This is a brief overview from the most recent issue of Natural Resources Management Today, which covers scientific findings and silviculture-related topics impacting urban forests across North America.
North Carolina Puts a Bounty on Bradford Pear
Bradford pear trees certainly are lovely when in bloom. No wonder so may people plant them in their yards. They probably didn’t know that the tree is highly invasive. So invasive that North Carolina is offering a bounty on them.
Bradford pears can breed with other varieties of pear trees and spread in natural forests, replacing native trees and creating “food deserts” for birds, according to the North Carolina (NC) State Extension. While being highly invasive, they emit a strong, distinctive scent, which some people describe as a stench. In addition, Bradford pear trees are structurally weak and often break during storms. They also can have thorns long and sharp enough to puncture car and tractor tires. And, as one might imagine, gloves and the soles of shoes. Ouch!
A recent New York Times article refers to the tree “an unstoppable villain.”
But maybe they are stoppable. The NC Bradford Pear Bounty program is a project of NC State Extension, the NC Urban Forest Council, the NC Forest Service, and the NC Wildlife Federation. NC homeowners who register and provide photos showing that they have cut down a Bradford pear receive free native trees in exchange, up to five trees per household.
Other states also are working to remove and replace Bradford pear trees. Ohio, South Carolina, and Pennsylvania have announced bans against the sale and planting of Bradford pears.
According to NC State Extension, Bradford pear trees are cultivars of the Callery pear, which was brought to the US from China in the early 1900s in an attempt to hybridize them with other pear trees and improve their disease resistance. By 1950, the Bradford cultivar had been planted widely, and other cultivars have been produced since. It was believed that these trees would not be able to spread. However, different cultivars are able to cross, allowing them to escape into our natural forests. These trees spread quickly, allowing them to outcompete native species. Because they produce leaves earlier than other trees, Callery pear trees can shade out wildflowers.
Happiness Happens in Urban Parks
People love their urban parks—no doubt about it. How much do they love them? To find out, scientists at the University of Vermont (UV), along with a team of collaborators, designed a study that measures the “happiness effects” of city parks in the 25 largest US cities, such as New York City and Los Angeles. Researchers found a powerful happiness benefit from city parks, which was present across all seasons, months, weeks, days, and times of the day—not just weekends and summer holidays. Perhaps most surprising: The happiness people feel when spending time in urban parks is roughly equivalent to the mood spike people experience on holidays such as Thanksgiving or New Year’s Day.
“These new findings underscore just how essential nature is for our mental and physical health,” said UV scientist Taylor Ricketts. “These results are especially timely given our increased reliance on urban natural areas during the COVID pandemic.”
The team analyzed 1.5 million Twitter posts to measure differences in online sentiment, comparing tweets posted inside city parks to those posted elsewhere.
“We understand the irony of using Twitter and technology to measure happiness from nature,” says lead author and recent UVM PhD student Aaron Schwartz, noting Twitter’s reputation for ‘doom-scrolling.’ “But our goal is to use technology for the greater good—to better understand the effect nature has on humans, which until now has been difficult to quantify in such large numbers.”
According to UV, the research is the largest study of its kind to quantify the mood boosting benefits on urban nature. The paper was published March 30 in the online science journal PLOS One.
- Los Angeles
- New York
- San Diego
- San Francisco
- San Jose
- San Antonio
- Fort Worth
- El Paso
Invasive Insects on the Rampage
Invasive, non-native insects such as the emerald ash borer have wreaked havoc in urban forests for years, and they aren’t about to stop. That’s the conclusion of a team of researchers who calculate that 1.4 million street trees will be killed by invasive insects by 2050. Street trees represent a small fraction of the total number of trees in most cities.
The researchers, led by Emma J. Hudgins, of McGill University in Montreal, used models of street tree populations in roughly 30,000 US communities and made species-specific spread predictions for 57 invasive insect species and estimates of tree death due to insect infestations for 48 host tree genera. They predict that 90 percent of all mortality will be due to emerald ash borer, which is expected to kill virtually all ash trees 6,000 communities; 23 percent of urban centers will experience 95 percent of all insect-induced mortality. The tree deaths will result in an average of US$30 million annually in tree removal and replacement costs
The scientists identify Asian wood borers of maple and oak trees as the highest risk future invaders, where a new establishment could cost US$ 4.9B over 30 years.
The full text of the study is available for online reading in the Journal of Applied Ecology.
This piece was originally published in the April 2022 edition of Natural Resources Management Today (NRM Today). Steve Wilent is Editor of NRM Today, a monthly digital newsletter for North American natural resources professionals who manage fish, forests, range, water, wildlife, and other resources, as well as for the people who depend on or enjoy these resources.