This story has been updated.

Louisville’s shrinking tree canopy has finally been quantified.

Jefferson County is losing trees at a rate of about 54,000 a year, according to a comprehensive assessment of the county’s trees released today.

If the loss continues at the current rate, combined with the threat of invasive pests like the Emerald Ash Borer, Louisville could be facing a future where only 21 percent of the city is covered by tree canopy.

Canopy trees have numerous environmental benefits for cities. They help shade paved surfaces, reducing the urban heat island effect. The phenomenon causes noticeable temperature variations between warmer urban cores and surrounding countryside. Trees also help clean the air, and also absorb stormwater runoff. The nonprofit American Forests recommends that cities have at least 40 percent canopy cover. According to the report, Louisville’s current canopy cover is at about 37 percent, and shrinking.

Louisville officials have known that the city’s tree canopy was shrinking at alarming rates for several years, but it’s been difficult to comprehensively address the problem without a clear inventory of the county’s trees. Now, with the completion of the $115,000 study by Davey Resources, Louisville’s urban forester and tree commission can begin addressing the issue.

Among the report’s key findings:

The tree canopies in every Louisville neighborhood declined from 2004 to 2012 except in three of the city’s most urban neighborhoods: the Central Business District (where the canopy increased by 16 percent), Russell (no change) and the Fairgrounds (no change). The most dramatic tree losses were in Edgewood (51 percent decrease), Tyler Park (23 percent decrease) and Wellington (22 percent decrease).

Tree canopies tend to be more robust in wealthier areas, as well as in areas with higher percentages of residents 45 years and older, in less densely populated areas and in areas with higher-educated residents.

Any solution will have to include tree planting on private lands, as well as public areas. Of the land deemed “realistic potential planting areas” 73 percent is privately owned.

The report lays out 42 recommendations—all of which are designed to either protect Louisville’s existing tree canopy, plant new trees or establish a supportive framework to grow and maintain the canopy.

You can read a draft of the report here. For the next 60 days, the city will be accepting comments on the proposal. To comment, e-mail communityforestry@louisvilleky.gov or comment on Sustain Louisville’s Facebook page.