Why urban forests?

Over half of the world's population lives in urban areas and this number is only growing. The incorporation of green spaces into urban environments is a significant part of urban planning and the U.S. Environmental Protection Agency and many city planners regard them as part of a city's "green infrastructure". However, many urban green spaces are being lost globally due to urban expansion and unplanned economic pressures. Individual trees are threatened by disease and pests, as well as drought, heat, soil compaction, pollution, and other hardships that result from growing in an urban environment.

Urban green spaces and street trees combat air pollution, shade streets and buildings, retain storm water, and help to alleviate climate change through carbon sequestration. They also provide a host of physical and psychological benefits, including increasing property values, encouraging exercise, decreasing crime, and beautifying urban areas. These are examples of ecosystem services, benefits to humans provided by the natural environment. Many of these services are vital to quality of life for city dwellers, and it would cost millions of dollars annually to provide these services in engineered ways. Understanding the dynamics of the urban forest is one of the first steps to planning for the future.

How are we studying urban forests?

Scientists use simple measurements of trunk diameter and species to understand urban forests. With a little training these measurements can also be made by citizen scientists like you. We then use mathematical models to predict growth, mortality, and ecosystem service provisions. Most of the academic studies and municipal surveys of urban trees capture information as a snap shot in time, which is useful for quantifying urban forest cover and valuing ecosystem services, but does not necessarily capture trends which may occur across years.

With the help of volunteers we aim to conduct repeated measurements of urban trees over time, which enables Earthwatch scientists to capture real-time growth and mortality rates and to map the spread of pests and disease. By tracking these changes and investigating specific research questions about how the built environment effects the growth and survival of individual trees we aim to provide information that will help to increase long-term urban forest health and thereby the benefits they provide back to the human communities that live there.

What benefits do urban forests provide?

Society benefits from a number of goods and services that that nature produces, these are called ecosystem services. They can provide cost effective solutions to some of our current urban challenges such as air pollution, extreme heat events, flooding, and poor human health.

Trees have a high potential to sequester carbon, diminish air pollution, mitigate flooding potential, and increase property values. Moreover, trees can directly provide human health benefits in at least two ways. First, climate change is creating more extreme heat events that threaten human well-being. Shade from trees reduces local air temperatures by 5° to 15° F, helping to cool our sidewalks and reducing the costs of cooling buildings. Secondly, exposure to nature and trees even within our cities provides psychological and mental well-being benefits. The ability to view trees and nature improves recovery rate of hospital patients, as well as students' test scores, and reducing stress.

Ecosystem service values for urban trees can be calculated based on a set of measurements that is easy to collect. Through a set of freely available tools developed by the United States Forest Service (e.g. i-Tree Tools) and others (e. g. National Tree Benefit Calculator), My Tree Tracker uses the diameter measurements and tree species to calculate the ecosystem service values for each tree, as well as for the entire city!

Go ahead and choose a tree to see the annual benefits it provides on our Tree Map!