How trees can save us

By Alissa Walker
On Dallas’s hottest summer days, Matt Grubisich would dispatch his colleagues at the Texas Trees Foundation to take manual air temperature readings across the city. “You think the number to go by is the weather station out at the airport,” he says, pointing to Dallas’s Love Field, five miles northwest of the city center. “But then we’d go to a parking lot downtown where it was 6 degrees warmer.”

As the director of operations and urban forestry for the Texas Trees Foundation, Grubisich was trying to demonstrate that Dallas needed to make major design changes to fortify itself against epic heat waves. “It’s easy to explain to people why they park under a tree when they drive to the grocery store,” he says. Getting local leaders and the population at large to take action to bring more trees to the city was a tougher sell.

Thanks to the city’s 2015 effort to map its urban forest, Grubisich and his team already knew that the city’s trees were not evenly distributed. Almost half of Dallas’s trees were located within the Great Trinity Forest, a 6,000-acre nature preserve. That didn’t leave a lot of trees for the rest of the city, where some neighborhoods only had tree canopy over 10 percent of their communities.
To make the case for rethinking the city’s approach to trees, Grubisich and the Texas Trees Foundation turned to data on a larger scale. The organization’s comprehensive urban heat study, released in 2017, showed that one-third of the city was suffering from a phenomenon called urban heat island effect. A full 35 percent of the city was covered by impermeable surfaces, like parking lots, roads, and buildings, which absorb sunlight and end up heating up the air around them.

“I knew we would have a rather robust urban heat island,” says Grubisich. “That number, that was the most alarming part. That was the catalyst.”

Dallas’s heat island was more than robust: Parts of the city were up to 15 degrees Fahrenheit warmer than their rural counterparts. The urban heat island was expanding so rapidly that the ninth-largest city in the country was warming faster than any other large U.S. city except Phoenix.

Source: How trees can save us – Curbed, 2019-07-10

The Detested Bradford Pear Tree Is Coming to a Forest Near You

By Amanda Kolson Hurley
In the 1960s, America fell in love with a new tree: the Bradford pear. Cultivated from Asian stock by scientists at the U.S. Department of Agriculture, Bradford pears display clouds of pretty blossoms in the spring and garnet leaves in the fall, and are hardy enough to grow just about anywhere. Thinking they had found the perfect ornamental tree, homeowners and public-works departments planted Bradford pears up and down the nation’s streets for decades, especially in the East, South, and Midwest.

Then the relationship soured. Bradfords are apt to split and break during storms, and they have a short life span, only 15 or 20 years. Although they are technically sterile, the trees cross-pollinate with other cultivars of the Callery pear species (Pyrus calleryana), producing fruit that splats all over sidewalks. And despite their delicate appearance, the blossoms emit a foul odor that’s been compared to rotting fish (among other things).Cities and states are trying to remove Bradford pears‚ but the “weed trees” have already intruded deep into some forests, a biologist warns.

Once admired for its hardiness, the Bradford pear is now considered an invasive species, which grows even in poor conditions, proliferates fast—thanks to birds that dine on its fruit and spread the seeds—and crowds out native species.

Cities are trying to put an end to the tree’s mischief. Pittsburgh’s Urban Forest Master Plan prohibits planting Bradford pears. This March, Fayetteville, Arkansas, started offering a bounty to anyone who cuts one down. (They can get a free native tree to replace it.)

The bad news is it’s not only in developed areas where the trees threaten to choke biodiversity. Theresa Culley, head of the Department of Biological Sciences at the University of Cincinnati, warns that wild Bradfords and other kinds of Callery pears are making inroads into Eastern forests.

Source: The Detested Bradford Pear Tree Is Coming to a Forest Near You – City Lab, 2019-07-02

Science can guide replanting trees for storm resistance

By Mark Tancig
We can use science to guide the replanting so that we choose wind-resistant species and implement other best practices to prevent future damage.

In the aftermath of Hurricane Michael, with our neighbors to the west still recovering, many folks may be questioning the wisdom of having trees near their house. The value of trees to our own health (oxygen, air purification, quality of life benefits), home values, energy savings, and wildlife habitat is pretty well agreed upon.

However, many of us, or someone we know, recently experienced a tree coming down on their house, car, or other valuables. There’s nothing like a tree falling through the roof to keep you from wanting to plant another one.

Yet, we need trees. With the continued loss of forests to development and the growing body of knowledge regarding current and future environmental issues we face (think climate change and loss of species), we can’t afford to not keep planting trees. In fact, we should be planting more!

So how do we justify planting more trees in a hurricane-prone area when many of us just witnessed a lot of damage caused by the trees? Well, we can use science to guide the replanting so that we choose wind-resistant species and implement other best practices to prevent future damage as much as possible.

