t tr nn vng chc. Tn l rng vi cnh vng chc gim nh xung ng ca sng, lm gim xung lc ca sng tc ng vo b bin. Nghin cu ca Yoshihiro Mazda v cc cng s (Yoshihiro Mazda, 1997) c kt lun rng, di rng ngp mn 6 tui vi chiu rng l 1,5km c th gim cao sng t 1 mt ngoi khi cn 0,05m khi vo ti b. S gim sng ph thuc vo loi cy rng ngp mn, iu kin thm thc vt, su mc nc v iu kin sng xut hin (Yoshihiro Mazda, 2006).

Cy rng ngp mn cng hn ch gi t bin vo lc a, lung gi thi t bin vo t lin khi gp ai rng ngp mn th cng ca gi s b gim i. Cc ai rng ngp mn c tc dng lm gim mnh cao ca sng khi triu cng. Nu gp ai rng dy v rng, lung gi s i hng vt qua tn rng, nhng khu dn c v c s h tng pha sau ai rng s c bo v, mc thit hi s gim i rt nhiu so vi tnh trng khng c ai rng bo v.

Nghin cu ca Y. Mazda v cng s x Thy Hi, huyn Thi Thy, tnh Thi Bnh trong thi gian c triu cng t ngy 17 n 21/11/1994 cho thy rng Trang (Kandelia candel) trng 6 tui vi chiu rng 1,5km gim cao ca sng t 1m ngoi khi xung cn 0,05m khi vo ti b m cua v b m khng b xi l. Cn ni khng c rng gn , cng mt khong cch nh th th cao ca sng cch b m 1,5km l 1m, khi vo n b vn cn 0,75m v b m b xi l.

Nm 2003, Trung tm nghin cu Sinh thi v Mi trng rng nghin cu tc bi lng ph sa ni c rng ngp mn: Bn chua + Trang v ni bi bi k bn, khng c rng ngp mn i chng ti x Tn Thnh - huyn Kin Thy - TP. Hi Phng. Kt qu cho thy ni c rng ngp mn phn b tc bi t ph sa trung bnh l 0,71 cm/nm, ni bi bi khng c rng ngp mn ch t 0,28 cm/nm (ch bng 39,4% so vi ni c rng ngp mn). iu ny cho thy rng ngp mn c tc dng lm tng tc bi lng ph sa cc vng ca sng, ven bin.

26

H thng r cy rng ngp mn cng gi li cc cht trm tch t t lin a ra bin. Cc cht trm tch ny trn vi lp thm mc, tn tch hu c c phn r lm cho nn t nng cao. Nh tc dng h tr ca ai rng ngp mn, cc bi bi hng nm ln ra bin vi chc mt thm ch ca sng Cu Long v mi C Mau ln ra bin hng trm mt.

nh 1.1. Xi l b bin ca sng Ci Ln - C Mau

nh 1.2. Rng ngp mn chn sng, bo v bin ti Hi Phng

27

1.4.2. Rng ngp mn l ngun dinh dng ca rt nhiu loi sinh vt vng ca sng ven bin

Nhng vng bi bin ngp triu v cc knh rch vng ca sng ven bin khi thu triu xung l nhng bi kim n l tng cho cc loi chim. Theo t chc ca cc Lut gia mi trng th gii (EJF, 2003), rng ngp mn vng ca sng, ven bin ng bng sng Cu Long c 386 loi v ph loi chim, 260 loi c, hng trm loi ng vt xng sng.

vng ca sng Cu Long, nghin cu ca Phm Trng Thnh v cc cng s (1998) Thnh Ph (Bn Tre) thng k c 27 loi b st, 8 loi lng c, 16 loi th v 60 loi chim. Mt s loi him v c nguy c b e da c pht hin y nh Tc k (Gekko gekko), K hoa (Varanus salvator), Ri c lng mt (Lutra perspicilata), Mo c (Felis viverina), B nng (Pelecanus philipensis), C lng xm (Mycteria cinerea).

V thy sinh vt, Trn Kim Hng v cc cng s (2003) thng k c 185 loi thc vt ni, trong , nhm Bacillariophyta chim (79%), c 93 loi ng vt ni, bao gm 57 loi ca nhm Arthropoda (62,29%), 90 loi ng vt y c xc nh, bao gm 41 loi thuc nhm Arthropoda (45,56%). Vng ca sng c 661 loi c thuc 319 h, trong s loi c sng tng y v gn y chim khong 72%, h c Mi (Priacanthidae) chim 54,43%, h c Kh (Canrangidae) chim 25,5%, h c Trc (Priancabidae) chim 3,79%,

Cc loi c sng tng ni chim 28%, tng trung v ni c cc loi c Bc m, c Nc, c Mi vch, c Chun en, c Chch trn, c Thu vch. S loi sng gn b chim 68% v c sng xa b chim 32%. C 20 loi tm trong khu vc, gm 12 loi tm bin (thuc 5 h), 8 loi tm nc ngt (7 loi thuc h Palaemonidae v 1 loi thuc h Caridae). Cc loi tm ch yu trong vng l nhng loi c gi tr cao nh Penaeus indicus; Metapeneusensis, M. lysanassa v M. spinulatus.

Nghu ging xut hin hu ht cc bi bi vng ca sng, em li ngun thu nhp rt quan trng cho ngi dn a phng. Nhng ngi nng dn sng lu nm khu vc C Lao Dung vo ma thu hoch Nghu, mi ngy c hng ngn ngi n thu hoch Nghu vng ny, thu nhp ca h c th t c t vi trm n hng triu ng mi ngy.

Cc nh khoa hc chng minh mi lin h khng kht gia vic bo v v pht trin rng ngp mn i vi nng sut thy sn vng ven bin v ngoi khi (Pedersen, A. et al. 1996). Mi hecta rng ngp mn h tr cho sn lng

28

nh bt hng nm khong 450kg (Hinrichsen, D. 1998), khong 2/3 sn lng c nh bt c ca th gii hng nm c cuc sng ca chng ph thuc vo s lnh mnh ca cc h sinh thi ngp nc ven bin (Hinrichsen, D. 1998). Ngun thc n u tin, phong ph v a dng cung cp cho cc loi hi sn l xc hu c thc vt dng ht hoc cn gi l mn b hu c, l sn phm ca qu trnh phn hy xc thc vt, bao gm: l, cnh, chi, r, ca cc cy ngp mn. Theo Snedaker (1978), lng l ri ca cy rng ngp mn Nam Florida l 10.000 - 14.000kg kh/ha/nm. Kt qu nghin cu rng c C Mau cho thy nng sut lng ri l 9.719,9 kg/ha/nm, ring l chim 79,71%. Hng nm rng c C Mau cung cp cho h sinh thi rng ngp mn y 8.400 - 12.000kg l/ha/nm (tnh theo trng lng kh) (Nguyn Hong Tr, Phan Nguyn Hng, 1984).

nh 1.3. Mt s loi hi sn di tn rng ngp mn ti m H - Qung Ninh

1.4.3. Cung cp nhiu sn phm trc tip cho ngi dn a phng

Cng dng ca cc loi cy rng ngp mn rt a dng, Phan Nguyn Hng v Hong Th Sn (1983) v (1994) thng k c 30 loi cy cung cp g,

29

than v ci; 14 loi cy cho tannin; 24 loi cy cho phn xanh, ci to t hoc gi t; 21 loi cy dng lm thuc; 9 loi cy ch th cnh kin ; 21 loi cy cho mt ong; 1 loi cy cho nha sn xut nc gii kht, ng,

c, Bn, Mm, Vt l nhng loi cy g c kch thc ln, tng trng nhanh. Cy c (Rhizophora apiculata) C Mau tng trng ng knh 0,75 cm/nm, chiu cao 0,85 m/nm, thng khai thc vi lun k 20-30 nm (Phan Nguyn Hng v Nguyn Hong Tr, 1983). Rng c trng c th t nng sut 20 m3/ha/nm. B Ra - Vng Tu (Tn Thnh), c trng thun loi c tng trng bnh qun 0,6-0,8 cm/nm (Phn vin iu tra Quy hoch rng Nam B, 2003). G c c s dng lm nh ca nh: Ct, ko, rng, nng, lm ct nh bt thy sn vng ven bin, cc loi cc g gi li, gi y u c lm bng cy c c kch thc di ti hng chc mt v ng knh cng t vi chccm.

Than hm t cc loi c, Vt l ngun nng lng quan trng. Nhn dn vng ven bin v nh bt hi sn rt a thch dng than hm. Trong mt s ngnh cng nghip, than c rt c a chung do c t khi, nhit lng cao tng t than (6.375 - 6.675 calo/kg). vng ven bin Nam B, cho n ngy nay, than c vn l sn phm c s dng rt rng ri. Nng sut than nc ta tnh theo trng lng g trung bnh l 20%, 1 ster ci nng 800kg sau khi t c 165kg than.

