The protection of endangered species is difficult and costly. Devoting the same protections to species that require significantly more funding, or to species that do not contribute much to the ecosystem, do not deserve the already sparse funds for conservation. Keystone species, for example, should be given more priority in conservation, as the structure of the environmental interactions in their habitat relies on them. Relatively insignificant animals that can be easily replaced should not be given the same priority as those who contribute to their ecosystem. Also, species that are more expensive to preserve should receive less priority. Temporary cost should not drastically shift the decisions on which species to save, but it should be kept in mind.