Showing posts with label Urban Heat Island. Show all posts
Showing posts with label Urban Heat Island. Show all posts

Wednesday, September 30, 2015

Why Urban Trees Solve So Many of Our Problems

Official magazine of the Sierra Club
 
 
Photo by iStock/chrishowey
 
Trees cover an estimated 20.9 million acres of urban land in the continental United States. That’s 3,659 square feet of urban forest per city dweller—about the size of a not-so-modest four-bedroom house. 
But like housing, trees are not equally distributed across American cities. Studies have shown that there is a higher demand for trees in wealthy neighborhoods. Conversely, areas with a higher proportion of African Americans, low-income residents, and renters enjoy less tree cover.
The unequal allocation of city greenery means that many low-income and non-white urbanites are missing out on the benefits of having trees on their city blocks, which, it turns out, are significant.
If your street is peppered with Magnolias and American Sweet Gums, your neighborhood will look better, sound better, and be less windy. Trees in urban spaces suppress noise, beautify monochromatic pavement, and reduce wind speeds.
If offensive city noises do traverse the leafy canopy outside your window, you’ll be less stressed about it.
In 1984, healthcare design researcher Roger Ulrich conducted a study that revealed post-operative patients with tree views have shorter hospital stays than their counterparts with brick wall views, which Ulrich believed was due in part to reduced stress. Since then, numerous studies have linked verdant surroundings to lower stress levels.
Green spaces will also help bring your community together; they provide opportunities for hands-on environmental education and foster outdoor recreation. Even your grumpy next-door neighbor loves them.
According to a 2010 study by the USDA Forest Service, more foliage also means fewer felonies. Because urban greenery indicates that a neighborhood is well maintained, potential criminals believe they are more likely to be caught and are therefore less likely to risk committing a crime, suggested researchers.
And, of course, urban trees are awesome for the environment. Every year, city vegetation removes nearly 784,000 tons of air pollution and reduces atmospheric carbon dioxide by about 100 to 200 pounds per tree.
Shady canopies help reduce urban temperatures, which are often hotter than neighboring rural areas. Cooler days temper AC usage, so trees help you save on utilities and reduce your carbon emissions.
Water and soil quality will also benefit from a few Acacias on your block. Trees filter out some of the harmful substances that wash off of roads, parking lots, and roofs during storms, while also reducing surface run-off and flooding risks.
They help out animals and birds, too, by providing sanctuary from the dangers of city living. A 2010 study pointed to the importance of maintaining urban forests as refuges for migrating birds looking for food and rest.
If you aren’t sold on the environmental advantages, city trees are also good for your health. Tree cover mitigates ultraviolet radiation, which can cause harmful skin damage with direct sunlight. City flora has also been associated with lower asthma rates in young children and fewer instances of cardio-metabolic conditions.
Unfortunately, the racially and economically skewed distribution of urban forests in the United States means that not everyone has access to the health benefits that trees provide. This is especially problematic because pollution disproportionately affects minorities and poor Americans.
So, urban forests can basically fix a lot of our problems, but only if everyone has equal access to the social, economic, and health advantages of a little extra tree cover.
WHAT YOU CAN DO
Convinced by now about the merits of urban trees? There are lots of ways you can help green-ify your city.
Talk to your local officials and city planners about building up your neighborhood’s leafy infrastructure. Urban forests are an essential part of our country’s infrastructure and, like public schools and highways, our government is primarily responsible for planting and maintaining them.
And if you have a yard, plant a tree in it. There are a ton of web-based resources to help you slect the right one. For example, if you live in a low-rainfall area, pick drought-tolerant species with the help of the USDA Plants Database and your state’s forestry agency. You can also try out a cool measuring tool like i-Tree to assess the costs and benefits of trees in your community.
 
