Biodiversity, Biotechnology and the Environment
Barbara A. Schaal
Department of Biology
Washington University
St. Louis, MO 63130
schaal@biology2.wust.edu
Abstract:
The widespread use of genetically modified crops has precipitated acrimonious
debate on the health effects, environmental safety, and ethics of genetically modified
agricultural species. The debate is contentious, often with unsubstantiated claims of both
potentially harmful and beneficial effects. Here we examine the possible effects of GM
agriculture on issues of the environment and biodiversity. Possible negative aspects of
GM agriculture include unanticipated effects on non-target organisms, gene flow between
GM crop or animal and closely related wild species, and hybridization resulting in new
weedy taxa. Positive effects include reduction in agrochemical use, reduction in harvest
pressure on native species, and new methods for bioremediation, among others. The
demand for GM crops in developing countries is expected to be high, due to their
potential for greatly enhancing yields. But, the widespread application of GM agriculture
to the tropics presents new challenges. In the tropics, systems of agriculture are both
variable and different than in developed countries. Tropical regions contain high levels
of native biodiversity, and many wild relatives of agricultural species are often growing
within the vicinity of their derived domesticated plants and animals. Assessment of the
environmental consequences of GM agriculture is essential. In some cases environmental
benefits may accrue, in other cases GM agriculture may negatively effect both the
environment and biodiversity. Only by carefully applying science-based knowledge can
the effects of GM agriculture, both positive and negative, be accurately determined.
Introduction:
The use of genetically modified organisms, both plants and animals, in agriculture
has resulted in an acrimonious debate. The wide spread planting of genetically modified
(GM) crops has generated contention around such issues as health, the environment,
economics, international relations, the business practices of large corporations and ethics,
among others. One of the most active areas of debate is the potential effect of GM
agriculture on the environment (NRC Board on Agriculture Report, 2002). The debate is
highly polarized with one extreme claiming that GM agriculture will greatly harm both
global agriculture and the environment. Strong advocates, on the other hand, maintain
that there are few, if any, new risks and that genetically modified crops may, in fact, be
the savior of both global agriculture and the environment. As with many highly polarized
debates, there is a vast middle ground that, in the case of GM agriculture, acknowledges
the great potential of biotechnology but also raises science based concerns. An
unfortunate aspect of the controversy is the tendency to see the issue in either black or
white; biotechnology is either good or bad. In fact, biotechnology involves many species,
both plants and animals, with a wide range of genetic modifications that are placed in a
diversity of agricultural and natural systems located across a wide range of geographical
sites. Whether or not an application of biotechnology has potential harmful, beneficial or
neutral effects on the environment is both species and context specific.
Biotechnology vs. traditional breeding:
Before we go on to examine the effects of biotechnology on biodiversity, our
topic here, we need to define what is a genetically modified organism. And, we need to
determine how genetically engineered varieties differ from conventionally bred plants
and animals. Currently most of the concern about biotechnology and the environment
centers on genetically modified agricultural plants (GM crops), although genetically
modified animals including mammals, fish and crustaceans are all being developed for
agricultural use. Genetically modified agricultural species, for our discussion here, are
those plants and animals that have specific genes introduced into them by modern
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methods of biotechnology, that is, the organisms are genetically transformed. The term
genetically modified organism (GMO), often used to describe a variant produced by
biotechnology, is somewhat misleading. All of our domestic species, plants and animals,
have undergone significant genetic modification from their original wild ancestors, first
during the course of domestication by early agriculturalists and then by modern breeding
(Wang, et al., 1999). Biotechnology is a way of genetically modifying organisms that is
based on methods of DNA manipulation, the ability to insert genes from one species into
the genome of another.
How does traditional plant and animal breeding compare to the production of new
varieties by biotechnology? Modification of wild species to make them more useful or
compatible to humans is an ancient process. Humans from the earliest times have
interacted with native biodiversity and have used this biodiversity for their own benefit.
