Ecosystem services are functions performed by ecosystems that are directly useful to humanity [1]. Common ecosystem services include air pollution removal, mitigation of storm water (reduction of runoff), water purification, control of erosion, protection from extreme storms, tourism, carbon sequestration, and provision of food, fuel and fiber. The Millennium Ecosystem Assessment report found that the functioning of the world’s ecosystems is declining, and that humanity is dependent on ecosystem functions and services for our well-being [2].

Understanding and valuing these ecosystem services is one important step towardprotecting and managing them. Two efforts are the i-Tree project and the Natural Capital Project.

“Natural coastline like this in Rehoboth Bay, Del., can protect homes and cities against storms” [3].







Readers of this blog may be familiar with the i-Tree project from other posts.  The i-Tree project continues to expand, aiming to further advance our understanding of ecosystem services and provide tools to help cities and communities improve the management of these resources.  One current research area is urban forest optimization (UFO – I want to believe!), also known as an urban forest decision support tool. This research aims to fill the need for a quantitative, scientifically informed means to maximize the various benefits of the urban forest and understand the tradeoffs between them.

These tradeoffs between ecosystem services can be quite complex. For instance, there is likely an optimal set of locations to plant trees to address stormwater retention, but a different set of optimal locations to address air pollution. When multiple ecosystem services are considered together, the problem gets rather complicated. A formal optimization analysis will help cities get the most out of their trees and urban forest budgets.

One local potential test case for the optimization or decision support tool is Onondaga County’s Save the Rain tree planting program that will plant 8,500 street trees in Syracuse, NY by 2018 [4]. About 1,200 trees have already been planted, so the remaining project provides an opportunity for testing the optimization algorithm. How could such a tool provide additional guidance on where to plant the remaining 7,300 trees or maximize other ecosystem services while still meeting Save the Rain’s goal of increasing stormwater infiltration?


Save the Rain’s street tree planting program trains community
members in the planting, maintenance, and identification of trees [5].

Where possible, the UFO project will further expand the scope of ecosystem services considered to include socioeconomic benefits including the effect of urban forests on physical activity and health and its contribution to neighborhood cohesiveness. Such largely unaccounted-for benefits of urban forests are a challenge to quantify or value, but if understood could advance our knowledge and practice of urban forestry in support of human health and well-being.   An additional area of focus will be on quantitative measures of inequality, such as spatial and demographic inequality in air pollution risk.  Recent work [6] has adapted quantitative inequality indices from the global development field for air quality and urban studies.


Coastal Systems and the Natural Capital Project
Another important focus related to ecosystem services is the resilience of ecosystems. How can ecosystems be managed to be more resilient against natural disasters and other stresses, and how can ecosystem management decrease the risk of disasters or extreme events to humanity? This is especially important for coastal regions.

Researchers at Stanford’s Woods Institute for the Environment and the Natural Capital Project quantified the risk to US coastal areas due to sea level rise and extreme storms. They calculated potential savings to property and lives saved, also calculating a hazard index based on risk to property value and human lives. They analyzed differences in risk and hazard ratings by age and income groups to examine potential disparity, and also compared risk indices between locations with and without significant natural coastal ecosystems. They compiled this information in a national map showing the risk indices, as seen below.


Coastal hazard index for the United States and human population
by state with and without natural coastal habitats [7].

According to the study, “the number of people, poor families, elderly, and total value of residential property that are most exposed to hazards can be reduced in half if existing coastal habitats remain fully intact.”  The study is useful to policy makers and managers because it shows where conservation and restoration of reefs and coastal vegetation have the greatest potential to protect coastal communities. It also shows the value of maintaining existing natural coastal systems [8].

As our understanding of ecosystems and the crucial services they provide grows, our ability to manage them and integrate human society with nature will improve.



1.  Another definition of ecosystem services is “the stream of vital benefits flowing from natural capital to people”, where natural capital is the “Earth’s lands, waters and their biodiversity”. (

2.  Millennium ecosystem assessment synthesis report. Millennium Ecosystem Assessment, 2005.


6.  Fann, Neal, et al. “Maximizing Health Benefits and Minimizing Inequality: Incorporating Local‐Scale Data in the Design and Evaluation of Air Quality Policies.” Risk Analysis 31.6 (2011): 908-922.

7.  Arkema et al. Coastal habitats shield people and property from sea-level rise and storms.  Nature Climate Change 2013. 

8.  ibid