About 375,000 shade trees have been given away to [Sacramento's] city residents in the past 16 years, and there are plans to plant at least 4 million more. To receive up to 10 free trees, residents simply call the Sacramento Municipal Utility District, a publicly owned power company.

"A week later, they are here to tell you where the trees should be planted and how to take care of them," said Arlene Willard, a retired welfare case worker who with her husband, John, has planted four SMUD trees in the back yard of their east Sacramento house.

Perhaps the most arresting feature of Sacramento's shade crusade is its rarity, despite federal research showing that carefully planted trees can lower summertime temperatures in cities, significantly reduce air-conditioning bills and trap greenhouse gases responsible for global warming.

Most American cities have shrinking tree canopies in relation to their growth. That's because of inadequate budgets to maintain older trees and a failure to plant shade trees in new residential and commercial developments, according to federal experts, tree-planting organisations and scholars of urban ecology.

'Creeping cancer'

A number of major cities have launched sizable tree-planting programmes - including Washington, Baltimore, Minneapolis, Chicago, Denver and Los Angeles. Still, the decline in tree cover has been accelerating since the 1970s, especially on private property and new development, according to American Forests, an environmental group in Washington that uses satellite imagery to document tree cover across the country.

"This is like a creeping cancer," said Deborah Gangloff, the group's executive director. "In the two dozen cities we have studied, we have noticed about a 25 per cent decline in tree canopy cover over the past 30 years. This is a dramatic trend that is costing cities billions of dollars."

And the trend continues even as cities heat up. Along with much of California, Sacramento set a record for heat this summer, with 11 straight days above 100 degrees.

Many major utility companies are declining to act on the connection between urban trees and energy savings, according to Agriculture Undersecretary Mark Rey, who oversees the Forest Service."It is one of our new focuses to give them information and incentives to do this," Rey said

Three shade trees strategically planted around a house can reduce home air-conditioning bills by about 30 per cent in hot, dry cities such as Sacramento, and a nationwide shade programme similar to the one here could reduce air-conditioning use by at least 10 per cent, according to Energy Department research.

Falling funds

Washington is among the cities with the largest reduction in dense tree cover, with a 64 per cent decline from 1973 to 1997, according to American Forests. Althouh there has since been considerable effort and expense to plant more trees in Washington, experts disagree about whether the tree canopy has been stabilised. They do agree that rapid canopy decline continues in Washington's outlying suburbs.

Although Bush administration officials say urban trees are a priority, spending on the federal Urban and Community Forestry Program has declined by about 25 per cent in the past four years, from a high of $36 million annually to a proposed $27 million in the coming year.

"People have been fighting for crumbs for so long," said Mark Buscaino, who quit this summer after three years as director of the federal urban trees programme. He is now executive director of the Casey Trees Endowment Fund, a private tree-planting group in Washington.

Tree-planting in U.S. cities has been championed as a way to beautify and civilize the hard edges of urban life. (Before air conditioning, it was also a primary strategy for keeping cities cool.) But a growing body of scientific research, most of it federally funded, shows that urban trees are also shrewd investments.

Sacramento's shade crusade easily pays for itself, with summertime energy savings about double what SMUD spends on trees each year. As they mature, trees already planted by the utility are expected to save enough electricity to power about 14,000 homes.

Cultural blocks

There are cultural reasons why the research findings have failed to sway the nation's utility managers, transportation engineers and municipal planners, according to Kathleen Wolf, a social science researcher at the University of Washington's College of Forest Resources.

"These people have not yet reconciled how a green living thing interacts with grey infrastructure," said Wolf, whose research is funded by the Forest Service. "There has not yet been a mind shift that says trees are technology. In most American cities and states, we are not having that discussion."

But it is not just engineers and road builders who balk. About one-third of Sacramento utility customers tell SMUD that they do not want to mess with more trees in their yards and will not accept free ones.

"Many people just don't like trees because they are dirty," said Buscaino, the former head of the federal urban forest program. "We have a lifestyle where the last thing on people's mind is trimming their trees."

Iowa is the only state with a long-term record of using state law to push private utilities to plant trees for energy conservation - and to allow them to recover the cost in electricity rates.

Over the past 15 years, the programme has been a spectacular success, according to the private utilities there and Trees Forever, a non-profit group that helps run the programme. In addition to the quantifiable benefits - half a million trees planted, reduced energy costs and savings on storm-water drainage construction - utilities say the programme has been a public relations bonanza.

"It is difficult to put a value on the community relationships we have built with the trees," said Karmen Wilhelm, a spokeswoman for Alliant Energy, a major utility in Iowa. "It has been wonderful for our reputation."

© 2006 The Washington Post Company

Blaine Harden is a Washington Post Staff Writer. The full text of this article appeared in that newspaper on September 4, 2006.

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