THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS 23 additional wealth flowing to homeowners and increase tax revenue), no studies have rigorously quantified potential economic harm caused by gentrification and displacement. Benefits Transfer A common technique within the environmental literature is the concept of benefits transfer. This method uses past rigorous research on the monetary benefits of environmental qualities to estimate the benefits of these same qualities in other contexts. This method has been used to estimate the economic value of parks and green spaces based on the composition of the space, meaning the types of land included (Trust for Public Land 2013). This method allows an estimation of impact where there is research on similar land types and where a reasonable argument can be made for the transferability of the monetary benefits to a new context; more complex analyses control for differences in the conditions and socioeconomic context of the analysis site (Colombo and Hanley 2008). Research on the validity of this methodology has underlined the importance of having equal benefit functions, meaning the benefits in both sites have similar effects (Brouwer and Spaninks 1999). Benefits Tools A few attempts have been made at providing tools to calculate the benefits of parks and green space. A prominent example is the Florida Recreation and Parks Impact Calculator, which includes health and environmental benefits. This tool uses fairly broad assumptions. Health benefits are calculated by counting the number of park users over age 65 and those under age 65, then using a multiplier based on national data on the health savings associated with park use ($2,406 for over age 65, $1230 for under age 65). The Oregon Parks and Recreation Department developed outdoor recreation metrics to quantify the contribution of physical activity to averted health care costs. They include 30 outdoor activities (such as biking, walking, and jogging on trails) to assess how environmental intervention correlates to health impacts in the state. They created an Outdoor Recreation Health Impacts Estimator tool that measured 503 billion kcals of energy used and $735 million to $1.416 billion in cost of illness savings associated with eight chronic illnesses affected by physical activity (Rosenberger and Dunn 2018). Such tools and metrics have to balance ease of use (availability of data, complexity of assumptions) with the rigor of the outputs.
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