Northern Research Station News Releases

Trees and Pavement are Testimony to the Lasting Effects of Housing Discrimination

Urban area with canopy in Syracuse, New York.  USDA Forest Service photo by David Nowak. Madison, WI, April 28, 2022 - In a big-picture examination of how a discriminatory housing practice known as redlining shaped the distribution of urban tree canopy and the associated benefits of trees, USDA Forest Service researchers found that 80 years later, “redlined” areas nationwide have more pavement and less tree canopy than other areas, and they face significant barriers to reversing that condition.

Redlining occurred between 1935 and 1940, when a federal government program called the Home Owners Loan Corporation (HOLC) mapped parts of many U.S. cities and assigned a level of risk for home loans; areas inhabited by immigrants, poor people, and non-White racial groups were shown in red, hence the name “redlining.” The HOLC maps enabled discriminatory lending practices that made it difficult or impossible for people of color or others in the so-called “high risk” classes to purchase homes.

In a study published recently in the journal Landscape and Urban Planning, retired Forest Service scientist David Nowak and Forest Service researchers Eric Greenfield and Alexis Ellis illustrated the effects of redlining on today’s urban forests and the benefits derived from trees. The research team combined national redlining data for 1,259 census places in which at least one of four HOLC classes were mapped with 2010 tree canopy data. Researchers also quantified the value of urban tree services not being realized in former redlined areas, such as cleaner and cooler air, storm water management, and reduced residential energy costs.

“An immediate effect of redlining was that it deprived people of opportunities to purchase homes,” Nowak said. “Our research shows that nationwide, less tree canopy continues to cost people in formerly redlined neighborhoods millions of dollars every year in terms of lost tree services.”

When the research team compared HOLC mapping with land cover maps they found that as HOLC risk categories increased, tree cover decreased and impervious cover increased. Redlined areas were often already areas with higher population density and pavement, and these areas tend to have lower tree cover today. Because these areas have more paved areas, there is not enough space available for the level of tree planting needed to match tree cover found outside of redlined areas. For formerly redlined areas to attain an equitable level of tree cover, urban areas would likely have to be redesigned with less impervious infrastructure, Nowak said.

The study, “The disparity in tree cover and ecosystem service values among redlining classes in the United States,” is online via the Forest Service’s Northern Research Station.


The mission of the Northern Research Station is to improve people's lives and help sustain the natural resources in the Northeast and Midwest through leading-edge science and effective information delivery.


The mission of the U.S. Forest Service, an agency of the U.S. Department of Agriculture, is to sustain the health, diversity and productivity of the nation's forests and grasslands to meet the needs of present and future generations. The agency manages 193 million acres of public land, provides assistance to state and private landowners, and maintains world-renowned forestry research and wildland fire management organizations. National forests and grasslands contribute more than $30 billion to the American economy annually and support nearly 360,000 jobs. These lands also provide 30 percent of the nation's surface drinking water to cities and rural communities; approximately 60 million Americans rely on drinking water that originated from the National Forest System.


USDA is an equal opportunity provider and employer. To file a complaint of discrimination, write to USDA, Assistant Secretary for Civil Rights, Office of the Assistant Secretary for Civil Rights, 1400 Independence Avenue, S.W., Stop 9410, Washington, DC 20250-9410, or call toll-free at (866) 632-9992 (English) or (800) 877-8339 (TDD) or (866) 377-8642 (English Federal-relay) or (800) 845-6136 (Spanish Federal-relay).

Last modified: April 28, 2022