Global Impact of Biotech Crops: Environmental Effects, 1996-2008
Graham Brookes and Peter Barfoot
PG Economics Ltd, Dorchester, UK
This article updates the assessment of the impact commercialized agricultural biotechnology is having on global agriculture from an environmental perspective. It focuses on the impact of changes in pesticide use and greenhouse gas emissions arising from the use of biotech crops. The technology has reduced pesticide spraying by 352 million kg (-8.4%) and, as a result, decreased the environmental impact associated with herbicide and insecticide use on these crops (as measured by the indicator the environmental impact quotient) by 16.3%. The technology has also significantly reduced the release of greenhouse gas emissions from this cropping area, which, in 2008, was equivalent to removing 6.9 million cars from the roads.
Key words: pesticide, active ingredient, environmental impact quotient, carbon sequestration, biotech crops, no tillage.Introduction
This study presents the findings of research into the global environmental impact of biotech crops since their commercial introduction in 1996. It updates the findings of earlier analyses presented by the authors in AgBioForum 8(2&3), 9(3), and 11(1).1
The environmental impact analysis undertaken focuses on the impacts associated with changes in the amount of insecticides and herbicides applied to the biotech crops relative to conventionally grown alternatives. The analysis also examines the contribution of biotech crops towards reducing global greenhouse gas (GHG) emissions.
The analysis is mostly based on that of existing farm-level impact data from biotech crops. Primary data for impacts of commercial biotech cultivation on both pesticide usage and greenhouse gas emissions is, however, limited and is not available for every crop, in every year and for each country. Nevertheless, all identified, representative, previous research has been utilized. This has been used as the basis for the analysis presented, although, where relevant, primary analysis has been undertaken from base data.
Environmental Impacts from Insecticide and Herbicide Use Changes
Assessment of the impact of biotech crops on insecticide and herbicide use requires comparisons of the respective weed- and pest-control measures used on biotech versus the ‘conventional alternative’ form of production. This presents a number of challenges relating to availability and representativeness. Comparison data ideally derives from farm-level surveys, which collect usage data on the different forms of production. A search of literature on biotech crop impact on insecticide or herbicide use at the trait, local, regional, or national level shows that the number of studies exploring these issues is limited (e.g., Pray, Huang, Hu, & Rozelle, 2002; Qaim & De Janvry, 2005; Qaim & Traxler, 2002) with even fewer (e.g., Brookes, 2003, 2005), providing data to the pesticide (active ingredient) level. Second, national-level pesticide usage survey data is also extremely limited; in fact, there are no published annual pesticide usage surveys conducted by national authorities in any of the countries currently growing biotech traits, and the only country in which pesticide usage data is collected (by private market-research companies) on an annual basis and which allows a comparison between biotech and conventional crops to be made is the United States.2
Unfortunately, even where national survey data is available on usage, the data on conventional crop usage may fail to be reasonably representative of what herbicides and insecticides might be expected to be used in the absence of biotechnology. When biotech traits dominate total production (e.g., for soybeans, corn, cotton, and canola in the United States since the early 2000s), the conventional cropping dataset used to identify pesticide use relates to a relatively small share of total crop area and therefore is likely to underestimate what usage would probably be in the absence of biotechnology. The reasons why this conventional cropping dataset is unrepresentative of the levels of pesticide use that might reasonably be expected to be used in the absence of biotechnology include the following.
While the levels of pest and weed problems/damage vary by year, region, and within region, farmers who continue to farm conventionally are often those with relatively low levels of pest or weed problems, and hence see little, if any, economic benefit from using the biotech traits targeted at these agronomic problems. Their pesticide usage levels therefore tend to be below the levels that would reasonably be expected to be used to control these weeds and pests on an average farm. A good example to illustrate this relates to the US cotton crop where, for example, in 2008, nearly half of the conventional cotton crop was located in Texas. Here, levels of bollworm pests (the main target of biotech insect-resistant cotton) tend to be consistently low, and cotton farming systems are traditionally of an extensive, low input nature (e.g., the average cotton yield in Texas was about 82% of the US average in 2008).
Some of the farms continuing to use conventional (non-biotech) seed traditionally use extensive, low-intensity production methods (including organic) in which limited (below average) use of pesticides is a feature (see, for example, the Texas cotton example above). The usage pattern of this subset of growers is therefore likely to understate usage for the majority of farmers if all crops were conventional.
