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  • Planning
  • Action
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The City has completed a comprehensive Climate Change Vulnerability Assessment and is developing a Climate Change Preparedness and Resilience Plan. The urban forest is viewed as both a resource with vulnerabilities to climate change and an asset in helping the community manage the impacts of climate change.
Sign that tells the public a new tree will soon be planted
a curb bump-out with a tree planted
a bicycle with a trailer used for watering with a city worker standing next to it
aerial view showing tree canopy locations

Project Area

Cooling potential of the city's urban forest
Cambridge is a dense, urban community located adjacent to Boston founded in 1630. About 106,000 people reside in the city’s 6.3 square miles. Based on 2009 LiDAR data, a University of Vermont analysis found that 30 percent of the city’s land area is covered by the urban forest canopy. There is a maximum potential to expand the canopy by another 35 percent, with the remainder being unsuitable for urban forest expansion. Institutional, commercial, and residential land uses dominate the landscape. Significant green space is located around Fresh Pond, a drinking water supply reservoir; the Alewife Reservation; Danehy Park located on a former landfill; and the Charles River Reservation. The City also has a significant network of neighborhood parks and recreation facilities.

Management Goals

urban landscape with a street, building, and some trees.

The City has completed a comprehensive Climate Change Vulnerability Assessment and is developing a Climate Change Preparedness and Resilience Plan. The urban forest is viewed as both a resource with vulnerabilities to climate change and an asset in helping the community manage the impacts of climate change. The vulnerability assessment includes an element focused on the urban forest. In addition, the City has worked with the Earthwatch Institute to assess the health of public trees. The goal of the City is to manage the urban forest to reduce its vulnerabilities and to expand and strengthen the urban forest to help mitigate the impacts from increasing temperatures and precipitation.

Climate Change Impacts

For this project, the most important anticipated climate change impacts include:
Increasing temperatures exacerbated by the urban heat island effect leading to more days of extreme temperatures, and more and longer heat waves.
Increasing rates of precipitation increasing the extent and depth of flooding from riverine systems and piped infrastructure.
Increased probability of insect and other vectors carrying diseases for both humans and trees.

Challenges and Opportunities

Climate change will present challenges and opportunities for accomplishing the management objectives of this project, including:

Challenges

Maintenance of trees during drought conditions
Insects and diseases that benefit from the changing climate and from the increased stress on trees
Most potential to expand the urban forest is on private property
Effects of urban pollution, particularly on street trees

Opportunities

The City Urban Forestry Division has a strong tree planting and maintenance program that has diversified the City tree species, has a 6 year pruning cycle, a watering program, and community partnerships, which can be built upon
The tree species list for new plantings can be updated to factor in climate change
The City will be preparing an urban forest master plan that views the urban forest as a system, covers both public and private property, and will address climate change
Engagement with property owners of all types can raise awareness of the urban forest in terms of its vulnerabilities and its potential to mitigate climate change, and to foster opportunities to expand the canopy

Adaptation Actions

Project participants used the Adaptation Workbook to develop several adaptation actions for this project, including:

Area/Topic
Approach
Tactics
1.1. Maintain or restore soils and nutrient cycling in urban areas.
1.2. Maintain or restore hydrology
Providing adequate soil volume, structure, and organic matter during street reconstruction
Replacing soil if toxicity or chemical levels are affecting tree growth
Restore hydrology with permeable paving, suspended surfaces, and/or Silva cells
5.1. Promote diverse age structure
Promote diverse age structure by planting trees in anticipation of mortality from Asian Longhorned Beetle and Emerald Ash Borer
8.1. Use seeds, germplasm, and other genetic material from across a greater geographic range
9.7. Introduce species that are expected to be adapted to future conditions
Use climate change projections to determine what region the City is anticipated to resemble in the future and select species appropriately
Use cultivars that will be better suited to a hotter climate and one that experiences ranges of drought and flooding

Monitoring

Project participants identified several monitoring items that could help inform future management, including:
The City maintains a GIS public tree inventory. The City Arborist uses a work management program called Cartegraph which is linked to the GIS tree inventory and allows each tree to be tracked over time.
The City has also mapped the entire urban forest canopy based on LiDAR data. A second mapping has been conducted and is being used to compare changes in the extent of the urban forest in Cambridge.

Next Steps

The City will continue implementing its planting, maintenance, and community engagement efforts and using data to continue improving urban forest management and planning. The next major step for Cambridge is the development of an urban forest master plan in 2018.

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Keywords

Diseases
Insect pests
Planting
Urban

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