Why are fossil fuels called non-renewable resources?

Coal, oil and natural gas are the remains of ancient forest plants buried deep underground, which were formed after high pressure and high temperature and a long geological age, so they are called fossil fuels. Their reserves are not infinite, and once they are consumed by combustion, they cannot be regenerated in a short time, so they are called non-renewable energy. The extensive use of fossil fuels has also led to serious problems such as deterioration of ecological environment, shortage of transportation capacity, regional conflicts and global warming.