USFS and Partners
Street Tree Diversity Reveals
a Legacy of Redlining
Authors:
Nancy F. Sonti, USFS Research Ecologist
Dexter H. Locke, USFS Research Social Scientist
Meghan L. Avolio, Associate Professor,
Johns Hopkins University
Karin T. Burghardt, Assistant Professor,
University of Maryland College Park
Fred Chalfant, Urban Forester, Baltimore
City Dept of Recreation & Parks
J. Morgan Grove, USFS Research Forester
Sam Seo, TreeBaltimore Manager, Baltimore
City Dept of Recreation & Parks
Christopher M. Swan, Professor, University
of Maryland Baltimore County
Phil Rodbell, USFS National Program
Leader for Urban Forestry Research
In a recent article published in the journal Ecology, our
research team reported that neighborhoods in Baltimore
that were redlined have consistently lower street tree
diversity and are nine times less likely to have large
(old) trees occupying a viable planting site. What does
this mean for those who live in these neighborhoods,
and what steps might cities like Baltimore take to mit-
igate this structural challenge in their urban forests?
For biodiversity experts, street trees provide a
unique study population because trees can live for
many decades, and patterns of street tree size, dis-
tribution, and diversity reflect both present-day and
historical public policy and management decisions.
Recent studies have discovered that exclusionary
housing discrimination and segregation, reflected
in the Home Owners' Loan Corporation (HOLC)
mapping program, left an imprint on both the social
and ecological landscape of American cities.
In this New Deal initiative created to expand home-
ownership following the Great Depression, the HOLC
classified and color-coded neighborhoods in 239 cities
by perceived mortgage risk—green was designated as
"best" for a loan while red was deemed "hazardous."
Neighborhoods that were "redlined" had characteris-
tics of high-density, poor housing stock, proximity to
undesirable land uses, and large percentages of Black,
Catholic, Jewish, or immigrant populations. These institu-
tionalized, race-based practices have had lasting impacts
on property values, generational wealth accumulation,
public health, and neighborhood investment in cities
across the United States. For example, redlining has
become associated with
lower homeownership rates,
shorter life expectancies, and poorer overall health.
Urban ecologists have also found that formerly A-graded
neighborhoods are
significantly cooler than D-graded
neighborhoods with
nearly twice the total vegetation and
tree canopy, and higher net ecosystem services. Thus,
the investment (or dis-investment) in a neighborhood
based on a program that ended in the 1960s can predict
environmental conditions 60 years later.In addition,
since the amount of plants, the base of the food chain,
varies within cities according to HOLC grades, it has
been proposed that
redlining may predict entire urban
food webs. Correlations between historic HOLC classifi-
cation and present-day patterns of biodiversity have >>
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