(Beyond Pesticides, June 26, 2013) Pesticide use has sharply reduced the regional biodiversity of stream invertebrates, such as mayflies and dragonflies, finds a study published in the Proceedings of the National Academy of Science. While previous research has shown similar decreases in individual streams, this new study analyzes the effects of pesticides over broad regions. This is one of several recent findings that show pesticides pose a long-term threat to important ecosystems.
The study, entitled Pesticides reduce regional biodiversity of stream invertebrates, notes that losses of biodiversity caused by anthropogenic activities during the past 50 years are unprecedented in human history. A team of researchers sampled 23 streams in the central plains of Germany, 16 in the western plains of France, and 24 in southern Victoria, Australia. Researchers classified streams according to three different levels of pesticide contamination: uncontaminated, slightly contaminated, and highly contaminated. Utilizing a model-based approach to account for other environmental variables, the team observed that losses in taxonomic diversity were, to a large degree, determined by the loss of species specifically vulnerable to pesticides. Overall, they found that there were up to 42% fewer species in highly contaminated than in uncontaminated streams in Europe. Highly contaminated streams in Australia showed a decrease in the number of invertebrate families by up to 27% when contrasted with uncontaminated streams. The pesticides analyzed from the streams sampled in the study include several organophosphates, organochlorines, pyrethroids and other pesticides currently banned in these countries.
Furthermore, the researchers note that species losses were detected at pesticide concentrations that current legislation considers environmentally protective. This means, according to the authors, that current ecological risk assessments of pesticides falls short of protecting biodiversity, and new approaches linking ecology and ecotoxicology is needed. “If the aims of slowing the biodiversity loss rate and minimizing the effects of contaminants on biodiversity are to be achieved, the existing pesticide registration, methods of application to fields, and mitigation practices (e.g., buffer zones near waterways) should be developed toward more protective standards,” the researchers state.
This study reinforces the findings of biologist Dave Goulson, PhD, of the University of Sussex, UK, who notes that bees, butterflies, moths, carabid beetles and birds (the groups for which good data are available) all show significant overall declines in recent years, particularly in agricultural regions. Dr. Goulson in his paper, An overview of the environmental risks posed by neonicotinoid insecticides, discusses the impact of the environmental persistence of neonicotinoid pesticides on a broad range of non-target species including pollinators, and soil and aquatic invertebrates, which threatens a range of ecosystem services. This paper also notes that consumption of small numbers of neonicotinoid-treated seeds offers a route to direct mortality in birds and mammals. Similarly, a recent report by Pierre Mineau, PhD. finds that the major contributor to the decline in farmland and grassland birds is pesticide use. This report finds that the best predictor of bird declines is the lethal risk from insecticide use modeled from pesticide impact studies. In 2012, one study reported that widely used herbicides adversely impact non-target invertebrate organisms including endangered species. Researchers found that adult numbers of the Behr’s metalmark butterfly dropped by one-fourth to more than one-third when its larvae were exposed to herbicides applied in the vicinity of the butterfly’s preferred food source, the naked stem buckwheat plant.
Research strongly indicates that biodiversity promotes environmental productivity, stability, and resilience. In general, communities with greater biodiversity generate more biomass (the combined weight of all organisms), are more resistant to environmental disturbances, such as drought, and bounce back more quickly after being affected by such disturbances. Beyond Pesticides’ report, Preserving Biodiversity, As if Life Depends on it, notes that by targeting individual species — both as commodities to produce and pests to attack— chemical-intensive practices sacrifice the benefits of biodiversity and jeopardize the very species that comprise it. While causing harm to biodiversity, chemical-intensive strategies in agriculture are not proven to be necessary in light of effective organic practices.
The conservation of biodiversity is both a core premise of organic land management. For more on how organic management preserves biodiversity visit the organic program page. Read Do-it-yourself biodiversity, for backyard gardening tips.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Nature News