Intact ecosystems have the capacity for self-regulation, which keeps their complex structure of species—such as animals, plants, fungi and bacteria—in balance. For example, when the population of a species increases, its per capita growth rate decreases, keeping population growth in check. Ecological stability is an important indicator of how well self-regulation works and how "healthy" ecosystems are. Measuring and assessing the stability of ecosystems is therefore crucial for monitoring and conserving biodiversity.