Final answer:
A forest or prairie is healthier with a variety of species because it helps in nutrient utilization, reduces nutrient losses, and supports a greater number of species in the ecosystem.
Step-by-step explanation:
In a forest or prairie, having a variety of species is healthier than planting a single species. This is because more species can better utilize and recycle nutrients, leading to reduced nutrient losses and improved soil fertility. Additionally, a diverse ecosystem with many different species can sustain larger populations, provide microhabitats and ecological niches, and support more species.