Pengambilan Keputusan Dalam Kehutanan_Kul 3 & 4

PENGAMBILAN KEPUTUSAN DALAM

KEHUTANAN

Oleh:Hari Kaskoyo, Ph.D

Magister Ilmu Kehutanan Fakultas Pertanian Universitas Lampung

Pendahuluan

• Pengambilan Keputusan: everyday, everytime maybe everywhere.

Beli buku or nonton ???

belajar or pacaran ???Tanam jati or

jabon ??? Investasi or menabung ?

??

menikah or bekerja ???

Why is decision making hard

• Complexity• Uncertainty• Multiple

objectives• Different

perspectives

Selanjutnya:Bagaimana seharusnya

sebuah keputusan

diambil menjadi faktor penting

TEORI PENGAMBILAN

KEPUTUSAN

Pengambilan Keputusan

• Keputusan : memilih dari setidaknya dua alternatif yg berbeda.

• Decision making can be considered from at least two points of view: – it can be analyzed, how the decisions should

be made in order to obtain best results (prescriptive approach), or,

– it can be analyzed, how people actually do decisions without help (descriptive approach) (e.g. von Winterfeldt and Edwards 1986).

Decision Making : Scientific and Art

Pengambilan keputusan sbg Ilmu (Scientific):• Aktivitas pengambilan keputusan

dilakukan dengan pendekatan sistematis, teratur dan terarah.

• Pendekatan ilmiah dengan menggunakan teknik-teknik pengambilan keputusan atas dasar perhitungan matematis dan statistik.

• Kajian pengambilan keputusan dapat dipelajari.

Decision Making : Scientific and Art

Pengambilan keputusan sbg Seni (Art):• Aktivitas pengambilan keputusan selalu

dihadapkan pada karakteristik yg unik dr faktor internal dan eksternal, diantaranya:– Internal: struktur institusi/org, budaya.– Eksternal: masyarakat, kondisi ekonomi

daerah/negara, sosial politik. – Karakteristik decision maker: personality, kecerdasan,

pengalaman, preferensi thd masalah, feeling/intuisi.• Kajian pengambilan keputusan tidak dapat

dipelajari.

Teori Pengambilan Keputusan : Definisi

• Ilmu dan Seni pemilihan alternatif solusi atau alternatif tindakan dari sejumlah alternatif solusi dan tindakan guna menyelesaikan masalah

Teori Pengambilan Keputusan : Fungsi

• Pemahaman secara komprehensif terhadap masalah, pemberian kerangka berfikir secara sistematis, membimbing dalam penerapan teknik-teknik pengambilan keputusan dan meningkatkan kualitas keputusan.

Komponen pengambilan keputusan

• Tujuan-tujuan (objectives).• Keterbatasan/kelangkaan (scarcity).• Ketidak pastian (uncertainty).• Alternatif2 pilihan (a list of alternatives).• Nilai manfaat (benefit) dari setiap pilihan.• Trade off dari setiap pilihan.• Model pengambilan keputusan

Insentif-insentif yang mendasari pengambilan keputusan

Menurut Lubis (1996) ada 4 insentif, yaitu:• Insentif Ekonomis, meliputi variabel2 ekonomi:

fluktuasi harga, akses pasar, modal (material, tenaga kerja, waktu), keb ekonomi rumah tangga.

• Insentif Ekologis, meliputi: porositas tanah, topografi lahan, perilaku tanaman.

• Insentif Sosial, meliputi: status sosial dan hubungan-hubungan sosial.

• Insentif Kultural, meliputi: pengetahuan, kepercayaan, dan nilai-nilai terkait dlm pengelolaan lahan hutan.

Model-model dalam pengambilan keputusan

• Models are abstract representations of the real world that are useful for purposes of thinking, forecasting, and decision making.

• Models may be very informal, mostly intuitive, and supported by experience and information that is not put together in any systematic manner.

Contoh-contoh model dlm kehutanan

• Peta • Persamaan volume tegakan• Persamaan pertumbuhan• Dll

Kondisi dan metode pengambilan keputusan

• Kondisi pasti: teknik program linear, metode simpleks, analisa jaringan kerja (CPM/PERT).

