Climate change

Climate change impacts biodiversity through a complex interaction of species and their habitats. Both the structure of habitats and their ecological functions will change in a new climate regime. But the movement of species into or out of a community will also affect both the physical elements of the ecosystem and other species. Changes to local conditions and resources will thus influence a species' ability to survive. And if a species can no longer survive in an ecosystem, it has two choices. If it can disperse rapidly enough and an accessible and suitable alternative habitat exists, it can relocate. Or it can gradually disappear in different locations and eventually go extinct.

Whether directly or indirectly, climate change can produce a variety of effects on populations, including:

- distribution changes: due to habitat loss;

- range changes: either contraction or expansion, relating to their dispersal ability;

- phenological changes: changes in timing of life stages;

- ecological changes: mismatching of species life cycle events and food sources, decoupled predator-prey relationships, new invasions and spread of already established invasive alien species.

Under a new climatic regime, therefore, individuals of some species may be able to colonise new, more suitable areas. But a variety of factors could limit the availability or accessibility of such areas, including land use changes and fragmentation, hydrological changes and nitrification, and sea level. New species assemblages and changes in the relative abundance of populations are expected in some ecosystems. Changes in species composition, habitat structure and ecosystem functioning will be noticed and, in combination, may affect the resilience of ecosystems and the services they deliver to humanity.