Why trees aren’t just colorful fall features
for our region’s neighborhoods
by Roger K. Lewis (Tunisia 1964-66)
President, Peace Corps Commemorative Foundation
The Washington Post
Oct. 25, 2019
October’s changing leaf colors, along with intrusive leaf-blower noise, are signals every year that fall is definitely upon us and winter will be arriving in a few weeks. But these sights and sounds also remind us how wonderfully verdant the nation’s capital is.
We are quite fortunate. Few cities match metropolitan Washington’s extraordinary amount of tree-covered, vegetated open space. Thousands of acres of interconnected, stream-valley parks thread around and through the region, which encompasses countless neighborhood public parks varying greatly in size, shape, topography, flora and function.
Complementing our urban and suburban public parkland are hundreds of thousands of private outdoor spaces — front yards, backyards, courtyards — all contributing in different ways to the fall color display.
Washington is an appealing place to live and work in part because of its greenness, its preserved natural ecologies as well as its designed landscapes. Especially valuable are the millions of trees, and not just for their beauty and colorful tree canopy transformation in the fall. Trees greatly benefit environmental and economic health.
Trees throughout the city add real estate value as well as significant aesthetic and ecological value. Ask any real estate broker or developer, and they will tell you that properties with trees typically are worth more than those without trees. Homes on tree-lined streets sell for more than homes on treeless streets.
When a site is being developed or redeveloped, considerable expense often is incurred to save and protect existing trees; to replace trees removed because of failing health or problems with location; or to increase the number of on-site trees. For some projects, agreeing to plant additional trees can be a requirement for building permit approval.
From April to October, and particularly during summer months, trees and canopies not only add attractiveness but also improve local microclimates by providing shade and filtering sunlight. Solar shading cools outdoor open spaces, pedestrians, roads, parked cars, buildings and especially homes. Solar shading, an essential tactic for achieving sustainability, enhances comfort while reducing electric energy needed for air conditioning.
Most sunlight hitting cities falls on paved streets and sidewalks, masonry walls and roofing materials, all of which absorb heat-producing solar radiation. Solar-induced heat is then reradiated or conducted directly back to the atmosphere, making dense central cities hotter than surrounding, less dense suburbs and exurbs. This is known as the urban “heat island effect.” And the best, most sustainable antidote to this is deciduous shade trees with full, leafy canopies.
As part of photosynthesis, trees — along with other leafy flora — absorb carbon dioxide and emit oxygen. This is why continuing destruction of large areas of the Amazon rainforest is of worldwide concern. Reportedly, Brazil’s rainforest accounts for a significant percentage of the planet’s natural, atmospheric carbon absorption capacity, suggesting that losing large amounts of tree cover anywhere on Earth could contribute to global warming and climate change.
Tree-covered, stream-valley parks and other intensely vegetated, public and private open spaces make Washington pleasantly habitable. Its parks and open spaces are also an inviting habitat for birds of all kinds, bats, squirrels, chipmunks, rats, raccoons, whitetail deer, possums, foxes and coyotes.
This is a mixed blessing, as animals can befoul or damage property, attack pets or transmit diseases. But some Washingtonians, my wife and I included, usually enjoy living in this verdant capital city. We especially appreciate all the birds that help keep the flying insect population under control.
Of course, the city looks quite different between November and April when deciduous trees and shrubs are leafless. Canopy shading is gone but much less necessary with winter’s shorter days, low sun angles and cooler temperatures. The public realm becomes much more visually transparent, and urban architecture more visible, with the richly complex tracery of tree branches arching overhead. Winter’s tree canopy porosity is also desirable because sunlight can penetrate into and warm building interiors.
Yet many of the city’s trees and shrubs are not deciduous. Evergreen trees and shrubs are part of the flora mix. By retaining their needles and leaves, evergreens are a reminder that this is a green city, even on freezing days when a foot of snow covers the ground.
Having grown up in Houston, I never experienced fall — nor snowfall — until I left Texas and the Gulf Coast to attend college in New England. That’s where I learned firsthand that four distinctly different seasons exist in this region of the United States.
Living and working in Tunisia as a Peace Corps Volunteer, I appreciated North Africa’s Mediterranean climate and environment, essentially two seasons like Houston: hot months and chilly months. But I missed the seasonal fall colors characteristic of this part of North America.
The next time you go outside, again look at and enjoy the orange, yellow and red hues spreading through Washington’s tree canopies. For many of us, living somewhere lacking this annual fall ritual of leaves turning would be a big sacrifice.
Roger K. Lewis is a retired practicing architect, a University of Maryland professor emeritus of architecture and a guest commentator on WAMU’s “The Kojo Nnamdi Show.” He has always combined teaching and practice, believing that one informs and energizes the other. His experience as a practitioner began in the Peace Corps in Tunisia, where he was an architect for the Ministry of Public Works and was responsible for designing more than 30 government-financed projects, over half of which were built. These included municipal auditoriums, shopping facilities, schools, a boy scout camp, a movie theater, a hotel, a historic mosque renovation, and public gardens.