soil fertility in the Mediterranean. It was not until the late 1940s that three key authors—Henry Fairfield Osborn, Jr, William Vogt, and Aldo Leopold—promoted recognition of human dependence on the environment. In 1956, Paul Sears drew attention to the critical role of the ecosystem in processing wastes and recycling nutrients. In 1970, Paul Ehrlich and Rosa Weigert called attention to "ecological systems" in their environmental science textbook and "the most subtle and dangerous threat to man's existence... the potential destruction, by man's own activities, of those ecological systems upon which the very existence of the human species depends". The term "environmental services" was introduced in a 1970 report of the Study of Critical Environmental Problems, which listed services including insect pollination, fisheries, climate regulation and flood control. In following years, variations of the term were used, but eventually 'ecosystem services' became the standard in scientific literature. The ecosystem services concept has continued to expand and includes socio-economic and conservation objectives, which are discussed below. A history of the concepts and terminology of ecosystem services as of 1997, can be found in Daily's book "Nature's Services: Societal Dependence on Natural Ecosystems". While Gretchen Daily's original definition distinguished between ecosystem goods and ecosystem services, Robert Costanza and colleagues' later work and that of the Millennium Ecosystem Assessment lumped all of these together as ecosystem services. Examples The following examples illustrate the relationships between humans and natural ecosystems through the services derived from them: The US military has funded research through the Pacific Northwest National Laboratory, which claims that Department of Defense lands and military installations provide substantial ecosystem services to local communities, including benefits to carbon storage, resiliency to climate, and endangered species habitat. As of 2020, research from Duke University claims for example Eglin Air Force Base provides about $110 million in ecosystem services per year, $40 million more than if no base was present. In New York City, where the quality of drinking water had fallen below standards required by the U.S. Environmental Protection Agency (EPA), authorities opted to restore the polluted Catskill Watershed that had previously provided the city with the ecosystem service of water purification. Once the input of sewage and pesticides to the watershed area was reduced, natural abiotic processes such as soil absorption and filtration of chemicals, together with biotic recycling via root systems and soil microorganisms, water quality improved to levels that met government standards.