Generally, up to 1 million species of plant and animal could be extinct within decades. Not just to do with climate change, but also because natural habitats are lost for use in agriculture.
Climate change will lead to things like: changes to their habitat where species live (eg. corals in the ocean where the water is getting too warm for them), changes to their food supply/availability, and changes to predators or invasive species. There may be others too!
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