Early farmers in the Middle East, Asia, South America and Africa began to grow plants
near their villages that they had collected for food or fiber, first in the wild. They chose
plants with traits that were most useful, the individual with bigger seeds or which had
longer and tougher fibers, and they used the seeds of these plants to begin the next
generation of plants. Over many generations morphological and genetic differences
accumulated between the domesticated crop and its wild relative. In some species such
as corn the process so changed the crop that the wild parent species of the crop is no
longer obvious by morphology alone. In the development of other crops, such as wheat
or kales, different species have been crossed, to incorporate genes from one species into
the genome of another (e.g. Simpson and Ogorzaly, 2003). The concept of using genes
from different species as a basis for improvement is a well-established principle of plant
and animal breeding. Early farmers developed plant varieties for their local region and
when the new varieties were useful, they traded seeds and animals over vast geographical
scales. Often these new, introduced varieties crossed on their own with local landraces
and native species. The introduction of a species or variety into new geographical
regions in many cases had a profound effect on biodiversity, by altering agricultural
practices, by introducing species which displaced native species, or by altering
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community dynamics. Agriculture has a long history of impacting both native
biodiversity and the environment.
What are some of the characteristics of traditional crop breeding today? First, a
source of new genes or traits is obtained. The source in traditional breeding is from
either other varieties of the same crop, or from wild relatives or closely related species.
Traditional crop breeding is an inexact science and many genes beyond those for the
selected trait are introduced. Sometimes whole sections of chromosomes are transferred,
which may introduce genes that produce an undesirable trait, such as early dropping of
seeds or that reduce crop yield (Simmonds and Smartt, 1999). After the initial cross, the
progeny and their progeny are crossed repeatedly over several generations in order to
eliminate these undesirable genes and to concentrate desirable traits. This process may
be very slow, particularly in the case of perennial crops such as bananas or cassava where
the generation length, the time to first flowering, may be several years. Even in annual
crops the process is slow. Of course, this is not to imply that traditional breeding is
unsuccessful. All of our crops are based on traditional plant breeding, including those
used in the US as well as those of the green revolution, which has increased the yield of
important crops such as rice in Asia. Regardless of future technological advances,
traditional plant breeding will be an important source of new varieties, or will provide the
background stock for new crops produced by genetic engineering. In fact traditionally
bred varieties of crops are extremely important in this age of GM varieties. The choice of
which background or variety to use for genetic transformation is critical. Some of the
earliest efforts at producing GM crops were far from successful because a relatively poor
variety was chosen as the stock for transformation--this happened in tomatoes making the
GM lineage commercially unviable.
Genetic engineering presents an alternative to traditional plant breeding. Using
the techniques of molecular biology, a single gene that codes for a desired trait, such as
insect resistance, increased protein content, or tolerance to drought is isolated and then
combined with a promoter sequence that will allow the gene to be expressed. This
combination of genes is then introduced directly into the plant genome. The concept is
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actually quite simple, although the techniques are technologically complex (see
Chrispeels and Sadava, 2003). The introduction into the plant genome of foreign DNA
can be done by physical means, particle bombardment, or it can be accomplished
biologically by the Ti plasmid of the bacterium, Agrogbacterium tumefaciens, which
causes crown gall disease in plants. Once the target cells incorporate DNA, these
genetically transformed cells are grown by tissue culture into whole adult plants that now
contain the foreign gene. These plants can produce seeds by standard cross pollination of
one plant by another. Thus the plants can reproduce and seed stocks built up. These
seeds will produce the next generation of plants that also will have the new, inserted
gene.
How do plants produced by genetic engineering differ from those produced by
traditional breeding? First the process is highly specific: only DNA for the selected
genes are introduced into the plant. A few, specific genes are added to the target species,
as contrasted to many genes introduced by traditional breeding. Second, genes can be
introduced from a wide variety of organisms. Traditional breeding is limited to closely
related species within the same plant genus for the most part. Genetic engineering can
use genes from across kingdoms. Plants can be engineered to contain genes from
bacteria, fungi, and animals which in turn can dramatically increase the range of traits
that a plant can express, such as anti freeze compounds from flounder that adapt plant
varieties to colder environments. Likewise domestic animas can be genetically
transformed; salmon engineered with growth hormone grow 2-3 times faster than normal
salmon. (GM salmon are particularly controversial because they are highly mobile and
thus have a possibility of escaping into native marine environments.) Plants are currently
being engineered to serve as factories to produce useful compounds that are not found in
plants in nature, such as the production of pharmaceuticals, plastics, and human vaccines.
