In a city with 45,000 hungry children, a growing homeless population and a school system that needs major improvements, why was the mayor of Washington standing under a tulip poplar yesterday talking about trees?

Mayor Anthony A. Williams posed that question himself in the chilly air swirling around Pierce Park in Northwest Washington's Adams-Morgan community. The answer, he said, is that trees are a symbol of how a city views itself. Trees matter.

"If we can't take care of our trees, how are we going to take care of our schools? How are we going to take care of our roads?" Williams said at a news conference he held to call attention to the plight of the District's trees. "Trees are a metaphor of public space. That's what we're fighting for--vital, robust public spaces."

Dating to Thomas Jefferson's presidency, Washington has had a reputation as one of the greenest world capitals, eventually picking up the moniker "City of Trees." The D.C. government pioneered one of the most diversified street tree planting programs in the nation, "not only making the District's trees famous, but also enhancing the prestige of the District itself," according to a 1968 street trees study.

A recent report by American Forests, a nonprofit conservation group, documents the loss of trees in the District. Another report by the Committee of 100 on the Federal City asks Williams to set a goal of planting 30,000 trees over the next three years.

American Forests brought satellite images to the mayor's news conference that showed the dramatic change in the city's tree cover since 1973. The group said the number of acres of heavy tree cover has dropped 64 percent since then, as trees fell victim to disease, development and natural attrition--and weren't replaced. The steady decline was visible in photos that showed a spreading dark image replacing splotches of green where trees once grew.

"It's quite straightforward: We need money," said Sarah Boasberg, of the Committee of 100 on the Federal City, a planning advocacy group. The committee also urged officials to be more aggressive about saving the District's remaining elm trees and expanding its program to remove hazardous trees and limbs.

Williams did not commit to the 30,000-tree goal but cited the strides the city has made in its tree planting and removal program. He said the city has budgeted $9 million for the tree program this year, about $6 million more than it was spending four years ago.

In 1995 and '96, the gloomiest days of the city's financial crisis, no trees were planted to replace the 4,000 trees a year that die. By contrast, about 3,000 trees were planted between October 1998 and April 1999, and the city has contracts for another 4,800 trees in the current planting season that runs through next spring.

A shortage of trees in East Coast nurseries is keeping the District from planting trees as fast as officials would like, said Sandra Hill, chief of the city's tree and landscaping division. The city is seeking oaks, maples, elms and male ginkgos between 2 inches and 2 1/2 inches in diameter but has frequently had to settle for smaller trees.

"Over the next two years," Hill said, "you're going to see a lot of progress made toward returning Washington to be 'the City of Trees.' "

The District has added a second full-time horticulturist and has three contracts with companies to trim trees and remove dead ones. Until now, it had only one such contract. The city has a backlog of about 6,000 dead trees, and as many as 20,000 trees need trimming.

The mayor showed an impressive knowledge of trees yesterday. He said the city has been planting the wrong trees, with weak root structures. And he's been talking to an arborist, who is urging the city to plant more trees on private property where they would have more room to grow.

"It's a quiet crisis," said James R. Lyons, a top U.S. Department of Agriculture official who oversees the federal urban forestry program--and who drives down East Capitol Street every day. He called the elms along his route "the signature of Washington. If we don't take care of them, we lose the character of D.C."

CAPTION: Green spaces such as this in Rock Creek Park are vital to the city, Mayor Anthony A. Williams said. He called trees "a metaphor of public space."

CAPTION: A jogger runs along the Tidal Basin. In 1995 and '96, no trees were planted to replace the 4,000 that die yearly.