 
 
 

Monday, September 22, 2014

New Study Shows White Roofs are Three Times More Effective than Green Roofs at Fighting Climate Change

by Lidija Grozdanic, 02/11/14
 
 
Green roofs offer a lot of environmental benefits – they provide additional insulation, reduce rainwater runoff, and can lower your electricity bill. However a new study suggests that roofs painted white might actually be more effective at fighting climate change. A study published in the Energy and Buildings Journal compared three types of roofs – green, black and white – and came to the conclusion that white roofs have great economic benefits, and they are also three times more effective than the other two at fighting climate change.
 
 
Researchers at the Lawrence Berkeley National Laboratory conducted an economic analysis of the costs and benefits of white, black and green roofs and found that white roofs are far superior in fighting climate change than the other two. While roofs painted black absorb heat and contribute to the urban heat island effect, white roofs reflect the sunlight back into the atmosphere and help cool down its lower parts. The study advises those concerned with global climate change to choose white roofs, adding to a host of other studies in the past decade that have allowed the “white roof movement” to gain momentum across the United States. However, things are not as simple as they seem.
A series of climate simulations carried out by Mark Z. Jacobson and Ten Hoeve of Stanford University showed some unexpected results. Despite their beneficial effects on the lower parts of the atmosphere, white roofs decrease the temperature difference half a mile above ground-a difference which drives cloud formation and less clouds means more sunlight reaching the Earth’s surface. This, among other issues like the impact on fossil fuel consumption and summer cooling vs. winter heating gains, is still subject of scientific debates. Meanwhile, it should also be noted that vegetated roofs offer built-in storm water management mechanisms in addition to some cooling benefits.
Although we are excited to find out how different roofing strategies may affect climate change, one should be aware of the fact that these investigations involve a wide spectrum of factors and potential consequences far too complex for a hotheaded (pun intended) thumbs-up verdict.
 



 
 
 
 

Thursday, August 21, 2014

A fight for urban trees: Seattle’s wealthier neighborhoods leafier

While this article is about Seattle, it could be about any urban area in the US.  Fort Lauderdale is currently developing a strategic plan to target areas in the city that are in most need of tree canopy.  - Gene
 

Trees can increase property value, benefit the environment and even lift people's mood and improve human health. Yet lower-income neighborhoods in Seattle tend to have fewer trees.

Seattle Times staff reporters
 
 
The benefits of trees — from their grace and beauty to their gifts of cool, clean air and stress relief — are well-known and documented in study after study. Yet as the city grows, it is struggling to hold onto its trees, especially in poorer areas.
Seattle's wealthiest neighborhoods are also its leafiest, a Seattle Times analysis shows.
On a recent hot summer day, brothers Stanley and Kenneth Mason were eating cherry pie under the cover of enormous bigleaf maples at their house in the Rainier Valley.
"We have the best spot on the lot," Kenneth Mason said. "We love our trees. When we are up here, it is quiet and peaceful. I love the shade and I know they are providing clean oxygen for me to breathe. They keep my air fresh."
They are among the lucky ones in their neighborhood, where big trees are scarce — and continue to fall to the saw.
A look at median household income in the most recent U.S. Census Bureau data, together with a map of the city's tree canopy by the city of Seattle, shows lower-income neighborhoods generally have the fewest trees.
Dividing the city's 53 neighborhoods, including park and greenbelt areas into three income tiers of low ($21,095 to $54,712), middle ($56,963 to $74,302) and high ($74,398 to $110,992) shows the higher-income neighborhoods have 29 percent tree cover, dropping down to 18 percent in the lower-income tier.
The city's most current estimate of tree-canopy coverage is seven years out of date and showed the city then was barely holding steady at 23 percent canopy overall. And that was before its current growth spurt, making it the fastest-growing big city in the U.S. in 2014, according to a census report.
Seattle isn't doing even as well as some of its neighbors. Bellevue's canopy coverage in 2007 — its most recent data — was 36 percent, even though the city has lost 20 percent of its tree cover since 1986, according to a report for the city by American Forests, a nonprofit forest-advocacy organization.
Portland gained tree cover in every zoning category between 2000-2010, when its coverage hit 30 percent citywide, according to a 2012 city report.
Redevelopment is the primary reason trees are cut down in Seattle. Also in the mix are a confusing matrix of city regulations, and underpowered enforcement to protect trees.
Regulation of tree cutting is scattered across three city departments — the Department of Transportation, the Department of Planning and Development and Seattle Parks and Recreation — depending on the type of tree and where it is growing.
 
