Ecol. aspects of transgenic crops summary (fwd)

[James J. Kruse]

This has been of considerable interest on this list in the past, so I
thought I would post it. 

Jim Kruse
University of California at Berkeley
Dept. of Environ Sci, Policy and Mgmt.
Div. of Insect Biology
201 Wellman Hall
Berkeley, California, 94720-3112
Voice: (510) 642-7410    Fax: (510) 642-7428
http://www.cnr.berkeley.edu/sperlinglab/kruse.html

---------- Forwarded message ----------

Executive Summary of the workshop on ecological impacts of transgenic
crops held on UC Berkeley Campus March 2-4, 2000.

International Workshop on the Ecological Impacts of Transgenic Crops
(March 2-4 ,2000)

Attended by 21 scientists from Universities (Berkeley, Santa Cruz, Cornell,
Guelph, Iowa State, Minnesota, Swiss Federal Institute of Technology,
Elmhurst College and Open University) , International Agricultural Research
Centers (CIMMYT, CIP), NGOs (Union of Concerned Scientists, Food First,
Consumers Union, AS-PTA Brasil) and Private Organizations (Dynamac Corp.)


EXECUTIVE SUMMARY

Miguel A. Altieri
University of California, Berkeley

Transgenic crops are increasingly becoming a dominant feature of the
agricultural landscapes of the USA and other countries such as China,
Argentina, Mexico and Canada.  Worldwide, the areas planted to transgenic
crops jumped more than twenty-fold in the past four seasons, from 3 million
hectares in 1996 to nearly 40 million hectares in 1999.  In the USA,
Argentina and Canada, over half of the average for major crops such as
soybean, corn and canola are planted in transgenic varieties.  Herbicide
resistant crops (HRC) and insect resistant crops (Bt crops) accounted
respectively for 54 and 31 percent of the total global area of all crops
in 1997. The rapid deployment and widespread commercialization of such
crops in large monocultures raises questions regarding the potential of
genetically modified crops (GMCs) to cause unacceptable impacts on the
environment.  Besides the widely acknowledged drawbacks of GMCs: a) the
spread of transgenes to related weeds or conspecifics via crop-weed
hybridization and, b)the rapid evolution of resistance of insect pests such
as Lepidoptera to Bt, the workshop was concerned about the overall
ecological implications of other more subtle effects that research is now
starting to unravel:

· accumulation of the insecticidal Bt toxin, which remains active in the
soil after the crop is ploughed under and binds tightly to clays and humic
acids;
· disruption of natural control of insect pests through intertrophic-level
effects of the Bt toxin on predators;
· unanticipated effects on non-target herbivorous insects (i.e. monarch
butterflies) through deposition of transgenic pollen on foliage of
surrounding wild vegetation;
· vector-mediated horizontal gene transfer and recombination to create new
pathogenic organisms, and
· reduction of the fitness of non-target organisms through the acquisition
of transgenic traits via hybridization.

By examining specific studies that describe such effects, the group was
able to assess the scale, magnitude and ecological significance of such
findings. 


Approach

The workshop was attended by a group of  21 scientists working on the
ecological aspects of transgenic crops in research organizations located in
the US, Europe, and Latin America. During the first day and a half of the
workshop, participants were able to examine through formal presentations
and group discussions, data on the environmental impacts of HRCs, Bt and
other pesticide-producing crops and virus resistant crops.  Discussions
focused on known documented impacts and their overall implications,
although emphasis was placed on research questions directed at dealing with
potential unknown, hard to detect or low magnitude impacts, but which
ecological theory predicts as probable and likely to scale up. Issues of
gene flow, fitness effects of introduced transgenics on wild relatives,
effects across multiple trophic levels and effects on soil ecosystems were
all analyzed from an integrated  and multidisciplinary perspective.  

The second half of the workshop was spent evaluating the level of knowledge
available on the ecological impacts of transgenic crops and the severity
and scope of risks that their field deployment represents. Following is a
summary of the main conclusion s and recommendations that emerged after two
and a half days of intense multidisciplinary deliberation.

