Expectations
The introduction of transgenic plants, 30 years ago, was accompanied by hopes of reducing the use of pesticides in crop cultivation. It was argued that this would be particularly beneficial to the environment, health and to farmers. The theory: genetic engineering could be used to make plants resistant to herbicides. The herbicide-resistant transgenic crops could then be sprayed with broad-spectrum herbicides, such as glyphosate, during the growing season. It was reasoned that the herbicides would only be used when needed, thus promoting a more environmentally-friendly agriculture.

Reality
Initially, there was in some cases an actual reduction in herbicide use. However, the continuous and widespread cultivation of herbicide-resistant transgenic crops, which in some countries, e. g. the USA, accounts for over 90 percent of the cultivated areas, was soon followed by a significant increase in herbicide use. In maize, soybean and cotton fields, especially in the main cultivation areas of North and South America, the use of glyphosate, glufosinate, 2,4-D or dicamba in particular has risen substantially. One major cause is the spread of herbicide-resistant weeds, especially to glyphosate, as regular use of the herbicides puts considerable pressure on wild plants to adapt.

Early predictions warning of the emergence of herbicide-resistant weeds soon became a reality. The ‘WeedScience’ database currently includes about 60 weed species globally that are glyphosate-resistant. Most have emerged through the cultivation of genetically engineered crops. These weeds can either no longer be controlled with glyphosate, or only with very high dosages. In the US, glyphosate-resistant weeds can meanwhile be found growing on about 60 to 80 percent of the land planted with corn, soybeans or cotton.

New transgenic plants were developed to solve these problems, and they now have multiple resistances to different herbicides (so-called ‘stacked events’). This has facilitated the use of additional herbicides during cultivation, which has again resulted in an overall increase in the use of pesticides. It has, in addition, furthered the development of multi-resistant weeds, some of which are now resistant to up to seven different active ingredients. The resulting economic and ecological damage is considerable.

In addition to the increasing pressure on weeds to adapt, genetic engineering is also affecting other factors that may have an impact on the amount of pesticide used. These include larger acreages, lack of crop rotation, decreasing diversification of cultivated crops and increasing dependence on large agrochemical corporations.

Consequences:
The positive effects on sustainability initially predicted have not materialized. On the contrary, in many regions, the cultivation of herbicide-resistant transgenic crops has contributed to the increasing environmental load with certain toxins, and thus to the destabilization of the affected agro-ecosystems. Furthermore, there is a risk that food and feed produced with the genetically engineered plants will typcially be loaded with a cocktail of these herbicide residues.

Experience gained from plants developed with ‘old’ genetic engineering must now lead critical scrutiny and forward-looking assessments of promises and expectations in regard to new genetic engineering. In many cases, the biotech industry is again advertising claims that ignore long-term consequences and are, instead, primarily focused on expected profits. Genetically engineered plants cannot be used as a substitute for an agricultural policy based e.g. on the findings of agroecology that promotes diversity in the fields. On the contrary, there is a high risk that incorporation of plants from new genetic engineering in industrial farming systems will perpetuate and even further expand undesirable farming methods.

Further information:
TA report