Colorado Springs officials announced this week that the emerald ash borer has been confirmed within city limits, a “significant milestone” city leaders were already preparing to tackle.

The is an invasive beetle that lays its eggs in the bark crevices of ash trees, and the larvae burrow into the wood to feed, damaging the trees. Emerald ash borers have killed millions of North American ash trees since the insect was first identified in the 1990s.

“While this confirmation is not unexpected, it is an important reminder that protecting our community’s tree canopy will require a coordinated effort,” City Forester Matthew Puckett said in a statement.

The bug was first found in Colorado in 2003 and has since spread to cities across metro Denver and Fort Collins. According to , Colorado Springs is the farthest south the insect has been detected on the Front Range.

City officials are launching a public awareness campaign to help residents learn about the emerald ash borer, including how to identify ash trees, recognize infestation and take steps to protect trees.

About 20% of the trees in Colorado Springs are ash trees, and left untreated the borer could kill every ash tree within 15 years, city officials said.

City crews will monitor trees on public property, but property owners are responsible for trees on private property, officials said in a news release.

The emerald ash borer, an invasive insect that����ap killed millions of trees across the United States, was discovered in several trees in the Congress Park neighborhood on June 17, city Parks and Recreation officials said Thursday.

City officials confirmed the wood-boring beetle’s presence with Colorado State University entomology experts and Denver’s forestry office.

“We’re grateful that our Office of the City Forester has been preparing for this inevitable discovery, yet this is not a low-stakes battle,” Parks and Recreation Executive Director Jolon Clark said in a statement.

Emerald ash borer beetles were first discovered in Michigan in 2002 and have since killed millions of ash trees nationwide. They are widely considered the most destructive tree insect ever introduced to North America, according to the

In Colorado, emerald ash borers were first found in Boulder in 2013 and later spread throughout the state, including into Broomfield, Fort Collins, Littleton, Carbondale and — last year — Lakewood.

The small-but-destructive green pests invade both healthy and stressed ash trees, killing them as soon as two years after the infestation starts. They pose a significant threat to Colorado’s urban forests, 15% of which are ash trees, state officials said.

Denver has been preparing for the arrival of the emerald ash borer since 2016 through public education, replacing small ash trees on city land and rigorous treatment of historic ash trees on city property, officials said.

So far, city foresters have removed more than 1,000 ash trees, treated 6,000 ash trees in parks and parkways, and planted 1,500 trees per year to make up for the loss to Denver’s tree canopy.

Treating ash trees for emerald ash borers is effective 95% of the time when done correctly, according to the city.

Foresters and city staff are “in this for the long haul,” city forester Luke Killoran said in a statement.

“We simply can’t stress enough how important it is for Denver residents to take action when it comes to identifying, treating and/or replacing their ash trees as soon as possible,” he said.

Denverites can learn more about the city’s public awareness campaign, “,” and apply for a free replacement tree online.

The insect was found “in a small area in central Lakewood” last week and in Jefferson County this week, said city spokesperson Amber Thill.

Emerald ash borer beetles infest and kill green and white varieties of ash trees, including the popular autumn purple ash. Approximately 15% of urban trees are ash trees, according to the city.

One tree on private property was confirmed as a host to the beetle, Thill said.

Ash trees infested by the beetles can be identified through “D-shaped” exit holes, splitting bark and “S-shaped” tunnels under the bark, city Forestry Supervisor Luke Killoran said in a statement.

Other signs include thinning tree canopy, abnormal shoots of growth, smaller leaves and lots of woodpecker activity.

In Colorado, the bugs were first found in Boulder County in 2013 and have since been confirmed in Adams, Arapahoe, Broomfield and Larimer counties. Arvada’s first beetle was discovered in 2020.

Lakewood city leaders have been monitoring and treating large, healthy ash trees on public property for several years knowing the ash borer would eventually make its way to the city, Thill said.

Residents may be able to protect healthy trees through preventative insecticide treatments but should make sure to use a certified arborist licensed by the Colorado Department of Agriculture as a commercial pesticide applicator, according to city officials.

The cicadas are unmistakable with their daily continuous choir of crooning. There are also insects, bugs and spiders afoot, and depending on your barometer for squeamishness, it is not a bad idea to consider whether the crawler or flyer is worth a swat, the spray of death or a free pass to carry on. Walk with me in my garden clogs to see some of the live action and learn how to manage your visitors.

A metallic green bee stands out in any buzzing crowd. I first noticed its iridescent qualities in June and most of the summer. A quick lookup in the book “Garden Insects of North America” by Colorado State University Emeritus entomologist Dr. Whitney Cranshaw confirmed it is an Agapostemon spp. bee. Its common name is sweat bee, although these particular green bees are more focused on gathering pollen and nectar from many garden plants in bloom than from perspiring gardeners.

Fortunately, this good-looking bee slowed down a bit on a coreopsis flower for me to snap a photo. They are ground nesting bees and dig deep nests in areas with flat or sloping soil, and can be solitary or nest in underground communities with other Agapostemons. No swatting or spraying is needed, because this is a good bee, a welcome insect in any garden.

On first glance, I thought this next bug seemed like it might be a good bug — perhaps a predator of an insect that was chewing a plant that shouldn’t be chewed. I was hoping he liked grasshoppers. He wasn’t camera shy while resting on the side of a patio container.

