Spokane’s trees provide more than aesthetic benefits to residents

More than 150 years have passed since the first Arbor Day, and Spokane is celebrating 20 years as a Tree City USA, a designation from the Arbor Day Foundation given to cities that make certain commitments to maintain and support their urban canopies.

A city’s trees can be a lot more than a beautiful bit of visual texture on an otherwise gray landscape or a spot of shade on a hot summer’s day.

“They’re so important,” said Katie Kosanke, urban forester for the city of Spokane. “There are human health benefits, socioeconomic and environmental benefits – there are so many things you don’t really think about.”

Spokane’s trees provide nearly $6 million in annual economic benefits, not just from boosting the aesthetics of the surrounding area, but also from stormwater interception, air quality improvements and energy improvements, according to a 2021 study by the city, in partnership with The Spokane Lands Council and Gonzaga University

That study estimated that the city’s trees provide more than a million dollars’ worth of benefits to Spokane and its residents annually just from removing particulate and other pollutants from the air and also by intercepting stormwater that the city’s utilities would otherwise have to manage.

A more recent study by Gonzaga found that areas with significant tree canopy coverage can be dramatically cooler on hot summer days, which reduces energy usage from cooling systems and prolongs the life of pavement.

The city’s trees also remove thousands of tons of carbon dioxide over the course of their lives, with the urban canopy in just the Latah/Hangman neighborhood sequestering 1,470 tons of carbon annually. This natural storage is estimated to be worth more than $44 million.

“They’re lovely and add to a neighborhood’s aesthetics, but we call them green infrastructure assets because of the value they provide to the community, and they appreciate in value over time,” Kosanke said.

In order to maximize these benefits, the city’s Urban Forestry division wants to see 30% of the city’s surface area covered by tree canopy by 2030.

A few neighborhoods have already met that goal, including Browne’s Addition, Cliff-Cannon, Grandview/Thorpe, Latah/Hangman, Manito/Cannon Hill and Rockwood. The Peaceful Valley Neighborhood had an estimated 29.9% canopy coverage in 2021.

Coverage from the urban tree canopy varies dramatically by  neighborhood and City Council district, with lower-income areas like the East Central Neighborhood generally having the lowest coverage. This means that the economic, health and other benefits from the city’s trees also are unevenly distributed.

The Grandview/Thorpe Neighborhood had the most canopy coverage of nearly 44% as of 2021, while the downtown Riverside Neighborhood’s canopy covers less than 8%. The city’s northeast council district had nearly 14% coverage, while the more affluent district south of the Spokane River had nearly 25%.

To meet the city’s canopy coverage goals while acknowledging the underlying economic disparities, Spokane’s Urban Forestry prioritizes planting in the neighborhoods with the fewest trees, Kosanke said.

“We want an equitable distribution of trees in the city,” she said.

“If you don’t have air conditioning, it’s miserable during the summer, and if you do, the cost involved in running it is significant,” she added. “Homes that are shaded are less burdened.”

Accomplishing the city’s lofty goal of 30% coverage in less than a decade can’t be done by the city alone, Kosanke noted. Private property owners are a key part of any community’s canopy strategy.

Volunteers have been dispersing throughout the city all week, as they do every spring and fall, as part of the city’s SpoCanopy program in partnership with The Lands Council.

“With these like-minded partnerships, we’ve been able to plant more trees than we could as a city alone,” Kosanke said.

On Thursday morning, volunteers met at Corbin Park, grabbed shovels and walked up to a mile throughout the surrounding neighborhoods to properties whose owners had agreed to care for magnolias, ginkgos and other trees brought for the occasion.

Spokane Mayor Nadine Woodward stood alongside young environmentalists, helping to dig holes in front of a nearby church to plant two ginkgos, which, if properly cared for, could still be standing hundreds of years after the end of her term in office.

“Spokane is such a giving community, so this was a way for the Mayor’s Office to volunteer side-by-side with other volunteers in a neighborhood and contribute to the tree canopy,” city spokesman Brian Coddington, who attended with Woodward, wrote in a text.

A lot more planning goes into the trees planted in urban environments like Spokane than those found growing wild in the mountains north of the city.

Street trees tend to be planted relatively young, no more than 2 inches in diameter, Kosanke said. It might be prettier to plant a fully grown tree, but older specimens tend to have a harder time adapting to their new environment. Smaller trees might be cheaper, but they’re also particularly susceptible to being damaged, including in storms or simply from a load of snow dumped on the curb by a snowplow.

Even those tiny trees are up to a decade old before they arrive in cities like Spokane, said Nancy Buley, communications director for the Boring, Oregon-based J. Frank Schmidt and Co., which supplies young trees to companies like Garden Gate Nursery in Pasco. Garden Gate in turns supplies many of Spokane’s trees.

Many of the trees that are sold by nurseries are cultivars, cultivated varieties of a species that might have desirable characteristics, such as a particularly vibrant autumn display. J. Frank Schmidt and Son grows tens of thousands of seedlings every year, which will each be a little different from their parents, the same way human parents resemble but don’t exactly match their children.

Once the company finds a seedling with desirable features, it will propagate that species asexually, such as by grafting, in order to maintain those genetic characteristics.

The process can get even more complicated with trees that should be grafted onto the roots of different cultivars or even different species. This is often done for disease and drought resistance, but can also be done for aesthetic reasons.

J. Frank Schmidt and Son grows eight cultivars of honey locust, Buley said, each with different preferable traits, but that would produce thorns along the trunk and lower branches if grown on their own roots.

Instead, they’re grafted onto the rootstock of a species that is naturally thornless. Those thornless honey locusts made up 2.2% of all city-managed street trees in 2013, the last year for which data is available.

While the city has a long way to go before it reaches its canopy goals, Kosanke expects major investments in urban forestry in coming years. The inflation reduction act included $1.5 billion for urban forestry, she noted.

While much of the work of urban forestry is about considering a city’s trees in aggregate, some standout groups and individuals are also noteworthy in their own right, Kosanke notes.

Many of them find their home at the Finch Arboretum. A group of dawn redwoods, which were long believed to be extinct, were grown from seeds from China, where the species was rediscovered in the 1950s. Nearby, there are also some particularly old ginkgos, which grow slowly but have been found to live for potentially thousands of years.

In the Indian Canyon area, there are some stands of Douglas fir that have grown there since before Spokane was incorporated as a city, spared from generations of logging.

“We have some real showstoppers throughout the park system and throughout town,” Kosanke said.