Many of the farmers using biotech traits have experienced improvements in pest and weed control from using this technology relative to the conventional control methods previously used. If these farmers were to now switch back to using conventional techniques—based wholly on pesticides—it is likely that most would wish to maintain the levels of pest/weed control delivered with use of the biotech traits and therefore would use higher levels of pesticide than they did in the pre-biotech crop days.
To overcome these problems in the analysis of pesticide use changes arising from the adoption of biotech crops (i.e., where biotech traits account for the majority of total plantings), presented in this article,3 actual recorded usage levels for the biotech crops are used (based on survey data), with the conventional alternative (counterfactual situation) identified based on opinion from extension advisors and industry specialists as to what farmers might reasonably be expected to use in terms of crop protection practices and usage levels of pesticide.4 This methodology has been used by others, for example Johnson and Strom (2007). Details of how this methodology has been applied to the 2008 calculations, sources used for each trait/country combination examined and examples of typical conventional versus biotech pesticide applications are provided in Appendices A and B.
The most common way in which changes in pesticide use with biotech crops has been presented in the literature has been in terms of the volume (quantity) of pesticide applied. While comparisons of total pesticide volume used in biotech and conventional crop production systems are a useful indicator of associated environmental impacts, amount of active ingredient used is an imperfect measure because it does not account for differences in the specific pest-control programs used in biotech and conventional cropping systems. For example, different specific products used in biotech versus conventional crop systems, differences in the rate of pesticides used for efficacy, and differences in the environmental characteristics (mobility, persistence, etc.) are masked in general comparisons of total pesticide volumes used.
In this article, the pesticide-related environmental impact changes associated with biotech crop adoption are examined in terms of changes in the volume (amount) of active ingredient applied but supplemented by the use of an alternative indicator, developed at Cornell University in the 1990s: the environmental impact quotient (EIQ). The EIQ indicator, developed by Kovach, Petzoldt, and Degni, and Tette (1992) and updated annually, effectively integrates the various environmental impacts of individual pesticides into a single ‘field value per hectare.’ The EIQ value is multiplied by the amount of pesticide active ingredient (ai) used per hectare to produce a field EIQ value. For example, the EIQ rating for glyphosate is 15.33. By using this rating multiplied by the amount of glyphosate used per hectare (e.g., a hypothetical example of 1.1 kg applied per ha), the field EIQ value for glyphosate would be equivalent to 16.86/ha.
The EIQ indicator used is therefore a comparison of the field EIQ/ha for conventional versus biotech crop production systems, with the total environmental impact or load of each system, a direct function of respective field EIQ/ha values and the area planted to each type of production (biotech versus conventional). The use of environmental indicators is commonly used by researchers, and the EIQ indicator has been, for example, cited by Brimner, Gallivan, and Stephenson (2004)—in a study comparing the environmental impacts of biotech and conventional canola—and by Kleiter et al. (2005).
The EIQ indicator provides an improved assessment of the impact of biotech crops on the environment when compared to only examining changes in volume of active ingredient applied, because it draws on some of the key toxicity and environmental exposure data related to individual products, as applicable to impacts on farm workers, consumers, and ecology. Readers should, however, note that the EIQ is an indicator only and does not take into account all environmental issues and impacts. It is therefore not a comprehensive indicator. Detailed examples of the relevant amounts of active ingredient used and their associated field EIQ values for biotech versus conventional crops for the year 2008 are presented in Appendix B.
Biotech traits have contributed to a significant reduction in the environmental impact associated with insecticide and herbicide use on the areas devoted to biotech crops (Table 1). Since 1996, the use of pesticides on the biotech crop area was reduced by 352 million kg of active ingredient (8.4% reduction), and the environmental impact associated with herbicide and insecticide use on these crops—as measured by the EIQ indicator—fell by 16.3%. In absolute terms, the largest environmental gain has been associated with the adoption of GM IR cotton and reflects the significant reduction in insecticide use that the technology has allowed, in what has traditionally been an intensive user of insecticides. The volume of herbicides used in biotech soybean crops also decreased by 50 million kg (1996-2008), a 3% reduction, while the overall environmental impact associated with herbicide use on these crops decreased by a significantly larger 16.6%. This highlights the switch in herbicides used with most GM HT crops to active ingredients with a more environmentally benign profile than the ones generally used on conventional crops.