A final difference between traditional breeding and genetic transformation to produce
new varieties is the time scale. Breeding studies take many years whereas transformation
can be accomplished relatively quickly. Genetic transformation is also more efficient. In
a perennial crop such as cassava or bananas, not only does it take a long time to complete
breeding studies due to generation time, it also requires vast amounts of space and labor
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to grow the large numbers of individuals to screen for selected traits. Genetic
transformation occurs in the laboratory and after it is successful then plants are
transferred to the greenhouse and ultimately field grown.
Genetically modified plants and animals:
Currently the most widely used varieties of GM crops carry introduced genes
either for insect resistance or for herbicide resistance. Insect resistance comes from a
natural insecticide gene found in the soil bacterium, Bacillus thruringiensis (Ananda
Kumar, et al., 1996). B. thuringiensis produces a family of crystalline proteins, (cry
proteins) which inhibit insect growth. The cry proteins are considered an
environmentally friendly insecticide; in fact, the bacterium is used as a natural insecticide
in organic farming. Crops such as soybeans, corn, and cotton have been genetically
engineered to produce one of these cry proteins and are resistant to several major insect
crop pests. The other major group of GM crops is engineered to be resistant to herbicides
(Dekker and Duke, 1995). Fields of herbicide-resistant crops can be sprayed with
herbicides such as glyphosate (Roundup); weeds are killed by the herbicide while the
crop is unaffected. Crop yields are greatly enhanced by this efficient herbicide treatment.
US farmers have embraced GM crops and the percentage of overall crop acres devoted to
GM crops has risen dramatically since 1995, when GM crops became widely available.
Moreover, there is much demand among US farmers for additional GM crops such as
wheat, sorghum, and rice.
The development of the next generation of GM crops is actively proceeding and
we can expect a diversity of new approved crop varieties. These crops will expand the
range of GM agriculture for the kind of species that is genetically modified, for the
geographical regions where GM crops are grown and for the type of trait engineered into
the crop. Currently being developed are new crops that have disease resistance to
pathogens, that have increased protein content, that have more healthful lipids, and that
are engineered to produce pharmaceutical compounds, among others. Development of
GM varieties is not limited to row crops such corn, soy, and cotton. Work is being
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conducted on producing new varieties of trees for wood and pulp, ornamental plants for
gardening and landscaping, and new forage grasses. A large effort is underway to
engineer new crops for the developing world. These varieties are being produced to
provide food security and alleviate nutritional inadequacies that are found so often in the
developing world. At the same time, animal biotechnology is rapidly proceeding. For
example, many Asian countries have large aquaculture industries and efforts are
underway to produce genetically transformed fish and crustaceans that are resistant to
disease, that grow rapidly and that are adapted to the conditions of aquaculture. These
applications of biotechnology present particular challenges since these animals are highly
mobile. While it outside of our discussion here, there are also well-established efforts to
genetically transform insects such as mosquitoes, to alleviate them as vectors of disease.
The Biotechnology in the Tropics: Issues
The development of genetically modified plant and animal varieties for the
developing world presents challenges for assessing their environmental impact.
Why do we need to specifically assess the environmental impact of GM agriculture in
tropical regions? Why are the lessons already learned from GM agriculture in the
developed world inadequate? There are several reasons: both the type of agriculture and
the environmental context of agriculture is different in tropical developing countries than
in the temperate developed world. First is the type of agricultural system. In developed
countries modern agriculture is characterized by fields of a crop grown in monoculture
with large inputs of fossil fuel in the form of agrochemicals, fertilizers, pesticides and
herbicides. Developing and tropical countries have a greater range of agricultural
practices. Indigenous people can use traditional intercropping or swidden agriculture that
utilizes many plant species and varieties with little to no agrochemical use. Many crops
are grown in small gardens, orchard or fields and come in close contact with local native
biodiversity. And, increasingly, modern agricultural methods are being employed for the
major crops such as corn and soy.