A photo text to a couple of garden friends led to the correct identification. He wasn’t a good guy assassin bug, but rather a bad guy leaf-footed bug (Leptoglossus clypealis) that was probably nibbling on some nearby developing tomatoes. If you check out this fact sheet from The University of California, , you will see photos of this nuisance bug in all life stages. I know without a doubt I’ve seen leaf-footed bug eggs and nymphs in our garden. I’m not too worried about ongoing fruit damage, but I’ll keep an eye out for group feeding and be ready to squish them on sight.

Joining in the musical insect summer chorus are impressive, broad-winged, bright green katydids (Microcentrum rhombifolium). Males use their forewings as instruments to make low, raspy trilling and clicking sounds nightly to attract a mate or stake out its territory. The traditional katy-did-katy-didn’t hum is more common to East Coast katydids. When found in Colorado gardens, usually on foliage that blends so well with the katydid, a second look is needed to confirm these two-inch, tall-bodied distinguished insects. Their camouflage helps them hide from predator birds, bats, other insects and rodents. If you find one, just admire it and consider katydids another insect of nature’s fine creation that just wants to chew on plant leaves (without causing too much damage) and live for a while. Read more about Colorado katydids at .

Without a doubt, the fast-moving quarter-inch spotted cucumber beetle pest caused distress to my summer yellow squash plants and me a couple of years ago. They just appeared one day in mid-summer and decided not to leave, multiplying faster than adult Japanese beetles on grapevine leaves. I had difficulty controlling them with organic sprays. Following that, my hair pulling led to pulling the plants entirely because they were feeding everywhere on the plant leaves, petals, fruit and pollen. Spotted cucumber beetles can feed on several different crops including cucumber, muskmelon, watermelon, pumpkins, squash and gourds.

It is important to clean up garden plant debris every fall so there aren’t places for pest insects to overwinter. Also, rotate crops and use floating row covers to keep pests out early in the season. However, remove the cloth when flowers are in bloom to allow them to be pollinated. There are cucumber beetle and other cucurbit-resistant varieties to plant, so do your homework when purchasing seeds — pest resistance should be listed in the description or on the package.

Every gardener eventually learns that ladybugs, also called lady beetles, are wonderful insect friends to have and protect in the garden. Their black spots vary in number depending on variety and their wing covers vary from bright orange to red. More than 80 species of lady beetles are found in Colorado, of which 70 are native. A single lady beetle can consume thousands of pest aphids, scale insects, mites and pest eggs in its brief lifetime. With their chewing mouth parts, both the adult and larva (or grub) life stages are beneficial as predator insects.

For lady beetles to find your garden, there needs to be pests for them to consume, so naturally there can be a lag time from when pest outbreaks occur to when they show up and start devouring the pests. The best advice is to live with the brief period of aphid outbreaks until they show up. Use a heavy spray of water on the aphids until the beetles arrive. Learn to identify lady beetle life stages too. In their larva or grub stage they can eat scores of aphids in an hour. Larvae resemble miniature black-red or black-orange alligators. They look rather mean, but they are do-gooders for pest control so keep them around all summer. Lady beetles also feed on pollen and nectar, especially before their winter hibernation, so grow plants with small flowers like dill, yarrow and butterfly weed for them to easily access. Learn more at .

As with most pest and disease concerns in gardens, the first step is to identify the problem and thoroughly work out the best solution. Many issues can be resolved without any intervention. Sprays, even organic ones, often have unintended consequences and can harm beneficial insects and pollinators along with the pests. There is generally a natural balance between pest and beneficial insects. Unfortunately, pest insects that normally do not live in Colorado, but somehow make their way here, thrive without natural predator insects to keep them in check, often resulting in serious plant damage and losses. The emerald ash borer and Japanese beetles are prime examples — but that’s a topic for another article.

Betty Cahill speaks and writes about gardening in the Rocky Mountain Region.

“Diameter is 17.9 inches,” Carbondale’s town arborist tells colleague and public landscape technician, Allison Uri.

While Uri logs the number into her phone, Meinecke stands back, looks up and inspects the tree’s crown. No obvious signs of damage — no thinning, no dead spots, no noticeably small leaves.

But all is not well in Carbondale.

While this particular green ash on Crystal Bridge Drive may appear healthy, the emerald ash borer — an invasive wood-boring beetle native to East Asia that has decimated tens of millions of ash trees — has come to this Roaring Fork Valley town of 6,500 situated between Glenwood Springs and Aspen. The discovery, confirmed this month by state officials, is the first sign that the borer has migrated to Colorado’s Western Slope, most likely by hitching a ride on firewood transported from the Front Range.

The grim news from Colorado’s high country comes on the eve of the 10th anniversary of the first detection of the ash-devouring pest in the state — Boulder was ground zero in September 2013 — which sparked an avalanche of doomsday headlines about the future of Colorado’s urban tree canopy.

In a paper , entomologists declared the emerald ash borer “the most destructive and economically costly forest insect to ever invade North America.” Approximately 15% of the trees in the state’s urban forest are ash, , with nearly 1.5 million casting shade in metro Denver.