• Kondisi beresiko: nilai harapan (expected value), nilai kesempatan yg hilang (opportunity loss value), nilai harapan informasi sempurna (expected value of perfect information).

• Kondisi tidak pasti: kriteria maximax, kriteria maximin, kriteria laplace, kriteria regret, teorema bayes, kriteria realism, decision tree.

• Kondisi konflik: teori permainan.

Pengambilan keputusan dalam kondisi pasti

• Program Linear: can be defined as a method to allocate limited resources (land, people, trees, time, or money) to competing activities in an optimal manner.

Contoh 1 • About 40 ha of the land he owns are covered

with red pine plantations. The other 50 ha contain mixed northern hardwoods. Having kept a very good record of his time, he figures that since he bought these woods he has spent approximately 800 days managing the red pine and 1500 days on the hardwoods. The total revenue from his forest during the same period was $36,000 from the red pine land and $60,000 from the northern hardwoods.

Formulasi masalah 1

• Tujuan: oMaximize Z = $ of revenues per year

• Decision variables are:o X1 = the number of hectares of red pine to

manageo X2 = the number of hectares of northern

hardwoods to manage

Formulasi masalah 1• Fungsi tujuan : Max Z = 90 X1 + 120 X2

($/y) ($/ha/y)(ha) ($/ha/y)(ha)

• Kendala lahan :o X1 ≤ 40 ha of red pineo X2 ≤ 50 ha of northern hardwoods

• Kendala waktu :o 2 X1 + 3 X2 ≤ 180(d/ha/y)(ha) (d/ha/y)(ha) (d/y)

• Kendala non negatif : o X1 ≥ 0 dan X2 ≥ 0

Formulasi masalah 1• Max Z = 90X1 + 120X2 • Subject to :

o X1 ≤ 40o X2 ≤ 50o 2X1 + 3X2 ≤ 180o X1, X2 ≥ 0

Contoh 2• This story deals with a pulp mill operating in a small town

in Maine. The pulp mill makes mechanical and chemical pulp. Unfortunately, it also pollutes the river in which it spills its spent waters. This has created enough turmoil to change the management of the mill completely.

Contoh 2• The previous owners felt that it would be too costly to

reduce the pollution problem. They decided to sell. The mill has been bought back by the employees and local businesses, who now own the mill as a cooperative. The new owners have several objectives. One is to keep at least 300 people employed at the mill. Another is to generate at least $40,000 of revenue per day. They estimate that this will be enough to pay operating expenses and yield a return that will keep the mill competitive in the long run. Within these limits, everything possible should be done to minimize pollution.

Contoh 2• A bright forester who has already provided shrewd

solutions to complex wood procurement problems is asked to suggest an operating strategy for the mill that will meet all these objectives simultaneously and in the best possible way. She feels that it could be done by linear programming. Towards this end, she has put together the following data:

Contoh 2– Both chemical and mechanical pulp require the labor of

one worker for about 1 day, or 1 workday (wd), per ton produced.

– The chemical pulp sells at some $200 per ton, the mechanical pulp at $100.

– Pollution is measured by the biological oxygen demand (BOD). One ton of mechanical pulp produces 1 unit of BOD, 1 ton of chemical pulp produces 1.5 units.

– The maximum capacity of the mill to make mechanical pulp is 300 tons per day; for chemical pulp it is 200 tons per day. The two manufacturing processes are independent; that is, the mechanical pulp line cannot be used to make chemical pulp, and vice versa.

Contoh 2• Given this, our forester has found that the management

objectives and the technical and financial data could be put together into a linear program. Next we show how she did it.

Formulasi Masalah 2

• ???

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Kompartemen 1120 ha

hardwood

Kompartemen 2180 ha

hardwood

100 hapine

100 ha pine

100 hapine

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• Luas kompartemen atau lahan dan hasil penebangan (dlm tons) per periode.

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• Variabel keputusan : XijDi mana : i adalah kompartemen/lahan j adalah periode penanaman

• Kendala : X11 + X12 + X13 = 120 X21 + X22 + X23 = 180 X11 + X21 = 100 X12 + X22 = 100 X13 + X23 = 100

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• Fungsi tujuan :Max Z = 16X11 + 23X12 + 33X13 + 24X21 + 32X22 + 45X23

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• Excel 1

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