Umbrella species are species selected for making conservation-related decisions, typically because protecting these species indirectly protects the many other species that make up the ecological community of its habitat. Species conservation can be subjective because it is hard to determine the status of many species. With millions of species of concern, the identification of selected keystone species, flagship species or umbrella species makes conservation decisions easier. Umbrella species can be used to help select the locations of potential reserves, find the minimum size of these conservation areas or reserves, and to determine the composition, structure and processes of ecosystems.
Two commonly used definitions are:
Other descriptions include:
The use of umbrella species as a conservation tool is highly debated. The term was first used by Wilcox (1984)  who defined an umbrella species as one whose minimum area requirements are at least as comprehensive of the rest of the community for which protection is sought though the establishment and management of a protected area.
Some scientists have found that the umbrella effect provides a simpler way to manage ecological communities. Others feel that a combination of other tools establish better land management reserves to help protect more species than just using umbrella species alone. Individual invertebrate species can be good umbrella species because they can protect older, unique ecosystems. There have been cases where umbrella species have protected a large amount of area which has been beneficial to surrounding species. Dunk, Zielinski and Welsh (2006) reported that the reserves in Northern California (the Klamat h-Siskiyou forests), set aside for the northern spotted owl, also protect mollusks and salamanders within that habitat. They found that the reserves set aside for the northern spotted owl "serve as a reasonable coarse-filter umbrella species for the taxa evaluated", which were mollusks and salamanders.
The bay checkerspot butterfly has been on the Endangered Species List since 1987. Launer and Murphy (1994) tried to determine whether this butterfly could be considered an umbrella species in protecting the native grassland it inhabits. They discovered that the Endangered Species Act has a loophole excluding federally protected plants on private property. However, the California Environmental Quality Act reinforces state conservation regulations. Using the Endangered Species Act to protect termed umbrella species and their habitats can be controversial because they are not as well enforced in some states as others (such as California) to protect overall biodiversity.