Greenprint Denver: Enhancing the city forest

By Tillie Fong
Denver, CO (September 8, 2009)- Greenprint Denver is halfway through its four-year plan to make Denver more sustainable. This is the fourth in a series looking at specific goals in the plan and the progress that has been made. Denver is leading the way in planting trees as part of the Tree by Tree – Mile High Million program, but it is not clear exactly how much progress the city has made in increasing its tree canopy.


Under the Greenprint Denver plan, the goal for enhancing Denver’s urban forest is to increase tree coverage to 18 percent from 6 percent. In 2006, Denver had 12.39 square miles of tree canopy, or roughly 10.5 percent of the city’s land mass. To reach 18 percent, Denver must have 21.42 square miles of tree coverage. It isn’t known, though, how many individual trees are needed to provide that canopy.
“Due to the variability of tree sizes, we are unable to translate the cover number into a tree count,” said Denise Stepto, spokeswoman for Greenprint Denver. The city doesn’t perform a census of individual trees, Stepto said. However, she said a sample inventory indicates that Denver has more than 355,000 street trees- trees that are planted close to streets and most public right-of-ways.
Although efforts in the past, such as the Denver Digs Trees program, have encouraged tree plantings, Denver did not have an active tree campaign until 2006. That’s when Mayor John Hickenlooper announced the Tree by Tree: Mile High Million program, also known as the Million Trees initiative. The goal is to add 1 milion new trees in the Denver area by 2025.
The program is regional, but it is administered by Denver’s Parks and Recreation Department. Greenprint Denver’s Web site lists 24 municipalities and districts as participants. Residents who plant trees can register them as part of the program.
While the program doesn’t outline specific quotas, the timeline suggests that about 55,555 trees would have to be planted each year in the Denver area in order to meet the 1 million goal by 2025. From April 2007 to Aug. 14, 2009, 178,531 trees have been registered under the program. Denver leads the way with 31,797 trees, followed by Broomfield with 6,923 trees and Aurora with 5,818. However, the bulk of the trees listed – 115,216 – are not registered with any specific city.
Of the total number of trees registered, 62,976 were planted by municipalities, nonprofits, community groups, and quasi-governmental organizations, and 1,315 by individuals. The remaining 114,240 were planted by landscapers or were registered without any information on who planted them. In Denver, the city planted 10,809 trees from July 2006 to August 2009, Stepto said.
Even so, the current size of Denver’s tree canopy isn’t known, which means it’s not clear how far the city has come in achieving its Greenprint tree goal. Also, the Greenprint goal doesn’t set a deadline for achieving the 18 percent tree canopy. “It is very difficult to put a time frame on canopy-increase goals, as trees are living things and can die,” said Stepto. “Many factors need to be taken into consideration when considering the time frame, such as drought events, budget cuts, invasive pest or disease infestations, and catastrophic weather events, to name a few.”
Much of the funding for Million Trees comes from Suncor Energy, which contributed $150,000 in 2007. Under an agreement with Denver, the company is committed to providing $1 million over five years to the campaign. Denver also recently won a federal grant for energy conservation, part of which will go toward planting 4,000 trees.
However, the city has been confronted this year with the potential loss of 6,000 trees from Thousand Cankers Disease, which afflicts black and English walnut trees. The disease is caused by a fungus carried by the walnut twig beetle, and, once infected, trees die within two to three years. The disease has no cure, so the trees must be removed.
As of last month, 125 to 130 black walnut trees in Denver- all on private property- were diagnosed with the disease, according to Pete Zoschg, arborist with Denver’s forestry division. None of the city’s black walnuts- 500 in public right-of-ways and 200 in parks- have been infected. But it will take years to determine how many trees Denver will eventually lose to Thousand Cankers Disease. Owners of diseased trees are encouraged to replace the black walnuts with other types of trees but are not required to do so. “The cost of the trees is a bit prohibitive,” Zoschg said. “So we push people to our Denver Digs Trees program.”
Denver Digs Trees, run by the nonprofit The Park People, complements Million Trees, although there are some differences. “They (Million Trees) do the larger plantings, in parks and golf courses, that we can’t do,” said Paige Heydon-McCrary, executive director for The Park People. “We focus on individual residents.”
Million Trees is also a regional initiative, whereas Denver Digs Trees is geared toward maintaining a sustainable tree program in the city itself. Denver Digs Trees offers free trees to residents in 21 neighborhoods identified as being “under canopied.” This year, two neighborhoods- Athmar Park and Montbello- were added to the list.
In the past 18 years, Denver Digs Trees has distributed 40,000 trees, Heydon-McCrary said. It typically sells or gives away more than 2,000 trees a year, although that number has increased in the past five years, averaging 2,900 trees a year. “Our numbers go up every year,” Heydon-McCrary said. “Very few are replacement trees. These are people who just want to add to what they already have.”
Denver Digs Trees usually holds an annual spring sale, offering trees for $45 to $65, or roughly 60 percent of the cost of a tree from a nursery. This year, thanks to a $35,000 grant, The Park People is also holding a sale in October, selling shade trees for $25. Because of this, Denver Digs Trees is expected to distribute 3,650 trees in 2009.
“When you start adding trees, crime goes down, and people go out more,” Heydon-McCrary said. “The neighborhoods become more livable, so there are a bunch of benefits.” According to notes from a Million Trees briefing last month to the Greenprint committee, Denver’s street trees provide $38.8 million in cumulative annual benefits, including improved air and water quality, reduced energy consumption, increased property values and reduced carbon emissions.
The Park People encourages all residents who get trees from Denver Digs Trees to register them with Greenprint Denver. “When people do that, they (the number of trees) count toward the Million Trees goal,” Heydon-McCrary said. “It took awhile for our two programs to iron out who does what. But we work well together.”
Related Resources:
Rocky Mountain Independent- Greenprint Denver: Enhancing the city forest
Denver receives $6 million grant to improve community energy efficiency
Denver Greenprint
The Park People