Transcript Environmental impacts and social responses to genetically

Environmental impacts and
social responses to genetically
engineered crops
L. LaReesa Wolfenbarger
University of Nebraska at Omaha
Potential benefits of transgenic
organisms: environmental, health, social
Why so much potential?
• Genetic engineering provides a greater
range of possibilities for transferring
desired traits into organisms.
The potential is biological novelty
• Genetic engineering provides a greater
range of possibilities for transferring
desired traits into organisms.
– A greater diversity of organisms may be
modified
– The quantity and quality of traits are limited
by the identification of useful genes and
are not constrained by existing variation
among interbreeding relatives
Are they good or bad for the
environment?
Yes, according to the plant
biotechnology industry
No, according to
environmental activist groups
Answer
• Environmental impacts vary on a case
by case basis
• Environmental tradeoffs most likely
• Values and not science determine
whether outcome is good or bad
Effect on environment
The role of science:
what are the environmental consequences?
x x
L
J
Level of disturbance to environment
Effect on environment
Social responses:
what consequences are acceptable?
x x
L
J
Level of disturbance to environment
One point of agreement
• Case-by-case environmental impacts
Overview
• Possible environmental consequences
• Environmental impacts of Bt corn and
Round up Ready soybean
• Social responses to these impacts
• Predicting environmental impacts of
future GE crops
What are the possible
environmental consequences of
GE crops?
Further
degradation
No change
Improvement
Using past experience to think of
possible effects
• Past experience with introductions of
chemicals
– Vary in toxicity, persistence
– Lethal, Sublethal, No effect
• Past introductions of species: intentional and
unintentional
– Unwanted spread of an organism or its
genes
Chemicals and rat mortality
Chemical Substance
Sucrose
Sodium chloride
Malathion
DDT
Nicotine
TCDD
Oral LD50 (mg/kg)
30,000
3,750
2,000
200
50
0.01
Persistence of chemicals varies
Dose
Chemical (kg/ha/yr)
Aldrin
1.1-3.4
Chlordane 1.1-2.2
Lindane
1.1-2.8
Endrin
1.1-3.4
Dieldrin
1.1-3.4
DDT
1.1-2.8
Half-life
(Yrs)
0.3
1.0
1.2
2.2
2.5
2.8
95% Loss
(Yrs)
3
3.5
6.5
7
8
10
Using past experience to think of
possible effects
• Past experience with introductions of
chemicals
• Past introductions of species: intentional and
unintentional
Past biological introductions
•
•
•
•
Intentional
Landscaping
Restoration/reintrod
uctions
Agricultural crops
Biological control
Unintentional
• Hitchhikers
Possible outcomes of biological introductions
Introduction
of plants
Survival or Death
Reproduction or not
Population dies out
Self-sustaining population
Never really spreads
Spread and persistence
Kudzu spread and persists beyond
its intended purpose
Can ecologists predict how
species will spread
• Can identify plants characteristics in
common
BUT
• Lag times can occur.
• Repeated introductions have different
results.
• Biological organisms can evolve.
Possible outcomes of biological introductions
Introduction
of plant
Pollen flows to
wild relative
Survival or Death
Hybrid formation
or not
Hybrid survival or death
Reproduction
Hybrid reproduction or not
Self-sustaining population
Self-sustaining hybrids
Spread and persistence
Gene flow from
crops to wild
relatives is
implicated in
enhanced
weediness in wild
relatives of 7 of
the world’s 13
most important
crops.
(Ellstrand, 1999)
Are current GE crops likely to spread?
Self-sustaining
populations
Outside of cultivation
Crop
HT Oilseed rape
Unlikely
HT Corn
Unlikely
Bt and GNA Potato
Unlikely
HT Sugar beet
Unlikely
Crawley et al. 2001. Nature 409: 682-683.
Summary of possible
environmental impacts
• Improvements if less toxic and does not
spread outside of cultivation
• Degradation if more toxic or spreads
uncontrollably
Less toxic to what?
Spread where?
The environment: Biodiversity
and interactions
Bigger predators
Predators
Herbivores
Plants
Ecological functions
Bigger predators
Predators
Pollinators
Herbivores
Plants: primary
producers
Decomposers
Impacts on the environment
occur through alterations of…
• what species are present
• how many individuals of each species
• the ecological function(s) of a species in
an ecosystem
• the biological interactions affecting a
species’ function in the environment
Humans are part of the
environment
• herbivores
• predators
• environmental engineers
Environments are a continuum
Grassland
environment
Agricultural
environment
Forest
environment
What general factors define the
context?
• The transgenic organism
• Where it is introduced
– environment
• Baseline for comparison and evaluation
– What GE crop will replace: regional
agricultural practices
How a GE plant will interact with
the environment
• Presence of transgenic crop
or its transgene
– plant above ground
– roots
– decomposing tissue
– pollen drift
– gene flow to wild relatives in
natural ecosystem
Other ways introducing a GE crop
will affect the environment
• Changes in agricultural
practices associated with
adoption of a transgenic
crop
– Pesticide use patterns
– Amount of agricultural land
– Tillage practices
– Crop diversity/rotation
Phytoremediation
• Remove and
sequester toxic
heavy metals
• Transform pollutants
into less toxic forms
What do we know about
environmental impacts of
current GE crops?
