Globally, as well as within North America, the variety of ecosystems contributes to the health and stability of the biosphere. Forests, grasslands, deserts, and other vegetation formations comprise the global ecosystem. On a smaller scale, biodiversity is important to the health and resilience of ecosystems as well. For example, food chains are built on the foundation of a healthy, diverse ecosystem of many different native plant species. This is referred to as species diversity .
Native plants provide food and cover for insects.
Insects in turn are a vital food source for many birds and mammals. The greater the diversity of plants, the greater the diversity of other species the ecosystem can support. Species diversity is a measure of both richness and evenness. Richness refers to the total number of different species in an area or community, while evenness is a measure of the number of individuals of each species. In general, diversity increases with richness and evenness.