The researchers observed a significant inverse association between higher levels of green cover and lower direct healthcare costs, including the finding that individuals living near the most green space had adjusted health care costs of $374 per person per year less than those living near the least green space. Those in the highest decile of residential green cover were more likely to be white, older, male, and have higher education and income levels. Even after adjusting for sociodemographic and socioeconomic factors, the findings were robust.

To quantify the green space, the researchers utilized the Normalized Differentiation Vegetation Index (NDVI) satellite data. NDVI data “reflects the greenness found in satellite images of land cover and has been commonly used in the geospatial assessment of vegetation presence and viability as well as in the study of green space and human health.” Healthcare costs were obtained from the internal Cost Management Information System which compiles data from health service centers (hospitals, labs, etc.). 

One key strength of this study is the size and diversity of the population where everyone shares the same health care system. Differentiations in health care access are greatly mitigated as all members of the Kaiser Permanente Northern California system have virtually equal access. Another strength is the variety of land use types and topographies over the large area (25,000 sq miles) covered. The green cover-cost relationship observed is not constrained to specific landscapes or geographic settings. 

These findings support several previous studies on the health implications of green space and they exemplify not only the health benefit but also the economic impact of living near more green space. Researchers noted the existing body of literature that ties living near more green spaces to short and long term health benefits. High levels of green cover have been associated with better mental health, maternal-fetal outcomes, and fewer occurrences of cardiovascular disease, respiratory conditions, and mortality. This study supports nationwide efforts to incorporate green spaces into residential neighborhoods and urban greening.

The Harvard Forest and Amherst College researchers found that communities in the lowest income bracket, and communities with the highest proportions of people of color, have access to only about half as much protected land near where they live. These disparities persist across urban, suburban, and rural communities, and across decades.

But Harvard Forest authors Lucy Lee and Jonathan Thompson – with colleagues Neenah Estrella-Luna of Boston, and Kate Sims and Margot Lurie (’21) of Amherst College – didn’t stop at identifying the inequities in conservation. They also created tools that will be part of the solution.

First, they looked at lands that rank highly with conventional conservation criteria – such as wildlife habitat, drinking water, and carbon sequestration – and mapped their relationship with lands that rank highly for human environmental justice criteria – including communities with low income, high percentages of people of color, and high percentages of English language learners. They found that the two don’t tend to overlap.

They created a new prioritization system to help state agencies and conservation organizations identify specific opportunities for future conservation based on environmental justice criteria, and built a free, online mapping tool to highlight these opportunities on the landscape. 

Although their analysis focused on conservation solutions for currently undeveloped land, they also pointed to the importance of restoring existing developed land, including improving forest canopy in marginalized communities, and conservation partnerships that can increase access to existing open space. 

“We know that protected lands provide important benefits to communities, including recreation, preservation of cultural heritage and wildlife habitat as well as improving water quality, decreasing flood risk, and increasing climate resilience,” said Kalinin. “But communities can meet opposition to conservation by those who are concerned about the impacts on property taxes.”

The research paper, Does Land Conservation Raise Property Taxes? Evidence from New England Cities and Towns, concludes that while there was significant new land protection, the tax impacts were small in most communities — a 1% increase in the percentage of town land protected was estimated to cause a 0.024% increase in the tax rate. This corresponds to an increase in a homeowner’s annual tax bill of $0.72 per $100,000 of taxable property value for the average annual increase in area protected of 85 acres. For the owner of a typical New England home (valued at $266,493), that would be an additional $1.92 on their tax bill of $3475. Where they had the greatest effects, the impact for 85 acres of new protection ranged from a $5 to $30 annual tax bill increase per $100,000 of property value.

In addition, these small impacts did not persist—the study found no impacts beyond three years.

“There is often concern that since protected land is taxed at a lower rate than developed land or removed from the tax base, it can shift the tax burden to other taxpayers,” said Sims. “But on the flip side, protected land typically requires fewer services, like schools and road maintenance, and permanent protection can boost the value of nearby properties, potentially increasing other revenues.”

While the findings overall showed a small impact, there were some cases where the tax increases were greater. “Considering differences across municipal types, we found more substantial tax rate increases when towns were growing slowly, had lower median incomes, fewer second homes, and less land enrolled in Chapter 61 current use programs,” said Thompson. “The size of these impacts ranged from $5 to at most $30 in additional taxes paid for each $100,000 in property.”

“While the tax impacts remain small, they seem to impact the towns least able to afford tax increases, said Meyer. “These disparities warrant further attention and may require increased funding from state, federal and private sources.”

The researchers used data from more than 1400 towns and cities in New England from 1990 to 2015 to assess the impact of new land protection on local property tax rates. New protection included private conservation easements and purchases by non-profit organizations, local governments, and state and federal agencies for conservation. To isolate the impacts on tax rates that can be attributed directly to land protection, they used data from the same municipalities over time and controlled for changes in employment, prior growth in the tax base, and economic and population trends. Read a Q&A with the authors here.

Alexey Kalinin is a natural resource economist and a post-doctoral researcher at Harvard Forest. His current research is focused on economic impacts of land protection in New England. 

Katharine Sims is a Professor at Amherst College, where she teaches economics and environmental studies. Her research seeks to understand when and how land conservation policies can achieve both economic development and improved environmental quality.

Spencer Meyer is the Director of Science Strategy and Stakeholder Engagement for NCX. He was a Senior Conservationist with the Highstead Foundation from 2016 to 2021, where he led the conservation finance and conservation science programs.

Jonathan Thompson is a Senior Ecologist at the Harvard Forest, a department of Harvard University. His research focuses on long-term and broad-scale changes in forest ecosystems, with an emphasis on quantifying how land use affects forest ecosystem processes and services.