Monocultural sowing in mesocosms decreases the species richness of weeds and invertebrates and critically reduces the fitness of the endangered European hamster

Abstract

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.

Weeds as a predominant food source: a review of the diet of common hamsters Cricetus cricetus in farmlands and urban habitats

“…), especially in late spring and summer (Kupfernagel , Tissier et al. ) and in the autumn (Holišová ; Table ). In farmlands, Asteraceae, Fabaceae and Poaceae are the most common families eaten (Fig.…”

“…), only four of the 15 studies reviewed considered this food category (Górecki & Grygielska , Holišová , Kupfernagel , Tissier et al. ). The lack of interest in this subject is most likely explained by the fact that most weeds are present in low percentages in the diet (<2%; Holišová ) compared to crops (but see Kupfernagel for exceptions), and are therefore frequently ignored, although the sum of weeds’ volume or occurrence can be important.…”

“…Monoculture is associated with a reduction in up to 82% in the reproductive success of hamsters, suggesting that it entails substantial nutritional constraints for hamsters (Tissier et al. ).…”

“…However, the deficiencies associated with maize consumption in hamsters do not seem to be counterbalanced under semi‐natural conditions, despite the presence of weed and animal food sources (Tissier et al. ). It is still unknown how far hamsters are limited to maize consumption in current European farmlands, and how the consumption of this crop could influence their consumption of other food items or could be counterbalanced by the consumption of animals.…”

“…(); 7, Tissier et al. (); 8, Hufnagl et al. (); 9, Ketzer (); 10, Górecki (); 11, Górecki (); 12, Feoktistova et al (); 13, Surov (); 14, Čanády (); and 15, Kupfernagel ().…”