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For our discussion of biodiversity and the environment, the most significant
difference between agricultural systems of the developed and developing world is the
ambient levels of biodiversity, both in natural habitats and as part of an agricultural
ecosystem. The tropics have the greatest natural biodiversity on earth, with a stunning
number of plants, animals, fungi, bacteria, etc. Moreover, the biological relationships
among species are complex. Species often have highly specialized ecological niches and
are often closely tied to other species in the community by feeding relationships, by
competition, parasitism or mutualisms. These intricate connections between species
potentially make tropical species and communities vulnerable when biological
perturbations occur. The concern is that tropical communities may be highly sensitive to
perturbations and because of the elaborate interrelationship, subject to ripple effects (the
relationship between community complexity and stability is a long standing debate in
ecology (eg, Tillman and Downing, 1994). The combination of high species diversity
and potential sensitivity to disturbance requires careful evaluation of the potential
environmental effects of GM agriculture in tropical regions.
Another important aspect of biodiversity in tropical regions needs to be
considered. In the US, most of our major crops have been imported from other regions of
the globe and are not grown here in contact with their wild ancestors. Thus corn, wheat,
rice and soy are all crops of either the old world (wheat, rice, soy) or Mesoamerica
(corn). In many cases there are no close relatives to the imported crop and the crop is
grown in genetic isolation from the native biodiversity. The environmental concerns
regarding gene flow between crop and wild relative and its effect on biodiversity are not
a major concern. As genetically modified plants and animals are developed for tropical
species and their use incorporated into the agriculture of developing nations, the effects
of gene migration between GM species and wild relatives will have increasing
importance. We might expect that for many species the contact between crop or GM
animal and wild ancestor will be more frequent in regions of high biodiversity. Close
contact, which raises the possibility of gene flow, is more likely in some tropical regions
for several reasons. First, many genera are species rich in the tropics which offers many
more native candidates for gene flow (cross pollination) between wild and domesticated
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species. Second, many tropical crops are not as highly domesticated as are the major
crops of the world. These local varieties may be genetically much more like their wild
ancestors or relatives that live near by and hence more likely to produce fertile offspring
when crossed. Finally, many regions in the developing world still use locally adapted
landraces of a crop; these landraces are of great importance since they contain valuable
agricultural biodiversity, and are a genetic resource for future crop improvement. It is
important to consider the effects of GM crops on this aspect of agricultural biodiversity
as well as the potential effects on native biodiversity.
Up to now we have drawn a distinction between the agriculture and biodiversity
of developed and less developed countries. This distinction is far from complete. In the
US several crops are grown in close association with their wild ancestors (e.g.
sunflowers) or weedy relatives have been introduced (rice, sorghum, pannicum). And,
large monoculture fields of GM crops are increasingly common in developing countries.
While the environmental issues that center on biotechnology are the same globally, their
relative importance varies with crop, geographical region, and community context.
Finally, before we consider the specific effects of biotechnology on biodiversity,
two important and related points need to be made. First, many of the issues that are
currently a concern for GM agriculture have been long standing concerns for traditional
agriculture as well. Harm to non-target organisms from pesticides and herbicides, gene
flow, and the production of weeds has all plagued agriculture. The fact that these are
concerns for conventional agriculture implies neither that these issues can be ignored for
biotechnology derived crops (supposedly since these are not new concerns), nor does it
mean that GM agriculture should be avoided because it, along with conventional
agriculture, affects the environment. Second, the debate regarding biotechnology is often
confined to whether there is harm from GM agriculture. It needs to be emphasized that
GM agriculture has not only potential liability for native biodiversity, but also potential
benefits for biodiversity as well. The potential effects of biotechnology can only be
determined correctly if they are assessed in the context of and compared to current
agricultural practices. Given that we are not going to stop the practice of agriculture, we
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need to determine the relative risk of GM plants and animals to the risk associated with
current varieties.
