According to a new study by an interdisciplinary team of colleagues led by a University of Maryland environmental economist, stream restoration filters pollutants out of nearby waterways and enhances the health of the Chesapeake Bay, but the Baltimore area neighborhoods where it would have the greatest impact on water quality are far less willing to pay for such projects.
The team discovered that while residents in the most densely inhabited areas, which tended to have lower incomes, were more willing to pay for restoration projects, they were less inclined to do so in the less densely populated and typically wealthier areas of their study zone.
The study, which was published in the journal Environmental Research Letters, should assist in educating decision-makers tasked with enhancing water quality. These individuals frequently must balance environmental impacts with community support.
“We see this strong urban-to-rural gradient where in urban areas there’s a higher economic potential as far as community support to pay for stream restoration, but less ecological potential to reduce nutrient pollution, and vice versa,” said David Newburn, an associate professor in the Department of Agricultural and Resource Economics at UMD and co-author of the study. “The overall trend is that there’s often a trade-off for environmental and economic benefits from stream restoration projects, and it’s hard to find the win-win locations.”
Although stream restoration initiatives vary significantly depending on the local environment, they are always intended to increase a stream’s capacity to absorb and process nutritional contaminants and stop them from flowing downstream.
These initiatives are essential to enhancing the water quality of the Chesapeake Bay and other watersheds worldwide. However, stream restoration can alter the surrounding environment by occasionally removing trees or introducing grassy meadows along streambanks.
In order to comprehend the complex relationship between the environmental advantages of stream restoration and the value that homeowners who usually pay for them through taxes and fees perceive them to be, Newburn and his colleagues conducted a study.
To gauge homeowner willingness to pay for various restoration project types, the team paired their analysis of one of the most complete data sets on urban stream water quality in the world with a homeowner survey.
In rural areas, you get this high environmental benefit, that has high potential to remove nitrogen pollution from waterways, particularly when you remove trees and have grassy streambanks to open up the streams to sunlight. But that’s where you get the lowest willingness to pay and sometimes even resistance to tree removal from nearby homeowners compared to doing restoration somewhere else.David Newburn
The Baltimore Ecosystem Study, which has been tracking streamflow and nutrient load (a measure of a waterway’s ecological health) across entirely forested, agricultural, and highly developed watersheds since 1998, provided the researchers with long-term sampling data. They calculated how much nitrogen will be eliminated by various stream restoration plans in various environments using contemporary ecosystem modeling tools.
They concentrated on tiny, headwater streams in the Baltimore area, which included urban, suburban, and exurban communities. Exurban neighborhoods are those without city septic systems and are characterized by the predominance of single-family residences on lots between one and five acres.
In the less densely inhabited exurban areas, where small streams are more common and have modest flows, Newburn and his colleagues’ hydrologic models demonstrated that stream restoration had the greatest effect on nitrogen reduction. When compared to streams with trees, streams with grassy buffers reduced nutrients the most.
According to the researchers, streams in these places had modest water flows, which allowed the water’s nutrients to be processed, and grassland buffers let more sunshine reach the water than stream banks with tree cover did.
Because it increases the efficiency with which algae in streams extract nitrogen from the water, sunlight is crucial. In Baltimore City’s most populous urban neighborhoods were the programs that reduced nitrogen pollution the least.
Urban runoff from impermeable surfaces like parking lots and rooftops causes local flooding in these communities during downpours, and the torrents of quickly flowing water do not provide streams enough time to remove a significant amount of nutrient pollution.
The next step was for the researchers to assess homeowner survey data regarding their willingness to pay for various stream restoration plans and map their findings across the study area.
“In rural areas, you get this high environmental benefit, that has high potential to remove nitrogen pollution from waterways, particularly when you remove trees and have grassy streambanks to open up the streams to sunlight,” Newburn said.
“But that’s where you get the lowest willingness to pay and sometimes even resistance to tree removal from nearby homeowners compared to doing restoration somewhere else.”
Because homeowners respect trees for their visual benefits, they frequently represent an amenity that has value. By removing trees, a neighborhood loses this amenity value. However, the reinstatement of grassy meadows or trees during restoration provides green-space amenities that are sometimes lacking, especially in lower-income urban communities where streams were more likely to be bordered by man-made infrastructure.
Newburn observed that decision-makers may take into account the social benefits of increased green space in metropolitan settings, which go beyond the improvement of the water quality.
He said that future studies on the additional advantages of restoration projects, such as lowering urban heat islands, restoring habitats, and improving quality of life, may show a stronger balance that clearly favors some projects over others.
Andrew Rosenberg earned his Ph.D. in Agricultural Resource Economics at UMD and is now a Research Agricultural Economist at the USDA.
This research was supported by National Science Foundation Coastal Science, Engineering, and Education for Sustainability Program (Grant No. 1426819), and the National Science Foundation Long-Term Ecological Research (LTER) Program (Grant No. DEB-1027188) for the Baltimore Ecosystem Study, and the U.S. Department of Agriculture, Economic Research Service.