Tannin l loi sn phm c t l cao trong v ca cc loi cy rng ngp mn. Theo Lm Bnh Li (1972) cho bit t l tannin cha trong v cc loi cy rng ngp mn nh sau: D (29,85%), Vt (13,6%), Cc (13,4%), c (12,2%).

Da nc (Nipa fruticans) c tc dng gi b knh khi b xi l, l lp nh, lm vch, qu n c, cc cht nha t cung cm hoa c th sn xut ng, ru, gim n. L da nc l sn phm quan trng nht ca loi cy ny, thng dng lm nh. Tuy nhin, tt c cc sn phm ca loi cy ny u c gi tr i vi i sng hng ngy ca ngi dn a phng.

1.4.4. L ni du lch, gii tr v nghin cu khoa hc

Do cnh quan thin nhin hoang s v hng v, kh hu mt lnh, lm cho cc khu rng ngp mn vng ven bin l nhng ni vui chi, gii tr l tng, cun ht du khch khp mi min trong nc v trn th gii. Nhiu khu rng ngp

30

mn nc ta l ni du lch sinh thi rt ni ting nh Cn Gi, Mi C Mau, H Tin. Khu vc C Lao Dung tnh Sc Trng cng l im du lch ni ting trong mng li du lch ca Vit Nam v quc t. S sinh ng v k b (misterious) ca h sinh thi rng ngp mn lun lun li cun s am m cc nh khoa hc trong nghin cu v sng to.

1.4.5. Bo tn cc gi tr vn ha v cc gi tr ca thin nhin

Cc khu rng ngp mn ven bin ca sng tnh Sc Trng c gi tr quan trng i vi vic bo v tnh hoang s nguyn thy ca vng t ngp nc, h tr cc qu trnh sinh thi vng ca sng, ven bin. c bit l duy tr qu trnh din th t nhin ca h sinh thi rng ngp mn vng ca sng Cu Long, mt trong 12 h thng sng ln nht th gii.

Ngun li thy sn ca rng Bn chua phong ph v di do. Thy hi sn vng ca sng Sc Trng c nhiu loi khc nhau v chng xut hin theo ma. Cc sn phm bao gm cc loi c Ngc, c Qut, c Bng, cua ging, c Ko, Nghu, S huyt, Cch thc nh bt cng a dng, ph hp cho tng gii v tng la tui. n ng th nh bt c, ph n v tr em bt cua ging, c Ko, Nghu, S huyt, Ngun li thy sn gp phn nui sng khng t h gia nh nhng lng ven bin. ai rng bn chua phng h gp phn to nn mi trng sinh thi thun li cho nui trng thy sn vng m. Rng Bn ng vai tr nh mt my lc nc khng l, gp phn lm sch nc trc khi bm vo ao nui v lm lng ng cc cht thi t ao nui x ra.

1.4.6. Tc dng ca rng ngp mn khi mc nc bin dng cao

Nhng nm gn y, tc hi ca bin i kh hu i vi ti nguyn thin nhin v x hi ngy cng r rt, vi quy m v cng ngy cng tng. Nhng vng t thp, ngp nc ven bin cng l i tng b e da ngy cng nng n. Tuy nhin, h sinh thi rng ngp mn cng l tc nhn hn ch cc tc hi ca s bin i kh hu, gim nh thit hi do nc bin dng.

Cc khu rng ngp mn do c h thng r dy c trn mt t nh h r hnh chn nm ca cc loi c, ng, r hnh u gi ca cc loi Vt, r th hnh chng ca cc loi Mm, Bn, ngn cn xung lc ca sng. Vi lp tn l dy cng vi thn, cnh cy to thnh lp ro bng vt liu mm gim sc cng ph ca sng triu (Phan Nguyn Hng, 2008).

Cng nh lp thm thc vt cn sng, lng ph sa v mn b hu c c tch ly ph sa cng mn b thc vt ti ch lm cho mt t c c nh v

31

nng cao. Nh , cc tr mm v qu, ht ca cc loi cy ngp mn nhanh chng ti sinh chim c vng bi bi.

Yoshihiro Mazda, Michimasa Magi, Mothoko Kogo, Phan Nguyn Hng (2005) nghin cu Vai tr chn sng ca rng ngp mn ng bng Bc B, Vit Nam cc tc gi cp n c im bin ng ca mc nc triu v nh hng ca rng ngp mn n mc nc triu.

V on Thi (2005) trong cng trnh Bc u nghin cu kh nng chn sng, bo v b bin trong bo qua mt s kiu cu trc rng ngp mn trng ven bin Hi Phng tin hnh nghin cu tc dng chn sng ca mt s kiu trng thi rng trng trong cc trn bo s 2, 6, 7 (nm 2005), ch tiu nghin cu l h s suy gim cao sng khi qua cc di rng ngp mn. Kt qu nghin cu cho thy rng ngp mn Hi Phng c tc dng lm gim ng k cao sng trong bo. Ti thi im i vi rng Trang 5 tui v 6 tui rng 650m, rng Bn chua 8 - 9 tui c rng 920m v 650m cao sng sau rng gim t 77 - 88%. Mc gim cao sng trong bo khi qua rng ph thuc vo kiu cu trc loi rng ngp mn v hng sng chuyn. Tc gi kt lun rng rng ngp mn c vai tr rt ln lm gim thiu tc ng ph hy t bin do sng bo.

nh 1.4. H r cy ngp mn c tc dng c nh t, gim xung lc ca sng

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Nguyn Danh Tnh (2007), trong ti Kh nng chn sng ca rng ngp mn mt s vng ven bin Thnh ph Hi Phng iu tra chiu cao sng cc im cch ba rng 0, 20, 40, 60 v 80m trn 6 tuyn qua 6 trng thi rng ngp mn in hnh ca vng bin Tin Lng - Hi Phng. Tc gi kt lun rng chiu cao sng v tr bt k trong ai rng c th c xem l hm s ph thuc vo chiu cao sng bin pha trc ai rng, khong cch ti ba rng, mt v ng knh tn trung bnh ca cy rng. Kt qu nghin cu ch ra rng chiu rng ai rng ngp mn cn thit chn sng khu vc nghin cu s dao ng t 600 - 1000m ty thuc vo mt v ng knh tn cy rng tui trng thnh.

Cc tuyn ngn mn huyn Thi Thy (Thi Bnh) di 86,6km, c xy dng t lu i, vic p ch yu bng lao ng th cng. Cc cn bo s 6 v s 7 nm 2005 ng vo lc triu cng gy ra sng ln nhng cc tuyn Thi Thy khng b xi l nh cc di rng ngp mn trng t sau khi Xun Hi b v nm 1996. Theo mt cng trnh nghin cu ca V Tn Phng, Trn Th Thu H (2006) v gi tr phng h bin ca rng ngp mn ti Xun Thy, Nam nh: Vi 3.100ha rng ngp mn phng h cho 10,5km bin hng nm trnh c chi ph tu b bin t 311 - 12.600 triu ng/nm.

Cc khu rng ngp mn cng gp phn hn ch xm nhp nc mn v bo v nc ngm. nhng thnh ph v th trn vng ven bin tnh trng triu cng gy ngp nhiu khu dn c, trong c mt nguyn nhn l hu ht cc knh rch c nhng di cy da nc v nhiu loi cy ngp mn khc nh Bn, Mm, S, Trang,... vn gi vai tr nh nhng ti cha nc t nhin b cht ph v lp t xy dng cc khu cng nghip, khu dn c cho nn khng c ch cho nc thot mi khi c ngp cc b do triu cng hay ma ln.

Rng ngp mn l ni bo v cc ng vt khi nc triu dng v sng ln. Nhiu loi ng vt y sng trong hang hoc trn mt bn, khi thi tit bt li, nc triu cao, sng ln tro ln cy trnh sng nh c Lc, cc loi Cng, Cy, c. Khi lng gi v triu xung thp chng tr li ni sng c. Do m tnh a dng sinh hc trong h sinh thi rng ngp mn tng i n nh. Nh cc mn b c phn hy ti ch v cc cht thi do sng mang n c phn gii nhanh to ra ngun thc n phong ph, thun li cho s hi phc v pht trin ca ng vt sau cc thin tai.

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1.4.7. nh lng cc gi tr ca rng ngp mn

Cc gi tr ca rng ngp mn c nhiu tc gi nghin cu. Theo ti liu ca UNEP/GPA 2003, do Batagoda, B.M.S. thc hin, gi tr kinh t ca rng ngp mn hng nm theo cc mc tiu s dng khc nhau trn mi hectare ca rng ngp mn Sri Lanka c xc nh nh sau:

- Ti nguyn rng ngoi g l 108 USD.