“I was maybe a little shocked — I wanted to not believe it,” Meinecke said as pointed to several ash tree stumps in front of the post office where the first signs of the beetle emerged in Carbondale last month. “I was hoping I wasn’t seeing what I thought I was seeing.”

Meinecke and his small team are trying to get ahead of the nascent scourge before it explodes across the 400 ash trees on town land, taking lessons from more than a dozen Front Range cities and counties on what they’ve done over the last decade to control the spread of the ash borer — be it pesticide treatments, removal of susceptible trees or even deployment of tiny parasitic wasps known to snack on the beetles’ larvae.

“Over 10 years in Boulder, unfortunately, we have lost thousands of ash across the city,” said City Forester Kathleen Alexander. “The good news is the EAB (emerald ash borer) is manageable. But you have to plan for it.”

Unlike in the Midwest and on the East Coast, where whole swaths of forest dominated by ash were denuded in short order, Colorado’s infestation has been more laggard and contained. It has to do with the state’s drier and more unforgiving climate and with the fact that ash trees are not as plentiful — and ash forests not as expansive and contiguous — as back east.

Dan West, forest entomologist with the Colorado State Forest Service, acknowledged infestation in the state “is a little slower moving.”

“Ten years later, I anticipated a few more communities to have been confirmed by this stage,” he said.

But slow doesn’t mean gone. Less than two weeks ago, Littleton became the latest Colorado community in its ash trees. The Arapahoe County suburb represents the Front Range’s southernmost infiltration of the beetle, which up to now has largely taken root in urban canopies north of Denver — from Fort Collins to Longmont and Thornton to Arvada.

West said the situation can be managed if taken seriously — but that starts with taking the emerald ash borer itself seriously.

“They’re incredibly adaptive,” he said.

Slow but steady spread

Native to China, Mongolia, Japan, the Korean peninsula and far eastern stretches of Russia, the emerald ash borer was . According to the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service, it most likely came to the U.S. on wooden pallets and packing materials used in cargo shipping.

The half-inch-long, dark green beetles lay eggs on the bark of ash as they feed on the tree. After hatching, the larvae tunnel into the bark and create S-shaped “galleries” that eventually disrupt the tree’s nutrient-carrying network, girdling and killing the tree.

Ash trees in North America have no natural defenses against the pest and the borer has few natural predators to control its numbers.

“This pest kills stressed and healthy trees and is so aggressive that ash trees may die within two years after they become infested,” the on its website. “It is possible for EAB to infest an ash tree for up to four years before visible signs of decline in the tree occur.”

That’s why Thornton began treating its ash trees before the beetle was even discovered in the city, said Craig Gress, Thornton’s arborist. Confirmation when Gress noticed an ash tree in decline in the parking lot of a city park.

He felled the tree and found a dead adult borer. He also spotted the distinctive D-shaped tunneling holes the adult beetles make. Then Gress peeled back the bark.

“I found the tunneling galleries that the larvae do underneath the bark,” he said.

Thornton has about a thousand ash trees on city property. Gress said the city hopes to treat 30% to 40% of its ash inventory, focusing on the most viable and healthy trees, known in the field as “high value” specimens.

“We’ve been going through that mitigation to treat our largest and most healthy trees,” he said.

Likewise, Westminster began planning for the emerald ash borer shortly after Boulder got hit, despite the Colorado Department of Agriculture placing a quarantine around Boulder County to prohibit the movement of all untreated ash plants and plant parts out of the infested area. The ash borer can fly about a mile or so from its birth tree in a year, and if that’s not good enough to make it to new wood, humans do the heavy lifting by moving infested firewood across long distances.

City Forester Brian McCoy said Westminster has been treating ash trees on city property for six years, even though detection of the beetle in the city didn’t happen until the fall of 2019. This past spring, the city conducted a right-of-way inventory and found 3,174 ash trees worth saving.

But local governments can only do so much — the vast majority of ash are on private property, over which municipalities have little control. In Westminster, there are nearly 70,000 ash in total, which works out to one in seven trees in the city. The city launched a cheekily named campaign — — to encourage homeowners to assess the health of their ash trees.

“This can be mitigated with the proper treatments and it doesn’t have to be like it was on the East Coast,” McCoy said.

Treatments can be expensive for homeowners, depending on how many trees there are on the property and how big they are. For a medium size tree 14 inches in diameter, the cost can run from $150 to $250 on average. Treatments, which take the form of soil drenches, trunk sprays or direct injections into the trunk, typically last for two years.

Michael Sundberg, district manager for the southeast office of Denver Davey, a tree care company, said removing a dead or dying ash tree is even costlier. Davey has treated thousands of ash trees on the Front Range over the last decade, while also removing hundreds.

“There will still be some tough decisions to make whether to pay for treating a tree long term or removing or replacing it depending on the tree’s inherent value to a property,” Sundberg said. “Treating all of their ash trees could be too costly for a given budget, but also having a lot of ash trees die and need to be cut down… could bust the budget too.”

If they can afford it, Sundberg said, “homeowners will have good management tools to preserve their ash trees as long as they know they have ash trees on their property and get in front of it.”