 
Complaints against illegal cutting can only be called in during regular city business hours, though often tree cutting happens earlier in the morning or on weekends.
The city has been working to reverse the trend of losses. It has created the Seattle reLeaf program, which dispatches volunteer tree ambassadors to neighborhoods and encourages planting trees, provided free by the city.
Since 2009, the city has helped Seattle residents plant 4,000 trees in yards and along streets through the Trees for Neighborhoods Program.
The city's Department of Transportation also planted more than 1,000 street trees in 2013, according to a progress report on the city's Urban Forest Stewardship Plan, adopted in 2013.
To combat blackberries, English ivy, holly and other invasive plants inundating trees in city green belts and parks, the city has partnered with Forterra, the land conservation nonprofit, other groups and countless volunteers to reclaim and replant aging forests before they become ecological dead zones.
The city's Heritage Tree program also allows residents to voluntarily nominate big, exceptional trees for special recognition, and protection. Except in an emergency, those trees aren't to be cut down without a prior permit indicating they are a hazard.
The city will have to plant a lot more trees to reach its goal of a 30 percent canopy cover by 2037.
That goal was set in Seattle's Urban Forest Management Plan in 2007, and reiterated in a 2013 update adopted by the city of Seattle's Urban Forest Coalition, an interdepartmental working group. Its goal is to protect the health and maintain the benefits of the urban forest.
Meeting the 30 percent goal, itself a downgrade from the 40 percent canopy cover the city enjoyed in the 1970s, will be hard in part because trees — especially big trees that provide the most benefit — need space. Not just for a little while, but for the long haul, to enable trees to reach the girth and height and spreading crown that makes an exceptional tree, or grove.
 
Disappearing canopies
It's been a struggle to keep pace with the encroachment of pavement in Seattle.
The city's redeveloping neighborhoods lost more than 35 percent of their tree cover between 2003 and 2007, city records show, "and we have lost a lot more trees since then," said Mark Mead, arborist for the city's Parks Department.
"What we saw was a denuding of the southern part of the city due to development," Mead said. "The land in the core and northern areas was too costly to develop, and the south wasn't, so the expansion of development went south, and the canopy disappeared down there."
Trees on private land in Seattle have little protection, and in the contest between people's desires for views, or sun, or space, the tree rarely wins, Mead noted.
"If someone has a view issue, the first words out of their mouth are usually, 'I love trees, just not those trees.' "
The result is a pull of people to the attraction of the Emerald City that is struggling to continue to live up to its name.
"People come here for the jobs and the great climate and because it's green," said Cass Turnbull, founder of the nonprofit Plant Amnesty, and TreePAC, a political nonprofit formed to advocate for urban trees.
"Pretty soon it will just be for the jobs," she said. "That would be sad."
The past 150 years of clearing, regrading and development have left only remnants of the once vast forest that cloaked the Puget Sound region. Today about 3,700 acres of natural areas in forested parks and greenways, in addition to street trees and trees on private land, comprise the city's total tree canopy.
Unlike on the East Coast, where non-American Indian settlement came earlier, leaving trees more time to regrow — and some truly mammoth older trees were never cut — the biggest, most venerable trees in the Seattle are just more than a century old, and most are far younger and smaller than that.
Even in city parks, more than half the trees are smaller than six inches in diameter, according to a city report.
 