Fortunately, the University of Florida’s Institute of Food and Agricultural Sciences (UF/IFAS) has faculty and staff who collect and synthesize data on how trees handle hurricanes so that citizens can use that information to make better, informed decisions. They noticed trends when studying information collected following nine hurricanes, from 1992 to 2005, that ranged from top winds of 85 to 165 miles per hour.

The researchers broke the results into three different areas that affected the resilience of trees and included lessons learned regarding the health of the community’s urban forest, the individual trees themselves, and the root zone conditions surrounding trees.

Some of the results will seem straightforward.

For example, more trees fall in higher intensity storms and older, poorly structured trees with damaged roots don’t perform as well. Other data collected provided insights into which trees and environmental conditions make for a more resilient urban forest, such as the fact that trees planted in groups fare better. Much information was gathered on which tree species performed best in the face of high winds.

Source: Science can guide replanting trees for storm resistance – Tallahassee Democrat, 2019-06-27

Light pollution hurts urban bats. Trees can help.

By Liz Langley
Green spaces within cities can lessen the impact of artificial light on bats, a new study says.

YOU’D THINK HALLOWEEN would be the battiest time of the year, but these winged mammals merit a second annual celebration.

In honor of National Bat Appreciation Day, we’re taking a look at urban bats and how they manage to live among us. (Get the truth behind six bat myths.)

Excessive artificial lighting, also called light pollution, can have a negative effect on many nocturnal animals, for instance by disorienting them or interfering with their reproduction.

But that hasn’t stopped bats from making their homes in cities. For instance, 18 of Germany’s 25 bat species live in Berlin, which is also made up of 20 percent forest.

“Trees provide a lot of benefits for bats,” including roosts, shelter from wind and predators, and better foraging opportunities, says Tanja M. Straka, a researcher at the Leibniz Institute for Zoo and Wildlife Research.

Source: Light pollution hurts urban bats. Trees can help. – National Geographic, 2019-04-17

Study suggests green infrastructure may solve city problems

One way to improve Jacksonville’s problems with stormwater flooding, crime, air pollution, job creation and mental health is simple – plant more trees, said Karen Firehock. As executive director of Green Infrastructure Center, a nonprofit based in Charlottesville, Virginia, Firehock and her team have been conducting a federally-funded independent review of Jacksonville’s urban canopy and its effect on stormwater and water quality.

During the second of three public meetings, which was sponsored by the San Marco Preservation Society and held in Preservation Hall February 28, Firehock explained how her organization is helping the City of Jacksonville map, evaluate and restore its urban forest while focusing on stormwater management. Jacksonville is one of 12 southern cities to be part of the study, which is funded by the United States Forest Service.

Study suggests green infrastructure may solve city problems
POSTED ON APRIL 1, 2019BY EDITORARTICLES, BROOKLYN, DOWNTOWN, SPRINGFIELD, NEIGHBORHOOD NEWS, RIVERSIDE, AVONDALE, ORTEGA, MURRAY HILL, SAN JOSE, SAN MARCO, ST. NICHOLAS, TOP STORIES

Study suggests green infrastructure may solve city problems
One way to improve Jacksonville’s problems with stormwater flooding, crime, air pollution, job creation and mental health is simple – plant more trees, said Karen Firehock.

As executive director of Green Infrastructure Center, a nonprofit based in Charlottesville, Virginia, Firehock and her team have been conducting a federally-funded independent review of Jacksonville’s urban canopy and its effect on stormwater and water quality.

LeAnna Cumber, District 5 City Councilwoman-elect with Karen Firehock of the Green Infrastructure Center
During the second of three public meetings, which was sponsored by the San Marco Preservation Society and held in Preservation Hall February 28, Firehock explained how her organization is helping the City of Jacksonville map, evaluate and restore its urban forest while focusing on stormwater management. Jacksonville is one of 12 southern cities to be part of the study, which is funded by the United States Forest Service.

During the meeting, which was sparsely attended, Firehock discussed specific ways the City can beef up its green infrastructure. At the end of the study, the nonprofit will provide the City with an online casebook, which Jacksonville residents can access with its recommendations and findings. The Green Infrastructure Center held its third and final meeting March 28 in Springfield.

“We want cities to understand that trees, wetlands, streams, and rivers are part of the cities’ infrastructure, and we need to manage them just like we manage our built assets,” she said, noting that “gray” infrastructure is comprised of sidewalks, roadways, pipes, and buildings. Jacksonville Urban Forester Richard Leon agreed. “We are looking at how urban trees affect our city’s water quality, and how we can incorporate trees, so they are looked at as infrastructure and not just as a commodity,” he said before the meeting.

