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My Sadness Condemning Trees

I am a consulting arborist. I inspect trees for health and try to look into the crystal ball to judge if a tree is safe to live under. Bad things happen when trees fall over here in Atlanta. 

Trees grow really fast here. They are huge!  Most of these big trees grow very close to homes and streets. Atlanta is the place to be if you are a tree lover. It’s the most heavily forested city in America.

There was one tree in particular I loved looking at. I would see it a couple of times each day as I drove home. I would slow down and admire it. Sometimes I would pull over. It was a giant southern red oak growing between two houses. It had a perfectly rounded crown with a spread over 80 feet across. The trunk was five feet across which would put it at about 100 years old.

My wife would slow to look at this tree as well. She is my business partner as well as a tree admirer. One day she stopped and decided to take a walk up to have a look at the base of the tree. She knocked on the door to get permission.  A mom and three little girls answered the door.

What my wife saw was a mushroom growing on one of the big root flares. She knew this particular mushroom was a bad sign. It indicated root rot. Oak trees fall over when the decay caused by this fungus attacks the anchoring roots. The mom gave my wife the phone number of the owner. A day later I went out to make the tree inspection.

I dreaded the thought at looking at this tree. This was a tree I admired. Part of me didn’t want to know the truth. The other part of me knew the tree would destroy two homes and probably kill people.

There is a scientific method to testing trees. You work off a data sheet that has you look at all of the parts of a tree. You also look at the targets, what a tree could hit if it fell. If you wanted to look inside the tree, you could drill it with a tiny drill bit that records the resistance of the wood against drill bit. The readout is on a strip of paper, much like an EKG.

I drilled four times. I was praying for the recording needle to register high on the strip of paper. I always talk to the tree when I drill. “Come on, you can make it! All right, all right! Looking good!” My spectators that day were three kids, a mom, my wife, three of my tree climbing students, and the owner of the property. They watched as I drilled different sides of the trunk. Two drillings showed signs of decay, two showed healthy wood.

“What do you think, what do you think?” Everyone wants a quick answer. Do we take it down or leave it. I was clearly in the judge’s chair. I was screwed if I made the wrong decision and left it standing. Yet it was one of the most majestic trees in Atlanta. I decided not to make a quick judgment.

I came back the next day with a fellow collogue and we drilled 5 more times. This time I drilled more times downward below the soil surface. This is where the decay lives. It’s called white rot. It turns hardwood into soft white spongy wood. These are the big anchoring roots that hold a tree up. I looked above me as I drilled. The tree was easily 50 tons in weight. The results were not good.

I had a numbing feeling of compassion as I looked at the tree one last time. I know trees aren’t supposed to have feelings. But I’ve heard them wailing for their lives when the big winds come through. I’ve seen them bow down and creak with the heavy weight of ice. Then there’s the aching moan when a two-trunk tree splits apart. Most people hear a frightening sound when trees break. I hear a goodbye.

There’s a ghost living in the spot where the tree used to live. I can see the silhouette of the tree where it used to be. I can see its cooling arms stretching out over the two houses. I see that tree in my minds eye. I don’t drive down that street any more. 

Do you have personal feelings about a tree? 

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I recently came across this resource, "Diverse Environmental Leaders National Speakers Bureau (DEL)" and wanted to share a link to the page. As you are planning urban forestry conferences in your state, perhaps one of these speakers can provide a presentation. In Georgia, we are fortunate to work with Na'Taki Osborne Jelks who has spoken about Proctor Creek and her work with the West Atlanta Watershed Alliance at several of our programs. In addition, you may be interested in following Audrey Peterman's blog at Legacy on the Land. 365 Parks in 365 Days is a real treat. I was honored to meet Audrey once and will never forget what an inspiration she was to me.

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Preparing Your Trees for the Winter

Healthy shade trees around homes provide many benefits including increasing property value by thousands of dollars, reducing soil erosion and stormwater runoff and providing a visual screen and noise buffer.

Despite these valuable benefits, homeowners may be concerned about the risk large trees provide, especially during the winter storm season in Georgia. While assessing tree risk requires training and experience by a Certified Arborist, there are some simple things you can do to get some peace of mind and determine if you need to seek a professional assessment. Start with a self-survey of each of your trees to identify the obvious risks.