An additional factor when considering whether to invest in treatment, Fort Collins City Forester Kendra Boot said, is the fact that ash trees punch above their weight. In her city, she said there are half a million trees, of which 60,000 to 70,000 are ash. But ash comprises a third of the urban canopy due to its propensity to grow big crowns and live for a long time.

Boot knew trouble was on the way in the spring of 2020, when the emerald ash borer was found just over the city line in unincorporated Larimer County. Fort Collins began proactively injecting its ash trees the following summer, splitting the city into three zones to get to all 7,400 ash trees on city property protected in a staggered fashion.

“We’re really trying to choose the big trees, 12 inches in diameter or bigger,” Boot said.

But she acknowledged the beetle has likely been in and around Fort Collins for several years. Just last month, the emerald ash borer was finally documented within the city itself, Boot said.

“If you drive by now, it’s pretty dramatic how many trees have died,” she said of an ash cluster at the northern end of the city where the borer was first found three years ago. “We’ll really start to see trees die here next year.”

Multifaceted attack

For the clearest illustration of the borer’s potential trajectory over time, Boulder is ground zero. According to the city’s , the city has removed 3,315 infested trees, treated 1,339 trees and planted more than 4,000 new trees to replace the canopy lost to the emerald ash borer.

Boulder has also implemented biocontrols in the form of tiny . Because the emerald ash borer doesn’t have much in the way of natural predators here, scientists with the U.S. Department of Agriculture traveled to China and Russia after the detection of the beetle in Michigan two decades ago and brought back some weapons.

Four species of stingless wasps — three of which attack borer larvae and one of which targets the beetles’ eggs — were brought to the United States. The agency conducted tests to make sure the wasps, which are the size of mosquitoes, wouldn’t attack other insects before releasing them.

Eight million wasps have been released across 30 states, starting with Michigan in 2007. A recent study conducted in that state and several northeastern states showed that the wasps kill 20% to 80% of emerald ash borer in ash trees that are up to 8 inches in diameter.

In Boulder, three species of parasitoid wasps were deployed. Alexander, the city forester, said the wasps have killed about 28% of the larvae.

“The ones we are releasing are the ones that are very host specific — they are only attacking emerald ash borer,” she said.

The city has also found that woodpeckers are also ravenous around the ash borers’ larvae, Alexander said, lapping it up like “ice cream.” Combined with pesticide treatments, Boulder’s holistic approach to controlling the emerald ash borer has “kept (infestation) under control” over the last 10 years, she said.

“If you can slow that progress down, through pesticides and biocontrols, you can flatten the curve,” Alexander said, borrowing familiar containment language from the coronavirus pandemic. “To me, that’s a success story.”

Back on Crystal Bridge Drive, John Burks is less sanguine about what might await Carbondale and the rest of the Western Slope. He saw the , from where he moved to Colorado five years ago.

“It was beginning to heavily affect our trees in Williamsport,” he said.

With a two-decade heads-up, Burks hopes Carbondale will have every tool at hand to keep the beetle at bay in a way that was not done — or was not possible — during the initial wave of emerald ash borer infestation in the eastern portion of the country.

“I’m hoping we here in Colorado are good students of that,” he said, looking up at two large shade-casting ash trees framing his driveway. “I think they’re beautiful. I think they’re precious.”

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But along the sun-splashed and parched Front Range, where increased urbanization threatens to boost temperatures faster than they are already rising, it may not be enough for Colorado’s fifth-largest city.

An in-depth tree canopy survey of the nearly 45-square-mile city, released this month, shows that trees cover 16% of Lakewood’s land mass. The city’s calls for a 30% tree canopy across Lakewood by 2025.

To reach that goal over the next three years, according to Lakewood forester Luke Killoran, would require the planting of half a million trees.

“It’s just unrealistic,” he said.

But that doesn’t mean Lakewood won’t work on continuing to gradually widen its canopy — coverage increased by 2% from 2011 to 2019, according to the study — but it should do so in ways that make the most sense for its residents and work within the confines of the natural habitat, Killoran said.

The canopy study estimated that Lakewood’s trees create environmental, economic and social benefits for the city amounting to $1.8 million annually. Aside from providing shade and a noise buffer, trees help clean the air, regulate temperature and help absorb the planet-warming gases humans release daily.

“As a community, we’d like a larger canopy,” Killoran said. “And there are opportunities for plantings.”

One of those locations is Coyote Gulch Park in the Rooney Valley neighborhood, at the western edge of Lakewood. The city plans to plant trees there next year in an effort to provide more shade in a space that today is mostly ballfields and sun-blasted open space.

But the site is feasible for tree planting largely because Coyote Gulch is water-ready. Many other areas of Lakewood — like the largely treeless Green Mountain Park and Bear Creek Lake Park — are not nearly as tree-friendly due to their almost desert-like conditions.

“This is an irrigated bluegrass park,” Killoran said of Coyote Gulch.

Austin Troy, a professor at the University of Colorado at Denver’s department of urban and regional planning, said the western United States’ drier and harsher climate makes it tougher to grow a forest than back east.

“Trees are not natural here, except in the river corridors,” Troy said of the Front Range’s ecology. “Planting trees is not enough — maintenance is really important.”