Table 1. Impact of changes in the use of herbicides and insecticides from growing biotech crops globally 1996-2008.
Important environmental gains have also arisen in the maize and canola sectors. In the maize sector, herbicide and insecticide use decreased by 141.5 million kg and the associated environmental impact of pesticide use on this crop area decreased due to a combination of reduced insecticide use (29.4%) and a switch to more environmentally benign herbicides (8.5%). In the canola sector, farmers reduced herbicide use by 13.7 million kg (a 17.6% reduction) and the associated environmental impact of herbicide use on this crop area fell by 24.3% due to a switch to more environmentally benign herbicides.
In terms of the division of the environmental benefits associated with less insecticide and herbicide use for farmers in developing countries relative to farmers in developed countries, Table 2 shows roughly a 50% split of the environmental benefits (1996-2008) in developed and developing countries. Three quarters of the environmental gains in developing countries have been from the use of GM IR cotton.
Table 2. Biotech crop environmental benefits from lower insecticide and herbicide use 1996-2008: Developing versus developed countries.
Impact on Greenhouse Gas Emissions
The methodology used to assess impact on greenhouse gas emissions combines reviews of literature relating to changes in fuel and tillage systems and carbon emissions coupled with evidence from the development of relevant biotech crops and their impact on both fuel use and tillage systems. Reductions in the level of GHG emissions associated with the adoption of biotech crops is acknowledged in a wide body of literature (CTIC, 2002; Fabrizzi, Morónc, & García, 2003; Jasa, 2002; Johnson et al., 2005; Lazarus & Selley, 2005; Liebig et al., 2005; Reicosky, 1995; Robertson, Paul, & Harwood, 2000; West & Post, 2002). First, biotech crops contribute to a reduction in fuel use due to less frequent herbicide or insecticide applications and a reduction in the energy use in soil cultivation. For example, Lazarus and Selley (2005) estimated that one pesticide spray application uses 1.045 liters of fuel, which is equivalent to 2.87 kg/ha of carbon dioxide emissions. In this analysis, we used the conservative assumption that only GM IR crops reduced spray applications with the number of spray applications of herbicides remaining the same for conventional production systems.5
In addition, there has been a shift from conventional tillage to reduced/no till. This has had a marked impact on tractor fuel consumption due to energy-intensive cultivation methods being replaced with no/reduced tillage and herbicide-based weed control systems. The GM HT crop where this is most evident is GM HT soybeans. Here, adoption of the technology has made an important contribution to facilitating the adoption of reduced or no-tillage farming.6 Before the introduction of GM HT soybean cultivars, no-tillage (NT) systems were practiced by some farmers using a number of herbicides and with varying degrees of success. The opportunity for growers to control weeds with a non-residual foliar herbicide as a “burndown” pre-seeding treatment followed by a post-emergent treatment when the soybean crop became established has made the NT systems more reliable, technically viable, and commercially attractive. These technical advantages combined with the cost advantages have contributed to the rapid adoption of GM HT cultivars and the near doubling of the NT soybean area in the United States (also more than a five-fold increase in Argentina). In both countries, GM HT soybeans are estimated to account for more than 95% of the NT soybean crop area in 2007/8.
Substantial growth in NT production systems have also occurred in Canada, where the NT canola area increased from 0.8 million ha to 2.6 million ha (equal to about half of the total canola area) between 1996 and 2005 (95% of the NT canola area is planted with GM HT cultivars). Similarly the area planted to NT in the US cotton crop increased from 0.2 million ha to 1 million ha over the same period (of which 86% is planted to GM HT cultivars) and has remained at this share of the total crop in 2007 and 2008.
