These are my seasonal tree paintings, inspired by Rafi Perez’s Seasonal Joy tree series and Damien Hirst’s cherry blossom paintings. I really enjoy painting these trees because I love using lots of colors and circles. I’m also in the process of painting some Pride flag inspired ones.
Anyway, it’s Arbor Day, so let’s talk about trees. Specifically, urban trees.
Back in the late 80s and early 90s, a few news articles claimed that trees caused (or otherwise contributed to) urban air quality problems. David J. Nowak, a research forester at the USDA Forest Service wasn’t haven’t it. At the 7th National Urban Forest Conference, he introduced the “TREE” pneumonic to help explain the benefits of urban trees.
The pnuemonic is:
Tempurature and Microclimate Effects
Removal of Air Pollution
Emissions of VOCs
Energy Conservation
Temperature and Microclimate Effects
Trees block sunlight in the summer, but don’t in the winter. The Shakers, a protestant utopist sect of the 1800s, knew this without scientific studies. They planted trees near their windows–in the summer, the trees blocked the sunlight, keeping the inside of the house cool. But in the winter, the trees didn’t have leaves and the sunlight could come in, warming the inside of the house.
Trees can cool the microclimate by not only providing shade, but also through the natural process of transpiration. Trees get nutrients from the soil and use water to send the nutrients throughout the tree. But the water then has to go somewhere, so the tree releases it onto the leaves. As the water evaporates, it absorbs heat. It’s a similar principle to how we sweat.
Trees also affect the microclimate by blocking wind.
Removal of Air Pollution
Tree leaves can uptake air pollutants, where it then sequestered into the tree. The bigger the tree, the more it can sequester–large, healthy trees can sequester 70x the amount of pollutants compared to small trees.
Air quality also improves with tree cover–the more trees, the better the air quality becomes.
While they are usually not trees, houseplants can also remove air pollution indoors. While leaves uptake some pollutants, most of the work by houseplants is actually done by the roots and soil! B.C. Wolverton, head of Stennis’ Environmental Research Lab, performed an experiment where he locked specific houseplants in a tank filled with specific pollutants. During the experiment, he cut off all the leaves, and the plants were almost just as good at removing air pollutants!
“Plant roots and their associated microorganisms then destroy the pathogenic viruses, bacteria, and the organic chemicals, eventually converting all these air pollutants into new plant tissue,” he concluded.
Of course, the study was done in a vaccuum and might not be completely applicable to a non-vaccuum space, like your house. If you’re interested, Wikipedia has a list of the houseplants studied.
Emission of VOCs
A VOC is a volatile organic compound. They are gasses that are released into the air. VOC is a very broad category–some are harmless, and some can cause cancer.
VOCs are why some plants have the smell that they do (such as pine trees smelling how they do)–they are also why old books have that “old book smell”. VOCs can also attract pollinators and deter pests.
Energy Conservation
Depending on where the tree is located, it could help lower energy use. A tree could provide shade to a building in the summer, and thus lead to people not wanting as much AC.
Of course, it’s a bit more complicated than that, because the tree could also block sunlight to the building in the winter, thus causing people to want more heat. Consequently, it’s important to be smart as to where you plant your trees.
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So, now you know! I hope you have learned something!
If you would like your own tree painting, I do take commissions! Information is at the bottom of the store page.
Sources/Further Reading
Trees Pollute? A “TREE” Explains lt All
THE EFFECTS OF URBAN TREES ON AIR QUALITY
Urban Trees and Human Health: A Scoping Review
Hancock Shaker Village, tour
The cooling effects of tree cover
NASA Plant Research Offers a Breath of Fresh Air
Volatile Organic Compounds (VOCs) – The Scent of Our Collections and the Things That Hold Them
MAC and Brie Make 
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