- Gi tr gii tr cp a phng l 933 USD.

- Gi tr gii tr cp ton cu l 1196 USD.

- Gi tr ca s la chn cp ton cu l 1039 USD.

- Gi tr ca s la chn cp a phng l 1491 USD.

- Gi tr di sn cp ton cu l 562 USD.

- Gi tr di sn cp a phng l 1714 USD.

- Gi tr tn ti cp ton cu l 1399 USD.

- Gi tr tn ti cp a phng l 883 USD.

- Li ch cung cp ni kim n cho c l 218 USD.

- Li ch kim sot xi l l 3,6 USD.

- Li ch bo tn a dng sinh hc l 18 USD.

- Li ch tn tr Carbon l 75 USD.

- Li ch bo v chng gi bo l 76 USD.

- Li ch x l nhim l 4494 USD.

Theo kt qu nghin cu ny, tng gi tr kinh t ca rng ngp mn c bo tn c c nh cho mi ha, hng nm l 12.229 USD.

Theo mt nghin cu khc c ng bi PNAS (Proceedings of the National Academy of Science), ngy 21 thng 7 nm 2008, nghin cu ca cc nh khoa hc ti vin Oceanography ti UC San Diego cho thy rng rng ngp mn ven bin Mexico lm tng nng sut thy sn vnh California.

Ngi ta tm thy 13 vng nh c khc nhau vnh California, sn lng bnh qun hng nm 11.500 tn gh xanh v c c ngun gc t rng ngp mn, trong giai on t nm 2001 n nm 2005, to ra khong 19 triu USD cho ngi dn a phng.

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Gi tr dch v ca h sinh thi rng ngp mn trn th gii c c tnh l 1,6 triu USD mi hecta mt nm. Cc dch v cho con ngi bao gm iu ho kh hu, bo v ngun nc sch, hn ch xi l ven bin, x l cht thi, cung cp sn phm v gii tr.

Cc nh nghin cu nh lng c cc gi tr kinh t, sinh thi v a mo ca rng ngp mn v xc nh rng cc di rng ngp mn ven bin ca vng vnh California c gi tr l 37.500 USD mi nm. Cc di rng ngp mn c bit quan trng v lu di i vi nhng ngi dn ph thuc vo ngun ti nguyn c vng ny.

Theo Nguyn Hu Ninh v Mai Trng Nhun (Nguyn Hu Ninh, 2003), ti nguyn thu sn trong rng ngp mn vng ca sng, ven bin tnh Sc Trng rt phong ph. Ti nguyn rng ngp mn ng gp ng k vo thu nhp v sinh k ca ngi dn a phng. Phng php thu hoch thu sn ca ngi dn y cng rt a dng ph thuc vo gii tnh v tui. Nhng ngun ti nguyn ny ng gp rt nhiu i vi sinh k ca nhng ngi dn sng vng ven bin.

Rng ngp mn y cng to ra nhng iu kin mi trng thun li cho nui trng thu sn vng m v gi vai tr nh nhng di m lc trong nc thi t cc khu nui trng thu sn v cc khu cng nghip ra bin.

t ngp nc vng ca sng c gi tr kinh t cao, gi tr ca rng ngp mn vng ca sng Cu Long c th t c l 3.099,36 USD/ha/nm, gm gi tr t ngun g v ci 16,35 USD/ha/nm v gi tr gin tip l 3.083 USD/ha/nm.

1.5. nh hng ca iu kin t nhin v kinh t - x hi n phn b rng ngp mn

Do c hnh thnh vng ven bin v ca sng nn rng ngp mn thng c nhn nh l nhng h thng sinh thi m (Opened ecosystem). Cc h sinh thi rng ngp mn lun lun trao i vi bn ngoi thng qua cc yu t thy triu, ngp l, trm tch, nhng yu t ny thay i th s c th lm thay i cc yu t mi trng ni m mi c th cy rng sinh sng. S thay i mi trng sng ca cc cy rng ngp mn (Howe, C.P, 1991) c th gy ra bi cc nguyn nhn sau:

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- Nhng tc ng lm thay i ch thy vn, ngn chn s lu thng ca thy triu;

- Nhng hot ng xy dng c s h tng, ngn chn dng chy;

- Cc hot ng cht ph lp thm thc vt, thu hoch cn kit h ng vt;

- Lm thay i nn t;

- Cc tc nhn gy nhim du, ha cht hoc cht thi.

a) Yu t t nhin

* Nhit khng kh

- Theo Chapman (1977) th rng ngp mn trn th gii ch phn b ni c nhit trung bnh ca thng lnh nht trong nm ln hn 20oC v bin dao ng ca nhit khng kh theo ma trong nm khng vt qu 10oC. Tuy nhin, Vit Nam rng ngp mn cng phn b t nhin vng ng Bc (Qung Ninh), mt nm c ti 4 thng lnh, c nhit khng kh trung bnh trong thng < 20oC v c 1 thng lnh nht trong nm (thng 1) c nhit khng kh trung bnh 14,7 - 15,8oC. iu ny lm cho rng ngp mn y ngho nn v s loi v mc sinh trng xu hn r rt so vi rng ngp mn phn b t nhin bn o C Mau, ni thng c nhit thp nht trong nm u > 25oC.

- huyn Tin Yn - Qung Ninh, trong hai ngy 17 v 18 thng 1/1961 xut hin sng mui, khi nhit khng kh xung thp ti 0oC lm cho cy Vt d bng b ho v kh l, mt s cy b cht.

- bn o C Mau gn nh nng quanh nm nn c s loi cy rng ngp mn rt phong ph, c ti 33 loi cy ngp mn thc th chim 98% tng s loi cy ngp mn thc th Vit Nam. Trong khi vng bin ng Bc (Qung Ninh) ch c 10 loi cy ngp mn thc th.

* Lng ma hng nm

- Theo Francois Blasco (1993) th ch ni t ngp mn ven bin c lng ma cao hn 1.200 mm/nm v trong nm khng xut hin ma kh di th mi c rng ngp mn phn b t nhin.

- vng ven bin Nha Trang, ni c lng ma thp (1000 mm/nm) rng ngp mn y ngho nn, cn vng bin Phan Rang (Ninh Thun) c lng

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ma thp 750 mm/nm, nm trong vng kh hu nhit i bn kh hn c ma kh di ti 9 - 10 thng v mc kh hn rt gay gt khng c rng ngp mn phn b t nhin.

- vng bin C Mau, ni c lng ma trung bnh hng nm 2.200 - 2.366mm, vi nhit quanh nm nng th rng ngp mn sinh trng rt tt, thnh phn loi a dng. Cy c trong rng 50 tui c ng knh trung bnh D1,3= 27,8cm v chiu cao trung bnh 27m. Nng sut g rng c 20 tui, vi mt cy 1.360 cy/ha cho nng sut 13,5 m3/ha/nm. Trong khi ven bin Vng Tu, gn nh nng quanh nm nhng lng ma ch c 1.357 mm/nm th rng c sinh trng km hn r rt, tuy cng trng trn mt lp a st mm nhng ch t nng sut g 6 - 7m3/ha/nm.

* Hot ng ca gi ma ng Bc

Vng ven bin pha bc Vit Nam chu nh hng trc tip ca gi ma ng Bc, mang khng kh lnh t cc Bc trn v, c bit vng ven bin Qung Ninh v vng ven bin ng bng Sng Hng. Trong mt nm c khong t 20 - 25 t gi ma ng Bc gy ra sng mui v nh hng rt ln n sinh trng v pht trin ca cc loi cy ngp mn, thm ch gy cht hng lot.

* Hot ng ca bo v dng

- Theo s liu thng k, t nm 1884 n nm 1989 (125 nm) th trong c nc c ti 493 trn bo v p thp nhit i b t bin ng vo t lin, trong min Bc (Qung Ninh v ng bng sng Hng) c 200 trn bo cn min Trung c ti 251 trn bo. Ring vng ven bin ng bng Nam b rt t khi c bo b vo t lin.

- Bo thng c gi v sng ln lm cho cy ngp mn sinh trng km hoc b gy. Do nhng vng nhiu bo th chiu cao ca cy rng ngp mn thng khng cao m thp.

* Yu t thy triu

- ng lc c vai tr quan trng n s hnh thnh rng ngp mn l thy triu, nu khng c s hot ng ln xung ca thy triu th s khng c cc rng ngp mn ven bin.

- Cc kt qu nghin cu trn th gii cho thy, nhng ni t ngp mn c ngp nc triu khi triu cng t 3 - 4 gi/ngy th rng ngp mn sinh

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trng tt. Nhng nu ch ngp nc khi triu cng vi thi gian qu ngn, t hn 2h30/ngy th rng ngp mn li bt u th hin s sinh trng xu. Nu ngp qu lu trong mt ngy th li khng c rng ngp mn phn b t nhin. Bin triu c mc chnh lch t 2 - 4m th rng ngp mn sinh trng tt.