% transgenic acreage
Adoption of GE crops in U.S.
100
90
80
70
60
50
40
30
20
10
0
Soybean
Cotton
Corn
6 97 98 99 00 01 02 03 04 05
9
19 19 19 19 20 20 20 20 20 20
Year
Source: Biotechnology Industry Organization and USDA
Bt crops protect plants against
specific insect pests
The story of Monarchs and Bt corn
Survival of monarch
larvae (%)
100
75
no pollen
non-Bt pollen
Bt pollen
50
25
0
Days
We saw the findings as an
illustration of how superficial
risk assessment [for
genetically modified foods]
was...The question still
remains, would this science
have been done if
the monarch wasn’t such a
beautiful butterfly?”
We saw an embargoed copy of
a Cornell press release where
we thought the risk seemed
exaggerated,”
Components of risk assessment
for monarch butterflies
Monarch
Monarch
Occurrence and Distribution
Behavior (oviposition preferences,
phenology)
•Toxic effect
(lethal/sublethal)
Environmental exposure
Bt corn
•Production and Distribution
•Pollen characterization
•Bt expression
•Pollen shed (timing, duration,
quantity)
•Deposition and dispersal
Risk
Milkweed
•Occurrence and Distribution
•(Regional, landscape, habitat,
abundance in corn)
Adapted from Sears et al. 2001.
PNAS 98: 11937-11942.
Monarch survival: 9 days after
onset of pollen deposition
• No differences
among Bt and Non3 m inside
Bt sweet corn
treatments
• Survival significantly
decreased in
presence of
insecticide treatment
100
Percent survival
3 m outside
80
60
40
20
0
Bt
Non-Bt Non-Bt
(T)
From Stanley-Horn et al. 2001. PNAS 98: 11931-11936
Studies with Bt corn underscore
importance of context
• Susceptibility of butterfly and moth
species varies
• Exposure varies geographically and
locally
• Susceptibility of lacewings (predatory
insect) varies with prey species
Results of formal risk
assessment
• The six studies published in PNAS
showed there was little risk to monarch
larvae from the two most commonly
grown types of Bt corn because the
pollen isn’t toxic in the concentrations
that monarch larvae would encounter in
the fields.
Components of risk assessment
for monarch butterflies
Monarch
Monarch
Occurrence and Distribution
Behavior (oviposition preferences,
phenology)
•Toxic effect
(lethal/sublethal)
Environmental exposure
Bt corn
•Production and Distribution
•Pollen characterization
•Bt expression
•Pollen shed (timing, duration,
quantity)
•Deposition and dispersal
Risk
Milkweed
•Occurrence and Distribution
•(Regional, landscape, habitat,
abundance in corn)
Adapted from Sears et al. 2001.
PNAS 98: 11937-11942.
Responses to EPA’s decision
“I felt that the conclusions
made from a one year
study that excluded
anthers were
premature,” Obrycki
says. “That’s why we
requested that EPA
shorten the
reauthorization period
until we had data from
subsequent studies.”
• the studies do not
rule out very small
effects, long-term or
sublethal effects
Epilogue
• Concern about
ingestion of other
plant parts
• Longer term studies
occurring
• Registration will
expire in 2006
My response and questions
• subtle effects seem likely
• Should this change the registration?
– no, minimize impacts on monarchs
• What if a broader number of butterfly
species are affected?
Reduced impacts from pesticides
Insecticide use in cotton
Number of
treatment/acres
3.5
3
2.5
Caution
Warning
Danger
2
1.5
1
0.5
0
1993 1994 1995 1996 1997 1998 1999 2000
Roundup ready soybeans are the best for
weed management
Lbs. AI (x106)
Herbicide use in U.S. soybean
production
100
90
80
70
60
50
40
30
20
10
0
1990
ACRES SOY
Glyphosate
TOTAL HERBICIDES
(Millions of Lbs AI)
Pendimethalin
Imazethapyr
Trifluralin
Fomesafen
1995
2000
2005
Compiled from USDA Agriculture Chemical Usage reports 1991-2002
http://usda.mannlib.cornell.edu/reports/nassr/other/pcu-bb/
Benefits from changing
agricultural practices with soy
No till and conservation tillage
• Reduce
erosion
• Decrease
water loss
• Increase soil
organic matter
% acres in US with no
tillage
Increase in No Till acreage
40
30
20
10
0
1989
1991
1993
Roundup
Ready soy
introduced
1995
Year
1997
2000
How do we predict future
impacts?
• Use past experience
• Expect tradeoffs
• Evaluate on a caseby-case basis
• Remember that
genetic engineering
is a tool