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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 96 997 998 999 000 001 002 003 004 005 9 1 1 1 1 2 2 2 2 2 2 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