- Cc nghin cu v nh hng ca thy triu n sinh trng ca rng ngp mn Vit Nam c kh nhiu v cho thy nh hng r rt ca ch thy triu n sinh trng v pht trin ca rng ngp mn.

- Vng bi bi ven bin huyn Ngc Hin, C Mau c ch bn nht triu vi bin triu dao ng trung bnh 190cm v bin triu cao nht l 307cm. Nhn chung, cc loi rng ngp mn y phong ph v c mc sinh trng tt nht Vit Nam. Nhng ti vng ven bin thuc tnh Kin Giang nm trong vnh Thi Lan, c ch nht triu vi bin chiu kh thp 60 - 70cm, trong thng 4, bin triu xung thp ch cn 27 - 28cm th rng ngp mn y nhn chung c mc sinh trng xu hn r rt so vi vng bn o C Mau mc d c iu kin kh hu v t ai tng i ging nhau.

b) Cc hot ng ca con ngi

* Cng tc qun l

- Rng ngp mn nhn chung cc tnh cha c ban qun l, cng tc qun l do U ban nhn dn cc x c rng ngp mn trc tip qun l.

- Cng tc qun l bo v rng l rt quan trng, thc t chng minh rng cng tc qun l bo v rng l khu quyt nh s tn ti ca nhng khu rng trng thnh v s thnh bi ca nhng din tch rng mi trng. Tuy nhin, trong thi gian qua cng tc qun l bo v rng ngp mn cha c quan tm ng mc nn hiu qu bo v rng cn thp. Hin tng chn th gia sc, cht ci t do trong rng ngp mn cn kh ph bin nhiu a phng, hot ng cht ph cy ngp mn ly mt bng lm m nui trng hi sn vn din ra t pht mt s ni.

- Vic khai thc li dng rng cha hp l, khng c k hoch, ngi dn khai thc ci, nh bt hi sn di tn rng m khng ch n vic phc hi li rng. Mt s h t ng cht b bt cy trong m khng theo mt phng thc no, kt qu lm gim mt cy qu mc (mt qu tha

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khng c coi l c rng) gy nn hin tng mt rng v nng sut nui trng thu sn ngy cng suy gim.

* Hot ng khai hoang ln bin

Khai hoang nng nghip lm gim din tch cc bi t ngp nc, trong c rng ngp mn. Kt qu l rng ngp mn, cc bi bi ven bin c kh nng trng rng ni c ngun li sinh vt v a dng sinh hc b bin thnh cc ng la c nng sut thp.

* Nui trng thy sn

Ngh nui trng thy sn Vit Nam c bit l cc tnh pha Bc ch yu da vo kinh nghim ca ngi dn, chnh quyn cha c u t ng k vo quy hoch chi tit cho cc khu vc nui trng thy sn, ngi dn t pht rng quy b bao lm m nui trng thy sn lm suy gim din tch rng ngp mn ng k.

* Khai thc rng ngp mn

mt s vng ven bin ca Vit Nam ngi dn vn c thi quen khai thc, cht rng ngp mn phc v cho nhu cu sinh hot hng ngy nh lm ci un. Ngoi ra, pha Nam ngi dn thng khai thc rng c ly cc lm nh, t g lm than ci,... Nhng hot ng ny gp phn trc tip lm suy gim din tch rng ngp mn v suy gim cht lng rng ngp mn Vit Nam.

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Chng 2

THC TRNG RNG NGP MN VEN BIN VIT NAM

2.1. Hin trng rng ngp mn

2.1.1. Din tch v phn b rng ngp mn

a) C s xc nh din tch t ngp nc pht trin rng ngp mn

Theo kt qu nghin cu v rng ngp mn ca Phan Nguyn Hng nm 1990, h thng phn loi t ngp nc Vit Nam (Phn Vin iu tra quy hoch rng II - 2004) v kt qu cc iu tra nghin cu khc, tiu ch quy hoch din tch pht trin rng ngp mn nh sau:

- t ngp nc mn ven bin, ngp triu khng thng xuyn trn th nn st bn, bn ct, bn ct th ln si, t than bn san h, ph sa b bin.

- t ngp nc mn vng ca sng khng thng xuyn trn th nn st bn, bn ct, ph sa.

- t ngp nc mn thuc m ph trn th nn st bn, bn ct, ph sa.

- nh hng pht trin kinh t, quy hoch s dng t ca cc a phng.

b) Phn b theo cc vng ven bin

Theo n phc hi v pht trin rng ngp mn ven bin giai on 2008-2015 ca B Nng nghip v Pht trin nng thn ( c Th tng Chnh ph ph duyt ti CV s 405/TTg-KTN ngy 16/3/2009), vng ven bin nc ta c th chia lm 5 vng. Tng din tch quy hoch cho mc ch pht trin rng ngp mn l 323.712ha. trong c 209.741ha c rng (152.131ha l rng trng v 57.610ha l rng t nhin), phn b ti cc vng nh sau:

- Vng ven bin tnh Qung Ninh v ng bng Bc B (QN&BBB), gm 5 tnh (Qung Ninh, Hi Phng, Thi Bnh, Nam nh v Ninh Bnh): 88.340ha. trong din tch c rng 37.651ha. phn b ch yu tnh Qung Ninh.

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- Vng ven bin Bc Trung B (BTB), gm 6 tnh (Thanh Ha, Ngh An, H Tnh, Qung Bnh, Qung Tr v Tha Thin Hu): 7.238ha. trong din tch c rng 1.885ha. phn b ch yu tnh Thanh Ha.

- Vng ven bin Nam Trung B (NTB): gm 6 tnh ( Nng, Qung Nam, Qung Ngi, Bnh nh, Ph Yn v Khnh Ha): 743ha. trong din tch c rng khng ng k.

- Vng ven bin ng Nam B (NB): gm 5 tnh (Ninh Thun, Bnh Thun, B Ra - Vng Tu, ng Nai v Thnh ph H Ch Minh): 61.110ha. trong din tch c rng l 41.666ha. phn b ch yu thnh ph H Ch Minh.

- Vng ven bin ng bng sng Cu Long (BSCL): gm 8 tnh (Long An, Tin Giang, Bn Tre, Tr Vinh, Sc Trng, Bc Liu, Kin Giang v C Mau): 166.282ha. trong din tch c rng 128.537ha. phn b ch yu cc tnh C Mau v Kin Giang.

Bng 2.1: Din tch v phn b rng ngp mn Vit Nam

a danh Tng Din tch c RNM (ha) Cha c

RNM Cng RTN RT

Ton quc 323.712 209.741 57.610 152.131 113.972

Qung Ninh v ng bng Bc B 88.340 37.651 19.745 17.905 50.689

Bc Trung B 7.238 1.885 564 1.321 5.353

Nam Trung B 743 2 2 741

ng Nam B 61.110 41.666 14.898 26.768 19.444

ng bng sng Cu Long 166.282 128.537 22.400 106.137 37.745

Rng ngp mn Vit Nam ch yu phn b tp trung ng bng sng Cu Long, thnh ph H Ch Minh, tnh Qung Ninh v ven bin chu th sng Hng, trong rng ngp mn phn b v pht trin tt min Nam, c bit bn o C Mau. min Bc cy rng ngp mn tuy thp v nh nhng c gi tr phng chng thin tai rt ln, c bit t trng rng ngp mn t nhin kh cao. Ti tnh Qung Ninh c 19.745ha rng t nhin trn tng s 37.650ha rng ngp mn.

c. Phn b theo h thng bin

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Rng ngp mn c vai tr to ln trong bo v h thng bin. Theo kt qu iu tra, kho st do Vin iu tra Quy hoch rng thc hin trong nm 2006, ti 3 vng c phn b rng ngp mn (QN&BBB, BTB v BSCL) hin c 1.113km trong tng s 2.438km bin c rng ngp mn bo v trc , tng ng vi din tch c rng l 69.611ha rng ngp mn, trong :

- Vng Qung Ninh v ng bng Bc b chiu di bin c rng ngp mn l 254/841km;

- Vng Bc Trung b chiu di bin c rng ngp mn l 67/338 km,

- Vng BSCL chiu di bin c rng ngp mn l 792/1.259 km;

(Vng Nam Trung b chiu di bin c rng bo v trn tng s chiu di bin l 73/501km (15%) tng ng vi din tch c rng l 898ha. tuy nhin rng trc vng ny l rng trn cn).