English ivy and other invasive vines should be removed to help inspect the base of the tree for cavities and other fruiting bodies, such as mushrooms which indicate root disease. Cut vines and let them die back and fall off naturally. Also, prune dead, diseased and dying limbs annually. During sidewalk replacement, utility work, or other excavation, avoid cutting roots or keep root damage to a minimum.

Lastly, it’s important to plant new trees to provide benefits to future generations and keep them healthy and safe. Trees that are not properly maintained or which are stressed can quickly become major liabilities to people and property from weather phenomena. Choose the right tree for the right place. Select trees with good form at the nursery and don’t plant trees too deeply. Regular watering, mulching and ongoing tree care is important to maintain healthy trees in your yard. December through February is the best time to plant new trees in Georgia.

The Georgia Forestry Commission has a host of resources that can help you find answers to some of the most commonly asked questions about trees at Ask The Arborist and a list of arborists certified by the International Society of Arboriculture (ISA) who conduct fee-based site visits to determine tree care needs. Trees and storm safety information can also be found at

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Removing large healthy trees is like polluting upstream.

 We need to do a better job conveying the importance of individual trees, particularly those with more than 20 years of remaining life span. Being canopy centric can lead to an emphasis on replanting. Large trees are inconvenient to urban development, but to destroy the big trees in the urban forest is the equivalent of polluting upstream, but the price paid is the degradation of the forest, soil, and the ecosystems around it. All urban dwellers should care about this, as we are what live downstream. Arborist have become much better at calculating risk using programs like Tree Risk Assessment Qualification that integrates the latest research on tree biology, health, and structure. These programs and arborists experiences can help access those trees that have the longest to live and present the least risk. 


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How to Shinrin-Yoku

Excerpted from an article by Barbara Brown.  Link to Full Article

Shinrin-yoku is a Japanese term that means “taking in the forest atmosphere,” or “forest bathing.” (In Japanese, shinrin means forest, and yoku, although it has several meanings, refers here to a “bathing, showering or basking in.”)

Researchers have found immediate and dramatic effects from even 15 minutes of wandering in the forest in a shinrin-yoku way. Shinrin-yoku is more than simply walking in the woods. It is breathing deeply and opening all the senses to receive the rejuvenating and restorative benefits of the forest. The idea is to let nature enter your body through the senses.

In fact, forest environments provide stimulation of various senses, such as vision (scenery), olfaction (smells of wood, grass, leaves, and flowers), auditory (sounds of running streams or the rustle of leaves) and tactile sensations (feel of the surfaces of trees and leaves). This sensory information is processed and transmitted in the corresponding areas of the brain that control emotions and physiological functions and may affect physiological changes.

Researchers have been amassing a body of evidence which supports the fact that spending time in nature has both long and short term health benefits, especially when we spend time with trees in a forest.  To participate go to a forested area and wander. Go to a park. Follow a trail. Smell the fragrances of the trees and shrubs. Listen to the water, the streams, the birds and the sounds of the forest, the breeze that sings in the leaves and needles.

Think of it as bathing in the full experience of the forest, engaging all your senses and letting the sights, sounds, fragrances and sensations wash over you.

• Set aside an hour or so at least three times a week and go to a forest.

• Leave your cell phone and camera behind.

• Gently walk or even just sit, quiet and still.

• Refrain from conversation.

• Listen attentively. Isolate the sounds of birds, breezes in the trees, even rain.

• Notice the changes of the birds and other forest life after they have become accustomed to your presence.

• Breathe deeply.

• Enjoy the different fragrances of the woods.

• Look closely at the details of leaves, needles, bark, rocks, etc.

• Touch and commune with nature.

Many studies suggest that incorporating a forest bathing experience is important for the health of seniors who are in rest homes or treatment centers. They can receive the healing benefits of nature while sitting in a wheelchair in a garden or a forest. Caregivers receive the benefits, too!

Barbara Howard is a marketing consultant and freelance journalist residing in Monterey. She specializes in natural health and LOHAS, Lifestyles of Health and Sustainability, and she blogs at Reach her at 521-8608 or

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Begun The Christmas Tree War Has

This is a great story re-posted from NPR.  When it comes to Christmas Trees do you prefer real or artificial?  Or as this story asks, are you a "Defender of Reality", "Advocate of Artifice", or "Proponent of Self Reliance" ?