The fuel savings resulting from changes in tillage systems used in this article are drawn from estimates from studies by Jasa (2002), CTIC (2002), and the University of Illinois (2006). The adoption of NT farming systems is estimated to reduce cultivation fuel usage by 32.3 liters/ha compared with traditional conventional tillage (CT; which has an average usage of 43.7 liters/ha) and by 19.33 liters/ha compared with (the average of) reduced tillage (RT) cultivation methods (which has an average usage of 30.72 liters/ha). In turn, this results in reductions of carbon dioxide emissions of 88.81 kg/ha for NT relative to CT and 35.66 kg/ha for RT relative to CT.7
Secondly, the use of ‘no-till’ and ‘reduced-till’ farming systems that utilize less plowing increase the amount of organic carbon in the form of crop residue that is stored or sequestered in the soil. This carbon sequestration reduces carbon dioxide emissions into the environment. Rates of carbon sequestration have been calculated for cropping systems using normal tillage and reduced tillage and these were incorporated in the analysis on how GM crop adoption has played an important facilitating role in increasing carbon sequestration, and ultimately, on reducing the release of carbon dioxide into the atmosphere. Of course, the amount of carbon sequestered varies by soil type, cropping system, and eco-region. In North America, the Intergovernmental Panel on Climate Change (IPCC, 2006) estimates that the conversion from conventional-tillage to no-tillage systems stores between 50 kg carbon/ha-1 yr and 1,300 kg carbon/ha-1 yr (average 300 kg carbon/ha-1 yr). In the analysis presented below, a conservative saving of 300 kg carbon/ha-1 yr was applied to all NT agriculture and 100 kg carbon/ha-1 yr was applied to RT agriculture. Where some countries aggregate their no- and reduced-till data (e.g., Argentina), the reduced-tillage saving value of 100 kg carbon/ha-1 yr was used. One kg of carbon sequestered is equivalent to 3.67 kg of carbon dioxide. These assumptions were applied to the reduced pesticide spray applications data on GM IR crops, derived from separate analysis and reviews of farm income literature impacts by the authors (see Brookes & Barfoot, 2009a) and the GM HT crop areas using no/reduced tillage (limited to the GM HT soybean crops in North and South America and GM HT canola crop in Canada).8
The United States: Over the 1996-2008 period, the area of soybeans cultivated in the United States increased rapidly from 25.98 million ha to 30.21 million ha. Over the same period, the area planted using conventional tillage is estimated to have fallen by 21.3% (from 7.5 million ha to 5.9 million ha), while the area planted using NT has increased by 62.3% (from 7.7 million ha to 12.5 million ha).
The most rapid rate of adoption of the GM HT technology has been by growers using NT systems (GM HT cultivars accounting for an estimated 99% of total NT soybeans in 2008). This compares with conventional-tillage systems for soybeans, where GM HT cultivars account for about 79% of total conventional-tillage soybean plantings. The importance of GM HT soybeans in the adoption of a NT system has also been confirmed by an American Soybean Association study (ASA, 2001) of conservation tillage. This study found that the availability of GM HT soybeans has facilitated and encouraged farmers to implement reduced-tillage practices; a majority of growers surveyed indicated that GM HT soybean technology had been the factor of greatest influence in their adoption of RT practices.
Based on the soybean crop area planted by tillage system, type of seed planted (GM and conventional) and applying the fuel usage consumption rates referred to in the methodology section,9 the total consumption of tractor fuel has increased by only 2.1% (15.9 million liters)—from 746.4 to 762.4 million liters (1996 to 2008)—while the area planted increased by 16.3%, some 4.3 million ha. Over the same period, the average fuel usage fell 12.2%—from 28.7 liters/ha to 25.2 liters/ha. A comparison of biotech versus conventional production systems shows that in 2008, the average tillage fuel consumption on the biotech planted area was 24.3 liters/ha compared to 36.5 liters/ha for the conventional crop (primarily because of differences in the share of NT plantings).
The cumulative permanent reduction in tillage fuel use in US soybeans is summarized in Table 3. This amounted to a reduction in tillage fuel usage of 834.7 million liters, which equates to a reduction in carbon dioxide emission of 2,295.3 million kg.
Table 3. US soybeans: Permanent reduction in tractor fuel consumption and CO2 emissions 1996-2008.
Based on the crop area planted by tillage system and type of seed planted (biotech and conventional) and using estimates of the soil carbon sequestered by tillage system for corn and soybeans in continuous rotation (the NT system is assumed to store 300 kg of carbon/ha/year, the RT system assumed to store 100 kg carbon/ha/year, and the CT system assumed to release 100 kg carbon/ha/year),10 our estimates of total soil carbon sequestered are (Table 4):
Table 4. US soybeans: Potential soil carbon sequestration (1996 to 2008).