General Ecological Concerns

The rushed commercialization of existing GMCs is unwarranted from an
ecological point of view as many scientists had already raised concerns
about obvious potential impacts of GMCs. Given this fact,  HRCs and Bt
crops have been a poor choice of traits to feature the technology given
predicted environmental problems and the issue of resistance evolution.  In
fact, there is enough evidence to suggest that both these types of crops
are not really needed to address the problems they were designed to solve.
On the contrary, they tend to reduce the pest management options available
to farmers. There are many alternative approaches, (i.e. rotations,
strip-cropping, biological control, etc.) that farmers can use to
effectively regulate the insect and weed populations that are being
targeted by the biotechnology industry. To the extent that transgenic crops
further entrench the current monocultural system, they impede farmers from
using a plethora of alternative methods. 

At issue is the potential for transgene insertions to cause expression of
not simply the target trait, but also unintended secondary outcomes that
could pose environmental risks.  Risk assessments of transgenic crops focus
narrowly on only the intended outcomes, virtually ignoring the possibility
of unintended outcomes or side-effects. The resulting phenotypes carry
novel hazards, and regulatory agencies must address these in appropriate
manners. From an ecological perspective, transgenic crops can not be
considered substantially equivalent to conventional crops, as the effects
of trangenes are often broader than expected, with pleiotropic or gene
insertion site effects common. Workshop participants were also concerned
about the genetic constructs used to transform plants and the possible
ecological impacts from promoter and marker gene sequences.


Gene flow

The general consensus of the group is that just as it occurs between
tradtionally improved crops and wild relatives, pollen mediated gene flow
will occur between GMCs and wild relatives or conspecifics despite all
possible efforts to reduce it. Little is known about the long-term
persistence of crop genes in wild populations or about the impact of
fitness-related crop genes on the population dynamics of weedy relatives.
The main concern with trangenes that confer significant biological
advantages that may transform wild/weed plants into new or worse weeds. In
the cases of  hybridization of HRCs with populations of free living
relatives will make these plants increasingly difficult to control,
especially if they are already recognized as agricultural weeds and if they
acquire resistance to widely used herbicides. A case discussed suggested
that transgenic resistance to glufosinate is capable of introgressing from
Brassica napus into populations of weedy Brassica napa, and to persist
under natural conditions.

Another case discussed suggested that introgression with genetically
modified oats, Avena sativa, resistant to barley yellow dwarf virus (BYVD)
would confer virus resistance to wild oats, Avena fatua.  This would
release wild oats, which are more susceptible to BYVD, from natural
suppression, thus potentially triggering a more severe weed problem.  

In addition to having high levels of agrobiodiversity, many developing
countries constitute centers of genetic diversity, and in such environments
the transfer of coding traits from transgenic crops to wild or weedy
populations of these taxa and their close relatives is expected to be high.
Genetic exchange between crops and their wild relatives is common in
traditional agroecosystems and transgenic crops are bound to frequently
encounter sexually compatible plant relatives, therefore the potential for
gene exchange via pollen transfer in traditional agroecosystems is worrisome.

Until recently, gene flow risk assessment research has centered on
addressing four basic questions:
1)	Can crops and their wild relatives produce viable offspring?
2)	What is the likelihood of progeny formation under field conditions?
3)	Do the progeny survive to reproductive maturity?
4)	What is the relative fitness of the F1 compared to the parents under
field conditions?

A problem with these questions is that they center largely on probability
of gene flow events. The data have been collected using simple genetic
markers and model systems that are in most cases of too small scale, and
involve only traditionally improved crop varieties.  One must question the
usefulness of continuing to collect data that may be of limited value in
truly estimating the risk of wide-scale GM crop release. Therefore, it is
suggested that risk assessment research begin to move away from these
probabilistic models and begin to address questions relating specifically
to consequences of gene flow events in agroecosystems at scales that are
comparable to modern agricultural settings.

The problem facing the ecological community centers on the identification
of the right sets of questions that will allow a direct rebuttal to the
USDA policy that "there is not problem until a problem is identified". The
data that have been collected for most crop-wild complexes are very clear,
the likelihood of gene transfer is high when the proper conditions for such
events are met (i.e. range overlap, sexual compatibility, and flowering
time synchrony). It follows that the potential for an "identifiable
problem" should be high.  Thus, more energy and resources must be directed
towards articulating the possible consequences of gene flow events
(vertical and horizontal) in agroecosystems so that appropriate experiments
can be proposed, and gaps in the data pool be filled.  One way to address
the deficiencies in our data set is to assess the long-term effects of
pollen flow from widely used traditionally improved crops to their
sympatric, compatible relatives.  Greater understanding of the historical
consequences of gene flow will allow us to better evaluate the possible
effects of introgression of a transgene into the wild populations.
Secondly, data addressing biotic and abiotic factors that limit the
distributions and abundance of the wild relatives needs to be collected, or
more likely, retrieved from the weed science literature. Again, these data
will provide us with the means to seriously consider the potential
consequence of transgene persistence and spread. 

