Edited for “Rooted in Research” by Casey Reynolds, PhD
If someone were to ask what it costs to build an athletic field, park, landscape, or other greenspace it would be relatively easy to determine, or at least accurately estimate, those costs. However, determining the cost of an item often is quite different than determining its value. If someone were to ask, what is the value of a landscape, athletic field, or other urban greenspace, an accurate answer to that question is often much trickier to determine. Real estate agents may tell you that a nice landscape or greenspace can add 10 to 12 percent to a home’s resale value, but is that really
the only value that greenspaces bring to urban and suburban communities? Researchers in the world of Ecosystem Services would tell you no, there is much more value to urban greenspaces than simply increased real estate prices.
A relatively new area of research called Ecosystem Services (ES) is bringing to light the value of natural capital in urban and suburban environments. Ecosystem Services is defined as the many and varied benefits that humans freely gain from the natural environment and properly functioning ecosystems. The Millennium Ecosystem Assessment group (MEA), which formed in 2001, grouped ecosystem services into four broad categories: supporting services, provisioning services, regulating services, and cultural services. Supporting services include processes such as nutrient recycling and soil formation that make it possible for other ES services to function. Provisioning Services support the production of food and raw materials, while Regulating Services include carbon sequestration, climate regulation, and water and air purification. Cultural Services include recreational experiences, cultural, spiritual, or historical experiences, and therapeutic uses, as well as education and science.
One example that illustrates the concept of Ecosystem Services can be found in Figure 1 which uses a heat map to show areas of high and low performance of an area in regard to Water Quantity Control.
Additionally, Figure 2 illustrates an Aesthetic Service Pathway indicating visual screening benefits from a manufacturing facility’s surrounding landscape. Most of the ecosystems previously measured for these services have been categorized into agricultural, forest, grassland, and aquatic ecosystems with urban and suburban areas largely being ignored for the role they play. However, an emerging trend in research on the importance of urban ecosystems and natural capital is beginning to shed light on the importance of these areas as well. For example, a recent report in Toronto, Canada, places the value of its urban forest at $14.2 billion.
That study states that the region’s urban forests store 2.7 million tons of carbon worth $70 million, remove $36.5 million worth of air pollution annually, and provide $20 million worth of energy savings.
This type of research is not limited to just forests, and Dr. Carly Ziter in the Department of Zoology at the University of Wisconsin-Madison has recently published research on the importance of other urban green spaces such as grasslands, open spaces, and developed residential lots. Dr. Ziter and her team quantified three ecosystem services which included carbon storage, water quality regulation, and runoff regulation in five land-cover classes: Deciduous forests, Grassland, Open Space, Low-density developed residential sites, and Medium-density developed residential sites. These land-cover classes represent a continuum from semi-natural to more developed land cover and span approximately 125 years in their time since development.
Another unique and interesting component of this study was that Dr. Ziter and her team also investigated land-use history, an integral but sometimes overlooked component of this type of research. This is of particular importance in suburban areas because as cities expand, agricultural land is often lost to housing. The impacts of many years of prior agricultural practices on these sites, particularly regarding soil-based ecosystem services such as carbon storage, water quality regulation, and runoff regulation, are vital to accurately accessing ecosystem services in these areas. Questions that Dr. Ziter and her team investigated included:
1) How do indicators of soil-based ecosystem services vary with land cover and time since development?
2) Do indicators of soil-based ecosystem services vary primarily among or within land-cover classes, or within sites?
3) What is the relative contribution of urban land- cover classes to soil-based ecosystem services at the citywide scale?
This study was conducted during the summer of 2015 in Madison, Wisconsin, USA. Madison is a city of 245,000 people with another 162,000 in surrounding suburbs. Madison is similar to many growing, urban areas in that it is situated in an agricultural watershed, developed on former farmland, and surrounded by agricultural farmland still in production. It is dominated primarily by low and medium-density developed land and open space, but also includes forests, high-density developed land, and grassland.