 
The value of trees
Urban trees are a lifeline to nature not only in Seattle, but for the majority of residents in the United States, where 80 percent of the population lives in urban areas.
Trees are not a luxury, or small matter: Study after study has shown that neighborhoods with more trees usually have higher property values, better neighborhood interaction and lower crime rates. People with trees in their environment generally experience less stress. They are happier and better able to focus and solve problems.
In public debate, the focus usually is on the ecosystem services of trees: their ability to clean the air, filter the water, soak up stormwater and lower energy bills by shading summer heat and blocking winter winds.
The city's urban forest was estimated to supply billions of dollars' worth of free stormwater retention and filtration and millions of dollars in energy savings per year, according to a 2012 report by a collaboration of Forest Service and University of Washington researchers.
But the more subtle, human benefits of trees can be beyond quantification.
Especially big trees have a special effect on people. Some cultures have long known and even deliberately embraced the healthful effects of trees. In Japan, the practice of so-called "forest bathing" is well understood, with walking paths designed for the pleasure of a walk in deep woods, notes Kathleen Wolf, a research social scientist at the College of Forest Resources at the University of Washington.
On research trips to Japan she noticed a "reverence, appreciation and tolerance for old, misshapen, crotchety trees," often supported with props, aflutter with prayers on notes attached.
 
City or forest?
But in Seattle big, old trees are often in the cross hairs.
Consider the case of Seattle's Heritage Tree No. 121, a grand, old American elm just down the street from where the Mason brothers were eating that pie.
The elm that filled a front corner of Deborah O'Neal's lot, gracing the house she grew up in, stood more than six stories high, and its crown spread 95 feet across. Its trunk was more than 4 feet around at chest height.
But O'Neal said she got tired of the tree's roots in the sewer line and worried about branches dropping on her fence, her car, even her neighbors' kids.
"Everyone wants to say the tree is pretty, but I have had (sewer) backup issues because of the roots, and it is a hazardous tree. It belongs in a forest, not a city," said O'Neal, who paid a tree service to cut it down last month.
She had petitioned the city to enroll the tree in its Heritage Tree listing for extraordinary specimens in 2007, but said she was disappointed the designation came with no financial assistance to care for the tree, not even a plaque.
"I am melancholy about it, but I knew for the greater good it had to be cut," O'Neal said. "It dropped big branches and if anyone gets hurt, I will be the Big Bad Wolf. I don't want to have that happen."
An alarmed neighbor called in a complaint to the city as the chain saws revved, but by the time the Department of Development and Planning responded within an hour, most of the cutting was already done.
The city is investigating whether the cutting was against its regulations protecting exceptional and heritage trees.
Neighbor Juli Cummings, who called in the complaint, lives down the street under a canopy of big copper beeches. But the elm was the biggest tree in the neighborhood, and something Cummings said she looked forward to seeing every day.
"It was like a family member," she said, looking at the stump.
 
Lynda V. Mapes: 206-464-2736 or lmapes@seattletimes.com
 
Gene Dempsey, City Forester
Public Works Sustainability Division
Office - (954) 828-5785  Fax - (954) 828-4745
 
 
 

Monday, August 11, 2014

To fight unemployment, India to plant 2 billion trees

Maybe we could/should do something like this in the U.S.!
 
A new initiative in India will employ up to 300,000 youths in an effort to improve air quality and provide opportunities to the unemployed.
Mon, Jul 21, 2014
 
What better way to clean the air along India's roadways than with trees? (Photo: seeveeaar/flickr)
 
Jadav "Molai" Payeng, the Indian man who single-handedly planted up 1,360 acres of forest, may soon have some competition on his hands. Or allies, depending on which way you want to look at it. Huffington Post reports that a new afforestation initiative from India's Rural Development Ministry aims to plant 2 billion trees along the nation's 62,137 miles of highways. The idea, says the article, is to both combat rural poverty and youth unemployment while also improving the environment and helping to clean up India's chronic air pollution:
 
“The country's Rural Development Ministry on Friday announced a new afforestation plan to plant 2 billion trees along the nation’s highways in an effort to tackle youth unemployment. The country’s Road Transport, Highways, Shipping and Rural Development Minister Nitin Jairam Gadkari said in a meeting in New Delhi that the new initiative would also help preserve the environment.
This plan cannot come soon enough. Not only does India have a youth unemployment rate of 10.2 percent, according to the World Health Organization, it is also home to six of the world's 10 cities with the worst air pollution. Given the deadly impact of air pollution worldwide, and the incredible power of trees to absorb emissions, this plan may have a significant impact not just on the economy and biodiversity, but on health as well.” 
 