Ecological, economic and agronomic implications of HRCs

World-wide in 1999, transgenic herbicide resistant crops were planted on 28
million hectares. In North America, there are now commercially available
transgenic glufosinate resistant cultivars of canola and corn, and
transgenic glyphosate resistant cultivars of soybean, corn, cotton, and
canola. Bromoxynil resistant transgenic cotton has also been developed.
Published research indicates that herbicide resistance has been transferred
successfully to many other crops using genetic engineering techniques. 

Transgenic herbicide resistance in crop plants simplifies chemically based
weed management because it typically involves compounds that are active on
a very broad spectrum of weed species, yet which do not damage the crop.
Post-emergence application timing for these materials fits well with
reduced or zero-tillage production methods, which can conserve soil and
reduce fuel and tillage costs. This is why in 1998 about 44 percent of
Midwestern soybean was glyphosate resistant (Roundup Ready).

However, HRCs also have significant problems. Reliance on HRCs perpetuates
the weed resistance problems and species shifts that are common to
conventional herbicide based approaches. The use of HRCs in areas where
weedy relatives of crops are present creates the additional possibility of
crop-to-weed resistance gene transfer. Herbicide resistance becomes more of
a problem as the number of herbicide modes of action to which weeds are
exposed becomes fewer and fewer, a trend that HRCs may exacerbate due to
the dictates of the marketplace and the limits of synthetic chemistry.
Pleiotropic effects may affect the performance of HRCs, as indicated by
recent evidence of stem cracking in glyphosate tolerant soybean under high
temperature conditions. Lower yields in transgenic glyphosate resistant
soybean varieties, compared with conventional non-transgenic cultivars, may
represent pleiotropic effects or a lack of attention from plant breeders.
If consumers reject GMOs in the marketplace, use of HRCs will further
decrease the prices farmers receive for low-value commodities. 

Perhaps the greatest problem of using HRCs to solve weed problems is that
they steer efforts away from crop diversification and help to maintain
cropping systems dominated by one or two annual species. Crop
diversification can not only reduce the need for herbicides, but also
improve soil and water quality, minimize requirements for synthetic
nitrogen fertilizer, regulate insect pest and pathogen populations,
increase crop yields, and reduce yield variance. Thus, to the extent that
transgenic HRCs inhibit the adoption of diversified cropping systems that
include perennial crops, cover crops and green manure, they hinder the
development of sustainable agriculture.

Ecological risks of Bt crops

Based on the fact that more than 500 species of pests have already evolved
resistance to conventional insecticides, pests can also evolve resistance
to Bt toxins present in transgenic crops. No one questions if Bt resistance
will develop, the question is now how fast it will develop. Susceptibility
to Bt toxins can therefore be viewed as a natural resource that could be
quickly depleted by inappropriate use of Bt crops. However, cautiously
restricted use of these crops should substantially delay the evolution of
resistance. The question is whether cautious use of Bt crops is possible
given commercial pressures that have resulted in a rapid roll-out of Bt
crops reaching 9 million acres in the USA in 1997.  Will the refuge
strategy of setting aside 20-30 percent of the land to non-Bt crops work?
Can such regional plans be enforced and will it be commercially viable for
farmers?  If instead 20-30 percent of the land was devoted to growing
soybeans and corn in a strip cropping design, would similar pest control
advantages emerge from such mixed and rotational cropping systems?  Data
from the Midwest shows that Bt corn saves on some insecticide use and
yields are 2.4 bu/acre higher than conventional corn but only under high
European corn borer infestations. On the other hand organic corn growers
use no insecticides and obtain yields (4.8-9 t/ha) similar or slightly
higher than conventional farmers (5.0-7.l t/ha) .

A concern of the group was the spill over effects resulting from the
massive use of Bt toxin in cotton or other crops occupying a larger area of
the agricultural landscape, onto neighboring farmers who grow crops other
than cotton, but that share similar pest complexes. Such farmers may end up
with resistant insect populations colonizing their fields.  As Lepidopteran
pests that develop resistance to Bt cotton move to adjacent fields where
farmers use Bt as a microbial insecticide, this may render farmers
defenseless against such pest, as the biopesticide becomes ineffective thus
farmers stand losing an important biological control tool. Among those most
affected would be organic farmers who rely on Bt based microbial
insecticides for their pest management programs.  