That’s because without sufficient water, trees won’t survive. And that’s a real challenge in a “semi-arid Western city” like Lakewood, Troy said. In December, Denver along with parts of Adams, Arapahoe, Boulder, Broomfield, Jefferson and Weld counties, were considered to be in an extreme drought, according to the National Drought Mitigation Center.

And metro Denver saw its first snow-free April in 20 years in 2022.

“How many trees can we afford to irrigate?” Troy said. “It’s more important to have trees in strategic locations where they are really needed.”

And where trees are needed, according to many urban planners and ecologists, is in poor and racially diverse neighborhoods that have long been neglected. A determined that “inequality in tree cover between low- and high-income blocks was widespread in the U.S., occurring in 92% of the urbanized areas we studied.”

The researchers found that on average, there was 15.2% more tree cover in richer parts of a city than in less affluent ones. And with fewer trees, there was higher heat — a phenomenon known as the “urban island heat effect,” where dense concentrations of pavement, buildings and other surfaces absorb and retain heat.

Denver has emerged as one of the nation’s most “impervious,” or paved-over, cities. Roughly 8% of Denver’s 155 square miles has been designated as parkland, compared with 21% in New York, 23% in San Diego, 15% in Minneapolis and 13% in Los Angeles, data from the Trust for Public Land showed in 2019.

That’s why Denver has been planting around 3,000 trees a year over the last few years, said Ben Rickenbacker, the city’s forestry operations supervisor. He estimates Denver has an 11% to 13% tree canopy.

“It’s going to take a while,” Rickenbacker said.

Ean Thomas Tafoya, Colorado program director for GreenLatinos, an environmental justice organization based in Boulder, and a candidate for Denver mayor, said Lakewood should use the data it collected from the canopy study “to reduce inequity — and that means targeting things where the health benefits will be seen.”

That might mean planting more trees along major transportation corridors in the city — like Wadsworth Boulevard, Kipling Street, Sheridan Boulevard, Colfax Avenue and Interstate 70 — places lower-income families often call home, Tafoya said.

According to the , a Washington, D.C.-based environmental advocacy group, Lakewood does fairly well on its index. For example, one neighborhood fronting Sheridan Boulevard with a 72% poverty rate scored higher on the tree equity index than a neighborhood on the west side of town near Green Mountain, where the poverty rate is just 8%.

But Killoran, Lakewood’s city forester, said having sufficient trees in a neighborhood is one thing — maintaining them so that they don’t weaken and pose a danger to people living below is another. And in that regard, the city faces challenges — from drought to insects to disease.

“We’re seeing a lot of stressed trees that weren’t stressed before,” he said.

Honey locusts are getting hit particularly hard with gummosis and thyronectria canker, Killoran said. And the city’s ash trees, which account for two to three of every 10 trees in Lakewood, are under threat from the emerald ash borer, a beetle that first arrived in Colorado nearly 10 years ago.

Its spread in Colorado has been slow. Largely confined to Boulder County for the first seven years it was in the state, the ash borer was found in Arvada two years ago. Last month, Thornton announced it too had discovered the ash-devouring beetle.

“It’s coming,” Killoran said. “How do we replace the ash trees with a more appropriate tree for our area?”

The good news for Lakewood is that the canopy survey concluded that there are 22 trees per acre in the city and four trees for every city resident. It also determined that 41% of the city’s land mass is considered a “possible planting area” for new trees, which serves as a vital offset to the 38% of the city that is considered impervious — or paved over.

“As a community, we’re doing pretty well,” Killoran said.

But urban ecologists and city officials say trees alone won’t be enough to keep Denver habitable as temperatures increase. They urge a far more ambitious expansion of greenspace.

“And concrete is definitely getting poured faster than we are planting trees,” city forester Mike Swanson told The Denver Post.

Heat islands — dense urban areas that are much warmer than their surroundings — have widened, data shows, with Denver emerging as one of the nation’s most “impervious,” or paved-over, cities. Older neighborhoods where houses have yards may be more resilient, researchers have found, because compared with redeveloped parts of the city, these landscapes don’t radiate as much heat.

Tree-planting “is going to be our focal point” for beating the rising heat, Denver Parks and Recreation planning director Gordon Robertson said, acknowledging the heat island problem. Doubled funding of $1 million will bolster tree-planting on public-access property and existing parks, concentrated downtown and in “low-equity” neighborhoods, Robertson said.

Creating open greenspace with trees, grasses and plants — instead of heat-radiating pavement — can help cool residents along sun-scorched streets, draw down heat-trapping carbon dioxide and clean the air.

However, Denver since 1998 has veered from its founders’ vision of being “a city within a park,” falling behind most other major cities in greenspace. Roughly 8% of Denver’s 155 square miles has been designated as parkland, compared with 21% in New York, 23% in San Diego, 15% in Minneapolis and 13% in Los Angeles, data from the Trust for Public Land  shows.

This means climate warming hits harder here. And Denver has faced rising temperatures, a record 75 days above 90 degrees this year, with projections showing 20 to 35 days a year topping 95 degrees by 2050.

More greenspace needed

Denver climate office director Grace Rink has called for more “connected greenspace” to help mitigate heat islands.

