Human influences put great pressure on ecosystems through activities like deforestation, overgrazing, pollution, and greenhouse gas emissions. Deforestation of tropical rainforests for agriculture leads to soil erosion and inability of the forest to regrow. Overgrazing and agriculture can remove plant cover exposing soil to erosion. Pollution from sewage, fertilizers, and fossil fuel combustion can cause eutrophication and lack of oxygen in bodies of water, harming ecosystems. The accumulation of carbon dioxide and methane in the atmosphere is thought to contribute to global warming and its environmental impacts. Conservation efforts aim to sustainably manage raw materials, habitats, species, water and energy resources.