In the case of cotton there is not demonstrated need to introduce the Bt
toxin into the crop at all, as the Lepidopteran pests of this crop are
pesticide-induced secondary pests.  Therefore, the best way to deal with
such pests is not to spray insecticides, but instead to use cultural and
biocontrol techniques.  In the Southeast, the key pest is the boll weevil,
a beetle immune to the Bt toxin. To fully assess the need for Bt cotton to
control Lepidoterans in the Southeastern USA, experimental tests need to be
conducted in areas not disrupted by insecticide misuse to determine the
real pest status of each species before the need for biotechnology or any
particular technology can be assessed. 

Bacillus thuringiensis proteins are becoming ubiquitous, highly bioactive
substances in agroecosystems present for many months. Most, if not all,
non-target herbivores colonizing Bt crops in the field, although not
lethally affected, ingest plant tissue containing Bt protein which they can
pass on to their natural enemies in a more or less processed form.
Polyphagous natural enemies that move between crop cultures are found to
frequently encounter Bt containing non-target herbivorous prey in more that
one crop during the entire season. This is a major ecological concern given
previous studies that documented that Cry1 Ab adversely affected
Chrysoperla carnea  reared on Bt corn-fed prey larvae.  These effects are
not unique to Bt crops, as researchers in Scotland found that predaceous
Coccinellidae feeding on aphids reared on GNA potatoes (containing snowdrop
lectin) had lowered fecundity than ladybugs fed on control potato aphids.
Such ladybugs lived twice as long as females fed on aphids from GNA potatoes. 

These findings are problematic for small farmers in developing countries
who rely for insect pest control, on the rich complex of predators and
parasites associated with their mixed cropping systems. Research results
showing that natural enemies can be affected directly through inter-trophic
level effects of the toxin present in Bt crops raises serious concerns
about the potential disruption of natural pest control, as polyphagous
predators that move within and between crop cultivars will encounter
Bt-containing, non-target prey throughout the crop season. Disrupted
biocontrol mechanisms will likely result in increased crop losses due to
pests or to the increased use of pesticides by farmers with consequent
health and environmental hazards. There is a clear need for tri-trophic
level studies to assess the long-term interactions of transgenic,
insecticidal plants with natural enemies.

Effects of Bt crops on the soil ecosystem  

There are many transgenic plants that are being considered, developed or
released which produce insecticidal, nematicidal, or anti-microbial
products. Due to natural wounding, senescence, root exudates, and
sloughing-off of root cells, along with tillage of plants into the soil,
soil biota will be exposed to these transgenic products. Because of the
importance of soil biota in mineralization and immobilization of nutrients,
physical and biochemical degradation of organic matter, biological control
of plant pests, and as food sources for other organisms, it is crucial to
evaluate the potential impacts of transgenic plants on soil ecosystems.
Research in this area has been quite limited but the little research
conducted has already demonstrated long term persistence of insecticidal
products (Bt and proteinase inhibitors) in soil. The insecticidal toxin
produced by Bacillus thuringiensis  subsp. kurskatki  remain active in the
soil, where it binds rapidly and tightly to clays and humic acids. The
bound toxin retains its insecticidal properties and is protected against
microbial degradation by being bound to soil particles, persisting in
various soils for at least 234 days. In another study researchers confirmed
the presence of the toxin in exudates from Bt corn and verified that it was
active in an insecticidal bioassay using larvae of the tobacco hornworm.
Given the persistence and the possible presence of exudates, there is
potential for prolonged exposure of the microbial and invertebrate
community to such toxins, and therefore studies should evaluate the effects
of transgenic plants on both microbial and invertebrate communities and the
ecological processes they mediate.  

Published research has already shown that exposure of soil organisms to
transgenci plants caused changes in population levels of collembola, and
changes in both levels and species composition of nematodes, bacteria and
fungi. Perhaps the finding of most concern from these studies is that
effects were not due to the transgenic products but rather from
unintentional changes in plant characteristics that resulted from the
process of genetic engineering. This suggests that responsible risk
assessment of transgenic plants must consider not only the engineered
traits but also attempt to account for unanticipated changes in the
engineered plant that may also impact the soil ecosystem. 