I tend to lean towards reality myself, I just love the smell of a natural tree, I love the Frazier fire gum stuck to my hands and I love tossing the ole tree onto the future wood chip pile after the first of the year.  Then every spring as I walk past a couple of historic magnolia trees in front of my town's rec center I re-live that wonderful smell as the city spread those chips under their boughs.

So which are you?  Tell us your story, and post a picture of your tree (I know you already have on on instagram!)

Here is the link to the NPR story:  Begun The Christmas Tree War Has

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Forests vs. Trees

The other day I attended a very comprehensive talk on the Canopy of Atlanta. The analysis included canopy coverage overlays combined with social demographics like income and race (there was a correlation between income and canopy but not race and canopy). The bottom line is that canopy tells an important story, but it only part of the story. Satellite images, GIS layers, and canopy studies do not tell you the structure of the forest. As an arborist, I look at one tree at a time and I get aggravated with the emphasis on the technology, GIS, and canopy. It is as if we miss the trees for the forests. Municipalities love canopy studies because it lets them avoid difficult questions/conflicts like which trees should be protected and how important are specimen trees.  As long as they replace canopy, they feel they have done their job.  The problem is that specimen trees and the soil around them is not easily replaced. Older trees put on substantially more wood per year than younger trees. If it is native tree, their role in the ecosystem can never be replaced in a human life time. A replant grown in crappy soil, will be a crappy tree. Yet the best trees of the urban forest are removed  because they are inconvenient to our land uses. It is time we started paying more attention to the individual trees and back up the canopy studies with "ground truthing, recognizing the big trees that we need to save to retain the character and function of the forest.  There are ways to build around healthy trees that is win win, but it takes some intention. To destroy the big trees in the forest is the equivalent of polluting upstream, but the price paid is the degradation of the forest and the ecosystems around it. All urban dwellers should care about this, as we are what lives downstream.

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The NUCFAC wants to hear from you!

Last year, the National Urban and Community Forestry Advisory Council (Council) polled attendees at the Partners in Community Forestry Conference in Pittsburgh and learned that you'd like to have more input into Council activities. We listened to your feedback and have worked diligently this year to gather additional input from our Urban and Community Forestry (UCF) constituencies throughout the country. As we prepare to finalize the 2016 UCF Challenge Cost Share Grant Program, please take the time to complete this brief survey and help inform the categories for our next grant cycle! 

Please feel free to forward this link to anyone that you think might be interested in participating.

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The Truth About Trees

Posted by Phillip Rodbell on December 1, 2014 at 10:53am 

 “The Truth About Trees is the first full-length documentary film series to explore the indispensable role of trees for all life on Earth. Like filmmaker Ross Spears' previous series, Appalachia, The Truth About Trees demonstrates that natural history and human history are utterly connected—that they are in fact part of the same story. The series is slated for release in 2015. This group is making video histories of people who care for trees nationwide. This project sponsored by the National Science Foundation, the MacArthur Foundation, US Forest Service and Bartlett Tree Experts. Learn more here.

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Tree Risk & Common Ground in the Urban Forest

I wrote the following letter to my neighbors after a healthy 51 inch white oak was removed. I had inspected the tree, it was a 125 years old, no decay present, and outside the buildable area of the property. Using TRAQ, I gave it a moderate risk rating.  Unfortunately, that rating was never officially recorded, although any tree rated moderate or higher may be removed in our community. It was removed to create room for detention for a renovation and because the owner felt it to be unsafe. After the removal someone chopped down their construction utility pole and placed a sign that said, "RIP."  In response to the vandalism the owner wrote an email which slowly disintegrated into us vs. them mentality. The neighborhood has roughly 80% canopy coverage with some very large and old trees.

Dear Neighbors,

As others already have, I wish to welcome Joy and her family. Our new neighbor followed the laws of Decatur and legally removed the tree. I understand that trees are removed especially when they present a danger to human life and property. As part of my job, I condemn risky trees on a weekly basis. I have also removed a specimen tree in my own yard. This still does not appease the remorse I feel when an old tree is removed.

