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Boulder's Tree Crisis 2019

Ash tree infected with EAB

Leaf on background Is this a tree crisis?

Yes. The City of Boulder is estimated to lose more than 70,000 ash trees to emerald ash borer (EAB) alone over the next 10 years. EAB, an invasive insect from Asia, is attacking our ash trees and will  destroy more than 25 percent of the city's current urban tree canopy by 2030 . EAB is considered a slow moving natural disaster. It has already destroyed hundreds of millions of ash trees in more than 30 states across the U.S. This is an unprecedented loss of tree cover in Boulder, so YES – this is a dire ecosystem and canopy threat needing immediate response by residents and the community. 

What the City is Doing about EAB Are there other threats?

Yes.  In addition to trees naturally declining due to old age, our trees are increasingly under threat from extreme weather events such as drought, dramatic temperature fluctuations, heavy snows and high winds. In November 2014, a 48-hour, 70-degree temperature drop caused the death of over 500 of Boulder’s mature trees. Many trees today are still showing varying states of decline and stress as a result of the 2014 freeze. 

As climate destabilization and movement of invasive organisms continue, many of Boulder’s trees face additional stress and insect and disease threats, such as drippy blight of red oaks, thousand cankers disease of walnut, pine wilt nematode of pine trees, Douglas-fir tussock moth, and mountain pine beetle.  

In many communities across the US including Boulder, land development and redevelopment also threatens the urban canopy, especially when sites include high-quality mature trees. As vacant lots are developed, existing homes rebuilt and streets and floodways widened, mature trees are often removed, or their health impacted by construction. 

what you can do What is the city doing to retain canopy cover? 

  1. Planting trees and making more trees available to residents.

    The best counter measure against EAB tree losses and future tree threats is to plant a more diverse tree canopy and protect our existing trees. Hence, the city is planting 500 new trees annually of a diverse palette of tree species in our city parks and public street rights-of-way. Since the discovery of EAB in Boulder in 2013, the City has planted over 2500 trees on public property.

    Understanding that a significant amount of canopy will be lost on private property due to urban forest threats, the City has made strides in providing trees to private property residents. Through subsidized tree sales and giveaways, the City has made an investment on private property in an effort to combat canopy loss. Since 2016, the City has provided over 3900 trees for residents to plant on private property within Boulder. 
  2. Treating high-value ash trees. 

    The Boulder Forestry team has a plan for every public ash tree (trees in city parks and in city street rights-of-way). Over 1,300 public ash trees are on an effective chemical treatment schedule and should continue to thrive and provide benefits to the community. 
  3. Education and outreach 

    ​The city is collaborating with the Boulder Tree Trust to advance public awareness of the importance of planting and properly caring for our PRIVATE trees as well. Approximately 75 percent of our urban tree canopy is on private property. The Tree Trust exists to help Boulder homeowners make informed tree care and planting decisions for their private trees. By joining together, we believe Boulder can create a sustainable and diverse tree canopy for the future.