The plan could potentially employ 300,000 youths, Indian outlet NDTV reports.  This isn't the only recent sign of environmental progress in India either. The country's new prime minister, Narendra Modi, has also announced a target of getting electricity to every home in India by 2019, relying largely on solar power to do so. According to The Hindu, the government is also working on plans to clean up the Ganga and Yamuna rivers. 
 
 
 

Tuesday, May 27, 2014

Forests & Cities: Urban Forests

From the American Forests.org website. 
Also, some of why I do what I do! 
The Challenge
  • Because of their proximity to human activity, urban forests are exposed to more man-made disturbances than their rural counterparts, which can negatively affect their health, growth and ability to perform ecosystem services.
  • Many non-native invasive species and diseases are introduced in urban areas, threatening the urban forest and potentially spreading to rural forests.
  • Urban areas are subject to much higher rates of pollution than rural areas, threatening the health of both people and urban forests.
  • As urban areas continue to expand, forests become fragmented and destroyed, decimating forest health and biodiversity.
  • Urban areas have lost more than 600 million trees to development over the last 30 years, and urban areas are expected to increase substantially over the next 50 years.
Why We Care
American Forests defines urban forests as “ecosystems composed of trees and other vegetation that provide cities and municipalities with environmental, economic and social benefits. They include street and yard trees, vegetation within parks and along public right of ways, water systems, fish and wildlife.” Thus, urban forests are not only just about the trees in the city, but rather they are a critical part of the green infrastructure that makes up the city ecosystem.
All trees provide certain benefits to their ecosystems. In an urban forest, many of those benefits are directly related to the people who live around them. Since more than 80 percent of Americans live in urban areas, it is important to understand the many ecosystems services that our urban forests provide.
Urban forest help purify the air we breathe. Just 100 trees can remove two tons of carbon dioxide from the air annually. Urban trees in the lower U.S. have been found to remove nearly 800,000 tons of air pollution from the atmosphere every year. In the modern day of bustling factories and countless cars on the road, this service of air purification has become more necessary than ever.
The third grade class at Comstock Elementary helps plant flowers and shrubs on campus
Urban forests help manage a city’s water. Because a city has so many impermeable surfaces, rainwater often builds up rather than being absorbed into the ground. This means that even a small rainstorm can cause flooding, as most of the water overflows into the stormwater system rather than into the ground. As the rainwater flows over the pavement, it becomes contaminated with pollutants and may eventually end up in our urban streams and waterways — and even our faucets. Urban forests help in several ways: They intercept rainfall, allowing the water to be absorbed into the tree, roots and soil. This often results in cities not having to build as many artificial stormwater controls, saving the city and its citizens money. Urban forests purify the water on its way into the ground by removing the pollutants collected. The water retained by the urban forest also helps to sustain the growth of the urban trees, parks and vegetation. These services, provided naturally instead of artificially, can save a city billions of dollars each year. In fact, a single front-yard tree can intercept 760 gallons of rainwater in its crown, reducing runoff and flooding on your property.[1]
Urban forests also help reduce energy demand. When planted in the right place, urban forests provide shade to homes, businesses, roads and parking lots. Anyone who has parked under a tree on a hot day can appreciate the cooling effects of foliage, but did you know that it could also improve your health and save you money? In parking lots, trees help keep the cars cool — 40-50 degrees cooler, in fact— and cooler cars produce less pollution. Shade around your home can do the same thing. Just three large trees around your home, two on the west side and one on the east, can provide enough shade to reduce your air-conditioning costs by 30 percent in the summer. And, when placed properly to reduce wind exposure, they can reduce heating bills in the winter by two to eight percent. In fact, 100 million mature trees growing around homes in the U.S. can save a collective $2 billion every year in energy costs.
These are only a few of the many benefits that urban forests can provide if kept healthy and cared for properly. They also provide bird and wildlife habitat and recreational opportunities, improve soil quality, reduce stress and crime rates, create a natural buffer to reduce the everyday noise of the city, add to your home’s property value and more.
 