Studies need to be performed that compare soil biota and processes in
fields under sustainable agricultural practices and conventional
agricultural chemical practices with fields containing transgenic plants.
Levels and species composition of arthropods, nematodes, protozoa,
earthworms, enchytraeids, bacteria and fungi should be monitored.  When
possible, multiple methodological approaches (microscopic, culturable,
metabolic, and molecular) should be employed to limit the bias introduced
by any one method.  Efforts should be made to characterize the food webs
and trophic interactions. In addition, evaluation of key soil processes
(e.g. decomposition, nutrient cycling) should be included to determine if
any observed difference in soil biota levels or community composition are
impacting biogeochemical cycles. Finally, above-ground measurements of
plant health (e.g. biomass, fitness, phenology, morphology, chemistry) are
needed to assess the ecological significance of any changes occurring in
the soil ecosystem resulting from the exposure to transgenic plants.  

If transgenic crops substantially alter soil biota and affect processes
such as soil organic matter decomposition and mineralization, this would be
of serious concern to organic farmers and most poor farmers in the
developing world who cannot purchase or don't want to use expensive
chemical fertilizers, and that rely instead on local residues, organic
matter and especially soil organisms for soil fertility (i.e. key
invertebrate, fungal or bacterial species) which can be affected by the
soil bound toxin. Soil fertility could be dramatically reduced  if crop
leachates inhibit the activity of the soil biota and slow down natural
rates of decomposition and nutrient release.  
Virus resistant crops

Some researchers have expressed concerns about the risks of new pathogens
evolving due to transgenic viral coat proteins. In plants containing coat
protein genes, there is the possibility that such genes will be taken up by
unrelated viruses infecting the plant.  In such situations, the foreign
gene changes the coat structure of the viruses and may confer properties
such as changed methods of transmission between plants. The second
potential risk is that recombination between RNA virus and a viral RNA
inside the transgenic crop could produce a new pathogen leading to more
severe disease problems. Some researchers have shown that recombination
occurs in transgenic plants and that under certain conditions it produces a
new viral strain with an altered host range.  

A number of studies have demonstrated that plant viruses can acquire a
variety of viral genes from transgenic plants:  
o	Defective red clover necrotic mosaic virus lacking the gene enabling it
to move from cell to cell, and hence not infectious, recombined with a copy
of that gene in transgenic Nicotiana benthamiana  plants, and regenerated
infectious viruses .
o	Transgenic Brassica napus containing gene VI, a translational activator,
from the cauliflower mosaic virus (CaMV), recombined with the complementary
part of the virus missing that gene , and gave infectious virus in 100
percent of the transgenic plants.
o	The same experiment carried out in Nicotiana bigelovii  gave infectious
recombinants that expanded the host range of the virus.  
o	Nicotiana bethamiana plants expressing a segment of the cowpea chlorotic
mottle virus (CCMV) coat-protein gene recombined with defective virus
mission that gene.

As all these experiments involved recombination between defective virus and
transgene, it was thought that under natural conditions, when viruses are
not defective, no recombinant viruses would be generated .

Although many questions still remain, based on the available information on
the potential effects of virus resistant transgenic plants,  the group
highlighted the importance of six points:

o	The recombination of viral genetic information takes place constantly,
and is a driving force in viral evolution. The literature is full of
evidence of the creation of new viruses by recombination. If genetic
engineering increases the potential for recombination between viruses, as
many think is the case, novel viruses will be created.
o	Use of entire, functional genes such as coat protein, movement protein,
and replicase genes will facilitate the creation of new viruses. Defective
copies may still provide enough material for effective recombination.
o	Genetically engineered satellite RNAs may be able to be replicated by
viruses other than their host virus, which may lead to new types of
infections and could increase (or decrease) pathogenicity.  
o	Very little is known about the distribution of plant viruses in nature,
and few researchers are currently working in the area of viral ecology.
Yet, information in this area is critical to conduct proper and
scientifically defensible risk assessments of plants genetically engineered
to resist viruses.
o	We know little more about the biology of viruses in plants, in particular
in multiple infections. Some evidence indicates temporal and spatial
separation of different viruses in multiple infections in nature, so that
recombination in non-GE plants is more rare than would be found in a plant
continually expressing a viral gene.
o	Non-pathogenic viruses that make their way into the host cell, and then
can't move, may have movement facilitated by the engineered transgene,
which might serve as a movement protein. Even though they are not normally
a pathogen of that particular plant, the non-pathogenic virus may be able
to cause disease in the presence of the transgene, and/or have the
opportunity to recombine with the transgene and in this way acquire
pathogenic potential.  