The Urban Forest of our neighborhood is special. I have written about it on several occasions over the years. It is a mature forest that gives us a glimpse of what the primeval forest once looked like before industrialization. While most rural forests reflect unabated logging and agriculture through the 20th century, the urban forests were often intentionally retained to provide shade and and give us a semblance of contact with nature. 

Our homes reside within this forest. As our forest matures and we expand the footprints of our homes we increase the likelihood of a negative encounter. How do we balance the beauty of the forest of which the oldest trees provide the very character of what makes it special but at the same time provide the most risk?

Both trees and ourselves are natural systems that sometimes compete for resources. Our relationship with trees is both reciprocal and antagonistic. Perhaps our depth of emotion about trees is that we have evolved with them and they are rooted deep within our existence. They embody so much that we attribute to life and death. I have yet to meet a person that is indifferent about them and cannot recite a personal tree story, often from their childhood. While our opinions might differ they always provide the opportunity for common ground. That they evoke strong feelings does not surprise me, but it is my aspiration that they help us communicate and relate with one another as individuals, neighbors, and Americans.

I work as both a tree inspector, so I have the privilege to work with trees everyday. Many prefer not to think about the risk trees present while others can not stop thinking about it. After many years of being confronted with this dilemma, the international governing body of arborist developed TRAQ or tree risk assessment qualification. The risk rating of low, moderate, hight, very high is based on target and health of the tree incorporating much research. The amount of research in regards to tree structure, heath, and biology has grown in leaps and bounds over the last decade. Using the TRAQ system the home owners is referred to the "tree risk managers" and the arborist the "tree risk assessor." As the owner must ultimately live with the consequences of the risk whether it be low, moderate, high, or very high, the final decision is theirs to make. The "tree risk assessor" applies their knowledge and experience and any mitigation (pruning, cabling, mulching, etc.) that might mitigate the risk. While the system is not used by everyone and incorporates some subjectivity it is a useful tool for the homeowner to make an informed decision weighing the costs and benefits retaining/removing the tree. As you might guess, the service is not free but ultimately can give you peace of mind and save you the cost of removal. 

It is important to not only measure a tree by its risk, but also understand trees for their many benefits many of which are not directly related to humans. For example, a native oak can support up to 523 species of caterpillars. A single clutch of Carolina Chickadees can consume up to 9,000 caterpillars in a 16 day period. It is also interesting to note that non-native species do not support nearly the level of ecosystem; as an example a Ginkgo will only support up to 5 caterpillar species in the Atlantic Region. Part of evolution is specialization, and it takes up to 1000s of years for a species to adapt to a food source that otherwise would be poisonous. Ginkgos have not been here long enough for caterpillars to adapt to its defenses. So retaining and planting native plants is not just about supporting that species, but also the biodiversity that has evolved around it for millions of years. Older trees also have more time to propagate a healthy biome. Last not all trees are equal, a white oak can have a life span up to 500 years, while a water oak is typically around 90 years.

In regards to the City of Decatur, it allows for residential properties to remove 3 trees within an 18 month period and any tree rated a moderate risk or higher. They also allow double credit for specimen trees, so if it has a tolerable risk to the tree risk manager (home owner, property manager, controlling authority), you will potentially have less to plant back to meet the canopy goal of 45%. As most specimen trees near homes will likely be a moderate risk, most any tree can be removed without penalty in the City of Decatur, although all tree removal requires a permit (can be completed online). If a land disturbance permit is being sought (do not need land disturbance permit to remove trees, typically just for new construction and renovations), they must comply to 45% canopy coverage. India Woodson, the City Arborist is working diligently towards making the ordinance work for as many people as possible. As with most new ordinances there are some flaws and confusing language. However, I respect the process by which it was composed and I think the City did an amazing job incorporating many different and emotional views. I hope to encourage the City to further encourage healthy specimen trees that have a potential remaining life span of at least 20 or more years. 
We have an amazing mature urban forest in our neighborhood. It is a joy and a responsibility. A nice ending to the tree removal on Mt. Vernon is that the mulch from the tree will be spread in the Glenn Creek Nature Preserve, completing its cycle in a way we can all benefit. Perhaps other possible projects to help find common ground is continuing our NeighborWoods program where we plant young trees. I would also be interested in identifying the trees that are over 100 years old. You might be surprised, some of the biggest trees are not necessarily the oldest. If you would like to help us spread the mulch, maintain trails, and pull english ivy, in the Glenn Creek Nature Preserve please join us Saturday, December 13th at 9am.  