Effects of Biotechnology on Biodiversity: Potential Concerns:
What are the concerns about the effect of GM agriculture on biodiversity and the
environment? First we consider the effect that biotechnology derived species might have
on non-target organisms. This issue was dramatically brought forward in a 1999 study of
Monarch butterflies and Bt corn (Losey, et al., 1999). Monarch caterpillars were fed Bt
corn pollen in a laboratory experiment. The caterpillars responded negatively to the Bt
pollen (Bt is particularly effective against lepidopterons) and the larvae either exhibited
stunted growth or were killed. After this initial report, which caused uproar, the question
was asked if this mortality actually occurs in the field. Scientific risk assessment showed
that, in fact, few larvae are likely to be affected by Bt pollen in the field due to a number
of factors (Sears, et al., 2001). The Bt corn used for the initial experiment had the Bt
toxin expressed in high levels in the pollen whereas new varieties of Bt corn have little
cry protein in pollen. Other studies show that the timing of pollen release, the dispersal
curve of pollen over distance and the proximity of milkweed (the larval food source) to
corn fields all were such that Bt corn would have a minimal effect the mortality of
milkweed larva. While the conclusions here were that Bt pollen may not be major factor
in monarch mortality, it raises significant questions about the effect of Bt toxins on other
insect species, particularly lepidopterons, and also about the effect of Bt in the soil and on
soil arthropods, bacteria, worms, etc. Such risk assessment studies have been done for
only a few organisms.
Another issues is the cross pollination between crop and closely related species
(Ellstrand, et al., 1999). Gene flow is the migration of genes from one population or
taxon into another. Gene flow has a homogenizing effect, making populations that
exchange genes genetically similar. Why is such gene flow or cross-pollination a
concern? First it can alter the gene pool of native species. When the native species are
wild relatives or ancestors of domesticated species, homogenization of populations can
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result in the loss of critical genetic biodiversity. One of the hallmarks of domestication is
a genetic bottleneck that results in a decline in genetic variability within the domesticated
plant or animal species. In some cases up to 80% of the genetic variation that was
originally in the wild species is lost during domestication (Olsen and Schaal, 2001).
Thus, populations of wild ancestors are extremely important for future crop
improvement, since they can potentially contain many useful genes. As an example, the
green revolution in Asia was fostered by new high yield varieties of rice. Genes were
incorporated from rice’s wild ancestor, Oryza rufipogon, and included such traits as
disease resistance, small stature, and response to fertilizers. Another concern with gene
flow from GM crops into the wild ancestor is that GM traits may cause selective changes
that sweep through wild populations and result in a decline in variation. Any loss of
variation would include some useful traits. Such loss of variation could also compromise
the ability of wild populations to adapt to environmental change, either biological or
physical.
Our own work on rice in Thailand indicates significant gene migration between
crop and wild ancestor. The gene flow curve for rice is leptokurtic; while most genes
migrate at small or moderate distances, there is a long tail of low levels of gene dispersal
across large distances. In the case of rice, we can detect hybridization between crop and
wild ancestor by detecting plants that are morphologically intermediate between
cultivated and wild species. Our rice work illustrates another concern, the production of
weedy hybrids. The worry is that when a GM crops hybridizes with a wild ancestor, the
hybrid offspring will lead to the formation of a vigorous weed (called super weeds by
some). This is again a situation found in conventional agriculture, where there are many
crop-weed systems. Such hybridization is of particular concern in Thailand, where the
wild ancestor of rice grows in close contact with cultivated rice. In Thailand, gene flow
results from changing agricultural practices and results in plant hybrids that are very
aggressive in growth, interfere with rice cultivation, and cause a decline in yield. The
concern for biodiversity is that these weeds will then spread outside of the fields and
negatively impact native species. Work of Allison Snow and colleagues on hybrids of Bt
sunflowers and native sunflowers has indicated that hybrids may have an enhanced
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fitness relative to the wild sunflowers (Snow, et al., 2002). The hybrid sunflowers have
incorporated the Bt gene from the transgenic sunflowers and are resistant to attack by
some lepidopterons. Bt hybrids have greater seed production than the wild sunflowers,
thus raising the specter of gene flow altering both the gene pool of the native sunflowers
and producing a new, weedy taxon. But, whether or not these negative affects actually
occur still needs to be accessed.
