Why are people concerned about the sustainability of fossil fuels?

Answer:

People are concerned about fossil-fuel sustainability because fossil fuels form over millions of years and are used much faster than they can be replaced. Their supplies are finite, so continued use can eventually lead to shortages. Burning them releases greenhouse gases that contribute to climate change, as well as pollutants that can harm people and ecosystems. Mining and drilling can also damage habitats and contaminate land or water. These concerns encourage conservation and a transition toward renewable energy.