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Thursday, June 18

Record high temperatures in Washington, DC and the crucial issue of preserving trees in cityscapes

Pundita has been suffering from the high heat and humidity.  So much so I haven't listened to weather reports since the heat wave began about two weeks ago. I just haven't wanted to know how long it's expected to continue. Last night I gave in and read a June 15 Washington Post report headlined Washington, D.C. is immersed in a period of record warmth, little relief in sight

It was the "record" word that got to me. Did I not mention recently I was tired of coming across that word along with the words extreme, unusual, historic, and extraordinary used to describe weather events during the past few years?

Which brings me to one of the consequences of the very strange and savage storm that barreled in a straight line from Chicago and swept through the Greater Washington, DC area on June 29, 2012. The type of storm, called a "derecho," was unknown to District residents (although it might have been a derecho that routed British troops when they invaded Washington, D.C. during the War of 1812 and drenched fires the troops had set.)

The storm was something like a cross between a tornado and fast-moving hurricane in its effects.  It uprooted hundreds of trees and knocked out electrical power for days for many residents.  Then PEPCO, the District's power company, went to work with buzz saws to cut down God Knows how many more trees that threatened power lines.  I haven't seen figures on how many damaged and healthy trees were cut down but all told it could have been 1,000 or even higher in addition to the trees felled by the storm.

There was considerable controversy in Montgomery County, Maryland, when the power company hacked into the area's beloved cherry trees to prune them of branches.  The rest is a long and complicated local story.  But the issue for the entire DMV (District, parts of Maryland and Virginia) was getting the power lines moved underground.

This made for more complication and controversy when some people wanted the power lines laid under the street to protect tree roots and others argued it was easier and more cost effective to lay them under sidewalks.

Eventually I stopped paying attention to the debate but I recalled it the other day when I came across this report:
Dying trees may force a new outlook on irrigation during droughtBy Matt Steens, Taylor Goldenstein and Tony Perry
 June 12, 2015
The Los Angeles Times
The unrelenting drought that has ravaged parts of California's forest land is now taking a toll on the trees that line urban parks, boulevards and backyards. From the traffic-clogged streets of L.A. to San Diego's scenic parks, the trees that locals have come to love are increasingly falling victim to years of hot weather and little rain.

[...]
According to a parks department survey ending in April, as many as 14,000 trees in L.A. parks — about 4% of the total — may have died during the last year of drought. The year before that, officials said only about 1% of trees were found dead. In a normal year, the tally would be even less.
Scientists say the death of so many trees could drive up temperatures, wreak havoc on habitats and limit the capture of water. They expect that even more trees could wither as Californians struggle to comply with new conservation rules.
 
[...]
Arborists and experts say that tree loss could have dire consequences.
Trees provide shade and help cool the environment, said Stephanie Pincetl, director of the California Center for Sustainable Communities at UCLA.
The average park in L.A. is about five degrees cooler than the neighborhood that surrounds it, Bauernfeind said.
Trees also absorb and store rain water that could otherwise cause flooding, Lipkis said. The estimated 350,000 trees in city parks capture more than 360 million gallons of stormwater every year, Bauernfeind said. Collectively, L.A. parks' tree inventory has a replacement value of $2.2 billion, she said.
[...]
Plenty more important points in the report but I want to repeat one sentence from the above:
The average park in L.A. is about five degrees cooler than the neighborhood that surrounds it.
Yes, I've noted that phenomenon; anyone who lives in a city who's paying attention has. And it's not just parks, as I mentioned last year. Even a street with a lot of trees lining both sides is markedly cooler than a viritually treeless business district just a few blocks away.

By the way the DMV wasn't the ony region to be hit by the same derecho. From Wikipedia's article:
The June 2012 Mid-Atlantic and Midwest derecho was one of the most destructive and deadly fast-moving severe thunderstorm complexes in North American history. The progressive derecho tracked across a large section of the Midwestern United States and across the central Appalachians into the mid-Atlantic states on the afternoon and evening of June 29, 2012, and into the early morning of June 30, 2012. It resulted in between 22 and 24 deaths. [,,,]
 And $2.9 billion in damages.
  
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