There are 3 types of environmental stewards: doers, donors, and practitioners. Doers go out and help the cause by taking action. For example the doers in an oil spill would be the volunteers that go along the beach and help clean up the oil from the beaches. A donor is the person that financially helps the cause. They can do anything from donating their money, to having galas or other fundraisers. They are typically governmental agencies. Lastly there are practitioners. They work on a day-to-day basis to steer governmental agencies, scientists, stakeholder groups, or any other group toward a stewardship outcome. Together these 3 groups make up environmental stewards and with the help keep the ecosystem running healthily. Anybody can be an environmental steward by being aware and knowledgeable of the world around them and making sure they do as little as possible to negatively impact our world. Without these groups it would be hard to get any sort of sustainability in our increasingly technology, pollution, industrial based world. 
^Leopold, Aldo. 1949. A Sand County Almanac. Oxford University Press, New York.
^Chapin, F. Stuart III, Gary P. Kofinas, and Carl Folke (eds). 2009. Principles of Ecosystem Stewardship: Resilience-Based Natural Resource Management in a Changing World. Springer. ISBN 978-0387730325.
^Walker, Brian, and David Salt. 2006. Resilience Thinking: Sustaining Ecosystems and People in a Changing World. Island Press. ISBN 978-1597260930.
^Increasing Capacity for Stewardship of Oceans and Coasts, P. 30
^National Research Council. (2008). Increasing Capacity for Stewardship of Oceans and Coasts. The National Academic Press, 500 Fifth Street, NW Washington DC 20001.