Climate change is now the third biggest threat to wildlife, after land use change, & hunting . This is for a few reasons:
HIGH TEMPERATURES: can kill animals when they simply cannot cope with heat stress . Koalas are vulnerable to this – the longer dry periods caused by climate change mean the leaves they eat contain less water, so they can die from dehydration . These are direct effects of climate change, but the indirect impacts can be worse…
INTERACTIONS: everything living in a certain place interacts with each other in complex ways . Animals eat plants, different plants compete for space and light, insects pollinate flowers, fungi infect plants, & so on . So, when one species is directly affected by climate change, this can have knock-on effects for many more species . This is VERY important . Most of the negative effects of climate change on wildlife will happen through these interactions .
A scary example: in the Puerto Rican rainforest, the average daily maximum temperature has increased by 2°C since 1970 . This has caused insects to die – scientists found 4-60x less insect “biomass” (the collective weight of insects caught) in 2012 compared to 1970 . Lizards, frogs and birds feed on insects, and these animals have also declined, due to lack of food . This suggests that climate change has driven a cascade of declines throughout the food chain . Similar collapses are likely occurring in other tropical ecosystems, but we do not have enough data to know how bad the situation is .
Interactions between threats are also important . For example, over 160 frog species seem to have gone extinct over the least 29 years, largely due to higher temperatures making them vulnerable to disease [1,2].
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