Forty-two percent of Duval County is covered with trees, although they are not evenly distributed. Having a healthy urban tree canopy is very beneficial. Not only do trees soak up stormwater – a single tree, depending on species and size, can soak up between 760 and 4,000 gallons of water per year – they provide “access to fitness,” clean the air, improve mental health, reduce crime, lower residential vacancy rates, encourage people to shop more, and attract small companies to cities,” Firehock said.

“Trees pick up particulate matter and clean the air. If you have a well-treed neighborhood, you are going to have better air quality than one that doesn’t have many trees. Trees improve mental health. We heal better when we see green. Less crime occurs in neighborhoods with lots of trees. Statistically, it is proven the more treed the area, the lower the crime rate,” she said, also adding that people shop longer and pay more per item with they visit tree-lined shopping districts. “It makes sense to spend money on trees and plant them right. You’ll get it back in property taxes and sales taxes. The trees will pay the city back.”

Source: Study suggests green infrastructure may solve city problems – The Resident Community News Group, Inc., 2019-04-01

How a Massive Tree-Planting Campaign Eased Stifling Summer Heat in New York City

By Sonja Dümpelmann
Many cities, in recent years, have initiated tree planting campaigns to offset carbon dioxide emissions and improve urban microclimates. In 2007, New York City launched MillionTrees NYC, a program designed to plant 1 million new trees along streets, in parks and on private and public properties by 2017. They hit their goal two years ahead of time.

These programs are popular for a reason: Not only do trees improve the city’s appearance, but they also mitigate the urban heat island effect – the tendency for dense cities to be hotter than surrounding areas. Studies have shown that trees reduce pollutants in the air, and even the mere sight of trees and the availability of green spaces in cities can decrease stress.

But as I show in my new book, “Seeing Trees: A History of Street Trees in New York City and Berlin,” trees weren’t always a part of the urban landscape. It took a systematic, coordinated effort to get the first ones planted.

Source: How a Massive Tree-Planting Campaign Eased Stifling Summer Heat in New York City – Discover, 2019-01-28

The architect transforming cities into ‘vertical forests’

By Oscar Holland
Stefano Boeri’s tree-covered towers in Milan won critical acclaim. Now he’s taking his urban forests global.

Architect Stefano Boeri has always been obsessed with trees. The Italian traces his fascination back to a novel he read as a child, “Il Barone Rampante” (“The Baron in the Trees”), in which a young boy climbs up into a world of trees and vows to never to return.
“I think trees are individuals,” Boeri said in a phone interview. “Each has its own evolution, its own biography, its own shape.”

Unsurprisingly, there is child-like wonder to the architect’s best-known building, Il Bosco Verticale, or the Vertical Forest. Built in his home city of Milan, the celebrated complex teems with greenery, its facades transformed into living, breathing organisms.

The project’s two residential towers — measuring 80 meters (262 feet) and 112 meters (367 feet) respectively — play host to around 20,000 trees, shrubs and plants. They spill out from irregularly placed balconies and crawl up the structures’ sides. By Boeri’s estimates, there are two trees, eight shrubs, and 40 plants for each human inhabitant.

The purported benefits of this garden architecture transcend aesthetics. Greenery, supposedly, provides shade to apartments, psychological benefits to residents and a home to wildlife. (There are, Boeri said, “hundreds of birds, more than 15 different species” nesting on the towers’ various floors.)
But the architect’s proudest claim is that the buildings absorb 30 tons of carbon dioxide and produce 19 tons of oxygen a year, according to his research, with a volume of trees equivalent to more than 215,000 square feet of forestland…

In September, Vertical Forest was named among four finalists for the RIBA International Prize, a biennial award honoring the world’s best new buildings. Amid the plaudits, Boeri claims the project’s real success is that it serves as a prototype.
The architect has far more ambitious designs. His firm has already unveiled plans for new Vertical Forest buildings in European cities including Treviso in Italy, Lausanne in Switzerland and Utrecht in the Netherlands.

In the Chinese city of Liuzhou, Guangxi province, he has masterminded an entire “Forest City,” scheduled for completion in 2020, which comprises tree-covered houses, hospitals, schools and office blocks over a sprawling 15-million-square-foot site. (Boeri said that he’s also been approached about producing similar “cities” in Egypt and Mexico.)

Source: The architect transforming cities into ‘vertical forests’ – CNN, 2018-11-18

Scientists thought they had created the perfect tree. But it became a nightmare.

By Adrian Higgins
A pear seedling selection named Bradford was cloned by the gazillion to become the ubiquitous street tree of America’s postwar suburban expansion. Then it turned invasive.

