The primary factor affecting species diversity in an ecosystem is habitat destruction. The loss, fragmentation, or degradation of habitats due to human activities such as urbanization, agriculture, and logging severely impacts the availability of resources necessary for survival. As habitats are altered, many species may struggle to find food, shelter, or reproduce, leading to declines in populations. Additionally, changes in environmental conditions can further stress ecosystems, affecting their resilience. Sustainable practices and conservation efforts are essential to preserving biodiversity and maintaining healthy ecosystems.