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Ecology of Transgenic Crops
鄭先祐
生態主張者:Ayo工作室
Ecology of Transgenic Crops
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Genetically engineered plants might
generate weed problems and affect nontarget organisms, but measuring the risk is
difficult.
資料取自: Marvier, M. (2001) Ecology of
transgenic crops. American Scientist
89(2):160-167.
Ecology of Transgenic Crops
基因轉植的問題
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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.
Ecology of Transgenic Crops
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.
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.
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Ecology of Transgenic Crops
反對者 vs. 贊成者
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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.
Ecology of Transgenic Crops
基因轉植的威力
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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)。
Ecology of Transgenic Crops
基因轉植的農作物:利與害
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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。
Ecology of Transgenic Crops
基因轉植的農作物:激增!
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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.
Ecology of Transgenic Crops
基因轉植,more than 育種?
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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.
Ecology of Transgenic Crops
DDT的案例
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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.
Ecology of Transgenic Crops
Fig. 2. DDT gets praise from an advertisement in the
June 30, 1947, issue of Time.
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Ecology of Transgenic Crops
Insect-resistant transgenic crops
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Creating new weeds
Troubles for non-targets
What is significantly safe?
Setting standards for sampling
Dealing with uncertainty
Ecology of Transgenic Crops
Creating new weeds
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The release of organisms with novel phenotypes
bears similarities to the introduction of nonnative 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.
Ecology of Transgenic Crops
Fig. 3. Purple loosestrife ranks as one of the most
economically costly and environmentally destructive
examples of non-native species.
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Ecology of Transgenic Crops
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。
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Ecology of Transgenic Crops
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.
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Ecology of Transgenic Crops
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↑Bt corn
corn 的蛀蟲↑
Ecology of Transgenic Crops
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
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Ecology of Transgenic Crops
windblown
corn pollen.
What is significantly safe?
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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.
Ecology of Transgenic Crops
批准申請案
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As of July 2000, the US 農業部已經批准50
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。
Ecology of Transgenic Crops
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 nontransgenic cotton.
 測試:14天。
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Ecology of Transgenic Crops
•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。
Fig. 6. The batches of
earthworms exposed to Bt
cotton increased in weight on
average by 49% (↑). The
earthworms exposed to nontransgenic cotton increased
in weight on average by
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78.5%
(→).
Ecology of Transgenic Crops
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。
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Ecology of Transgenic Crops
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 nontransgenic 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。
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Ecology of Transgenic Crops
A scientific advisory panel
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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
Ecology of Transgenic Crops
Dealing with uncertainty
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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
Ecology of Transgenic Crops
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Ecology of Transgenic Crops