Do herbicides alter ecosystems around the world? Scant research makes it hard to prove

Professor Heinz Köhler and Professor Rita Triebskorn from the University of Tübingen's Institute of Evolution and Ecology (EvE) have published a study on the link between pesticides and changing ecological systems in the latest edition of Science. The two ecotoxicologists cite deficits in the research which have prevented recognition of the consequences of biochemical pesticide effects on a species population or on the composition of biological communities. "Although there are many indications of animal populations and ecosystems changing because of pesticides, there are few studies proving the connection without a doubt," Köhler and Triebskorn say. The researchers point to mathematical and experimental approaches which can be used to recognize links between the effects of pesticides in individuals and ecological changes in biological communities and ecosystems in regions where intensive farming is practiced.

An important role is played by number of rare studies combining experimental fieldwork and research on sections of ecosystems, as well as a broad selection of chemical and biological analyses. An interdisciplinary approach can plausibly demonstrate connections between the effects of chemicals in humans and animals and the often indirect consequences on the population, community and ecosystem levels.

Köhler and Triebskorn also postulate interdependent effects between pesticides and global warming. The researchers forecast changes to "natural" selection, the spread of infections, and the sexual development and fertility of wild animals. This in turn could have a knock-on effect on populations, ecosystems and food chains. The researchers say it is a further challenge for science to show how strongly the effects of pesticides are influenced by climate change -- and to find out which ecological processes are especially sensitive to this interdependence. "The links to the effect of pesticides at every level of increasing biological complexity require more thorough research," say Köhler and Triebskorn.