Any city's streets boast thousands of trees lining the boulevards, to say nothing of the thousands of others of various types planted around homes.

Each one of them represents a small picture of our environment and how we're wasting it and its resources.

On one hand, we can understand how beneficial trees can be. All you have to do is drive into a shaded suburb on a hot summer's day and you'll find it's about five degrees cooler in the shade.

The trees provide a cover which prevents the sun's rays from fading draperies inside the home. They also create homes for thousands of birds which, in turn, provide enjoyment to those who like watching avian antics.

But the trees also grow. Every year, new branches appear, and old ones die. Leaves drop, and the homeowner has to find a rake. Sometimes it gets to be too much, and it's time to call in the wood butcher who will snarl his chainsaw through decades-old branches.

Which brings me to my point: why do we, literally, throw away millions of dollars worth of valuable lumber every year, in the form of unwanted tree trunks?

The best approach would be to preserve our urban forests. But prudent cutting and use is definitely the next best option. It's really not that different than the issues that come up around the harvesting of large forests. If trees are cut selectively, those precious natural resources can be used sustainably.

Mature older trees can be "harvested," just like they do in the forests. That means cutting down the tree in a sensible way, realizing they're a resource and not a nuisance.

After all, in eastern parts of the country, some farmers figure their life's contribution has been in the wood lot, where they've harvested trees their grandfathers planted -- and where they've planted new trees for their grandchildren.

That old elm or maple that's threatening the power lines might be worth a lot more than the average homeowner realizes. There's a whole new profession -- the "urban sawyer" -- who can harvest the tree and its lumber and save it from the land fill.

Normally, tree trunks and branches go directly to land fill sites. The exception is if an area has a problem with Dutch Elm Disease, all elm tree trunks must be destroyed -- the wood isn't infected, but the bark is.

But the urban sawyer, if the job's big enough, will bring a portable sawmill to your house once the tree's been chopped down. Then he'll rip the trunk into boards, which are then dried and, a few months later, planed into fine hardwood lumber.

That lumber -- elm, maple, birch or whatever kind of tree that's been growing in your yard for years -- is worth a lot of money. Try and find a length of good hardwood in your average lumber yard -- but take your gold card with you! Hardwood sells for something like $10 a board foot.

Next time you want to take down that tree that's been blocking your view for years, think a little about recycling. It doesn't just apply to tin can, but everything in our lives -- trees included.

When we start believing in re-using all our resources, we won't have an "energy crunch" or a "garbage crisis." We'll be back to the way humans have done things for centuries.