In global regions with high biodiversity, we expect that many related species will
be growing in close proximity to crops. The likelihood of gene migration between
closely related taxa is an issue that needs to be carefully evaluated. We expect that the
results of such evaluations will vary depending on crop species. In some cases where the
crop is growing in adjacent to the wild ancestor, where the crop has not accumulated
major genetic differences that isolate it from the wild ancestor, and when there is no
reproductive isolation or lack of pollinators, gene flow is likely. On the other hand for
some species there will be no gene migration between crop and wild relatives due to lack
of compatibility, variation in flowering time, or spatial isolation of the crop from wild
relatives. This conclusion is both encouraging and discouraging, since either the
detection or risks or the absence of risks in one species does not bear on risk assessment
of gene flow in other agricultural species. Each species needs to be carefully accessed
separately and any generalizations need to be drawn with great care.
The Effects of Biotechnology on Biodiversity: Potential Benefits:
Up to this point we have explored potential negative consequences of GM
agriculture on biodiversity. But, there are also some potential positive aspects as well.
These benefits frequently stem from a mitigation of current agricultural practices such as
pesticide or herbicide application. Most of the world uses agrochemicals in varying
amounts for their fields and crops. Different regions of the globe use different kinds of
chemicals and in vastly different amounts, with tropical agriculture of developing
countries often having very high rates of pesticide application. Some rice fields in SE
Asia are sprayed with pesticide several times a week, jeopardizing farmers, their families,
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and the entire ecosystem with pesticides (Phipps and Park, 2002). Bt crops such as corn
and cotton produce their own pesticides by genetic modification and potentially require
less insecticide spray. Data from cotton fields show a clear reduction in pesticide use
over conventional agriculture, but possible reductions for some other crops are not
always well documented. Any reduction in insecticide use would be of great benefit not
only for human health but also to non-target organisms and the native biodiversity of the
region. Reductions in agrochemical use simply exposes species to less pesticide, either in
the form of direct contact or as sequestered in the food chain.
Another major concern is the application of herbicides that are used extensively in
western agriculture and increasingly in developing countries. Some herbicides can be
toxic, degrade slowly, or are difficult to assay. Glyphosate (Round Up) is
environmentally benign with little if any toxicity and degrades quickly. Roundup ready
crops use applications of glyphosate as an alternative to more toxic herbicides, thus the
switch to glyphosate resistant GM crops potentially reduces any toxic effects of
herbicides, a change in agrochemical use which, in turn, can enhance biodiversity.
Moreover, herbicide use reduces plant biodiversity and thus indirectly affects other
species in a food chain. Less diverse plant community may lead to a less diverse
arthropod, mammal, bacterial, etc. populations. Such changes can then have a ripple
effect through the food chain.
New varieties of GM crops that are currently being developed will be engineered
to respond more readily to fertilizers or are drought resistant. Such crops afford the
possibility of reducing fertilizer application and irrigation, both processes that
significantly modify native habitats and lessen biodiversity
Other potential benefits include providing alternative, cash generating crops for
local farmers in the developing world. In many regions of the developing world with low
agricultural production, local farmers subsidize their diets by hunting animals. Such
“bush meat” may often be species that are rare or even endangered. Economic stability
from new cash crops can reduce the harvest pressure on native biodiversity. One of most
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intriguing aspects of GM for environmental benefit is the use of genetically engineered
plants that have been modified to take up and sequester toxic substances such as heavy
metals (Bizily, et al., 2000). These specialized plants, developed for bioremediation, are
sown as a lawn on a toxic spill site, grown, and the resulting plants then harvested and
disposed of as toxic waste. Several years of treatment can effectively remove
contaminants and dramatically reduce the levels of toxins in the soil.
