Crop heterogeneity and beneficial insect diversity

The rapid expansion and intensification of agriculture has altered the composition of communities and disrupted ecosystem services, yet it is also inevitable, given the high population of humans and their food demands. Therefore, sustainable agriculture that can provide both sufficient food and protection of ecosystem services has been one of the most ambitious research focuses in agroecology. My research work is also dedicated to studying farming practices that could balance both crop production and biodiversity within intensive agricultural systems in which levels of agrochemicals are not controlled.

A major finding of agroecology is that retaining some kinds of natural vegetation in proximity to agriculture conserves biodiversity; however, to keep such vegetation, farmers must forego planting on all their land, at some economic cost. Another economically feasible idea is that the heterogeneity of crops itself could positively affect biodiversity, as heterogeneity generally allows for more ecological niches. Having a high number of crops in relatively small crop fields, with a large amount of field margins (including some area for non-crop vegetation) is thus one potential strategy for preserving biodiversity.

In a recent study, we tested whether a structurally diversified crop-mosaic (see Figure 1) can be a positive force for biodiversity of some beneficial insect groups in subtropical smallholder agroecosystems in southern China. In addition to pollinators (bees, wasps and butterflies), we studied dung beetles and dragonflies as they provide key ecosystem functions/services and are among the best indicators of habitat disturbance. We found a strong relationship between crop compositional heterogeneity (i.e. the number and evenness of crop types) and dung beetle and dragonfly diversity, whereas pollinating insects increased with increasing crop configurational heterogeneity (greater field margin length). We also found that spatial adjacency of dissimilar crop types can have a positive influence on farmland biodiversity. The presence of a vegetable crop on one side of the field margin increased the beneficial insect diversity, compared to non-vegetable monoculture crops (e.g. rice, sugarcane or corn) on both sides. Given high population levels, pressure for increased productivity from Asian farmlands will only increase, but our results suggest that biodiversity and ecosystem services can be retained through promotion of more diverse, small-scale farming.

How to cite our article: Priyadarshana, T. S., Lee, M.-B., Ascher, J. S., Qiu, L., & Goodale, E. (2021). Crop heterogeneity is positively associated with beneficial insect diversity in subtropical farmlands. Journal of Applied Ecology, 00, 1–13. https://doi.org/10.1111/1365-2664.14005 Written by: Tharaka Sudesh Priyadarshana