Restoration ecology is the investigation of ecological principles and field methodologies that increase the ability to successfully alter ecosystems for restoration. This process requires transforming an area into a precisely defined, indigenous historic ecosystem that replicates the structure, function, diversity, and dynamics of the ecosystem. It is practiced across a wide variety of natural communities (such as grasslands, forests, wetlands, lakes, and rivers), and is done for a number of purposes (such as detoxifying polluted lands, creating habitat for endangered species, and restoring natural beauty to parks for human enjoyment). Restoration is a challenging task, and to date, most restoration projects have failed.