Using citizen science data to reveal the role of ecological processes in range changes of grasshoppers and crickets in Britain

Climatic and land use changes are affecting the distributions of many species and habitats. A detailed understanding of these impacts is critical for conservation and adaptation planning, but much interspecific variability remains unexplained. One reason may be that studies have tended to consider only effects of changes in mean climate, not of annual variation. Using data of the Orthoptera Recording Scheme and additional field observations, I investigated effects of species traits and seasonal variability in weather on the pattern and process of distributional changes of grasshoppers and crickets in Britain over recent decades. I found large changes in the distributions of several species, and relatively greater increases for habitat generalists, species that oviposit in vegetation, and for those with a southerly distribution. In a study of the rapid range expansion of two wing-dimorphic species, Conocephalus discolor and Metrioptera roeselii, I found some of the first evidence for effects of seasonal weather on annual colonisation rates, and for an interaction between the effects of temperature and precipitation. The findings suggest that for some species weather may concentrate dispersal into waves in climatically favourable years. This may increase successful establishment through greater numbers of colonists, and may also be advantageous in fragmented landscapes, allowing species to invest in dispersal only sporadically and under favourable conditions. The results also highlight the importance of considering interactive effects of temperature and precipitation when examining species’ responses to climatic variability. Studies like these are made possible by large-scale, long-term distribution recording by volunteers. However, the unstructured and evolving nature of this "citizen science” makes the data prone to biases that need to be taken into account during analysis. I reviewed current recording of Orthoptera and the scope for its development, and propose a protocol for Orthoptera abundance monitoring by volunteers for future research and conservation applications.