Hin nay, cn 1.325km bin (trong c 1.197km ti 3 vng Qung Ninh v ng bng Bc b; Bc Trung b v BSCL, tng ng vi 55% tng chiu di h thng bin cha c h thng rng bo v. Trong s chiu di cha c rng bo v, hin c 418km pha trc c bi, tng ng vi din tch khong 13.000ha c th trng rng ngp mn. Mt s khu vc cn li cha th trng rng ngp mn do trc khng cn bi hoc bi b st l, bn, ph sa long. Cho nn song song vi vic trng rng ngp mn cn c cc gii php cng trnh nh xy k, m hn, ng cc, b sung t, bn,....

Bng 2.2: Din tch rng ngp mn theo h thng bin

Vng/ tnh ven bin

Tng

chiu di

tuyn

(km)

Chiu di c bi u tin xy dng RNM bo v

c rng trc C th

trng mi

Chiu di

(km)

Theo din tch Chiu

di

(km)

Din tch

(ha) Tng

(ha)

Bo v

(ha)

Trng

b sung

(ha)

Tng 2.438 1.113 69.611 64.853 4.758 418 13.593

ng bng Bc B 841 254 27.209 23.04 4.169 187 7.770

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0

Bc Trung B 338 67 5.393 5.393 88 1.997

B sng Cu Long 1.259 792 37.00

9 36.420 589 143 3.826

(Ngun: R sot, quy hoch rng phng h ven bin - Vin TQHR -2006)

d) Phn b theo 3 loi rng

Tng din tch rng ngp mn l 323.712ha. c quy hoch nh sau:

- Rng phng h: 153.294ha. trong din tch c rng 115.950ha.

- Rng c dng: 41.666ha. trong din tch c rng 28.311ha.

- Rng sn xut: 128.752ha. trong din tch c rng 65.480ha.

Kt qu chi tit v s phn b ca rng ngp mn ven bin Vit Nam theo 3 loi rng (rng phng h, rng c dng v rng sn xut) c tng hp ti bng 2.3.

Bng 2.3: Quy hoch rng ngp mn phn theo 3 loi rng

n v: ha

TT a danh Tng Phn theo 3 loi rng

RPH RD RSX

Ton quc 323.712 153.294 41.666 128.752

Din tch c rng 209.741 115.950 28.311 65.480

t cha c rng 113.972 37.344 13.355 63.272

1. Qung Ninh v BBB 88.340 43.776 8.589 35.975

1.1 Din tch c rng 37.651 30.928 4.489 2.234

1.2 t cha c rng 50.689 12.848 4.100 33.741

2. Bc Trung B 7.238 4.420 - 2.817

2.1 Din tch c rng 1.885 1.341 - 544

2.2 t cha c rng 5.353 3.080 2.273

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TT a danh Tng Phn theo 3 loi rng

RPH RD RSX

3. Nam Trung B 743 - - 743

3.1 Din tch c rng 2 - - 2

3.2 t cha c rng 741 741

4. ng Nam B 61.110 41.511 900 18.699

4.1 Din tch c rng 41.666 38.468 16 3.182

4.2 t cha c rng 19.444 3.043 884 15.517

5. ng bng sng Cu Long 166.282 63.587 32.177 70.518

5.1 Din tch c rng 128.537 45.213 23.806 59.518

5.2 t cha c rng 37.745 18.374 8.371 11.000

(Ngun: R sot hin trng rng ngp mn - Vin TQHR - 2007)

e) Hin trng rng ngp mn phng h chn sng ln bin

Rng ngp mn phng h chn sng ln bin c din tch 153.294ha (115.950ha c rng v 37.344ha t trng ngp mn). Din tch cc trng thi rng ngp mn phng h chn sng ln bin thng k ti bng 2.4.

Bng 2.4: Hin trng rng ngp mn phng h chn sng ln bin

n v: ha

TT Kiu, trng thi Tng cng

Phn theo vng

QN&BBB BTB NB BSCL

Tng 115.950 30.928 1.341 38.468 45.213

I Rng t nhin 37.876 18.147 126 12.917 6.686

Cp I 13.125 6.874 100 3.500 2.651

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Cp II 18.172 8.139 26 7.217 2.790

Cp III 6.579 3.134 0 2.200 1.245

II Rng trng 78.074 12.781 1.215 25.551 38.527

Cp I 23.245 12.781 1.215 0 9.249

Cp II 38.151 0 0 25.551 12.600

Cp III 16.678 0 0 0 16.678

Rng t nhin c din tch 37.876ha. chim 32,7% tng din tch rng ngp mn phng h hin c. Rng t nhin ch yu l rng thun loi. Cc kiu rng c, Mm, S, cc tnh vng ng Nam B, ng bng sng Cu Long v cc kiu rng Bn, S, Trang, Vt cc tnh Qung Ninh, ng bng Bc B v Bc Trung B.

- Rng cp I c din tch 13.125ha. chim 34,7% din tch rng t nhin hin c. y l dng rng phc hi sau cc hot ng khai thc, canh tc nui trng thy sn b hoang,... Rng c mt bnh qun thp 600 - 800 cy/ha, ng knh bnh qun t 3 - 6cm, chiu cao bnh qun t 3 - 9m cc kiu rng pha Bc v ng knh bnh qun t 6 - 10cm, chiu cao bnh qun t 12 - 18m i vi cc kiu rng cc tnh pha Nam. Trng thi ny tp trung ch yu cc tnh Qung Ninh v ng bng Bc b. i vi trng thi rng ny cn c bin php chm sc, bo v v trng b sung.

- Rng cp II c din tch 18.172ha. chim 48,0% din tch rng t nhin hin c. Trng thi rng ny c mt bnh qun t 1000 - 1500 cy/ha. ng knh bnh qun t 12 - 16cm, chiu cao bnh qun t 18 - 28m. Trng thi ny tp trung ch yu cc tnh Qung Ninh, ng bng Bc b v ng Nam b.

- Rng cp III c din tch 6.579ha. chim 17,4% din tch rng t nhin. Rng c mt bnh qun t 1000 -1500 cy/ha, ng knh bnh qun t 18 - 24cm. y l trng thi rng c kt cu tng i n nh.

- Rng trng c din tch 78.074ha. chim 67,3% tng din tch rng ngp mn phng h hin c. Rng trng trong my nm qua ch yu l rng thun loi

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vi cc loi cy ch yu l c, Mm, Trang, S, Bn,... Din tch, trng thi rng trng nh sau:

+ Rng cp I c din tch 23.245ha, chim 29,8% din tch rng trng. y l din tch c trng trong khong thi gian thi gian t nm 2001 n nay. Tuy nhin, do nhiu nguyn nhn nn cht lng rng km. Mt bnh qun t 800 - 1000 cy/ha. ng knh bnh qun, ty theo loi cy trng, song dao ng t 1 - 6cm. Trng thi rng ny phn b ch yu cc tnh Qung Ninh, ng bng Bc B v ng bng sng Cu Long. i tng rng ny cn c bin php chm sc trng b sung.

+ Rng cp II c din tch 38.151ha. chim 48,9% din tch rng trng ngp mn. y l din tch rng trng ngp mn tng ng cp tui II c mt bnh qun t 2.000 - 3.000 cy/ha, ng knh bnh qun dao ng t 6 - 18cm ty theo loi cy. Trng thi rng ny v c bn n nh, tnh hnh sinh trng tt.

+ Rng cp III c din tch 16.676ha. chim 17,4% din tch rng trng, phn b ch yu vng ng Nam B v ng bng sng Cu Long. Rng c mt bnh qun t 2000 - 3000 cy/ha. Rng c kh nng phng h tt cng nh cung cp lm sn v lm sn ph.

Hin cha c nhng nghin cu nh gi y v kt cu ti u c th ca rng ngp mn bo v phng chng thin tai, song mt s nghin cu nh gi ch ra rng, rng c mt cao, nhiu tng th kh nng phng h cao hn rt nhiu so vi rng c mt thp, thun loi.

Din tch rng ngp mn k c rng trng v rng t nhin ca Vit Nam hin nay u c mt thp v n loi do vy cn phi c cc gii php trng b sung to ra cc l rng ngp mn phng h a loi, a tng. Hin c 36.370ha. (32.870ha thuc khu vc rt xung yu) bao gm rng t nhin phc hi v rng trng cht lng km cn phi tin hnh trng b sung.

Cng theo cc kt qu iu tra, kho st th tnh hnh ti sinh t nhin trong rng ngp mn kh tt c trong din tch c hon cnh rng v nhng din tch t trng l bi bi, in hnh nh vng pha Ty tnh C Mau. Khoanh nui xc tin ti sinh rng t nhin kt hp trng b sung l mt gii php lm sinh cn c ch trong vic phc hi v pht trin rng theo hng lu di.