Cumulatively, since 1996 the increase in soil carbon due to the increase in NT and RT in US soybean production systems has been 10,370 million kg of carbon which, in terms of carbon dioxide emission equates to a saving of 38,057 million kg of carbon dioxide that would otherwise have been released into the atmosphere (Table 5). This estimate does not, however, take into consideration the potential loss in carbon sequestration that arises when some farmers return to conventional tillage and therefore should be treated as a maximum potential rather than an achieved level.
Table 5. US soybeans: Potential additional soil carbon sequestration attributable to NT/RT systems (1996 to 2008).
Argentina: Since 1996, the area planted to soybeans in Argentina has increased by 188% (from 5.9 to 17 million ha). Over the same period, the area planted using NT and RT practices also increased by an estimated 672%, from 2.07 to 15.98 million ha, while the area planted using CT decreased 73%, from 3.8 to 1.02 million ha.
As in the United States, a key driver for the growth in NT soybean production has been the availability of GM HT soybean cultivars, which, in 2008, accounted for 97.8% of the total Argentine soybean area.
Between 1996 and 2008 total fuel consumption associated with soybean cultivation increased by an estimated 169.6 million liters (80.2%), from 211.6 to 381.2 million liters/year. However, during this period the average quantity of fuel used per ha fell 37.34% from 35.8 to 22.4 liters/ha, due predominantly to the widespread use of GM HT soybean cultivars and NT/RT systems. If the proportion of NT/RT soybeans in 2008 (applicable to the total 2008 area planted) had remained at the 1996 level, an additional 1,635.9 million liters of fuel would have been used. At this level of fuel usage, an additional 4,498.79 million kg of carbon dioxide would have otherwise been released into the atmosphere (Table 6).
Table 6. Argentine soybeans: Permanent reduction in tractor fuel consumption and reduction in CO2 emissions.
Applying a conservative estimate of soil carbon retention of 150 kg/carbon/ha/yr for NT/RT soybean cropping in Argentina (tillage data in Argentina does not differentiate between NT and RT), a cumulative total of 11,927.8 million kg of carbon—which equates to a saving of 43,775.1 million kg of carbon dioxide—has been retained in the soil that would otherwise have been released into the atmosphere (Table 7).
Table 7. Argentine soybeans: Potential additional soil carbon sequestration (1996 to 2008).
Paraguay and Uruguay: NT/RT systems have also become important in soybean production in both Paraguay and Uruguay, where the majority of production in both countries are reported by industry sources to use NT/RT systems.
Using the findings and assumptions applied to Argentina (see above), the savings in fuel consumption for soybean production between 1996 and 2008 (associated with changes in NT/RT systems, the adoption of GM HT technology and comparing the proportion of NT/RT soybeans in 2008 relative to the 1996 level) has possibly amounted to 195.9 million liters. At this level of fuel saving, the reduction in the level of carbon dioxide released into the atmosphere has probably been 538.7 million kg. Applying the same rate of soil carbon retention for NT/RT soybeans as Argentina, the cumulative increase in soil carbon since 1996—due to the increase in NT/RT in Paraguay and Uruguay soybean production systems—has been 2,163.2 million kg of carbon. In terms of carbon dioxide emission, this equates to a saving of 7,938.94 million kg of carbon dioxide that may otherwise have been released into the atmosphere.
The analysis presented below relates to Canada only and does not include the US GM HT canola crop. This reflects the lack of information about the level of NT/RT in the US canola crop. Also, the area devoted to GM HT canola in the United States is relatively small by comparison to the corresponding area in Canada (0.39 million ha in the United States in 2008 compared to 5.4 million ha in Canada).
Since 1996 the cumulative permanent reduction in tillage fuel use in Canadian canola is estimated at 347.5 million liters, which equates to reduction in carbon dioxide emission of 955.39 million kg (Table 8).
Table 8. Canadian canola: Permanent reduction in tractor fuel consumption and CO2 emissions 1996-2008.
In terms of the increase in soil carbon associated with the increase in NT and RT in Canadian canola production, the estimated values are summarized in Table 9. The cumulative increase in soil carbon equals 3,227 million kg of carbon, which in terms of carbon dioxide emission equates to a saving of 11,842 million kg of carbon dioxide that would otherwise have been released into the atmosphere.
Table 9. Canada canola: Potential additional soil carbon sequestration (1996 to 2008).
Herbicide-tolerant Cotton and Maize
The contribution to reduced levels of carbon release arising from the adoption of GM HT maize and cotton is likely to have been marginal, and hence no assessments are presented. This conclusion is based on the following.
