What could cause a drop in the number of wild horses in an environment?

A drop in the number of wild horses in an environment can be caused by factors such as habitat loss due to urban development or agricultural expansion, which reduces their living space and access to resources. Additionally, competition for food and water with other wildlife or livestock can lead to decreased survival rates. Environmental factors like drought or harsh weather conditions can further strain their populations, while increased predation or human activities, such as hunting and poaching, may also contribute to their decline.