 

Tuesday, September 10, 2013

Plant Street Trees to Clean the Air

By Dan Shapley

Planting trees is good for the environment, good for the soul, good for the local economy... and, it turns out, even better for our health than previously thought.
A recent study published in Environmental Science & Technology found that trees and other green plants can reduce two key air pollutants eight times more than previously known.
Nitrogen dioxide and fine particulates are two key components of smog and soot, which can damage lungs, make outdoor exercise unsafe and send asthmatics running to the emergency room at high rates. Both pollutants, however, can be reduced by as much as 40% (nitrogen dioxide) to 60% (fine particulates) if trees, shrubs, ivy and even grass are planted in so-called "urban street canyons." Trees, in fact, may be less effective than smaller greenery, since pollutants may be trapped beneath the tree canopy in some cases.
While city dwellers, particularly renters, often don't have the right to plant trees or other greenery outside their buildings, we can all urge neighborhood associations, co-op boards and local governments to invest in plantings that beautify the streetscape and cleanse the air. Outside of cities, homeowners should take note of local codes before planting street trees, too.
Trees, of course, have many benefits, in urban, suburban or rural environments. Strategically planted, trees can also reduce home energy use by as much as 30%, according to the Arbor Day Foundation, and street trees may boost home values in the neighborhood by more than $10,000, according to a 2010 Forest Service study.





Thursday, August 15, 2013

Top 22 Benefits of Trees


Here are 22 of the best reasons to plant and care for trees or defend a tree’s standing:

Trees combat the greenhouse effect
Global warming is the result of excess greenhouse gases, created by burning fossil fuels and destroying tropical rainforests. Heat from the sun, reflected back from the earth, is trapped in this thickening layer of gases, causing global temperatures to rise. Carbon dioxide (CO2) is a major greenhouse gas. Trees absorb CO2, removing and storing the carbon while releasing the oxygen back into the air. In one year, an acre of mature trees absorbs the amount of CO2 produced when you drive your car 26,000 miles.

Trees clean the air
Trees absorb odors and pollutant gases (nitrogen oxides, ammonia, sulfur dioxide and ozone) and filter particulates out of the air by trapping them on their leaves and bark.

Trees provide oxygen
In one year an acre of mature trees can provide enough oxygen for 18 people.

Trees cool the streets and the city
Average temperatures in Los Angeles have risen 6°F in the last 50 years as tree coverage has declined and the number of heat-absorbing roads and buildings has increased.
Trees cool the city by up to 10°F, by shading our homes and streets, breaking up urban “heat islands” and releasing water vapor into the air through their leaves.

Trees conserve energy
Three trees placed strategically around a single-family home can cut summer air conditioning needs by up to 50 percent. By reducing the energy demand for cooling our houses, we reduce carbon dioxide and other pollution emissions from power plants.

Trees save water
Shade from trees slows water evaporation from thirsty lawns. Most newly planted trees need only fifteen gallons of water a week. As trees transpire, they increase atmospheric moisture.

Trees help prevent water pollution
Trees reduce runoff by breaking rainfall thus allowing the water to flow down the trunk and into the earth below the tree. This prevents stormwater from carrying pollutants to the ocean. When mulched, trees act like a sponge that filters this water naturally and uses it to recharge groundwater supplies.

Trees help prevent soil erosion
On hillsides or stream slopes, trees slow runoff and hold soil in place.

Trees shield children from ultra-violet rays
Skin cancer is the most common form of cancer in the United States. Trees reduce UV-B exposure by about 50 percent, thus providing protection to children on school campuses and playgrounds - where children spend hours outdoors.

Trees provide food
An apple tree can yield up to 15-20 bushels of fruit per year and can be planted on the tiniest urban lot. Aside from fruit for humans, trees provide food for birds and wildlife.

