While rainforests contribute little to atmospheric oxygen levels, deforestation releases large amounts of carbon dioxide into the air by burning forest plants, contributing to global warming. Scientists state that tropical deforestation releases 1.5 billion tons of carbon each year. Forests also help stabilize the biosphere by extracting carbon dioxide and pollutants from the air. Burning fossil fuels releases carbon dioxide trapped underground for millions of years too quickly for plants and trees to absorb, increasing the carbon dioxide levels in the atmosphere and causing global warming and unpredictable climate changes. Reducing fossil fuel use can help mitigate extreme weather risks.