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The Scientific Benefit of Trees: A literature review

This review covers and provides citations for research on the benefits of trees. Click here for a printable PDF version.

Compiled by Jessica Turner-Skoff, PhD
The Scientific Benefit of Trees for People
By 2050, an estimated 66% of the total world’s population will be urban1. Urbanization, coupled with a changing climate, is a challenge on a global scale that greatly impacts the health and well-being of humans. In order to establish healthy and vibrant communities, trees need to be part of the global discussion. Over the past 30 years, science has demonstrated how trees in our landscapes benefit people and that well-maintained trees are an important asset to keep a community healthy and safe. Planting and maintaining trees, as part of urban planning and engineering solutions, can serve as a nature-based solution to many challenges communities face: managing stormwater, supporting mental and physical health for people, reducing crime, addressing pollution, and providing wildlife habitat. Despite the critical importance or urban forest, urban tree cover continues to decline nationwide each year 2.
Investing in trees through planting, care, and maintenance will produce a significant return on investments, especially as older and larger trees provide the most benefits3. Trees are a long-term solution for many issues people face and they are a valuable resource for every community, especially those in urban or suburban settings. Botanical gardens and arboreta play an important role in this pursuit for a healthy and vibrant urban forest. These institutions provide valuable insight and leadership due to their expertise in botany and horticulture, as well as an established track record of public outreach and training. The future of urban forestry should focus on protecting large trees, as well as improving age structure, standards and planning management.
While not comprehensive, this list provides an overview of the many scientific benefits that trees, and greenspace with trees, provide to people both directly and indirectly.
Trees have a high return on investment due to ecosystem services
Experts suggest that every dollar invested on tree planting and management can result in a high return on investment 4,5, even as high as over 500%4. The compensatory value of the urban forest in the continental US is estimated to be worth more than $2.4 trillion6, with $18.3 billion worth of ecosystem benefits occurring annually7. Trees and greenspace provide important direct and indirect benefits social and biological benefits 8,9, such as:
● Reducing stormwater runoff 10–12
● Reducing air and water pollution13–17
● Reducing energy costs and use associated with heating and cooling18–21
● Reducing the urban heat island22
● Protecting roadways and reducing the amount of asphalt sealers required 23
● Reducing noise pollution24
● Providing valuable carbon storage and sequestration 25,26
● Increasing food security of urban areas 27,28
Trees stimulate the local economy The presence of well-cared for trees encourages shoppers to spend more time at a business district, and they will travel a greater distance to visit that center, research has shown. Further, shopping areas with trees are more likely to be ranked as being more comfortable and having better upkeep, friendlier staff, and higher quality products29. Additionally, having well-maintained trees along city streets and retail areas, as well as in residential areas can:
● Increase rental rates of business properties30
● Increase the sale price of a home31–34
● Decrease the time a house is on the market34
Trees keep citizens healthy and happy
The presence of trees and green space on people can:
● Increase attention, memory,35,36, reflection37 and focus38
● Reduce stress39 or increased ability to recover from stress40
● Increase life satisfaction41 and positive thoughts or emotions42–44
● Lower mortality rates from non-accidental deaths45–47
● Shorten recovery times in the hospital48 and increased perception of health49
● Increase physical activity50
● Reduce diastolic blood pressure51
Children and students benefit from the presence of trees, which can:
● Reduce symptoms of attention deficit disorders52,53 and increase attention54,55
● Increase in classroom engagement56
● Improve test scores in reading and mathematics57
● Improve the mood of teenagers and lower their emotions of depression, anger, and fatigue58
● Increase self-discipline, impulse inhibition, and concentration in young girls54
● Improve physical health59
Trees encourage a sense of community and keep people safe
Trees evoke positive strong emotions in people60. Urban residents value trees 61 and people like looking at trees62. Well-maintained trees can reduce crime in a neighborhood. In fact, the loss of trees in neighborhoods due to pest infestation has been positively associated with increases in crime63.
This phenomenon of trees reducing crime rate has been observed in numerous studies:
● Well-maintained trees are related to lower crime rates64–66
● A green view from a home can lower aggression and violence in that home67
● Well-maintained trees are related to reduced property crimes and violent crimes68
Trees encourage people to gather in common outdoor space, causing:
● Increased social capital69,70 and ultimately increased supervision of children71
● Increased sense of community and safety69,72,73
Large, old trees provide the most benefit
Large, old trees are critically important worldwide from an ecological and cultural perspective3. Despite their importance, these trees are declining globally74. While trees in natural environments can survive for 100’s of years, the half-life of an inner street tree is 10 to 15 years75. It is difficult to develop a universal definition for a large, old tree3, largely given the diversity of tree species worldwide3,76, so there are limited management and conservation plans3. Nevertheless, emphasis must be made to preserve large, old trees as they provide numerous benefits3, especially in urban environments77. Once large old trees are lost from the community, it is difficult if not impossible to replace their cultural and ecological function 3.
Large trees provide critical benefits for their role in:
● Creating habitat for other species3,77,78
● Managing important environmental cycles and processes 3
● Storing and sequestering significant amounts of carbon79
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3. Lindenmayer, D. B. & Laurance, W. F. The ecology, distribution, conservation and management of large old trees. Biol. Rev. Camb. Philos. Soc. 92, 1434–1458 (2017).
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