Most Sincerely,  

Neil W Norton
ISA Certified Arborist, SO-4158A
ISA Tree Risk Assessment Qualified
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The Role of Urban Forests in Biodiversity Restoration

In the Atlantic region, Oaks support 545 species of caterpillars while a Ginko only supports 5. Why should we care? It has a direct impact on biodiversity. For example, to raise one clutch of Carolina Chickadees requires 6,000 to 9,000 caterpillars over a 16 day period. Why do so few caterpillars appreciate the Ginko in the Atlantic region. Part of evolution is specialization, and it takes up to 1000s of years for a species to adapt to a food source that otherwise would be poisonous. Ginkos have not been here long enough for caterpillars to adapt to its defenses. So planting native plants is not just about supporting that species, but also the biodiversity that has evolved around it for millions of years. One additional challenge is the Urban Forest Ecological Trap, where even if we create biodiversity in our plants, which than propagate native insects , which than supports bird populations, there is a high likelihood they get eaten by a cat (3.7 billion birds killed annually) or hit a window (1billion birds). It is a long roe to hoe, but consider planting native species and keeping the cat indoors. See the video below for sources and full explanations.

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The Scary Truth About Structurally Weak Trees

Davey Tree wrote an excellent blog reminding us of the "The Scary Truth About Structurally Weak Trees." In the article the author nice summarizes a 3 step process for inspecting trees in your yard, and I think it worth repeating here.

1. What’s happening with the roots? Visually inspect the root zone and root collar for damage, decay or fungus. Some signs that a tree’s roots are decaying include peeling, cracking or loose bark. 

2. Turn to the trunk. Inspect the trunk for obvious swelling that could identify advanced decay within the trunk.

3. Look up to the crown. Check for dead or hanging branches, or limbs that lack bark and show no sign of life. Dead or hanging branches are not only scary looking, but they could also fall down at any time. Check for a lack of fine twigs that have living buds at the end of branches. A decaying crown can indicate the entire tree is on the decline.

If you have any suspicion your tree is starting to struggle or decline,contact a certified consulting arborist. Most can conduct a full inspection to let you know whether your tree has crossed the line from asset to liability.

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They are conservancies, sustainable sites, and green infrastructure.

  1. Conservancies are public-private partnerships, which  raise money for, consolidate, and effectively run, many of the city parks and green spaces. Read more:
  2. Sustainable sites uses standards and measurements to foster a transformation in land design and development practices to  bring the essential importance of ecosystem services to the forefront of decision-making and implementation. It works similarly to LEED but is oriented to the landscape. Read more:
  3. Green infrastructure includes park systems, urban forests, wildlife habitat and corridors, and green roofs and green walls. These infrastructure systems protect communities against flooding or excessive heat, or help to improve air and water quality, which underpin human
    and environmental health. Read more:



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The Institute for Environmental Solutions (IES) Wheat Ridge Preserve the Greenbelt Elementary Education final report is now available! Check out our website,, for information and to see the report.  The IES Wheat Ridge Preserve the Greenbelt Elementary Education project has improved the Wheat Ridge Greenbelt by teaching kids to plant and care for trees in their own backyard.  Fourth graders at Kullerstrand Elementary School and third graders at Mountain Phoenix Community School in Wheat Ridge planted 200 native saplings to restore areas in the Greenbelt that had suffered from tree loss. 

Esther Valdez, Principal at Kullerstrand Elementary, said that the project was “very valuable to our school and our community. We’re really committed to building awareness in our students about global citizenship, community involvement, and pride in their community. I truly appreciate IES’s commitment to our school and our community.” In addition to the two elementary schools that participated, Wheat Ridge High School Career Exploration students helped to prepare the planting sites and also planted new trees.

