Lessons from Lilliputian landscapes: The impacts of habitat fragmentation and climate change on biodiversity and ecosystem function
Many ecosystems are currently undergoing dramatic changes in biodiversity due to habitat loss and fragmentation. This century will see an increase in the combined impacts of habitat fragmentation and climate change as impending extinctions begin to affect ecosystem function. Uncertainties remain regarding the causes of particular trajectories of extinction under single vs. multiple forms of environmental change, and whether knowledge of species traits can be used to predict extinction and subsequent ecosystem impacts. Landscape-level fragmentation experiments have a clear role to play in identifying key ecological responses, and for testing and developing the models required to predict biodiversity change.
Here, I present the results after two-years of a landscape fragmentation and climate change experiment using a bryophyte-based natural model system (NMS) in the subarctic. The experimental treatments altered moisture, temperature and habitat connectivity. We measured the response of the diverse and functionally important group of microarthropods associated with this NMS. Stable isotope analysis was used to infer the response of trophic structure to the treatments.
Community disassembly was linked to species traits, particularly body size. Small increases in summer temperatures maintained greater species richness, whereas drought stress had a significant negative effect on community-level abundance and species richness. These effects were reflected in modifications to the community-wide body-size spectra. Habitat openness alleviated biodiversity loss in the larger-bodied species of the most abundant taxonomic group, but did not fully mitigate the effects of drought. The most striking result of this experiment was an overall contraction of the food web among species persisted under drought stress. These results suggest that major changes in microarthropod community structure are likely to occur in response to global change. More generally, we found that community disassembly initiated by the interaction between climate change and habitat fragmentation differs from disassembly due to habitat loss alone. It was the combination of species-specific environmental tolerances and spatial habitat constraints (e.g. that likely affected migration) of the landscape that interacted to structure community composition and function.
The next step is to extend these experiments to more complex patterns of habitat loss, and to track responses over many generations to capture the effects of extinction debts. Habitat fragmentation experiments conducted at the landscape-level will inform regional climate-ecosystem models and so will have a pivotal role to play in identifying the causes and consequences of biodiversity change over the coming century.