So first its important to read the question. As climate change mitigation and adaptation are two differnet things, and so two clearly differentiated answers are required. I would write on the side of the quesiton paper one or two words as to what adaptation and mitigation are. For example, adaptation = targeting cause of CC, mitigation = reducing impacts of CC. With this you don't even necessarily have to have learnt in depth material about the topic and basic logic from GCSE science can be applied. Whereby in terms of adaptation, trees photosynthesize, so would act as carbon sinks and take CO2 out of the atmosphere, reducing the rate of climate change. Then for mitigation, trees could act as buffers from flooidng or sea level rise. As when it rains heavily, instead of surface run off, trees would encourage infiltration and so increase lag time of water reaching the river channel, reducing the likelihood of flooding.