Nearly three weeks have passed, and still the terrible whine of chain saws fills the air and the dreadful bareness of the sky persists where green branches once provided a canopy of shade and beauty.

Minneapolis lost more than 5,000 trees on public and private property, and St. Paul nearly 1,000, during waves of storms that started the night of June 20. Cleaning up the mess will take the rest of the summer; refilling the emptiness will take decades. Our cities and inner suburbs should be accustomed by now to mourning the repeated loss of trees. Nature has been at war with our urban forest for 40 years, but these losses don't get easier.

Dutch elm disease struck in the 1970s, destroying forever the graceful green archways that once gave our streets a storybook charm. The elms were replaced by fast-growing ash, which quickly became targets for the insidious emerald ash borer. And now, almost certainly fueled by a changing climate, summer storms have become more frequent and more violent to the point that homeowners and city forestry departments are struggling to keep up with the losses.

"We're not giving up on trees," Jayne Miller, superintendent of the Minneapolis park system, insisted.

While she understands the "why bother" attitude coming from some quarters, Miller said that trees are more important than ever, both ecologically and aesthetically, in a climate that's getting warmer and more volatile. They're needed for managing stormwater, she said, as well as for cooling the urban "heat island" and for absorbing the atmosphere's excessive carbon dioxide. "We recognize that we have challenges, but the benefits of trees far outweigh any thought of not replacing them."

We agree. Trees are an increasingly important element in the urban ecology, a word that is coming to mean not just harmony with nature but the interdependence of many economic, social and cultural forces. It was in that context that Minneapolis Mayor R.T. Rybak asked three provocative questions that deserve answers, especially considering the likelihood that frequent blowdown storms are here to stay:

• Is there a more secure and reliable way to deliver electrical service than to continue stringing lines overhead only to see them blown down time and again? Underground lines are clearly more expensive to install. But have those costs been measured against the long-term repair savings and against the productivity gains that would result from a half-million people not losing power for days at a time?

• Should city public works departments reconsider their sidewalk designs in order to accommodate tree roots? Anecdotal evidence from the June event suggested that new sidewalk construction severed roots and compromised the stability of many mature trees. Permeable, elevated or grated sidewalks might pay off in some places, helping not only tree roots but drainage.

• Should cities consider planting sturdier or more flexible varieties of trees, even if they don't provide quite the overhead spread and shade that residents hope for?

Rybak doesn't yet know the answers, but suggests that his city and others explore the best ways to adapt to the reality of climate change. "We've found out the hard way that you can't win a war against nature," he said. "A better response is to try to get back to the most natural state as possible."

As for the growing burden of cleanup and replanting, neither the Minneapolis nor the St. Paul parks departments can yet assess the impact of the June storms on their replanting budgets. Minneapolis has been planting 5,000 to 6,000 trees a year and St. Paul about 2,500, but now they may need to rely more on private sources to keep up the pace.

"We're not going to give up on shade," said Rybak. "It's a critical piece of cooling the city in a warmer world."