Given the possibility that transgenic virus-resistant plants may broaden
the host range of some viruses or allow the production of new virus strains
through recombination and transcapsidation demands careful further
experimental investigation.

General Conclusions and Recommendations

The available scientific information allowed the group to conclude that
although no catastrophic impacts have yet been recorded from the massive
use of transgenic crops, the known and potential risks are substantial from
an ecological point of view. It was generally agreed that because of the
widespread use of transgenic crops, and the impossibility of effectively
removing them once they are released, even more effects might persist and
accumulate and eventually cause serious ecological impacts. For example
nobody can really predict the impacts that will result from the Bt toxin
that is released into the soil from roots during the growth of  thousands
of hectares of  Bt corn , or the effects to the soil and general ecosystem
from pollen during corn tasseling and as a result of the incorporation of
tons of  plant residues after crop harvesting. 

Not enough research has been done to evaluate the environmental and health
risks of transgenic crops, an unfortunate trend as most scientists feel
that such knowledge was crucial to have before biotechnological innovations
were upscaled to actual levels. There is a clear need to further assess the
severity, magnitude and scope of risks associated with the massive field
deployment of transgenic crops.

Much of the evaluation of risks must move beyond comparing GMC fields and
conventionally managed systems to include alternative cropping systems
featuring crop diversity and low-external input approaches. This will allow
real risk/benefit analysis of transgenic crops in relation to known and
effective alternatives.  

The potential for ecological risks is to a large extent "event and
context-specific".  The particular risks which may be identified for the
first wave GE offerings do no exhaust the list of potential risks from
events yet in the pipeline. By the same token, ecological risks identified
in the US or Canada may not be relevant to risks in Malaysia or Mexico -
whether due to gene flow issues or to disruption of natural pest controls
in more biodiverse environments.  Risks in a "normal" weather year may not
be predictive of those in a dry year (e.g. RR soybean stem splitting in
Georgia), or to those experienced by farmers burdened by sporadic pest
outbreaks. In short, identification and quantification of  risks seems
likely to remain an obligate and ongoing complement to the development and
release of each new GE crop.

The repeated use of transgenic crops in an area may result in cumulative
effects such as those resulting from the buildup of toxins in soils. For
this reason, risk assessment studies not only have to be of an ecological
nature in order to capture effects on ecosystem processes, but also of
sufficient duration so that probable accumulative effects can be detected.
The application of multiple methods will provide the most sensitive and
comprehensive assessment of the potential ecological impact of transgenic
crops.

Further empirical studies of the ecological impact of commercial-scale
cultivation of transgenic plants are clearly needed, particularly with
regard to the following questions:

o	Which cultivated plants have sexually compatible wild relatives that
could become troublesome weeds after inheriting fitness-related transgenes,
and to what extent will this conversion to weediness occur?
o	Will the propagation of certain transgenic plants result in the evolution
of newly resistant plant pests (microbial pathogens, insects, and weeds),
and if so, how can the evolution of these resistant biotypes be delayed or
avoided?
o	What effects will plant-produced pesticides have on the population
dynamics of non-target organisms, especially beneficial predators,
parasitoids, pollinators, components of soil food webs, and fundamental
ecological processes?

Ecologists can provide valuable input in the planning and evaluation of
high-risk genetically engineered plants, but does documenting the risks of
such crops entails the best use of scarce ecological talent?  Or should
ecologists devote their time and skills to developing the best
environmentally sound approaches to deal with real agricultural
limitations, which in many cases are management options not related to
biotechnology but rather to agroecology?

Overall the group felt that although biotechnology is an important tool, at
this point alternative solutions exist to address the problems that current
GMCs are designed to solve. The dramatic positive effects of rotations,
multiple cropping, and biological control on crop health, environmental
quality and agricultural productivity have been confirmed repeatedly by
scientific research. Biotechnology should be considered as one more tool
that can  be used, provided the ecological risks are investigated and
deemed acceptable, in conjunction with a host of other approaches to move
agriculture towards sustainability.





***************************************
Miguel A. Altieri, Ph.D.
University of California, Berkeley
ESPM-Division of Insect Biology
201 Wellman-3112
Berkeley, CA 94720-3112
Phone: 510-642-9802  FAX: 510-642-7428
Location: 215 Mulford, Berkeley campus
http://nature.berkeley.edu/~agroeco3
***************************************