This blog contributed by TREE Research Associate Snousha Glaude.

What is the difference between conservation and afforestation? Afforestation is planting new trees. Whereas conservation is protecting and maintaining mature trees. But a tree is a tree, right? Not exactly.

We often overlook how mature trees offer benefits to urban landscapes that surpass that of young saplings. While both juvenile trees and mature trees operate the same physiologically —?the benefits of big trees to our health, communities, and wildlife are far reaching.

Positively Impact Economy

Mature trees provide an economic return on investment.

In storm water management for the United States alone, trees contribute $3 billion in services. Mature tree roots are adept in mitigating erosion and flooding by redirecting surface water run off deep beneath the ground.

Trees are also used in waste water treatment systems to reduce nitrogen and phosphorus from gray water. Bald Cypres is commonly used in waste treatment centers in Florida since it can manage high nitrogen and phosphorus loads without incurring critical damage. Nitrogen and phosphorus when not managed properly can create algae blooms, goopy green sludge that terrorizes lakes, fish, allergies, and local economies.


Sweetwater Wetlands Park
Sweetwater Wetlands Park Waste Management Center, Gainesville, FL
Source: Plants Ou La La

Although the investment aspect intimidates some developers, well planted and maintained trees offer decades of unyielding services.

Environmental Benefits

Promote Public Health through Sense of Belonging

Mature trees promote fellowship — conversations arise as colleagues, townspeople, and strangers seek reprieve from a long trek, blistering weather, and blue light overload from desktop screens beneath a billowing bough. Trees are a third space, a term coined by Ray Oldenburg that refers to where people build community outside of work and home.

Third Spaces drive public health. A meta study of over 300,000 participants across all ages indicates that there is a significant increase in life expectancy in socially active adults. Typically smoking, alcohol consumption and obesity are at the forefront of public health conversation. Although increasingly, social interaction is used as a medically relevant metric to improve quality of life and life expectancy interventions.


Washington Monument
Photo by Harrison Mitchell on Unsplash

But flybye, groaning about the weather beneath a shady branch is only a facet of how trees draw people together. Mature trees serve as a symbol in our communities. Pecan festivals, cherry blossom spectaculars, tropical fruit fairs, autumn leaves extravaganzas and so on drive local tourism, co-create a city’s identity, promote singles, neighbors, families and out of town vacationers to commune and rejoice. We need Third Spaces to detach from dangerous internet silos that have become the norm. People today are more polarized than any time in history. A shared love of nature encourages people of all generations, abilities, ethnic groups, marital status, faiths and professions to meet who may not otherwise. This creates a ripple effect from the sense of belonging, to establishing a local identity, to feeling more safe, to personal responsibility to protect local traditions.

Habitat for Local Wildlife

Mature trees support bees, butterflies, raptor, song birds, frogs, peacocks, bats and the occasional strong willed botanist.

These animals are not just intriguing; they’re hardworking members of our society. Insects and birds cross pollinate for thousands of miles collectively, allowing the dazzling blooms, nectar, and fruit we rely on.

Vultures remove roadkill that without public health intervention would lead to disease.

Flying bird
Photo by Chris Briggs on Unsplash

Likewise raptors manage rodent, snake and pest populations in urban setting. Mature trees are habitat for these birds who perch on branches to exert territorial dominance. In addition, raptors have been assessed as biological controls for agricultural pests on farmlands?(namely voles, squirrels, and rabbits). The effectiveness of raptors as total biological controls requires further study and research design. As natural predators of these organisms, the question isn’t whether they are providing these services but moreso to what extent and how much farmers must supplement rodent management services with rodenticide and traps. Perhaps raptors silently provide these services to urban gardens, although their urban contributions require more study.

Photo by Joydeep Sensarma on Unsplash

Urban Heat Island Effect

Urban Heat Island effect was first observed in the 1800s by English scientists who noted that it is hotter inland towards the city than in rural and suburban areas. While most people tolerate heat with floppy hats and sunscreen, many are not as fortunate. Heat stress can quickly become life threatening. A study by the National Hospital Discharge Association found that in the year 2004 alone, over 440,000 patients were admitted into urgent or emergency clinical care due to dehydration, totaling over $5 billion in hospital fees. But why are cities so hot anyway?

The increased, localized temperature in urban areas is due to a combination of factors including higher carbon emissions from cars and factories, and a higher surface area of radiation trapping materials like concrete and non-reflective surfaces.

Street view with 2 men
Photo by Kat Maryschuk on Unsplash


Also contributing to Urban Heat Island effect is the cities geometry; tall building create funnel shapes that siphon heat. Of course, highly urbanized areas are predicated on the clearance of trees. A trade-off of which is waving goodbye to the special resources mature trees provide, namely solar radiation distribution, shade, carbon sequestration, and transpiration; AKA cooler feeling air.


Sustainable Design and Development Chart
The dips and spikes in surface temperatures over the pond area show how water maintains a nearly constant temperature day and night because it does not absorb the sun’s energy the same way as buildings and paved surfaces.


A case study found that impervious (treeless) urban surfaces were as much as 1.3 Celsius (34.34 Fahrenheit) than areas shaded by vegetation. The cooler temperatures create a ripple effect since utilities like air conditioning for commercial properties decrease, causing less industrial waste and carbon emissions. Trees also participate in transpiration. Transpiration is the release of water from specialized plant leaf cells called stomata. As water is evaporated from the plant’s surface, heat is absorbed, lowering surrounding temperature. As temperatures and urban populations climb, trees are gaining reverence among city residents.

Erosion Mitigation

Erosion occurs when sandbars are diminished after storms. Hurricanes, flooding, and heavy rains eliminate the deposit between properties and coastal areas. Coral reefs, oyster reefs, and aquatic plants are common barriers. Mechnically barriers exist also. But protected trees such as mangroves protect against erosion. It is estimated that billions of damage is caused to assist in erosion efforts. Even trees more inland have an impact, such as the cypress trees in man-made lakes mentioned earlier. The trees maintain a presentable appearance of these entrapments and provide sustainable resources like habitat for animals.

Scooter on sidewalk
Photo by Fons Heijnsbroek on Unsplash

When salt water interacts with freshwater sources, the ecosystem changes. Fish, plants, and other animals must adapt or find new environments.

Salinization of freshwater sources becomes increasingly frequent due to sea level rise.

Trees, halophytes especially, impact the water upstream. Although they do not de-salinate the water, via mitigating erosion, there’s a secondary impact slowing the process of salinization of freshwater and continued balance within local ecosystems.

Reduced Crime


In communities where trees are available there is an inverse association with crime. Although causation does not equate to correlation, urban planners apply this knowledge towards new development.

Researchers in Philadelphia, Cincinnati, and Portland, Oregan have studied the inverse relationship with levels of crime and tree presence. Reduced delinquency is important because everyone would like to live in safe communities. Plus the cost of expanding police forces to accommodate rising crime accounts for billions of dollars annually. Therefore implementation of street trees in urban planning is a cost effective avenue towards the overall goal of crime reduction.


Sidewalk Cafe
Photo by Lily Banse on Unsplash

Trees impact every aspect of urban living including public health, civic engagement, reducing crime, and stimulating economy.