Climate change impacts including droughts, crop failure, flooding, sea-level rise and extreme weather events are already being felt across the world, with the poorest people and vulnerable ecosystems hit hardest.
There is an increasing weight of scientific evidence that observed changes in climate have already adversely affected biodiversity at the species and ecosystem level, and current levels of climate change are modest compared to most projections. Plant and animal ranges are shifting poleward and upward, and studies suggest many species will not be able to keep up with their changing climate space.
One global study estimates that 15–37% of species could be committed to extinction by 2050 as a consequence of climate change; another that each degree of warming could drive another 100-500 bird species extinct. Temperature rises beyond 2 °C are predicted to lead to catastrophic extinction rates, with few practical conservation options left.
Over the past 50 years, humans have changed ecosystems more rapidly and extensively than during any comparable period of time in human history, largely to meet rapidly growing demands for food, fresh water, timber, fibre and fuel. The result has been a substantial and largely irreversible loss in biodiversity. Climate change exacerbates these impacts.
Impacts include increased extreme weather (floods and droughts), the retreat of mountain glaciers, the thawing of permafrost, later freezing and earlier break-up of ice on rivers and lakes, lengthening of mid- to high-latitude growing seasons, poleward and altitudinal shifts of plant and animal ranges (resulting in declines in some plant and animal populations, and the potential extinction of species where no such shift in range is possible) and phenological changes, such as the earlier emergence of leaves and insects and the timing of migration and breeding of species, usually genetically 'programmed' to coincide with optimal climatic circumstances and hence food availability. Adapting to a changed climate requires evolutionary change which can take a very long time. Very rapid climate change as the one we are currently witnessing could mean that many species will fail to adapt and face massive starvation and breeding failure.
These and other problems may lead to further declines in bird populations with currently common species becoming rare, and rare species disappearing from vast parts of Europe and some species risking complete extinction. The loss of species and decline of wild birds populations makes our world poorer but is also contributing to weakening the ecosystems on which we ultimately depend. Healthy ecosystems are even more important in times of rapid climate change as complex ecosystems can better buffer some of the consequences of climate change such as extreme weather events and spread of invasive species.