Once upon a time, Cleveland was the Forest City. When Moses Cleaveland arrived to survey Connecticut’s Western Reserve in 1796, the area was heavily forested. It was said that a squirrel could travel from the Atlantic Ocean to the Mississippi River without ever touching the ground.
These days, only the moniker remains. We still have Forest City Enterprises, Forest City Brewery, Forest City Portage, etc. The trees? Not so much.
According to Cuyahoga County’s Urban Tree Canopy Assessment, just 19.2% of the city remains forested. Nearly all of the trees that existed during Cleaveland’s trip to the city that (largely) bears his name are gone today. In 1946, city officials identified 150 trees that likely existed in 1796. When the city updated this inventory in 1975, just 92 remained; of these, only 15 still had the plaques that were installed in 1946.
Only two of Cuyahoga County’s 59 communities have less tree cover than Cleveland, and the city lags behind comparable cities, including Cincinnati (38%) and Pittsburgh (40%). According to projections, unless Cleveland reverses this trend, its tree canopy will fall to just 14% by 2040. This would represent a loss of 97 acres of urban forest annually over the next 25 years.
When you consider some of Cleveland’s pressing challenges – a 56% child poverty rate, violent crime, population loss – the number of trees within city limits may not seem like a big deal. But we cannot consider the city’s environmental challenges as distinct from its general urban challenges; they are intrinsically connected. Our tremendous urban struggles exacerbate our environmental issues, including tree cover, and these environmental issues subsequently compound these broader issues.
Cleveland’s trees are terrific
When I think about trees, my mind immediately goes to that strangely catchy 1970s commercial from the National Arbor Day Foundation:
And it’s true, trees are terrific. In fact, they’re freaking incredible. But, as the singing cardinal in that commercial indicates, sometimes we take for granted the best things ever planted.
For many Clevelanders, trees may seem like more of a hassle than they’re worth. They produce tons of leaves, fruit, and sap that coats lawns and clogs gutters. They can damage sidewalks. Their roots may get into water and sewer pipes. They may fall in a storm and damage your property or that of a neighbor.
But the costs of trees only outweigh their benefits when we fail to account properly for the latter. Fortunately, the City of Cleveland and a number of partner organizations have placed a price tag on the myriad benefits that our trees provide in The Cleveland Tree Plan (PDF), which was released last October.
Utilizing the U.S. Forest Service’s i-Tree model, the document estimates that the city’s trees provide more than $28 million in ecosystem services each year. Cleveland’s trees intercept 1.8 billion gallons of rainwater, which helps to mitigate our ongoing challenges with flash flooding. The trees shade homes, lowering energy costs by $3.5 million each year, as well as increase property values by $4.5 million. They also play an important role in mitigating climate change, as they remove 42,000 tons of carbon dioxide per year.
In the plan’s appendices (PDF), which you have to be a massive nerd like me to read, the Tree Plan actually lays out these ecosystem services by neighborhood. As the table below shows, there is a clear overlap between the extent of a neighborhood’s tree canopy and a host of other issues, including energy costs, asthma rates, and property values. The correlation between a neighborhood’s tree canopy and its urban heat island risk, for instance, is extremely strong (0.7609) and statistically significant (p < 0.0001).
Trees and mortality rates
On its surface, all of this makes sense. It’s fairly obviously that trees filter out air pollution, mitigate stormwater runoff, store carbon, beautify neighborhoods, and shade homes. But trees can do so much more, including extend your lifespan.
A recent study in the journal Environmental Health Perspectives examines the relationship between “greenness,” a measure of vegetation cover (including trees) and mortality rates among a cohort of female nurses in the U.S. The researchers, led by up Dr. Peter James from the Harvard School of Public Health, utilized satellite images to measure the amount of vegetation within 250 and 1,250 meters of each woman’s residence. The 250-meter diameter represented the vegetation directly accessible from each woman’s home, while the 1,250-meter buffer accounted for vegetation within a 10- to 15-minute walk.
The authors considered four main pathways through which exposure to vegetation can affect mortality rates: physical activity, air pollution, social engagement, and mental health. They also controlled for a range of potentially confounding factors, including race/ethnicity, smoking status, socioeconomic status, region, and whether the person lived in a urban area.
According to James et al., higher levels of “greenness” significantly lowered mortality rates among the women in the study cohort.
Analyses showed a consistent relationship between higher greenness and decreased mortality that was robust to adjustment for individual- and area-level covariates. In fully adjusted models, those living in the highest quintile of cumulative average greenness in the 250m area around their home had a 12% lower rate of mortality compared to those in the lowest quintile. Results were consistent for the 1,250m radius, although the relationship was slightly attenuated.
Greater exposure to vegetation significantly reduced mortality rates from cancer, respiratory disease, and kidney disease by 13%, 35%, and 41%, respectively. Of the four pathways studied, the effects were greatest for mental health and social engagement, though “greenness” also reduced mortality related to fine particulate matter and a lack of physical activity.
Based on their research, James et al. conclude,
[T]hese findings suggest that green vegetation has a protective effect, and that policies to increase vegetation in both urban and rural areas may provide opportunities for physical activity, reduce harmful exposures, increase social engagement, and improve mental health. While the recognized benefits of planting vegetation include reducing wastewater loads, sequestering carbon, and mitigating the effects of climate change, evidence of an association between vegetation and lower mortality rates suggests a potential co-benefit to improve health, presenting planners, landscape architects, and policy-makers with an actionable tool to grow healthier places.
Clearly, city officials should work to expand urban tree canopies in order to mitigate the myriad social, environmental, and health issues that plague cities like Cleveland. Fortunately, Cleveland has taken the first step on this road with the release and adoption of its tree plan. Hopefully we can work together to expand the city’s tree canopy in order to tap into the numerous benefits that trees provide.
Maybe the next time you look out your window at your tree lawn, you will see the tree standing there in a different light. It’s time we appreciate and better care for our trees in Cleveland. They just might extend your life.