GM agriculture offers the hope of reducing agrochemical use by developing
plants that produce their own insecticides, thereby reducing the need for pesticide
application, by developing plants that are resistant to herbicides which allows
modification of application schedules (see below) and by developing plants that require
less fertilizer application. Such potential benefits are particularly important in tropical
regions where pest pressure on crops is exceedingly high and very large amounts of
pesticide can be used. In a recent study of potential use of GM crops in developing
countries, Qaim and Zilberman (2003) illustrated that the demand for GM crops could be
high in developing countries due to their expected enhancement of yield. At the same
time, data from India on cotton indicates that Bt cotton greatly reduces the use of
pesticides to reach the same yield. To prevent a loss of 20% yield, Bt cotton requires
pesticide application of .8 kg/ha while non-Bt cotton requires an application of 4.8 km/ha,
a six-fold increase (Qaim and Zilberman, 2003). Not only are such reductions in
pesticide good for biodiversity, they are critical for the health of local farmers who often
suffer from the effects of frequent applications of toxic pesticides, pesticides whose use is
often banned in the US.
While many studies have speculated that any reduction of agrochemical use
would enhance biodiversity, relatively little supporting data are available. A recent study
examines the effect of the timing and use of herbicides on arthropod community diversity
in forage beet populations in Denmark (Standberg and Pedersen, 2002). In this study the
biodiversity of arthropods was compared in fields treated with conventional herbicide
application (non GM crop), to a GM Roundup Ready crop (GM) with applications of
herbicide according to label recommendations and with a late application of Roundup.
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Interestingly, there was no significant difference between the arthropod communities for
the conventional crop and the roundup ready beets treated according to label directions.
But, the late application herbicide had nearly double the number of arthropod species.
The authors speculate that letting weeds remain longer in the field enhanced arthropod
species diversity. Such research demonstrates not only that GM agriculture can enhance
species diversity relative to conventional agricultural practices, but also the necessity of
fine tuning agricultural practices for specific crops and location.
Such studies will be criticized, pointing out that if no herbicides were used at all,
then there would be an even greater biodiversity. This is of course correct, but the
assessment of agricultural practices needs to be made realistically and in comparison with
current practices. Biodiversity would be greatest if we had no agriculture at all;
agriculture since the time of the earliest plant domestication has reduced native
biodiversity. But, such arguments ignore the global requirements of human populations.
We need agriculture to feed populations in cities and the expanding populations of the
developing world. The best way to minimize the negative effects of agriculture, both GM
and non-GM is to carefully apply the learned scientific principals from ecology, genetics,
molecular biology, agronomy, etc to each agricultural situation.
Conclusions:
It is clear that many of the issues that relate to the potential environmental effects
and biodiversity for GM agriculture are location and crop specific. Fore example, there is
no risk of gene flow between GM corn and the wild ancestors of corn in the US. But in
central Mexico such gene flow may be a threat to the few remaining populations of
teosinte, corn’s wild ancestor. The wealth of biodiversity of tropical regions is a
particular challenge for GM agriculture. In the tropics many species are cultivated in
contact with their wild ancestor and some tropical crops may have little genetic
differentiation from their wild ancestor, thereby increasing the chances of gene flow.
Moreover, environmental interactions in the tropics are complex with food chains and
connections between species often intricate. Thus one might expect perturbations of
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local species to pass through other components of the ecosystem. At the same time,
pesticide use is high in tropics with a cost to humans, the environment and biodiversity.
The only way to determine the effect of biotechnology on the environment and on
biodiversity is conduct appropriate scientific studies including the assessment of relative
risk, measures of gene flow, determine the fitness of hybrids, assessing the effects on
non-target species and ecological monitoring for things gone wrong (Kjellsson and
Strandberg, 1995). This is not a well-received answer to the general question: Is
biotechnology harmful, neutral or beneficial to the environment? This question can only
be answered for a specific case and depends on the genetically modified plant or animal,
the geographical region where the organisms are placed, and the local biological
environment. Moreover, the effects of a genetically modified organism need to be
compared to the effects of the current local agricultural practices on the environment and
biodiversity as well. While such work is complex and often tedious, careful scientific
assessment of the environmental risks of biotechnology will assure that biotechnology
will develop in concert with local biodiversity and it will ultimately help in gaining the
public’s confidence in and acceptance of these technologies.
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