Right now, it's at 8 percent and falling.
That means, in order to meet its goal, Tucson would need about 2 million more trees than the estimated 1.6 million it has now. That's a daunting task, to say the least.
"We have fewer trees in Tucson than we had ten years ago," said Tom Ellis, the director of Tucson Clean and Beautiful. "If we don't change where we are going, we will definitely have less trees in the future than more trees."
Trees are often taken for granted, but they provide a variety of benefits such as cleaner air, energy savings, noise abatement, water management, and shade.
"There's less crime in neighborhoods that have trees," said Meg Johnson, of the Garden District Neighborhood. "And that's due to other features like a sense of community."
The Garden District has plenty of that. A tree planting movement twenty years ago, ended up with a thousand trees being planted. But it hasn't stopped there.
"We had 215 trees planted and have 100 homes that volunteered to have those trees planted," Johnson said of a recent effort.
Still despite some of their best efforts, many of the older, more valuable trees planted decades ago are dying.
"We are losing some of our old trees," Johnson said. "Climate change has made it so there is less water and more extreme heat.
Signs of that are dotted on street corners all over the city.
At Park and Bantam stands a tree, an aleppo pine 60 feet tall, on the northeast corner, which is dead. It's not an unusual sight as more and more older trees die all over town. It was probably planted in the 50's or 60's, when about 100,000 of them were planted.
"I've got a friend in the tree business in Tucson and she says there are at least several thousand that are declining or dead already," Ellis said.
Business support is especially important because many have one, two or three per cent coverage, when it could be much more.
"It's in their best interest to give up a little pavement in their parking lot," said Ellis. "When you go to a parking lot, what's the first thing you look for - shade."
People will travel to places that have trees, it's good for commerce and tourism Ellis said.
But homeowners can see a benefit too.
"Every mature tree you have adds a thousand dollars or more to the value of your home," Johnson said. "Curb appeal you can't beat."