The cultivation of GM IR cotton has resulted in a significant reduction in the number of insecticide spray applications (e.g., Gianessi & Carpenter, 1999). During the period 1996 to 2008, the global cotton area planted with GM IR cultivars (excluding China and India)12 has increased from 0.86 million ha to 3.94 million ha in 2006 before falling back to 2.41 million ha in 2008.13 Based on a conservative estimate of four fewer insecticide sprays being required for the cultivation of GM IR cotton relative to conventional cotton and applying this to the global area (excluding China and India) of GM IR cotton over the period 1996-2008 suggests that there has been a reduction of 119.6 million ha of cotton being sprayed. The cumulative saving in tractor fuel consumption has been 124.99 million liters. This represents a permanent reduction in carbon dioxide emissions of 344 million kg (Table 10).
Table 10. Permanent reduction in global tractor fuel consumption and CO2 emissions resulting from the cultivation of GM IR cotton 1996-2008.
No analysis of the possible contribution to reduced level of carbon sequestration from the adoption of GM IR maize (via fewer insecticide spray runs) and the adoption of corn rootworm (CRW) resistant maize is presented. This is because the impact of using these technologies on carbon sequestration is likely to have been small for the following reasons.
The analysis of pesticide use changes arising from the adoption of biotech crops shows that there have been important environmental benefits, amounting to 352 million kg less pesticide use by growers (an 8.4% reduction in the amount of active ingredient applied). As weight of active ingredient applied is a fairly crude measure of environmental impact, the analysis considered impacts using an alternative (more rounded) measure, known as the EIQ. Based on this, the environmental benefits have been more significant at a 16.3% reduction in the environmental impact associated with insecticide and herbicide use on the global crop area planted to biotech traits (1996-2008). The most significant environmental benefits derived have been associated with the adoption of GM IR cotton, which has resulted in a substantial reduction in insecticide applications on cotton. There have also been important environmental gains associated with the adoption of GM HT technology, which has seen a switch to the use of more environmentally benign active ingredients.
The analysis also shows that biotechnology trait adoption has made important contributions to reducing GHG emissions associated with cropping agriculture, and a summary of the total carbon sequestration impact of GM crops is presented in Table 11. This shows that the permanent savings in carbon dioxide emissions (arising from reduced fuel use of 3,137 million liters of fuel) since 1996 have been about 8,632 million kg and the additional amount of soil carbon sequestered since 1996 has been equivalent to 101,613 million tonnes of carbon dioxide that has not been released into the global atmosphere.14 The reader should, however, note that these soil carbon savings are based on saving arising from the rapid adoption of NT/RT farming systems in North and South America for which the availability of GM HT technology has been cited by many farmers as an important facilitator. GM HT technology has therefore probably been an important contributor to this increase in soil carbon sequestration but is not the only factor of influence. Other influences, such as the availability of relatively cheap generic glyphosate (the real price of glyphosate fell threefold between 1995 and 2000 once patent protection for the product expired), have also been important, as illustrated by the rapid adoption of NT/RT production systems in the Brazilian soybean sector, largely in the absence of the GM HT technology.15 Cumulatively the amount of carbon sequestered may be higher than these estimates due to year-on-year benefits to soil quality; however, equally with only an estimated 15-25% of the crop area in continuous NT systems, it is likely that the total cumulative soil sequestration gains have been lower. Nevertheless, it is not possible to estimate cumulative soil sequestration gains that take into account reversions to conventional tillage because of the lack of detailed, disaggregated farm- and field-level tillage data for the 1996-2008 period. Consequently, the estimate provided above of 101,613 million tonnes of carbon dioxide not released into the atmosphere should be treated with caution and clearly represents a potential maximum rather than a realized level.
Table 11. Summary of carbon sequestration impact 1996-2008.
Further examining the context of the carbon sequestration benefits, Table 12 shows the carbon dioxide equivalent savings associated with planting of biotech crops for the latest year (2008) in terms of the number of car-use equivalents. This shows that in 2008, the permanent carbon dioxide savings from reduced fuel use was the equivalent of removing nearly 0.534 million cars from the road for a year, and the additional soil carbon sequestration gains were equivalent to removing nearly 6.4 million cars from the roads. In total, biotech crop-related carbon dioxide emission savings in 2008 were equal to the removal from the roads of nearly 6.9 million cars, equal to about 26% of all registered private cars in the United Kingdom.