Cho n nay cha c mt cng trnh kim k hoc iu tra, nh gi c h

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thng v c th v din tch, cht lng rng ngp mn cng nh nhng nghin cu v cc tiu chun, tiu ch h thng ai rng ngp mn phng h phng chng thin tai bo v bin,y l vn i hi cc nh khoa hc cc nh nghin cu cn b sung trong thi gian ti.

Rng ngp mn phng h chn sng ln bin c phn cp phng h nh sau:

* Din tch c rng: 115.950ha:

- Vng rt xung yu (RXY) 54.256ha. trong :

+ Rng t nhin: 27.078ha. trong c 9.625ha rng km cht lng cn trng b sung;

+ Rng trng: 27.493ha. trong c 23.245ha rng km cht lng cn trng b sung.

- Vng xung yu (XY) c din tch 61.694ha. trong :

+ Rng t nhin: 10.799ha;

+ Rng trng: 50.895ha.

* Din tch t ngp mn cha c rng 37.344ha:

- Vng rt xung yu (RXY): 18.858ha. trong :

+ C iu kin trng rng: 13.593ha.

+ Cha kin t nhin trng rng (st l, ph sa long,....), cn phi c cc gii php cng trnh trc v trong qu trnh trng rng: 5.265ha.

- Vng xung yu (XY): 18.486ha. trong :

+ Din tch trng rng tp trung: 12.771ha;

+ Din tch c th trng rng kt hp nui trng thy sn: 5.714ha.

Vng rt xung yu l nhng vng ven bin trc , khong cch tnh t b bin lc triu cao trung bnh l 200m hoc nhng vng ca sng c p, hoc khng c p v nhng vng ang b xi l,.... Vng xung yu l nhng vng ven bin khng c , p khong cch t 200 - 500m tnh t b bin lc triu cao trung bnh.

2.1.2 Din bin rng ngp mn

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Theo s liu thng k ca Vin TQHR, Vin Khoa hc Lm nghip (B Nng nghip v PTNT) v B Ti nguyn v Mi trng, din tch rng ngp mn ton quc qua cc thi k nh sau:

- Nm 1943: 408.500ha;

- Nm 1962: 290.000ha;

- Nm 1982: 252.000ha;

- Nm 2006: 209.741ha.

Din tch rng ngp mn lin tc gim trong hn na th k qua. Cc nguyn nhn gy mt rng ngp mn k t sau khi kt thc chin tranh, theo th t nh sau:

- Ph rng ngp mn v p b k lm m nui trng thy sn (NTTS) ngn cn s lu thng nc mn lm cht rng ngp mn xy ra kh ph bin ti hu ht cc tnh c rng ngp mn trong ton quc. in hnh mt s v vic gn y ti cc a phng, nh: huyn Kim Sn (Ninh Bnh); cc huyn An Bin v An Minh (Kin Giang); huyn Ho Bnh (Bc Liu); cc huyn Nm Cn, Ngc Hin, Ph Tn, m Di,... tnh C Mau. Ch tnh ring din bin din tch rng 2005 - 2006, c hn 4.000ha rng ngp mn l rng t nhin b mt, trong hn 50% l do cht ph rng ngp mn lm m nui thy sn v cc mc ch khc.

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Hnh 2.1. Ph rng ngp mn nui tm ti Hi Phng

Hnh 2.2. Ph rng ngp mn nui tm ti Thi Thy - Thi Bnh

49

Hnh 2.3. M hnh nui tm bn thm canh, thm canh ti Kim Sn - Ninh Bnh

- Gi bo, sng bin tn ph rng st l. Ti nhiu a im ven bin hin tng st l do sng bin, hi lu c bit l nh hng ca bo gy st l b bin, nh bt gc cy rng ngp mn nht l rng mi trng, rng trng bng tr mm,...

- Khai thc g, ci rng ngp mn v ti nguyn thu sn lm dng qu mc.

- nhim mi trng: Do chu nh hng nng n ca vic thi ba bi cc cht rn, cht lng trong sinh hot v cng nghip, mt s lng ln phn ho hc, thuc tr su d tha trong nng nghip vo sng rch nh hng xu n rng ngp mn.

- Cha c chnh sch to ng lc thu ht ngi dn v cng ng a phng tham gia vo vic bo v v pht trin rng ngp mn.

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2.2. nh gi khi qut vic qun l v pht trin rng ngp mn thi gian qua

a) H thng t chc qun l rng ngp mn

- H thng t chc qun l rng ngp mn cc a phng c hnh thnh t tnh n huyn, x nhng cha thng nht.

- Vic phi hp lin ngnh rt lng lo k c nhng tnh c quy nh ring v qun l, s dng rng ngp mn nh C Mau, TP. H Ch Minh cng gn nh ch c ngnh Nng nghip & PTNT quan tm.

b) Cng tc giao khon bo v rng ngp mn

- Nhn chung, phn ln din tch rng ngp mn c giao cho cc t chc nh nc qun l v s dng vo mc ch lm nghip. Trong tng s 153.000ha rng ngp mn quy hoch cho rng phng h chn gi, sng bin, 51% din tch hin do cc Ban qun l rng phng h qun l, 29% do UBND cc x qun l; 10% do cc h gia nh v tp th, 10% do cc doanh nghip v trang tri v mt din tch khng ng k do cc ch th khc.

- Cc tnh vng ven bin pha Bc hu ht giao t rng v rng ngp mn cho cng ng thn xm, cc t chc x hi, rng c bo v tt v trnh c xung t v ngun li thu sn.

- Hin tng nhng bn t lm nghip c giao, hoc t pht chuyn t lm nghip c giao sang nui trng thu sn thiu kim sot din ra kh ph bin cc tnh pha Nam (cc tnh Kin Giang, C Mau, Bn Tre,...).

c) Cng tc trng rng ngp mn

- Tr ngi ln nht i vi cng tc trng rng ngp mn l sut u t trng rng cn thp trong khi iu kin t ai khng thun li (t bi triu khng m bo t l ph sa, xi mn, st l,...). Mt khc, loi, cht lng cy trng cha c chn lc, k thut lm sinh cha c quan tm, vic trng rng cn mang tnh qung canh nn cht lng rng hn ch, mt khng hp l, kh nng phng h khng cao.

- Chng trnh trng mi 5 triu ha rng (D n 661) c trin khai trn phm vi c nc, trong hu ht trn a bn cc tnh gip bin u thc hin vi quy m din tch l 450.308ha (chim 26,9% din tch t nhin). Hng mc

51

u t ch yu l trng rng, bo v, khoanh nui phc hi rng. Tuy nhin, so vi cc vng khc th d n 661 u t cho vng ven bin cha nhiu, nht l i vi vic trng rng ngp mn.

- Chng trnh trng rng ngp mn phng nga thm ha (do Hi Ch thp Nht Bn v Hi Ch thp an Mch ti tr) c trin khai t nm 1994 trn a bn 8 tnh ven bin t Qung Ninh n H Tnh vi phm vi quy m 19.957ha. Theo tng kt ca Hi Ch thp Vit Nam, tnh n nm 2005, Chng trnh trng v chm sc c gn 22.400ha rng ngp mn. Tuy nhin, y ch l con s thng k cng dn tin tc nghip, nhiu ni phi trng i trng li nhiu ln.

- D n Bo v v Pht trin nhng vng t ngp nc ven bin min Nam Vit Nam (CWDP) c trin khai trn a bn cc tnh C Mau, Bc Liu, Sc Trng v Tr Vinh (vng ng bng sng Cu Long) giai on 2000 - 2005 vi phm vi 65.936ha (chim 3,9%). Hng mc u t ch yu ca d n bao gm qun l, bo v h sinh thi v trng rng ngp mn, h tr kinh t k thut cho cc h gia nh, pht trin x hi cho nhng x ngho, ti nh c, gim st v nh gi s dng t, cht lng nc, a dng sinh hc,... Mc d tng kinh ph ln, song D n bao gm nhiu hot ng, trong mang nng ni dung chuyn giao k thut, nng cao nhn thc nhiu hn l u t trc tip cho trng rng ngp mn.

- Hiu qu u t khng cao, li sut cho vay cao, th tc phc tp nn ngi dn kh tip cn vay vn trng rng ngp mn.

- Thiu cc nghin cu c s k thut trng hn loi, t l din tch rng/tm, k thut thm canh cao trng rng ngp mn.

- Mc d c s u t trng bo v rng ngp mn thng qua cc chng trnh, song din tch mt rng qua cc nm vn ln hn din tch ti to, bao gm ti sinh phc hi rng t nhin v trng mi.

