The main environmental factor affecting biodiversity is habitat loss, driven primarily by human activities such as urbanization, agriculture, and deforestation. As natural habitats are destroyed or fragmented, the species that reside in these ecosystems face challenges in finding food, shelter, and mates, leading to declines in population and, eventually, extinction. Other factors, like climate change, pollution, and invasive species, also impact biodiversity, but habitat loss remains the most critical and immediate threat to the survival of many species and the health of ecosystems.