And Denver voters repeatedly have demanded re-greening. In 2017, they passed a green roofs initiative requiring developers to install gardens atop new buildings, which city leaders later relaxed to allow alternatives such as funding off-site solar energy projects. In 2018, voters passed an open space tax to create more and better parks that raises $37 million a year.

Since then, city leaders have purchased a few parcels for new parks, covering less than five acres overall. They say they’ll acquire more land. Robertson said officials were negotiating to purchase 10 acres along Sand Creek.

Establishing new greenspace has proved difficult because well-funded developers compete for practically every parcel and City Council members have directed only a portion of the open space tax revenues for land acquisition — $20 million in 2018 and now about a third of that each year.

“And if we acquire one acre downtown, we blow through $10 million to $15 million,” Robertson said.

Denver imposes few fees on developers. There’s no requirement, as in other cities, to fund or install greenspace. While housing and commercial projects covering more than 10 acres in Denver must include some space designated as “open,” it needn’t be green.

The greenspace crunch reflects a worldwide challenge as United Nations demographers project 70% of the planet’s 9.7 billion people in 2050 will be living in cities, up from 55% now — straining habitability as temperatures rise. Denver’s population has increased by 47% since 1998, from 498,402 to 734,134, and density has reached 4,789 residents per square mile, census data shows, with projections for 857,000 people by 2040.

Hotter neighborhoods

Heat islands jack up daytime temperatures, reduce cooling at night, worsen air pollution and exacerbate heat waves, Environmental Protection Agency scientists have determined. This contributes to heat-related deaths, general discomfort and illness including respiratory ailments, cramps, heat exhaustion and strokes, the EPA says.

Between 2004 and 2018, the Centers for Disease Control and Prevention recorded 10,527 heat-related deaths nationwide. Colorado health data showed 475 heat-related emergency room admissions statewide in 2018. Colorado Health Institute researchers have found people living in poverty, children, the elderly and those with diseases such as asthma suffer disproportionately.

“Tree-planting alone is inexpensive, and often politically palatable, but it is a drop in the bucket. … You’re not going to make a dent in the heat that way,” said Vivek Shandas, a Portland State University ecologist and member of Portland’s forestry commission, who co-authored a national study of heat dynamics in cities that was published this year in the science journal Climate.

“We see a green squeeze in most cities. We want to do dense development, put in more housing units, because we see more people moving in. … so there’s not available space any more. You’re left with this tiny little strip between the sidewalk and the street,” Shandas said.

Politics have pitted urban affordable housing advocates who support new construction in the belief this will lead to lower prices against climate action advocates who prioritize public health, ecological integrity and long-term quality of life in a hotter, drier world.

Meantime “there are all these developers maximizing profits by building over the entirety of lots,” Shandas said. “It’s very easy to take out greenspace and put in gray space. It’s harder to take out gray space and bring back greenspace — not only costly but politically challenging to take out a parking lot or a street,” he said, urging a rethinking of urban design organized around natural space.

The heat islands study measured surface and air temperatures in 108 cities including Denver and has found that radiation of heat from asphalt landscapes amplifies temperature by up to 20 degrees. In the relatively paved-over parts of Denver, summer temperatures measured 12 degrees hotter than in older neighborhoods with trees and lawns.

Average temperatures measured highest in areas once “redlined” by the government to restrict financing for disenfranchised residents, which now have been redeveloped, such as the apartment complexes northwest of Coors Field where trees cover 1.5% of the area and 70% of surfaces are paved. The study found that residents in South Park Hill, with a 25% tree canopy and 25% imperviousness, faced average temperatures more than 10 degrees lower.

Looking for relief

For computer software programmer Mike Lipsitz, who moved from New York to Denver seeking better opportunities to be outdoors cycling and walking his dogs, the Coors Field neighborhood offered luxurious living but he searched for greenspace. Last summer, he moved to Baker, south of downtown, where houses have yards.

“There’s more shade. Just walking from sun to shade, that’s the biggest difference. Now, we get more shade,” Lipsitz said. “This is definitely nicer. And, as for the virus, it’s nicer that we run into fewer people on walks than we did downtown.”

University of Colorado Denver biologist Diana Tomback, who studies forest ecology, walks her dogs in parks on the east side of Denver and has observed more people than ever flocking to parks during the pandemic. Tomback links this with mental health and human evolution as a species tied to nature, and doubted tree-planting alone can ensure habitability as the population grows.

“If we are concerned about heat islands, it is not going to be enough to do things like make people install rooftop greenery. We ought to have more open space,” Tomback said. “Parks are important, not only to counter the heat island effect but psychologically for people.”

At least, last-remaining riparian areas along rivers must be preserved, she said. “It is absolutely essential that we keep the greenspace along the South Platte River. It is a biodiversity corridor for wildlife.”

Developers with city support plan a “River Mile” complex for 15,000 residents with apartment towers up to 59 stories on the 62-acre former Elitch Gardens property in the Platte Valley. However, city parks officials indicated they’re engaged in a complicated challenge of encouraging innovative development while also protecting mental and physical well-being.

“What this challenge may mean is jack-hammering out un-needed parking lots,” Robertson said. “It’s not going to happen overnight.”