Carole Bergmann pulls her small parks department SUV into an aging 1980s subdivision in Germantown, Md., and takes me to the edge of an expansive meadow. A dense screen of charcoal-gray trees stands between the open ground and the backyards of several houses. The trees are callery pears, the escaped offspring of landscape specimens and street trees from the neighborhood. With no gardener to guide them, the spindly wildlings form an impenetrable thicket of dark twigs with three-inch thorns.

Bergmann, a field botanist for the Montgomery County Parks Department, extricates herself from the thicket and in the meadow shows me that what I take to be blades of grass are actually shoots of trees, mowed to a few inches high. There are countless thousands, hiding in plain sight in Great Seneca Stream Valley Park. If it were not cut back once a year, the meadow would become like the adjacent screen, wall upon wall, acre upon acre of black-limbed, armored trees worthy of Sleeping Beauty’s castle.

“You can’t mow this once and walk away,” said Bergmann, who began her 25-year career in the department as a forest ecologist but has been consumed by an ever-pressing need to address the escape of the Bradford pear and other variants of callery pear, a species that originated in China, along with other invasive exotics.

Source: Scientists thought they had created the perfect tree. But it became a nightmare. – The Washington Post, 2018-09-17

Carbon Offsets for Urban Trees Are on the Horizon

By Maria Dolan
Austin, Texas, and King County, Washington, are testing carbon credits for planting and protecting urban trees.

The evidence is in: Urban trees improve air and water quality, reduce energy costs, and improve human health, even as they offer the benefit of storing carbon. And in cities across the country, they are disappearing.

A recent paper by two U.S. Forest Service scientists reported that metropolitan areas in the U.S. are losing about 36 million trees each year. The paper, by David Nowak and Eric Greenfield, was an expansion of the same researchers’ 2012 study that found significant tree loss in 17 out of the 20 U.S. cities studied.

This arboreal decline is happening even in some areas that promote “million-tree” campaigns, Arbor Day plantings, and street-tree giveaways. Cash-strapped municipalities just can’t find enough green to maintain the green. Additionally, many cities are adjusting to population booms, and to temperature increases and drought due to climate change—both conditions that can be hard on trees (while increasing their value as sources of cooling and cleaner air). There’s also a growing recognition of the inequity of tree-canopy distribution in many cities, with lush cover in wealthy neighborhoods and far fewer trees in disadvantaged areas.

To find more funding for urban trees, some local governments, including Austin, Texas and King County, Washington (where Seattle is located), are running pilot projects with a Seattle-based nonprofit called City Forest Credits (CFC). The nonprofit is developing a new approach: generating funding for city tree canopies from private companies (and individuals) that wish to offset their carbon emissions by buying credits for tree planting or preservation.

The vast majority of forest carbon credits worldwide have been issued for trees in tropical rainforests and other forests far from urban areas. A study released last year of the forest offsets in California’s cap-and-trade program found that they are effective at reducing emissions.

Source: Carbon Offsets for Urban Trees Are on the Horizon – Citylab, 2018-08-28

Major urban forest threatened by beetle

By Neil Shaw
JOHANNESBURG — One of the world’s largest urban forests is under threat from a tiny beetle.

The polyphagous shot hole borer is thought to have made its way to Johannesburg from Southeast Asia on packing crates or through the trade in plant materials.

Trudy Paap, a forest pathologist at the University of Pretoria, discovered the beetle in the Pietermaritzburg Botanical Gardens last year. She published her discovery in the journal Australasian Plant Pathology, calling it part of “the surge in the global spread of invasive forest pests” because of globalization.

The beetle has since moved to Johannesburg, 200 miles away, and spread across its urban forest, which according to the Massachusetts Institute of Technology initiative Treepedia has the world’s sixth-largest green canopy cover.

Today, many of Johannesburg’s estimated 6 to 10 million trees are dying, a crisis obscured only by the current winter season. Some of the infected trees have the telltale holes the 2-millimeter-long beetle makes in their bark.

“This beetle doesn’t actually eat the trees,” Paap said. Instead it carries a fungus that blocks the vessels that transport water and nutrients, “which ultimately leads to die-back and death of the tree.”

Though scientists don’t know just how many trees have died from the beetles’ invasion, the outlook for Johannesburg is grim: “The city is going to lose a lot of trees.”

The trees do not have an evolved resistance to the polyphagous shothole borer, unlike in Asia where the beetles naturally occur.

It is the older, more established trees that are at risk, said arborist Neil Hill. “So that’s going to leave a gap in the landscape. And if we don’t start to plant straight way with new trees that gap is going to become more and more of a concern as far as urban blight, pollution, aesthetic beauty.”

Source: Major urban forest threatened by beetle – Philidelphia Tribune, 2018-08-21