The potential of rainforests to store carbon may decline as a result of climate change. This is because the rate of photosynthesis in the leaves of rainforest species decreases at higher temperatures, and the trees’ natural cooling systems fail during droughts. Increased heat endangers animals that store the most carbon. A new thesis from the University of Gothenburg shows this. Some tree species can withstand rising temperatures in the tropics by sucking huge amounts of water from their leaves and transpiring through wide-open pores in their leaves. These are mainly fast-growing trees that establish themselves early in rainforest development. The same cannot be said of the trees that form the canopy of ancient rainforests. They grow more slowly, but become more elaborate and taller, and their leaves don’t have the same ability to cool themselves through transpiration.