Agriculture is a key driver of global land use change and profoundly affects natural ecosystems. Although organic agriculture is promoted as a more environmentally friendly alternative to conventional agriculture, how impacts differ between both farming systems is still debated. Comparative studies focus mainly on terrestrial systems and rivers, whereas small lentic waterbodies, like ponds, are ignored. This is despite the fact that ponds are abundant in agricultural landscapes, largely contribute to regional biodiversity, and are very sensitive to environmental change. Here we compare the impact of conventional and organic agriculture on biodiversity and evolutionary trajectories of pond biota. First, we compared α, β and γ-diversity of macrophytes, zooplankton and macroinvertebrates in ponds located in organic and conventional farms. We found a moderately positive effect of organic farming on aquatic biodiversity, particularly for macrophytes and at larger spatial scales, but the variation in biodiversity among ponds irrespective of agricultural type indicates that other factors such as land use intensity might be more important for biodiversity. Then, we assessed whether Daphnia magna populations from organic and conventional farmland ponds genetically adapt to specific types of pesticides used in each agriculture type. We found that D. magna populations differentially adapt to pesticide use in organic and conventional farming. These results show that both types of agriculture exert different selection pressures that impact the genetic features of non-target species.

Primary Presenter: Rafaela Almeida, KU Leuven (rafaela.almeida@kuleuven.be)

Authors:

Rafaela Almeida, KU Leuven  (rafaela.almeida@kuleuven.be)

Pieter Lemmens, KU Leuven  (pieter.lemmens@kuleuven.be)

Kristien Brans, Vrije Universiteit Brussel  (kristien.brans@kuleuven.be)

Luc De Meester, KU Leuven  (luc.demeester@kuleuven.be)