I made some comments about that in my initial remarks, but I think we know both instinctively and empirically that trees make a huge difference to the value of individual properties. It is much more difficult to quanitfy. I've done some research in this area in making presentations to the City of Winnipeg, for example, and there are numbers all over the place. Certainly no Canadian research was useful, but there's lots of research from the U.S.
I can give you a negative when it comes to replacing trees, Moscow planted a million trees at great expense when they came out from behind the Iron Curtain, and 80% of them died. You can see the difficulty if you don't keep up your urban infrastructure.
I don't know if anyone here has been to Truro, but the trees there were subjected to the emerald ash borer back in the early part of the century when the ash borer came to Canada. It took away nearly 100% of the trees. There may be a handful left. If you go to that town, you get a really strong sense of the impact. They stripped the bark off their elm trees, and turned them into icons that celebrate their pioneers and all the good things in their community. That's how much the trees mean to them.
While it is hard to attach dollars and cents to some things because the studies are few—and I think Mark has one that he can point to— certainly you can see all around you the difficulties you have if you don't include the maintenance of trees. Many of them were planted at the beginning of the last century, 80 to 100 years ago. Some of them can live to be 200 or 300 years old. Replacing them would take that much more time and that much more money.