There are potentially millions of animal and plant species that are yet to even be discovered! If deforestation continues at the current rate, not even a quarter of these will be discovered before they are killed off! 137 rainforest species are exterminated completely every single day.
The rainforest helps to regulate the worlds water cycle. Trees play an important part in the water cycle, grounding the water in their roots and releasing it into the atmosphere. In the Amazon, more than half the water in the ecosystem is held within the plants. Without the plants, the climate may become dryer and growing food could become impossible for many.