Monocultural sowing in mesocosms decreases the species richness of weeds and invertebrates and critically reduces the fitness of the endangered European hamster
Résumé
Intensive cereal monoculture is currently the main cause of biodiversity decline in Europe. However, it is difficult to disentangle
the effects of intensive monoculture (e.g. pesticide use, mechanical ploughing and reduced protective cover), let
alone evaluate how far the reduction of crop diversity affects biodiversity. It remains unclear to which extent the consequent
decrease in food resources affects farmland biodiversity, and particularly vertebrate species. We therefore designed this
study in mesocosms to investigate the effects of monoculture crops (organic wheat or corn seeds) and mixed crops (a combination
of organic wheat, corn, sunflower and alfalfa seeds) on (1) the species richness of weeds and invertebrates and (2)
the reproductive success of the European hamster (Cricetus cricetus), a critically endangered umbrella species of European
farmlands. We found a negative impact of organic monoculture crops on plant and invertebrate species richness, with values
respectively 38% and 28% lower than those obtained for mixed organic crops. The reproductive success of hamsters was
reduced by 82% in monoculture mesocosms. These results highlight that monoculture per se can be detrimental for farmland
biodiversity (i.e. from plants to vertebrates), even before taking into account the use of pesticide and mechanization. We
believe that future research should further consider how food reduction in agroecosystems affects farmland wildlife, including
vertebrates. Moreover, we argue that conservation actions must focus on restoring plant diversity on farmland to reverse
the observed trend in farmland wildlife decline.