Large parks covering more than 150 acres, of the sort city leaders established in the 19th century, have been seen as politically unlikely under pro-development Mayor Michael Hancock, possibly with the exception of the 155-acre former Park Hill Golf Course, where a conservation easement purchased by Denver taxpayers blocks development. Westside Investment Partners paid $24 million for that property and plans development on up to 95 acres. City attorneys say the City Council has the power to change the easement.

“It is our hope that a portion of the Park Hill Golf Course becomes a significant park,” Robertson said.

Another option: expanding greenspace along the ” around the city, closed to vehicle thru-traffic during the pandemic, so that residents could walk safely outdoors maintaining physical  distance.

Grassroots petitions have surfaced to make these permanent, and Robertson said he has proposed converting shared streets to greenspace by removing asphalt and planting native vegetation. “I would love to go in with water quality folks and really enhance these — plant trees.”

This would address an emerging challenge in the current tree-planting strategy for managing heat islands — simply finding enough space.

Concrete and asphalt is spreading as city crews, with many volunteers, work to establish more trees, said Swanson, the city forester. “This is increasing the heat islands. It eliminates tree-planting sites,” he said.

“It also will increase your storm-water bills. It will increase your heating and cooling bills. It creates more pollution. It makes for a sterile environment.”

Shade will help

Over the past few years, city crews have been planting about 6,700 trees a year (mostly oak, elms and Kentucky coffee trees), achieving survival rates as high as 90%. Their goal is to expand Denver’s overall tree canopy, which currently shades about 13% of the city, to 20%.

By blocking sunlight, trees help reduce the absorption of heat, and trees’ retention of and release of moisture cools surrounding areas, particularly when there’s wind.

Hotter, drier conditions threaten trees. City crews have been looking for heartier species that can endure extremes from traditional winter cold snaps to scorching hot summers.

The emerald ash borer beetle is spreading, threatening the ash trees that comprise 15% of Denver’s current canopy. By 2040, the paved-over surfaces that city records show covering 49% of Denver’s urban landscape may expand to 69%, and pavement covers 90% of newly-developed areas, University of Colorado urban design and land use professor Brian Muller and a team of researchers have determined.

Denver leaders have turned to tree-planting before to try to maintain quality of life. Former Mayor John Hickenlooper, who became Colorado’s governor and recently won a seat in the U.S. Senate, declared a “Mile High Million” goal in 2006 of planting 1 million new trees by 2025. Swanson said 260,000 have been planted.

While more trees won’t entirely offset heat island intensification of climate warming, shade will help, the city forester said.

“But we ought to be planting at least 10,000 trees a year,” Swanson said. “This is a community problem — heat. Everybody needs to be part of the solution. Or else we will have more asthma. More heart disease. It just gets bad. Nobody will want to live in Denver. Yes, Denver needs more trees. And we need to stop pouring concrete.”

Colorado has the distinction of being the first state in the country to find and identify another non-native insect — the Asian mud dauber. When I found it, I had no idea it was a newbie to the state and America. Other non-native, plant-destroying pests like Japanese beetle and Emerald Ash borer first arrived in America from their native regions and then populated the eastern and mid-western parts of the United States before making it to Colorado.

The Asian mud dauber, which I first found in my landscape in 2016, is native to Asia, India, Pakistan and Nepal and since the 1970s has been established in parts of Europe and more recently Quebec, Ohio and Michigan. It is a hunting wasp, not at all like familiar social wasps we know — yellowjackets, paper wasps and hornets that build wasp colonies to raise their young.

Hunting wasps, including the Asian mud dauber, are like many other established hunting wasps in Colorado. They share the same behaviors where the female works alone to build solitary nests somewhere in the yard, under or above ground, near and on structures. After building the nest they search for specific insects to paralyze and return to their nest to feed to their developing larvae, also called grubs. Hunting wasps may look fearsome, yet they rarely sting — unless of course you try to catch one and hold it in your hand.

The Asian mud dauber (Sceliphron curvatum) was first found in Colorado in El Paso County in 2014 by Eric Eaton’s wife, Heidi. How exactly they arrived in Colorado is anyone’s guess — packing material, shared plant material or hitchhiking in a car? I am the second person to find them in Colorado and they are now in several counties.

Eric Eaton, a Colorado Springs resident and author of “The Kaufman Field Guide of North American Insects”, said that finding the Asian mud dauber was happenstance by his wife and that any gardener who wishes to “observe and record” insects in their garden could be the first to find something new. You simply need to be the first person, at the right time, in the right place, and have some curiosity.

The Asian mud dauber is a relative to the Colorado well-established black-and-yellow mud dauber (Sceliphron caementarium) and blue mud dauber (Chalybion californicum). All three can be up to an inch or more in length and share a similar body shape, very unmistakable if you see one. They have a narrow body plus an extremely thin petiole (waist) between the thorax and abdomen. Their names coincide with their coloring, except for the Asian mud dauber, which is dark, brown-black with brown-reddish legs and yellow or orange-yellow bands.

The females of all three types do the heavy lifting in making mud homes for their progeny. The differences between the three is where they make their nests (location, location, location) with some variations in construction methods. The blue mud dauber, the prettiest of the three, with her blue-black sheen, takes an easy path — she does not build new mud nests or cells, she seeks existing abandoned mud nests and takes them over. She is more of a renter than a builder. Another difference between the three is the type of insect each mud dauber targets to provision the nests — any backyard-sleuth entomologists out there might find this the most interesting habit of mud daubers. They seek out spiders as insect prey. Not just any spider, each type of mud dauber has their own special list of spiders to pursue.