Thank you everyone involved for the successful program! The project video is on IES’s YouTube channel ( and website ( The video shows the replanting of vital areas in the Wheat Ridge Greenbelt and classroom hands-on ecology workshop activities.  The recent issue of Exposures, publication of ASLA Colorado, features a great article about IES's Preserve the Greenbelt Elementary Education project!  The ASLA-CO publication is on-line at For more information about IES environmental and health improvement programs, check our website or email


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Tree Planting Fatigue Reality

My neighborhood in Georgia has roughly 80% canopy coverage. Most these trees were volunteers from the days before air conditioning and less housing density. By the 1990s most these trees were huge and many were going into decline. Neighbors were also expanding the foot prints of their homes, particularly in the late 90s and over the last few years. The neighborhood consists of around 500 homes, mostly of one third acre lots. Each year I would notice at least 20-30 large trees being removed, signaled by the unique pitch of a chainsaw against wood. Most the yards were well manicured and volunteer saplings, representing future canopy, were being removed. I began to worry about the legacy of our neighborhood forest and in 1998 starting started a NeighborWoods tree planting program. The first four years were awesome and we planted over 40 trees, but after that program fatigue set in and we planted around 40 over the next ten years. Momentum is difficult to sustain in tree planting. One major difficulty is the amount of time between planting seasons which inhibits a consistent momentum and separately it gives time for leaders to get distracted. To demonstrate the difficulty, I offer an additional story.  Last year, during the creation of our tree ordinance it was determined we needed to plant 125 trees a year (City wide) to retain a net zero loss of our canopy. A community business leader thought the City was making too big a deal over the difficulty of planting that many trees and he said he would get some citizens together to plant 500. One year later, despite using his numerous resources, I believe he has planted less than 10, and this fall the program has not even been brought up again.  I did not enjoy watching this failure, but it did reinforce what I know to be the difficulty of maintaining a consistent tree planting program.  In yet another example, a car dealership in our area wanted to plant 100,000 trees in our county.  They developed partnerships with the county government and other NGOs.  They quickly downsized to 10,000 and it took four years and many more resources than they ever thought possible.  My point is not to discourage, but to help us be realistic in setting our goals.  It also makes you appreciate organizations like Trees Atlanta that have planted 100K trees in 29 years.  Remember though, they have more than 10 full time employees and a multimillion dollar annual budget.  So while tree planting fatigue is a reality, it can be overcome knowing what to expect at the beginning and then planning around it and allocating proper resources.  This year our NeighborWoods project aspires to plant 20 trees! 

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Georgia Fall Leaf Color Report #GAfallcolor

The Georgia Forestry Commission has started our fall leaf color reporting. Follow the Sustainable Community Forestry Program blog for the full reports!

Recent cool mornings mean good things are on the way for Georgia’s fall foliage season!

Georgia Forestry Commission foresters say dropping temperatures, shorter days and a 10-day forecast that suggests more sun than clouds and rain can be expected to kick the annual color show into gear.

In both northwest and northeast Georgia, foresters are seeing some evidence of fall color on our highest ridges and summits (above 3500 feet elevation.) Maples, sumac and sourwood are beginning to tinge deep red. Yellow poplars are beginning to show their trademark yellows. However, north Georgia canopies are still green for the most part, with color change estimated at just five percent.

Significant color is still a couple of weeks away.

The Georgia Forestry Commission will provide weekly updates on where the colors are peaking and suggest some viewing areas for enjoying the season. #GAfallcolor

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US Marines helping kids plant trees Garden in Seattle hosted a volunteer forest restoration work party during Marine Week, part of the 2014 Seafair summer festival.A bus load of Young Marines came to this Seattle city park to learn from their mentors by helping create a new forest of evergreen trees.Kubota Garden was started in 1927 by a Japanese immigrant who needed a plant nursery & demonstration showcase to display landscape features to potential clients. The garden was listed on the registry of historic landmarks in 1980, & the city purchased the property from the Kubota family in 1987.Gradually, the city added vacant land around the perimeter of the garden to conserve the Mapes Creek watershed in the southeast Seattle neighborhood of Rainier Beach. The Green Seattle Partnership began clearing underbrush & planting trees in 2010.
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To Save the Planet, Don't Plant Trees.....What?!

