Designing Urban Forests


Trees add texture and services (shade and temperature modification) in urban environments. (Photo by Rod Kindlund).

Urban forestry managers can find it useful to assess their cities’ programs using a cost-benefit analysis, many of which have been incorporated into the free online tool iTree, developed by the U.S. Forest Service with collaborators. Species selection can influence both the quantitative and qualitative values of the urban forest as discussed below.

The Importance of Diversity

The metaphor comparing biological diversity …

Cost-Benefit Approach to Urban Forests: A Western Analysis


Urban tree programs have expenses for planting, maintenance, even sidewalk repair. Yet the benefits of urban trees in five western cities analyzed outweighed the costs by ratios of 1.37 to 3.09.

For the analysis, samples of 30 to 70 randomly selected trees from each of the most abundant species were surveyed in five cities: Fort Collins, Colorado; Cheyenne, Wyoming; Bismarck, North Dakota; Berkeley, California; and Glendale, Arizona. All of these cities were surveyed by the U.S. Forest Service during the …

Trees and Local Temperature

Trees shading parking lot.
Figure 1. Trees shade an urban parking lot.

Written by Melanie Lenart

Urban forests can help keep cities within a healthy temperature range, although the exact temperature reduction from urban forests is difficult to measure. The extent of the effect varies in space and in time, which complicates the issue, but large parks or tracts of urban trees can cool daytime summer air temperatures by about 10°F (McPherson and Simpson 1995).

Increasing the green cover of cities by 10% or …

Climate Mitigation by Urban Forests


Planting trees in urban areas can help mitigate carbon dioxide levels because trees can sequester carbon and offset some energy use for cooling, as some studies have illustrated in California.

urban trees The California Global Warming Solutions Act of 2006 (AB32) requires a reduction in greenhouse gas emissions to 1990 levels by 2020. This amounts to a reduction of 173 million metric tons from the level projected for 2020.

Aerial photography revealed 242 million potential sites for planting individual trees …

The Debate about Assisted Migration

Adapted from McLachlan, J.S., J.J. Hellman, and M.W. Schwartz. 2007. A framework for debate of assisted migration in an era of climate change. Conservation Biology. 21(2):297-302. Quotes taken from: Nijhuis, M., 2008. Taking wilderness in hand: rescuing species. Orion Magazine, May/June 2008.
Figure 1. The Torreya Guardians have already begun to transplant members of the southeastern conifer Torreya taxifolia beyond its native habitat in Florida and Georgia, an issue that sparks debate about assisted migration. Photo: U.S. Fish and Wildlife

Carbon Budgets

Excerpt from Ryan, M.G., M.E. Harmon, R.A. Birdsey, C.P. Giardina, L.S. Heath, R.A. Houghton, R.B. Jackson, D.C. McKinley, J.F. Morrison, B.C. Murray, D.E. Pataki, and K.E. Skog. 2010. A Synthesis of the Science on Forests and Carbon for U.S. Forests. Issues in Ecology, Report Number 13, Spring 2010.

Forests store large amounts of carbon in their live and dead wood and soil and play an
active role in controlling the concentration of CO2 in the atmosphere (Figure 1). In …

Climate Change and Planting Trees

Written by Chris Schnepf, University of Idaho

Climate change questions are especially important for tree planters to consider. Gardeners and farmers usually only have to anticipate climate over the coming months. However, tree planters must anticipate climate over the next 30 years or more and consider not only the average anticipated climate conditions but, more critically, extremes of temperature, drought, and other environmental conditions the trees may have to endure. This is difficult enough for a given site assuming past …

Assisted Migration

Written by Glenn Ahrens, Oregon State University
Figure 1. A lodgepole pine provenance experiment in New Zealand (Wright 1976).

Trees are genetically adapted to local climate. As climate changes, local populations may become maladapted. Because many tree species do not produce seed for several years after establishment, and because multiple generations are required for adaptation to occur, climate is expected to change faster than species or populations can adapt. One potential solution is assisted migration – the deliberate establishment of …

Techniques for Treating Bark Beetle in Forest Stands, Individual Trees, and Firewood

Written by Tom DeGomez, University of Arizona Cooperative Extension

Large-scale infestations of bark beetle can create havoc on landscapes, costing landowners thousands of dollars in damage and lost revenue. Based on historical records, bark beetle outbreaks are relatively short lived and are rarely sustained for long periods of time. However, high tree densities and expected changes in drought conditions, especially for the southwestern United States, may also alter the severity and extent of bark beetle outbreaks in many areas. The …

Silviculture and Climate Change

Written by Ronald Mahoney

Silviculture deals with management decisions in ecosystems dominated by trees. But other organisms and ecosystem components besides trees are affected by climate change. Trees are the most visible barometer of change, and because they are usually the dominant organisms in forests, changes in trees have many ecological as well as economic consequences. Most temporary changes as well as long-term changes are beneficial to some organisms and detrimental to others.

Silviculturists, other natural resource professionals, and landowners …