Denver foresters confirm emerald ash borer arrival; urban forest strategic plan guides response

Denver city foresters told the Parks, Arts and Culture Committee that the emerald ash borer (EAB) has been confirmed in multiple neighborhoods and described how the city’s new Urban Forest Strategic Plan will guide responses and longer-term work to grow and protect canopy.

Luke Killoren, Denver City Forester, said inspectors confirmed EAB on a private-property tree in Congress Park; since that discovery the pest has been identified in Fort Logan, Harvey Park, Westwood and Congress Park. Killoren said "if you have an ash tree and you don't treat it, you should expect to lose it," and that the city expects continued spread.

The presentation included baseline urban-forest statistics: about 2,200,000 trees across Denver when public and private trees are included, roughly 300,000 of which the city manages; a 15% canopy cover based on a 2020 assessment; and more than 400 tree species recorded in the city inventory. Foresters said downtown has a much lower canopy (about 4%) and that canopy coverage varies significantly across neighborhoods.

On EAB response, staff said the city has performed preventive treatments but lacks capacity to treat all at-risk ash trees. Killoren told the committee the city treated approximately 1,800 public trees this season and will reprioritize treatments: the department plans to preserve larger and culturally or sentimentally important ash trees while asking adjacent property owners to shoulder more responsibility for routine treatment and maintenance under the cited municipal code (referred to in presentation as Chapter 57.18). The forester said the city will continue targeted removals and remove-and-replace work for smaller trees; residents may request city removal and replanting for ash trees 12 inches and under at no charge in qualifying cases.

The Urban Forest Strategic Plan (UFSP), completed last year and described as a 20-year framework with five-year updates, sets three high-level goals: increase canopy citywide, promote and invest in community stewardship, and recalibrate city urban-forestry practices. Killoren and Urban Forestry Planner Elizabeth Judd said the plan contains 38 action and sub-action items (four complete, 15 underway, 14 ongoing, five not yet started) and calls for a mix of short- and long-term measures.

Key work under way includes a public resource hub, an updated interactive city-approved street-tree list, educational videos (English and Spanish) on tree protection and planting, a public-facing annual report with interactive maps, a priorities map for planting opportunity, and a proposed package of municipal code changes expected late this year or early next year. Staff reported a deep-dive staffing analysis and a review of rotational pruning cadence: internal park-tree structural pruning currently returns on a roughly 21-year cycle while contracted parkway pruning is closer to a seven-year cycle, the latter closer to industry norms.

Committee members raised concerns about deferred maintenance in medians and parks, irrigation failures, and how to help residents on fixed incomes pay for removals. Killoren said there are assistance options (an FNI program) for qualifying residents and that the forestry team is willing to review specific cases and, where appropriate, use city contractors who can sometimes provide lower-cost removal billing when a city notice to remove is issued.

Foresters described the urban forest as a city asset with estimated replacement value in the presentation exceeding $1.5 billion and urged residents to use the public tree inventory and reporting tools on the department website. The briefing did not include a formal committee vote; staff provided numerous operational next steps and invited council follow-up.