Ecology of Transgenic Crops

Ecology of Transgenic Crops

鄭先祐

生態主張者： Ayo 工作室

Ecology of Transgenic Crops2

Ecology of Transgenic Crops

Genetically engineered plants might generate weed problems and affect non-target organisms, but measuring the risk is difficult.

資料取自： Marvier, M. (2001) Ecology of transgenic crops. American Scientist 89(2):160-167.


基因轉植的問題 On May 20, 1999, a short article in Nature

called attention to a potential ecological problem with a genetically engineered, or transgenic, crop.

Losey and his colleagues at Cornell Univ. reported that a variety of transgenic corn could kill the larvae of monarch butterflies.


Fig. 1. Monarch caterpillars feed on a milkweed leaf dusted with pollen from corn that was genetically engineered to resist pest. Plant breeders can transfer a gene from a bacterium called Bacillus thuringiensis into corn, which causes it to produce an insecticidal compound, commonly called Bt toxin.

Losey and his colleagues found that only 56% of the monarch larvae survived when fed milkweed plants coated with transgenic corn pollen, whereas 100% of larvae survived when the plants were coated with non-transgenic corn pollen.


反對者 vs. 贊成者 Opponents of transgenic crops help up the

report as evidence of the potentially devastating environmental impact.

Proponents largely dismissed this laboratory-based research as unrepresentative of conditions on real farms.


基因轉植的威力 Genetic engineering makes it possible to

transfer genes from virtually any species – animal, bacteria, plant or virus – into almost any other species, no matter how unrelated the two species might be.

如此可以創造出將水母的發光基因轉植入植物，有各種顏色的草 (Monsanto 公司 ) 。


基因轉植的農作物：利與害利益：增加生產量、增進味道和營養成分，

以及抗病力 ( 減少農藥的使用 ) 。害處：對人體健康有過敏原 (allergens) 和

致癌因素 (carcinogens) 。對環境而言，產生新的 pests ，對 non-target species 的傷害， disruption of ecosystem processes 。

然而，對這些可能的害處，學術界的研究卻是很有限。


基因轉植的農作物：激增！ In 1996 ，商業栽植基因轉植的農作物的農

地面積有 430 萬公頃。 In 1998 ，農地面積激增至 6,950 萬公頃。 With such rapidly in creasing use of

transgenic crops, scientists and society must weigh whether the potential benefits outweigh the potential risks.


基因轉植， more than 育種？ Do transgenic crops pose different risks from

those common to crops created through traditional methods of plant breeding?

Genetic engineering can create many more combinations of genes and new traits than can traditional breeding.

This greatly enhanced novelty diminishes anyone’s ability to predict the safety of a transgenic organism on the basis of past experience.


DDT 的案例 Scientists and manufactures considered

DDT totally risk-free when first marketed in the late 1940s, and data that documented ill effects took nearly 20 years to surface.

Similarly, major problems might result from transgenic crops over time.


Fig. 2. DDT gets praise from an advertisement in the June 30, 1947, issue of Time.


Insect-resistant transgenic crops

Creating new weeds Troubles for non-targets What is significantly safe? Setting standards for sampling Dealing with uncertainty


Creating new weeds

The release of organisms with novel phenotypes bears similarities to the introduction of non-native species.

許多的證據顯示，許多外來種，可能如同雜草(weeds) ，造成對環境和經濟的傷害。

抗蟲的植物，可能會有較強的擴散能力，如同雜草。

Hybridization between a transgenic crop and a related non-crop plant can spread novel traits to additional species.


Fig. 3. Purple loosestrife ranks as one of the most economically costly and environmentally destructive examples of non-native species.


Fig. 4. Invertebrate herbivores can limit plant reproduction. This graph represents the pooled results from many experiment on the impacts of invertebrate herbivores on plant-reproductive performance.

有蟲和無蟲， production of flowerers, fruits or seeds 的量，相差可高達 25 倍。


Troubles for non-targets

案例： a plant that is toxic to Colorado potato

beetles could conceivably also be toxic to non-pest beetles or to beetles that actually benefit farmers, including ladybird beetles.

Losey and his colleagues studied the effects of pollen produced by transgenic corn that resists lepodopteran pests.

Ecology of Transgenic Crops17 ↑Bt corn corn 的蛀蟲↑


Fig. 5. This corn releases an insecticidal compound (red) through its roots into the soil. That compound can remain insecticidal for 230 days or more and could impact populations of soil organisms. In addition, pollen from Bt corn (blue) can travel as far as 60 meters, where it coats the surface of non-crop plants. Non-target insects, including monarch butterfly larvae, consume some of the windblown corn pollen.


What is significantly safe?

Transgenic crops that produce insect toxins must undergo two separate reviews of environmental safety before they can be sold commercially in the U.S.

1. EPA reviews laboratory studies assessing a crop’s effects on particular non-target organisms, including pollinators, predatory insects and, often, soil invertebrates.

2. Sufficient field data regarding a crop’s performance and safety.


批准申請案 As of July 2000, the US 農業部已經批准 5

0 個申請案。其中有 14 個是具有抗蟲的農作物，且都是運用 Bt toxin 。

目前通過申請案運用 Bt toxin 的農作物有玉米、棉花、馬鈴薯和蕃茄。


樣品數極少！申請通過的案例：編號： #97-012-01p 內容： A variety of Bt cotton In experiments designed to test this transgenic

crop’s impact on soil invertebrates, investigators placed four replicate batches of earthworms– with 10 worms per batch– in soil that included ground leaves from either transgenic or non-transgenic cotton.

測試： 14 天。


Fig. 6. The batches of earthworms exposed to Bt cotton increased in weight on average by 49% (↑). The earthworms exposed to non-transgenic cotton increased in weight on average by 78.5% (→).

•兩者間平均差距有 29.5% ，但是統計的結果是差異不顯著。•這明顯的是因為樣品數過少所造成的結果。•另外，實驗的時間只有 14 天，這也明顯的太短。


Setting standards for sampling

案例：編號： #94-257-01p 內容： a Bt potato 情況：研究者當發現實驗結果是有顯著的

差異時，就再重複進行實驗。重複進行至結果是沒有差異時，才停止實驗。


案例： The Swiss Federal Research Station found that

green lacewings, which are beneficial predatory insects, experienced 62% mortality when fed a diet of pests reared on Bt corn, but only 37% mortality when fed pests reared on non-transgenic corn.

樣品數： 200 個體 per treatment. 而且認為應該要進行 over the entire life span 的

測試。


A scientific advisory panel

Met in December 1999 to review the EPA guidelines and recommended the following:

The agency (EPA) should consider how the data will be used and establish an acceptable level of statistical power. Based on these decisions, appropriate tests and sample sizes can be determined.

http://www.epa.gov/scipoly/sap/1999/index.htm


Dealing with uncertainty

Risk analysis should reveal how the public good might suffer if new technologies backfire.

We could assume that a transgenic product is unsafe until the manufacturer demonstrates its safety.

Further exploration ： http:// www.americanscientist.org/articles/01articles/ marvier.html

http://www.americanscientist.org/articles/01articles/marvier.html

http://www.americanscientist.org/articles/01articles/marvier.html


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Ecology of Transgenic Crops