This study:
Liu, Xiangping, Laura O. Taylor, Timothy L. Hamilton, and Peter E. Grigelis. "Amenity values of proximity to National Wildlife Refuges: An analysis of urban residential property values." Ecological Economics 94 (2013): 37-43.
Abstract. This research quantifies the property value benefits of National Wildlife Refuges near urban areas on the eastern coast of the U.S.A. Our approach is made possible through access to confidential U.S. Census data identifying property values surrounding all refuges with high geographic resolution. Results from hedonic property value models suggest that the amenity values of refuges located near urbanized areas are capitalized into the value of homes in very close proximity, averaging $11 million per refuge. These capitalized values add directly to the local tax base and are considerable complements to the annual economic value created by the refuge system.
Was picked up by NPR's 90 Second Naturalist (" A daily glimpse into the natural world from Thane Maynard, President of the Cincinnati Zoo and Botanical Garden") on October 7. The podcast is here: http://www.npr.org/podcasts/404960608/the-90-second-naturalist.