Once the mud cells are built or found they hunt live spiders found outside around plants and other areas in the landscape. The female mud dauber knows just how to approach the spider she wants and when found gives it a paralyzing sting. The stunned spider, and many more that will fill up the cocoon nest, are brought back to await the final pièce de résistance from the female mud dauber. She lays one single egg on top of the mass of spider prey, for future sustenance once the egg grows to the next stage — a hungry larva, or grub.

Before flying off to start another build, the female mud dauber seals the cell with one last dab of mud. The developing larva will feed on the spiders until it pupates and emerges as an adult. This is the part where you want to know if the spiders are alive after being stung, hauled from their locale, given a helicopter ride followed by being stuffed and trapped in a mud structure only to be eaten by a developing grub. The short answer, yes.

If the Asian mud dauber is like the black-and-yellow mud dauber then it will produce a second generation in one summer. Late summer larvae will hold in place (diapause) in the cocoon until next summer when they will pupate and begin the cycle again.

The more common black-and-yellow mud dauber’s nests are more like mud condominiums with several cells built closely together, then mudded over for a consistent plaster look. These can be found under eaves, in corners of buildings, places that remain dry, so the condo is kept intact. Again, the blue mud dauber will fill her nests with spiders in stolen cells originally built by the black-and-yellow mud dauber and possibly the Asian mud dauber. Her favorite spiders to add to her mud queue are western widow and comb-footed spiders. She knows exactly how to lure them from their web or simply pluck them straight out.

Fast forward to our house in August 2016. While I was cleaning windows, I was surprised to find stacked (up and down) and consecutive (across the top) rows of cylindrical mud cocoons attached to the inner frame channels of our hinge-styled windows. I was expecting to find a dead gnat or two, not Asian mud daubers. I did some research for identification and reached out to a few people, but they were not confirmed as Asian mud daubers until 2018 by Whitney Cranshaw, Ph.D., an entomologist at CSU.

Next trip to Denver he stopped by to examine and dissect some of the cocoons and check out the type of spiders they most preferred as prey. He found jumping spiders, prowling and running crab spiders.

These types of spiders are found crawling around and on plants as opposed to web-building spiders.

Great, so now I know what these mud cells are in our windows, what����ap next? Will they be back next year and the next? Will they make nests elsewhere on or near our house? Answers — yes, they’ll be back next year and the next; yes, they can find other hidden, often tucked away places to build nests. One year we found them in the garage on the underneath frame of our patio furniture. A friend of mine found some in her garden shed under a shelf.

The Asian mud dauber’s arrival to Colorado shouldn’t be a big deal, they are not displacing other common mud daubers and there are plenty of spiders to go around in landscapes.

Spiders are beneficial in their own right — eating earwigs, flies and mosquitoes. Asian mud daubers won’t harm us, however, their mud nests may leave remnants on surfaces when removed.

I guess I can’t blame them for tying to raise their family, but really, in our windows, every summer!?

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The city on Thursday announced that state officials have for the first time confirmed the presence of the emerald ash borer in Arvada, seven years after it first arrived in Colorado. The non-native, wood-boring beetle that is responsible for the death or decline of tens of millions of ash trees in North America was first detected in Boulder in 2013.

It has since been found in other communities, like Broomfield, Longmont, Berthoud, Lyons and Westminster.

The emerald ash borer was first discovered in Michigan in 2002, and since then it has spread to at least 35 states. The insect lacks predators as it is not native to the United States.

Arvada officials said they do not know how the beetle finally found its way into the city, whether it was by natural spread or via accidental human transport such as in firewood or other raw ash material. The emerald ash borer is capable of travelling a half-mile each year on its own.

Approximately 97,000 ash trees on both private and public land in Arvada could eventually be affected by the beetle. Over the last several years, forestry staff in the city have completed an inventory of the size, location and health of all 1,500 ash trees on city property, and city staff has to a potential infestation.

The ash borer was discovered in an ash tree from private party three miles southwest of Berthoud in an unincorporated part of Larimer County. An arborist brought a log from the tree to the Loveland recycling center because he suspected infestation, the news release said. From there, a Colorado State University Extension agent passed the insects along to an expert on the Fort Collins campus who confirmed it as being the species of invasive beetle.

“Residents should first determine if their property has any ash trees, and if so, then evaluate the condition of each tree now and in the upcoming spring,” the news release said. “They also should decide whether to have ash trees treated next spring, or removed and replaced.”

The emerald ash borer was first detected in Colorado in Boulder in 2013, quickly spreading to nearby Longmont, Lafayette, Superior and Lyons. In September, Broomfield County confirmed the beetle’s presence. A quarantine in Boulder County was in place to prevent spread, but it is likely being lifted

It’s unclear how the insect made its way to Berthoud, nearly 30 miles north of Boulder and nearly 40 miles north of Broomfield, but the common way the beetle spreads is by hitching a ride on firewood or another form of accidental human transport. The beetle is capable of migrating a mile a year.

In the meantime, residents with questions are advised to contact .