Be sure to read the responses to this op-ed below.

By Nadine Unge, New York Times, 9/20/14

NEW HAVEN — AS international leaders gather in New York next week for a United Nations climate summit, they will be preoccupied with how to tackle the rising rate of carbon emissions. To mitigate the crisis, one measure they are likely to promote is reducing deforestation and planting trees.

A landmark deal to support sustainable forestry was a heralded success story of the last international climate talks, in Warsaw last year. Western nations, including the United States, Britain and Norway, handed over millions of dollars to developing countries to kick-start programs to reduce tropical deforestation. More funds are promised.

Deforestation accounts for about 20 percent of global emissions of carbon dioxide. The assumption is that planting trees and avoiding further deforestation provides a convenient carbon capture and storage facility on the land.

That is the conventional wisdom. But the conventional wisdom is wrong.

In reality, the cycling of carbon, energy and water between the land and the atmosphere is much more complex. Considering all the interactions, large-scale increases in forest cover can actually make global warming worse.

Of course, this is counterintuitive. We all learn in school how trees effortlessly perform the marvel of photosynthesis: They take up carbon dioxide from the air and make oxygen. This process provides us with life, food, water, shelter, fiber and soil. The earth’s forests generously mop up about a quarter of the world’s fossil-fuel carbon emissions every year.

So it’s understandable that we’d expect trees to save us from rising temperatures, but climate science tells a different story. Besides the amount of greenhouse gases in the air, another important switch on the planetary thermostat is how much of the sun’s energy is taken up by the earth’s surface, compared to how much is reflected back to space. The dark color of trees means that they absorb more of the sun’s energy and raise the planet’s surface temperature.

Climate scientists have calculated the effect of increasing forest cover on surface temperature. Their conclusion is that planting trees in the tropics would lead to cooling, but in colder regions, it would cause warming.

In order to grow food, humans have changed about 50 percent of the earth’s surface area from native forests and grasslands to crops, pasture and wood harvest. Unfortunately, there is no scientific consensus on whether this land use has caused overall global warming or cooling. Since we don’t know that, we can’t reliably predict whether large-scale forestation would help to control the earth’s rising temperatures.

Worse, trees emit reactive volatile gases that contribute to air pollution and are hazardous to human health. These emissions are crucial to trees — to protect themselves from environmental stresses like sweltering heat and bug infestations. In summer, the eastern United States is the world’s major hot spot for volatile organic compounds (V.O.C.s) from trees.

As these compounds mix with fossil-fuel pollution from cars and industry, an even more harmful cocktail of airborne toxic chemicals is created. President Ronald Reagan was widely ridiculed in 1981 when he said, “Trees cause more pollution than automobiles do.” He was wrong on the science — but less wrong than many assumed.

Chemical reactions involving tree V.O.C.s produce methane and ozone, two powerful greenhouse gases, and form particles that can affect the condensation of clouds. Research by my group at the Yale School of Forestry and Environmental Studies, and by other laboratories, suggests that changes in tree V.O.C.s affect the climate on a scale similar to changes in the earth’s surface color and carbon storage capacity.

While trees provide carbon storage, forestry is not a permanent solution because trees and soil also “breathe” — that is, burn oxygen and release carbon dioxide back into the air. Eventually, all of the carbon finds its way back into the atmosphere when trees die or burn.

Moreover, it is a myth that photosynthesis controls the amount of oxygen in the atmosphere. Even if all photosynthesis on the planet were shut down, the atmosphere’s oxygen content would change by less than 1 percent.

The Amazon rain forest is often perceived as the lungs of the planet. In fact, almost all the oxygen the Amazon produces during the day remains there and is reabsorbed by the forest at night. In other words, the Amazon rain forest is a closed system that uses all its own oxygen and carbon dioxide.

Planting trees and avoiding deforestation do offer unambiguous benefits to biodiversity and many forms of life. But relying on forestry to slow or reverse global warming is another matter entirely.

The science says that spending precious dollars for climate change mitigation on forestry is high-risk: We don’t know that it would cool the planet, and we have good reason to fear it might have precisely the opposite effect. More funding for forestry might seem like a tempting easy win for the world leaders at the United Nations, but it’s a bad bet.

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