Table 12. Context of carbon sequestration impact 2008: Car equivalents.
The impacts identified in this article are, however, probably conservative, reflecting the limited availability of relevant data and conservative assumptions used. In addition, the analysis examines only a limited number of environmental indicators. As such, subsequent research of the environmental impact might usefully include additional environmental indicators such as impact on soil erosion.
1 Readers should note that some data presented in this article are not directly comparable with data presented in previous articles because the current article takes into account the availability of new data and analysis (including revisions to data for earlier years).
2 The US Department of Agriculture also conducts pesticide-usage surveys, but these are not conducted on an annual basis (e.g., the last time corn was included was 2005) and do not disaggregate usage by production type (biotech versus conventional).
4 In other words, Brookes and Barfoot draw on the findings of work by various researchers at the National Center for Food and Agriculture Policy (Carpenter & Gianessi, 1999; Johnson & Strom, 2007; Sankula & Blumenthal, 2003, 2006; also see http://www.ncfap.org). This work consults with in excess of 50 extension advisors in almost all of the states growing corn, cotton, and soybeans and therefore provides a reasonably representative perspective on likely usage patterns.
5 Evidence from different countries varies, with some countries exhibiting on average no change and others showing a small net reduction in the number of spray runs.
8 Due to the likely small-scale impact and/or lack of tillage-specific data relating to GM HT maize and cotton crops (and the US GM HT canola crop), analysis of possible GHG emission reductions in these crops have not been included. The no/reduced-tillage areas to which these soil carbon reductions were applied were limited to the increase in the area planted to no/reduced tillage in each country since GM HT technology has been commercially available. In this way, the authors have tried to avoid attributing no/reduced-tillage soil carbon sequestration gains to GM HT technology on cropping areas that were using no/reduced-tillage cultivation techniques before GM HT technology became available. Also, the development of the no-tillage soybean crops have not been attributed to the plantings of GM HT crops in Brazil due to the rapid development of this production system before GM HT soybean technology was permitted in 2003.
9 Our estimates are based on the following average fuel consumption rates: NT 11.4 liter/ha, RT 30.73 liters/ha (the average of fuel consumption for chisel plowing and disking) and conventional tillage 43.7 liters/ha.
10 The actual rate of soil carbon sequestered by tillage system is, however dependent upon soil type, soil organic content, quantity, and type of crop residue, so these estimates are indicative averages.
12 These are excluded because all spraying in these two countries is assumed to be undertaken by hand.
13 This is in line with the general fall in total cotton plantings.
14 These estimates are based on fairly conservative assumptions and therefore the true values could be higher. Also, some of the additional soil carbon sequestration gains from RT/NT systems may be lost if subsequent plowing of the land occurs. Estimating the possible losses that may arise from subsequent plowing would be complex and difficult to undertake. This factor should be taken into account when using the estimates presented in this section of the report.
15 The reader should note that the estimates of soil carbon sequestration savings presented do not include any for soybeans in Brazil because we have assumed that the increase in NT/RT area has not been primarily related to the availability of GM HT technology in Brazil.
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Table A1. GM IR corn (targeting corn-boring pests) 2008.
Table A2. GM IR corn (targeting corn rootworm) 2008.
Table A3. GM IR cotton 2008.
Table A4. GM HT soybeans 2008.
Table A5. GM HT corn 2008.
Table A6. GM HT cotton 2008.
Table A7. GM HT canola 2008.
Table A8. GM herbicide-tolerant sugar beet 2008.
Table B1. Estimated typical herbicide regimes for conventional reduced/no till soybean production systems that will provide an equal level of weed control to the GM HT system in Argentina 2008.
Table B2. GM HT soybeans Argentina 2008.
Table B3. GM HT versus conventional corn Argentina 2008.
Table B4. Typical herbicide regimes for GM HT soybeans in South Africa.
Table B5. Typical herbicide regimes for GM HT maize in Canada.
Table B6. Typical insecticide regimes for cotton in India 2008.
Table B7. Data sources (for pesticide usage data).
Suggested citation: Brookes, G., & Barfoot, P. (2010). Global impact of biotech crops: Environmental effects, 1996-2008. AgBioForum, 13(1), 76-94. Available on the World Wide Web: http://www.agbioforum.org.
In This ArticleTable 1
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