Human activity is probably most responsible for the modifications witnessed in the world's rainforests.
The humans thrive in the rainforests and affect it extremely. The activities like logging have resulted in the loss of almost 137 animal and plant species each day due to deforestation. The activities of humans like the production of toxic by-products, oil spills, and mining incidents, and the continuous dumping of wastes are endangering the rainforests and the species living in there.
The humans also practice the slash and burn agriculture that then results in infertility of the soils and makes vegetation to stop growing. The lack of plants eventually results in an increase of carbon dioxide in the atmosphere, thus, causing global warming.