Agriculture and Environment: Soybeans
Environmental Impacts of Production: Groundwater Contamination
In the United States the main herbicide used with GM soybean production is glyphosate (trade name Roundup). While glyphosate has been touted by the manufactures as benign, and they can back up their claims with research they have supported, other studies suggest otherwise.
Impacts of glyphosate
For example, these studies allege that the chemical has been linked to reproductive disorders, genetic damage, liver tumours, disrupted embryo development, and development delays in mammals (e.g., Cox 1998).
While some producers claim that one application of herbicide is all that is needed for an entire growing season with herbicide-tolerant soybeans, studies show that both the total amount of herbicide used and the number of applications have increased.
Jump in chemical usage
Chemical usage summaries from the National Agricultural Statistics Service of the United States Department of Agriculture (USDA 1991) show that in the United States total herbicide use on soybeans increased from 56.4 million pounds in 1995 to 75.2 million pounds in 2000.
The use of glyphosate (Roundup) increased from 6.3 million pounds to 41.8 million pounds in the same period. In 1995 glyphosate was used on 20% of the soybean crop, but by 2000, just 4 years after the 1996 release of Roundup-ready soybeans, it was used on 62% of the crop (Tengnas and Nilsson 2002). Furthermore, the applications increased from one application per crop to 1.3 applications.
In the danger zone - Brazilian Amazon River floodplains
There is concern (but not yet evidence) that agrochemicals such as the herbicides trifluralin (Treflan), lactofen (Cobra), fomesafen (Reflex), bentazon (Basagran), imazethapyr (Pursuit), sethoxydim (Poast), and clethodim (Select) will contaminate lakes and lagoons in the Brazilian Amazon River floodplains.
During the dry season, the waterways dry up and any contamination within the separate water bodies would become more concentrated (Fearnside 2000 and Leibold 2001a). In the Brazilian Amazon high humidity and heavy rains have already caused the spread of fungus and blights. This, in turn, is resulting in the increased use of fungicides.
Similarly, as production continues in the same area over a number of years, pest populations will increase, which will be followed by an increase in the use of chemical controls. Because Brazil has no frost, the different pests will adjust more rapidly to whatever chemicals are used to prevent them than they do even in the United States, where pests have rapidly developed resistance to the chemicals used to control them.
Soybeans massive share in chemical usage
The FAO and others estimate that 25% of all pesticides used in Brazil are used in soybean cultivation, and that in 2002 an estimated 50,000 metric tons of pesticides were used by Brazilians on soybeans (World Bank 2002). Because of the rapid expansion or area planted to soybeans, pesticide use is increasing at a rate of 21.7% per year.
However, the growth in pesticide use is increasing even faster than the growth in either area cultivated or overall soybean production. While part of this can be explained by the lack of frost and pests developing resistance to pesticides due to increased use, there are other factors involved.
Production is expanding into areas with insufficient labour and pesticides are used to reduce labour costs. Areas planted to soybeans are becoming larger and therefore mechanisation makes the application of pesticides more cost-effective.
More work needs to be done on analysing the full range of agrochemicals used in the cultivation of both traditional and GM soybeans as well as their long-term movements in the environment, their impacts, and the development of resistance to them.Credits