52

2.3. T chc qun l rng - mt s kt qu sn xut lm nghip trn a bn cc tnh c rng ngp mn khu vc pha Bc

2.3.1. V t chc qun l rng

Hnh 2.1. S qun l rng ngp mn

ca cc tnh c rng ngp mn khu vc pha Bc

M hnh qun l rng ngp mn ca cc tnh thng l do UBND tnh giao cho S NN&PTNT qun l; di S l Chi cc Lm nghip hoc phng Lm nghip, Vn Quc gia, khu bo tn v Ban qun l rng ngp mn; tip n l Phng Kinh t huyn sau cng l n cng ng x, thn bn (M hnh trn). Qua iu tra th m hnh qun l trn l hp l. Vic qun l rng ngp mn cc tnh pha Bc l do x qun l, x giao cho cng ng thn bn. Hng ngy ngi dn vo rng ny khai thc ngun li thu hi sn, do vy vic cng ng qun l rng ngp mn l c hiu qu hn c, trnh xung t v ngun li kinh t ca c dn a phng.

Vic qun l cng ng ny cng cn phi c nhng quy nh c th, thng pht nghim minh th mi c th gi c ti nguyn rng m vn m bo c ngun li kinh t cho ngi dn.

UBND tnh

S NN&PTNT

Chi Cc LN Phng LN VQG, KBT, BQL

Phng KT huyn

Cng ng, t chc XH khc

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2.3.2. Cng tc trng rng

Cng tc trng rng ngp mn ti Qung Ninh v cc tnh ng bng sng Hng ch yu c thc hin bng ngun vn ca cc d n 327, 661 v ca cc t chc quc t nh Hi ch thp , Nht Bn, an Mnh,

Cy trng ph bin:

- Ni bi triu gn ca sng l: Bn chua, Bn chua + Trang hoc Bn chua + S.

- Ni bi bin xa ca sng (vng nc li mn) l: Trang, c vi hoc Mm bin (ni c mn cao v t c hm lng ct cao).

Nhn chung, t l thnh rng t cc phong tro v cc d n trng rng ngp mn khng cao, xp x 50%, vi loi Trang l ch yu. Nguyn nhn l do rng ngp mn thng c gy trng trn din tch tng i rng, k thut trng n gin (bng qu) v khng phn bit cc dng lp a trng rng c bit l nhng lp a kh khn.

Din tch trng rng ngp mn ti Qung Ninh v cc tnh ng bng sng Hng nm 2009 c th hin bng 2.5.

Bng 2.5: Din tch trng rng ngp mn ca cc tnh c rng ngp mn khu vc pha Bc nm 2009

Tnh/Thnh ph Din tch trng mi nm 2009 (ha)

Qung Ninh 214,5

Hi Phng 582,4

Thi Bnh 153,0

Nam nh 0,0

Ninh Bnh 100,0

Tng 1.049,9

(B Nng nghip v Pht trin nng thn, 2010)

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Nhn chung, din tch trng rng ngp mn nm 2009 khng nhiu, cao nht l Hi Phng 582,4ha. thp nht l Ninh Bnh 100ha v Nam nh khng c din tch trng mi.

2.3.3. Tnh hnh giao khon bo v rng kt hp nui trng thy sn

* Tnh hnh giao khon, bo v rng

- Trong nhng nm qua, vic giao t rng v rng ngp mn hu ht cc a phng l cho cng ng, cc t chc x hi ca cc a phng l vic lm hp l. T trnh c xung t v ngun li thu hi sn ca cc c dn a phng sng vng bin c rng ngp mn.

- mt s a phng vic giao khon rng ngp mn cho cc h gia nh l khng hp l, bi v cc h gia nh t s dng t khng theo ch o ca S NN & PTNT, t nh hng n vic trng, bo v v pht trin rng ngp mn ti a phng, nh hng n chc nng phng h ven bin ca rng ngp mn. Th d nh Hi Phng, n nm 2002 thnh ph Hi Phng giao cho 128 h vi din tch giao l 1.331,95ha, chim khong 43% din tch giao.

- Trong thc t vic giao t giao rng ngp mn cc a phng mang tnh cht nh tnh l ch yu, cha xc nh c chnh xc din tch cc l khonh, cha xc nh c hin trng rng, cha cm mc r rng v cha c th hin trn bn ; dn n tnh trng tranh chp gia cc cng ng dn c vi nhau.

* Tnh hnh nui trng thy sn

Trong nhng nm qua ngh nui trng thu hi sn pht trin mnh. Nhiu doanh nghip (va v nh) v h gia nh ng k kinh doanh nui trng hi sn c cp php. Bn cnh , mt s c nhn v h gia nh cng t pht m din tch nui trng hi sn. Do vy, din tch rng khng ngng b thu hp li, nh hng rt ln n vai tr phng h ven bin, gy ra hin tng v bin.

Din tch nui trng hi sn trn t ngp mn theo thng k ca cc tnh l: Qung Ninh 14017.86ha; Hi Phng 5.615ha; Thi Bnh 2.852ha; Nam nh 5.800ha v Ninh Bnh l 220ha. Ngoi ra, cn mt s m nui tm trong rng ngp mn (lm ng kt hp) v mt s m nh ri rc cha thng k c. Cc loi c nui l tm S, Cua, Ngao,...

55

Vic tng nhanh din tch nui trng hi sn nh hng ln ti rng ngp mn. Trong nhng nm qua, nht l nhng nm 2000 n nm 2004 nhiu din tch rng b ph i nui tm cng nghip. Nhiu din tch rng ngp mn b cht do b p m, thiu nc mn. Hin ti mt s m b st l, b v do tc ng ca cn bo s 2 (nm 2005) trn qua lm thit hi hng t ng. Qua thc t cho thy, ngh nui trng hi sn pht trin c bn vng v t hiu qu cao th vic gi gn v pht trin rng ngp mn l khng th thiu. Ngoi chc nng phng h che chn an ton cho cc m nui hi sn, rng ngp mn cn l ni c tr, sinh sn ca cc loi c, tm, cua,... v cc sinh vt ph du cung cp b sung thc n cho cc loi hi sn nui, iu ho lm sch mi trng t, mi trng nc, mi trng thc n trc v sau khi c hot ng nui trng hi sn gip sn xut t nng sut cao v n nh. V vy, pht trin nui trng hi sn nhm thu li cao v kinh t nhng phi ch trng gi gn v pht trin rng ngp mn, nhm xy dng mi trng sng trong sch cho hi sn nui v to bc bnh phong bo v cho nui trng hi sn khng b thin tai ph hi.

Hnh 2.4. Ph rng Trang nui tm ti Thi Thy, Thi Bnh

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Hnh 2.5. m nui tm cng nghip ti Mng Ci - Qung Ninh

2.3.4. Cc hot ng khc

* Du lch sinh thi

Nhiu vng bin nc ta ni chung v cc tnh min Bc ni ring c nhiu im du lch hp dn, nht l Qung Ninh, Hi Phng, Nam nh, Thi Bnh. Hng nm ngnh du lch ny mang li ngun thu ln cho cc tnh, nhng mt tri ca hot ng ny l rc thi gy nhim mi trng sinh thi, nhim nc bin, nh hng ti sinh trng ca cy ngp mn.

* Pht trin cng bin

Mt s ni do c nhng iu kin thun li v v tr a l, ti nguyn t ai sn c, cc khu cng nghip cng v ang c xy dng ti cc vng ven bin nh: Cc cm cng nghip cng ven sng Cm, sng Bch ng, sng Lch Tray v khu cng nghip nh V,...

Cc khu cng nghip cng lun gy nhim mi trng nc v khng kh do cc cht thi cng nghip gy ra lm nh hng xu n pht trin rng ngp

57

mn v nui trng thu sn. Song vic pht trin rng ngp mn i i vi pht trin cc khu cng nghip cng l rt cn thit phng h , chng xi l v gim thiu nhim mi trng.

2.4. Nhng im mnh, im yu, c hi v thch thc trong bo v pht trin rng ngp mn

iu kin t nhin v kinh t - x hi trong vng l nhng nhn t quan trng tc ng ti kh nng phc hi v pht trin bn vng rng ngp mn cc tnh duyn hi pha Bc Vit Nam.

a. Nhng im mnh - im thun li

- a hnh mt s ni thun li cho cy ngp mn sinh trng v pht trin hn rt nhiu so vi khu vc min Trung.

- mn ven bin thch hp cho nhiu loi cy ngp mn sinh trng v pht trin.

- H thng giao thng thun li m bo vic cung ng vt t k thut thun tin, kp thi phc v cho trng v bo v rng.

- Vng ven bin cc tnh pha Bc c lc lng lao ng di do, trnh dn tr kh cao nn d dng tip thu nhng k thut mi trong gy trng v s dng rng.

- Thng qua mt s d n c trin khai trc y, i sng ca mt b phn nng dn vng ven bin c ci thin, t ngi dn tin tng vo ch chnh sch ca ng v sn sng tham gia d n.

