BOULDER - The idyllic vision of a college campus is one marked and shaded by mature, historic trees – many of which are as old as the school itself. High school juniors who toured the University of Colorado’s Williams Village in 2014 saw a campus that met that criteria.

Those same students moved in surrounded by a markedly different landscape in Williams Village the fall of 2016.

Once lined by a grove of mature, 30-foot-tall ash trees, the west side of the village along 30th Street is now tree-less. The emerald ash borer (EAB) is to blame.

Just four years after the invasive pest was discovered in Boulder, the city is seeing the clear impact, losing hundreds of untreated ash trees to the infestation.

The devastation isn’t unique to Boulder. EAB has killed millions of ash trees in more than 25 states, making it the most destructive forest pest in U.S. history. What is unique is how the pest exited the quarantine zone in the Midwest and bypassed several areas that still remained free of infestation in 2017 before arriving in Boulder.

Though it has not been confirmed, EAB likely arrived in Boulder the same way it arrived in the U.S. from its native home in northeast Asia — through the shipment of wood. Despite efforts to curtail the practice, firewood is often transported across state lines in the U.S., and EAB may well have traveled to Boulder along with such a shipment.

Hoping to educate other municipalities, Boulder’s City Forester Kathleen Alexander developed tours open to other municipalities and interest groups allowing a unique in-person opportunity to see the destruction caused by the small green borer.

Since arriving in Boulder, EAB was most recently discovered in Longmont in the summer of 2016. It has led Denver, where there are 1.45 million ash trees in the Metro area alone, to develop a proactive defense campaign.

Dubbed Be A Smart Ash, that campaign launched in the spring of 2016.

“The City has been anticipating the Emerald Ash Borer’s arrival in Denver and working to reduce its impact,” Parks and Recreation Executive Director Happy Haynes said. “We’re advising Denver residents to Be A Smart Ash, not just because we need to heighten awareness, but also because we need community support.

“Through this campaign, we strive to give residents the information they need to be part of a movement that will have a significant and long-term impact.”