This must be the hardest way to investigate why the trees of the Amazon are so important - climbing right up into them. Down on the ground a scientist, Erika Berenguer, is asking for samples of the leaves.Erika has studied the same batch of trees for ten years now, measuring exactly how they're growing and how they affect the climate. This matters to the whole world because of sheer size of this forest.We've used graphics to show how the billions of leaves are breathing in carbon dioxide - a gas which is heating up the planet.