- i b phn nhn dn vung bin hiu vai tr ca rng ngp mn n mi trng sinh thi, c bit l vai tr phng h chng bo ven bin i vi cuc sng ca con ngi. Do vy, h c tinh thn, trch nhim cao i vi vic pht trin v bo rng ngp mn ven bin.

b. im yu - hn ch

- Din tch rng ngp mn phn b khng tp trung, ri rc nn kh thnh lp ban qun l m ch yu giao cho UBND cc x ven bin c rng ngp mn trc tip qun l.

- t ngp mn ven bin mt s ni c lng bn mng, ngho dinh dng

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do lng ph sa cc sng thp. Bin dao ng nhit trung bnh cc thng trong nm ln. Gi ma ng Bc mang khng kh lnh v kh lm cn tr kh nng sinh trng ca cy ngp mn. Hu ht cc loi cy ngp mn trong vng u c ng knh nh, chiu cao thp.

- Mi trng bin, t ngp mn ang b nhim nng bi rc thi, tnh hnh khai thc m than, nh hng ti sinh trng ca cy ngp mn.

- Hin nay, nhiu a phng cha c c ch v chnh sch khuyn khch ngi dn tham gia bo v v pht trin rng ngp mn.

- Do tc ng mnh m ca nn kinh t th trng, xu hng chuyn mc ch s dng t t rng, bi bi sang cc ngnh c li nhun cao nh nui trng thu hi sn, giao thng vn ti bin, xy dng, dch v ngy cng tng gy kh khn cho cng tc bo v v pht trin rng.

Hin nay rt nhiu m thu sn c quy p tu tin ngay c trong ch gii 100m bo v bin lm cht rng ngp mn, vi phm php lnh iu, nh hng xu n an ton bin.

- Vic nui trng thu sn cn mang tnh cht qung canh nh bt c t nhin. Hin tng quai m ln chim rng nui tm vn cn, lm gim vn rng ngp mn.

- Cc hot ng nh bt thu sn t nhin ca nhn dn ven bin nh: dun te, ko li cy, o bi tm kim hi sn,... gy nh hng xu n rng trng.

- Sut u t cho trng v chm sc rng ngp mn cn thp, cha thu ht c ngi dn tham gia tch cc.

- Cng tc qun l bo v rng ngp mn ti a phng cn chng cho v thiu s phi hp gia cc ngnh lin quan cng nh khng thng nht gia cc a phng trong c nc.

- Cha c cc quy trnh, bin php k thut gy trng rng ngp mn cho nhng iu kin t nhin khc nhau, c bit nhng vng xi l mnh nh C Mau.

- H thng c s d liu, bn phc v qun l rng ngp mn cn thiu v cha mang tnh h thng.

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- Cng tc quy hoch v qun l quy hoch s dng t, s dng rng ngp mn km hiu qu v thiu s phi hp thng nht gia cc ngnh lin quan.

- Vic vn dng, p dng c ch, chnh sch ca Nh nc cn th ng. Cha to ng lc thu ht ngi dn v cng ng a phng tham gia vo vic bo v v pht trin rng ngp mn.

- Thiu u t nghin cu v p dng tin b khoa hc, cng ngh trong vic qun l, bo v, pht trin v s dng bn vng h sinh thi rng ngp mn.

- Ngoi ra, do iu kin t nhin khc nghit, kh hu cc oan, tnh trng st l b bin dn n nhng kh khn trong cng tc trng v bo v rng ngp mn.

* C hi:

- Trong bi cnh bin i kh hu ton cu ang din bin phc tp, Vit Nam li l mt nc nhit i hng nm chu nh hng ca hng chc cn bo t bin ng vo nn vai tr ca rng ngp mn phng h li cng c khng nh thu ht c s quan tm u t ca khng ch ng v Nh nc m cn l ca ton x hi.

- Vng ven bin Vit Nam c nhiu h sinh thi rng ngp mn c hu, c vai tr quan trng c c th gii cng nhn nh: Vng t ngp nc Xun Thy - Nam nh c UNESCO cng nhn l vng t ngp nc c tm quan trng quc t cn phi bo tn, khu d tr sinh quyn rng ngp mn Cn Gi vi vai tr l l chn, l phi xanh cho khu vc thnh ph H Ch Minh vi tnh a ng sinh hc v cc loi ng thc vt rt cao. Do vy, thu ht c s quan tm nghin cu v u t ca rt nhiu cc t chc, c nhn trong v ngoi nc.

- Trng rng ngp mn c ng v nh Nc ta xc nh l mt mc tiu rt quan trng th hin vic ra n khi phc v pht trin rng ngp mn giai on 2008 - 2015, do vy nhn c s quan tm u t rt ln v kinh ph, k thut cng nh to c cc c s vng chc v php l.

* Thch thc:

- S khc nghit v yu t kh hu, thi tit, lp a trng khng n nh, khng c o che chn v thng xuyn hng chu cc cn bo ln trong nm ca cc tnh c rng ngp mn khu vc pha Bc gy kh khn rt ln cho cng tc trng v pht trin rng ngp mn. Thc t cho thy, nhiu vng t phi trng i

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trng li ti my ln nhng vn khng th thnh rng, t l sng ca cy l rt thp, cy trng cn cha kp n nh b r th b sng bin nh bt tung ln.

- Bi ton cn i gia nhu cu pht trin kinh t ca ngi dn vng bin thng qua ph rng nui tm, nh bt hi sn v khai thc khong sn vi vic bo tn, pht trin rng ngp mn thc s l mt thch thc rt ln.

- Cc tnh khu vc min Trung mc d nhu cu phng h ven bin l rt ln, tuy nhin vi iu kin thi tit khc nghit, b bin dc nn kh lng ng ph sa v cc cht tch t to lp a n nh, khng c o che chn, l tr ngi ln nht pht trin rng ngp mn.

2.5. Nhng nguyn tc bo v, qun l v s dng tng hp rng ngp mn

a. Mc tiu qun l h sinh thi rng ngp mn

- Rng ngp mn l mt b phn khng th tch ri trong qun l tng hp ven bin;

- Bo v cc im nng v a dng sinh hc trong vng rng ngp mn;

- Cng ng vn da vo ti nguyn h sinh thi rng ngp mn c s tham gia;

- Qun l trn c s s dng bn vng v bo v mi trng;

- Phc hi cc vng rng ngp mn b tn ph hoc suy thoi;

- Quan tm n kin thc bn a v gi tr vn ho truyn thng.

b. Phng php tip cn phng nga trong qun l

- Kin thc truyn thng, tn ngng v phong tc tp qun a phng.

- Qun l bo tn nhng rng ngp mn nguyn sinh hay gn nguyn sinh.

- Rng ngp mn trng im a dng sinh hc cao, duy tr sinh cnh v bo v cc loi c hu, loi qu him c lit k trong sch .

- Bo v nghim ngt rng ngp mn phng h gim nh ti a thit hi do thin tai.

- Kim sot cc loi ngoi lai v cc sinh vt bin i gen vo h sinh thi rng ngp mn

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c. Khung chnh sch v php l

- Loi b v sa i nhng quy nh khng cn ph hp.

- Bo tn, khai thc hp l kt hp ci thin, phc hi t ngp nc.

- u tin bo v ngun li v cc sinh k truyn thng a phng.

- Tun th php lut c th l cc quy nh v quy tc v bo tn.

- Tng hp v tm tt quy nh php lut ch cht thnh mt bn hng dn d hiu.

- Quy nh trch nhim r rng, tng cng hp tc gia cc c quan chc nng.

- Trnh cc hot ng phng hi n sinh cnh rng ngp mn v h thng thu vn.

- Quy hoch c th cc vng rng ngp mn, chc nng v hin trng ca tng vng.

d. Thc hin v phi hp

- Tip cn sinh thi qun l rng ngp mn, ch cc hot ng u ngun.

- Xy dng cc k hoch qun l kh thi ph hp vi khung php l, sinh k.

- Thnh lp hi ng lin b tng cng hp tc, lin kt gia cc c quan chc nng.

- C chuyn mn ph hp, ngun ngn sch, quy ch ti chnh thc hin.

- Xy dng chin lc hnh ng quc gia v qun l v bo tn h sinh thi rng ngp mn.

- nh gi tc ng mi trng cc d n u ngun cng nh khu vc ven b.

- y mnh cc nghin cu lin ngnh v rng ngp mn nhm h tr cho cng tc qun l.

- Cn nhn thc tm quan trng ca rng ngp mn hn ch tc hi ca thin tai.

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e. nh gi rng ngp mn

- nh gi hin trng h sinh thi rng ngp mn, kho st, o c, kim k din tch.

- Phi hp d liu c bn vi k thut vin thm v GIS.

- C s d liu quc gia, thng xuyn cp nht cc thng tin.

- Thng tin v rng

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