Pesticides and Soil Biodiversity

It is well known that some pesticides have a negative impact on bees, birds, insects and even on human health. However, the impact of pesticides on belowground life is still poorly understood. Here we present results from large Swiss, European and Worldwide networks assessing the impact of pesticides on soil biodiversity. We assessed the occurrence of over 100 different pesticides residues in agricultural and natural soils of over 40 countries and we tested for links with a wide range of soil organisms, including fungi and bacteria. Data were obtained from over 60 Swiss vineyards (including both organically and conventionally managed fields), from the LUCAS data-set of the Joint Research Centre of the European Union, spanning over 350  sites in over 25 European countries and over 500 locations from the Global Crop Microbiome and Sustainable Agriculture initiative. The number of pesticides residues found dependend on land use and were highest in agricultural soils were pesticides are regularly applied. However, natural locations such as grassland or forest also often contained traces of pesticides. Using statistical analysis, we observed that pesticides are a major driver of soil biological communities. For some biological groups, pesticides were, after soil properties, the second most important factor explaining richness and community compostion. Pesticides altered microbial functions, including phosphorus and nitrogen cycling and suppressed beneficial taxa, including arbuscular mycorrhizal fungi (beneficial plant symbionts) and bacterivore nematodes. In Swiss vineyards fungal richness was negatively linked to the number of pesticides. Copper also had a strong influence on microbial community structure in Swiss vineyards and this effect was the same in organic and conventionally managed fields. Interestingyl some soil micro-organisms also responded positively to pesticides, especially those reported having the ability to degrade pesticides and use pesticides as energy (food) source. Overall, this work demonstrates that pesticides have a significant impact on belowground processes and on biodiversity.