environmental impacts and social responses to genetically engineered crops l. lareesa wolfenbarger...

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

Level of disturbance to environment

Effe

ct o

n en

viro

nmen

tThe role of science:

what are the environmental consequences?

x x

Level of disturbance to environment

Effe

ct o

n en

viro

nmen

tSocial responses:

what consequences are acceptable?

x x

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?

No changeFurther

degradation 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

Persistence of chemicals varies

ChemicalDose

(kg/ha/yr)Half-life

(Yrs)95% Loss

(Yrs)Aldrin 1.1-3.4 0.3 3Chlordane 1.1-2.2 1.0 3.5Lindane 1.1-2.8 1.2 6.5Endrin 1.1-3.4 2.2 7Dieldrin 1.1-3.4 2.5 8DDT 1.1-2.8 2.8 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/

reintroductions• Agricultural crops• Biological control

Unintentional• Hitchhikers

Survival or Death

Reproduction or not

Self-sustaining population

Spread and persistence

Possible outcomes of biological introductions

Introductionof plants

Population dies out

Never really spreads

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.

Survival or Death

Reproduction

Self-sustaining population

Spread and persistence

Pollen flows to wild relative Hybrid formation

or not

Hybrid survival or death

Hybrid reproduction or not

Self-sustaining hybrids

Possible outcomes of biological introductions

Introductionof plant

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-sustainingpopulations

Outside of cultivation

HT Corn

Bt and GNA Potato

HT Oilseed rape

HT Sugar beet

Unlikely

Unlikely

Unlikely

Unlikely

Crop

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

Plants

Herbivores

Predators

Bigger predators

Ecological functions

Plants: primary producers

Decomposers

HerbivoresPollinators

Predators

Bigger predators

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?

0102030405060708090

100

1996199719981999200020012002200320042005

Year

% transgenic acreage

SoybeanCottonCorn

Source: Biotechnology Industry Organization and USDA

Adoption of GE crops in U.S.

Bt crops protect plants against specific insect pests

The story of Monarchs and Bt corn

0

25

50

75

100

DaysSurvival of monarch

larvae (%)

no pollennon-Bt pollenBt pollen

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

Bt corn•Production and Distribution•Pollen characterization

•Bt expression•Pollen shed (timing, duration, quantity)•Deposition and dispersal

Milkweed•Occurrence and Distribution

•(Regional, landscape, habitat, abundance in corn)

MonarchOccurrence and DistributionBehavior (oviposition preferences,phenology)

Environmental exposure Risk

Monarch•Toxic effect (lethal/sublethal)

Adapted from Sears et al. 2001.PNAS 98: 11937-11942.

Monarch survival: 9 days after onset of pollen deposition

0

20

40

60

80

100

Bt Non-Bt Non-Bt(T)

3 m outside

3 m inside

• No differences among Bt and Non-Bt sweet corn treatments

• Survival significantly decreased in presence of insecticide treatment

From Stanley-Horn et al. 2001. PNAS 98: 11931-11936

Per

cent

sur

viva

l

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

Bt corn•Production and Distribution•Pollen characterization

•Bt expression•Pollen shed (timing, duration, quantity)•Deposition and dispersal

Milkweed•Occurrence and Distribution

•(Regional, landscape, habitat, abundance in corn)

MonarchOccurrence and DistributionBehavior (oviposition preferences,phenology)

Environmental exposure Risk

Monarch•Toxic effect (lethal/sublethal)

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

0

0.5

1

1.5

2

2.5

3

3.5

1993 1994 1995 1996 1997 1998 1999 2000

CautionWarningDanger

Num

ber

of

trea

tmen

t/acr

es

Roundup ready soybeans are the best for weed management

0102030405060708090

100

1990 1995 2000 2005

Lbs. AI (x106)

ACRES SOY

Glyphosate

TOTAL HERBICIDES(Millions of Lbs AI)

Pendimethalin

Imazethapyr

Trifluralin

Fomesafen

Compiled from USDA Agriculture Chemical Usage reports 1991-2002http://usda.mannlib.cornell.edu/reports/nassr/other/pcu-bb/

Herbicide use in U.S. soybean production

Benefits from changing agricultural practices with soy

No till and conservation tillage

• Reduce erosion

• Decrease water loss

• Increase soil organic matter

Increase in No Till acreage

0

10

20

30

40

1989 1991 1993 1995 1997 2000

Year

% acres in US with no

tillage

Roundup Ready soy introduced

How do we predict future impacts?

• Use past experience• Expect tradeoffs• Evaluate on a case-

by-case basis• Remember that

genetic engineering is a tool