Adaptation for Future Climate Warming: the role of habitat creation in promoting species' range shifts

Climate-driven range expansions at leading-edge (northern) range margins are evident in a wide variety of species. However, for many species, losses of habitats have prevented range expansion because newly-available, climatically-suitable habitats are too remote to be colonised. Thus many species are failing to track current climate. The creation of new habitats and the improvement of existing habitats are recommended to facilitate species dispersal and range expansion in fragmented landscapes, but there is no consensus as to the likely success of such adaptation measures. The dynamic modelling techniques necessary for this type of investigation are still in their infancy, and the development of new models formed a novel and important part of the research programme. The main aims of the project were (a) to develop new dynamic models to predict rates of range expansion, (b) to determine the extent to which climate or habitat availability are constraining range expansions, and (c) to assess whether habitat creation could be effective in enabling species to track climate and expand their ranges through modern fragmented landscapes.

(a) Developing new dynamic models. We have developed ‘SPEED’ that is a spatially-explicit, individual (agent)-based dynamic model that includes the dispersal ability of species, as well as their population dynamics, and simulates range changes of species across real landscapes in relation to temporal and spatial variation in climate suitability and habitat availability. We successfully have used the model to simulate range expansion of Pararge aegeria (speckled wood butterfly) in the UK.

(b) Examining factors constraining range expansions. Species respond individualistically to climate change, and we examined whether responses are consistent over time by comparing responses of British butterflies over two study periods. In general, the responses of species were inconsistent over time. The idiosyncratic responses of the study species likely reflected the balance of climatic and habitat drivers of species distribution and abundance changes. We have also examined how the characteristics of local environments explain variation in the extent to which British butterfly species expand their geographic ranges in response to climate warming. We conclude that stable (or positive) abundance trends are a prerequisite for range expansion. Thus mobile generalist species with good dispersal ability and high availability of habitat may not always successfully track climate warming if their abundances are declining.

(c) The role of habitat creation in promoting range expansion. We developed a model to simulate range expansion across a heavily fragmented landscape in Britain, and investigated the effectiveness of six habitat creation strategies for woodland, grassland, heathland, and wetland habitats. A strategy aimed at linking clusters of habitat patches was most effective for facilitating range expansion for three of the four habitat types. Our results also highlighted that the best spatial pattern to facilitate range expansion is different from the best pattern to prevent extinction.