Trees heal
Studies have shown that patients with views of trees out their windows heal faster and with less complications. Children with ADHD show fewer symptoms when they have access to nature. Exposure to trees and nature aids concentration by reducing mental fatigue.

Trees reduce violence
Neighborhoods and homes that are barren have shown to have a greater incidence of violence in and out of the home than their greener counterparts. Trees and landscaping help to reduce the level of fear.

Trees mark the seasons
Is it winter, spring, summer or fall? Look at the trees.

Trees create economic opportunities
Fruit harvested from community orchards can be sold, thus providing income. Small business opportunities in green waste management and landscaping arise when cities value mulching and its water-saving qualities. Vocational training for youth interested in green jobs is also a great way to develop economic opportunities from trees.

Trees are teachers and playmates
Whether as houses for children or creative and spiritual inspiration for adults, trees have provided the space for human retreat throughout the ages. 

Trees bring diverse groups of people together
Tree plantings provide an opportunity for community involvement and empowerment that improves the quality of life in our neighborhoods. All cultures, ages, and genders have an important role to play at a tree planting or tree care event.

Trees add unity
Trees as landmarks can give a neighborhood a new identity and encourage civic pride.

Trees provide a canopy and habitat for wildlife
Sycamore and oak are among the many urban species that provide excellent urban homes for birds, bees, possums and squirrels.

Trees block things
Trees can mask concrete walls or parking lots, and unsightly views. They muffle sound from nearby streets and freeways, and create an eye-soothing canopy of green. Trees absorb dust and wind and reduce glare.

Trees provide wood
In suburban and rural areas, trees can be selectively harvested for fuel and craft wood.

Trees increase property values
The beauty of a well-planted property and its surrounding street and neighborhood can raise property values by as much as 15 percent.

Trees increase business traffic
Studies show that the more trees and landscaping a business district has, the more business will flow in. A tree-lined street will also slow traffic – enough to allow the drivers to look at the store fronts instead of whizzing by.






Tuesday, March 13, 2012

USING TREES and VEGETATION in the URBANLANDSCAPE

USING TREES and VEGETATION in the URBAN LANDSCAPE

Trees and vegetation are most useful as a mitigation strategy when planted in strategic locations around buildings. Researchers have found that planting deciduous species to the west is typically most effective for cooling a building, especially if these trees shade windows and part of the building's roof. Shading the east side of a structure also reduces air conditioning demand. Planting trees to the south generally lowers summertime energy demand for air conditioning.
Trees and vegetation absorb water through their roots and emit it through their leavesthis movement of water is called "transpiration." A large oak tree, for example, can transpire 40,000 gallons of water per year; an acre of corn can transpire 3,000 to 4,000 gallons a day. Evaporation, the conversion of water from a liquid to a gas, also occurs from the soil around vegetation and from trees and vegetation as they intercept rainfall on leaves and other surfaces. Together, these plants take water from the ground through their roots and emit it through their leaves, a process known as transpiration. Water can also evaporate from tree surfaces, such as the stalk, or surrounding soil. processes are referred to as evapotranspiration. Evapotranspiration cools the air by using heat from the air to evaporate water. Evapotranspiration, alone or in combination with shading, can help reduce peak summer air temperatures. Various studies have measured the following reductions:
Peak air temperatures in tree groves that are 5ºC cooler than over open terrain.
Air temperatures over irrigated agricultural fields that are 3ºC cooler than air over bare ground.
Suburban areas with mature trees that are 2 to 3ºC cooler than new suburbs without trees.
Temperatures over grass sports fields that are 1 to 2ºC cooler than over bordering areas.
Trees and other large vegetation can also serve as windbreaks or wind shields to reduce the wind speed in the vicinity of buildings. In the summertime, the impacts can be positive and negative. In the wintertime, reducing wind speeds, particularly cold north winds, can provide substantial energy benefits. 
Please email comments and questions to GDempsey@fortlauderdale.gov.
Gene Dempsey, City Forester
Environmental Services
Office - (954) 828-7704 Fax - (954) 828-7897
Think before you print!