The city plans to mulch some of these trees for use on public playgrounds, which are due for a collective overhaul over the next 10 years.
But some, depending on where they are, could become beams in new homes or offices, thanks to work by an innovative Madison business.
WholeTrees was founded in 2007 by architect Roald Gundersen and Amelia Baxter in Stoddard, near La Crosse. They moved the business to an office on Williamson Street in April 2013.
WholeTrees' vision is both wide-ranging and simple: take invasive, fallen, diseased trees and forest byproducts — like smaller trees from a crowded stand — and use them whole, to maximize their strength and beauty.
Ash trees slated for demolition on Madison streets "could absolutely be used" in homes and other buildings, Baxter said. "They have tremendous structural capacity.
"What it requires is a market. Our role as a company, in part, is to prove there is a growing market for round timber. We are working with Madison owners who want to put ash in their buildings ... but it's all market-driven."
For WholeTrees, that market has exploded since a 2009 article in the New York Times attracted a lot of attention for the company.
In the story, reporter Anne Raver noted that whole, unmilled trees "can support 50 percent more weight than the largest piece of lumber milled from the same tree."
Also, she wrote, "taking small trees from a crowded stand in the forest is much like thinning carrots in a row: the remaining plants get more light, air and nutrients."
Whole trees used as timber are peeled, air- or kiln-dried and treated with insecticide and fire retardant. They're "greener" than steel and, according to WholeTrees, more fire resistant, too (they char, but do not burn or melt).
"For every ton of wood, a ton-and-a-half of carbon dioxide is locked up," Gundersen told Raver.
"Producing a ton of steel releases two to five tons of carbon. So the more whole wood is used in place of steel, the less carbon is pumped into the air."
Since that story ran, WholeTrees has expanded from six employees to 17. In 2009, the business grossed $150,000; in 2013, that number was about $1 million.
They have also raised $1.1 million in federal research grants, working extensively with the U.S. Department of Agriculture Forest Products Laboratory in Madison.
The response to the Times story "told us we were on the right track," Baxter said.
"People are drawn toward the use of this material, and the feel of the tree in buildings," she said. "We knew we were in a place where we needed to scale something commercial."
Since then, Madison has become WholeTrees' hub for outreach and research work with the USDA. The first office is still located near La Crosse near 130 acres of farm forest, Baxter said. That's where the company makes "custom, beautiful work."
The look of whole trees in urban environments doesn't have to be "lodge-y" or rustic, she said — instead, it can be "avant garde and intelligent."
As demand for whole tree lumber started to rise, the business moved away from general contracting and now does primarily architecture and engineering as a subcontractor.
"Now we’re beginning to source timber from the Wisconsin River Valley," Baxter said. "We're working with the DNR and some private forest owners. We've worked with the Army Corps of Engineers to use black locust, an invasive species, in construction."
"Black locust is a brilliant exterior tree; it doesn’t rot for decades," she added. "But it's also an invasive in Wisconsin, so it's a wonderful piece of inventory for us."
Baxter, whose background is in sustainable land management and agriculture, noted that when it comes to using whole trees in buildings, the product itself is in bountiful supply.
"The resource itself is so abundant," Baxter said. "Forests nationally are so undermanaged that one could tap into this waste stream for decades to come on an annual basis and still not be over-harvesting the small diameter timber that needs to be removed."
And as for Madison's urban ash trees, what needs to happen if they are to be harvested whole is for people to say they want to use them.
Laura Whitmore at Madison Parks confirmed that parks staff and WholeTrees have talked about how the company might harvest the trees.
Though it might be hard to extract entire trees from urban areas, Baxter is confident that there will be many options.
"We're talking about thousands of trees," Baxter said. "We've done scouting in Madison and Chicago and there's plenty of opportunity to fell larger portions (of ash) when the economic value makes it worth it."