11 Reasons Why You Should Plant a Tree for Arbor Day
The benefits of trees are incalculable, from providing oxygen and cooling our streets with shade, to helping us relax and connect with nature.
But in a world experiencing increasingly extreme weather, many tree species are at risk. For instance, last year's devastating hurricanes—Harvey, Irma and Maria—snapped and downed innumerable trees, altering treasured landscapes in Texas, Florida and the Caribbean.
So in celebration of National Arbor Day, consider these 11 amazing facts about trees (via the Arbor Day Foundation):
Trees help clean our air.
- Global forests removed about about one-third of fossil fuel emissions annually from 1990 to 2007.
- Trees remove pollution from the atmosphere, improving air quality and human health.
- Roadside trees reduce nearby indoor air pollution by more than 50 percent.
Trees contribute to our health.
- A study of 10 cities found community forests save an average of one life each year. In New York City, trees save an average of eight lives every year.
- Office workers with a view of trees report significantly less stress and more satisfaction.
Trees provide us with oxygen.
- One large tree can provide a day's supply of oxygen for up to four people.
- More than 20 percent of the world's oxygen is produced in the Amazon Rainforest.
Trees help clean our drinking water.
- Forested watersheds provide quality drinking water to more than 180 million Americans.
- In 1997, New York City spent $1.5 billion to preserve the forested watershed that supplies New York City's drinking water by purchasing thousands of upstate acres of forested watershed. A filtration plant large enough to clean New York City's water supply would have cost more than $6 billion dollars.
- Today, New Yorkers enjoy some of the cleanest drinking water in the world, and New York City has won regional water taste competitions.
Trees provide much-needed cooling.
- Trees lower surface and air temperatures by providing shade. Shaded surfaces may be 20–45°F cooler than the peak temperatures of unshaded materials.
- Trees cool the city by up to 10°F by shading our homes and streets and releasing water vapor into the air through their leaves.
- Evaporation of water from trees has a cooling influence.
Trees help reduce the effects of climate change.
- Trees absorb carbon dioxide (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 by a car driven 26,000 miles.
- During one year, a mature tree will absorb more than 48 pounds of carbon dioxide from the atmosphere and release oxygen in exchange.
- Nearly 20 pounds of carbon dioxide are produced from burning one gallon of non-ethanol gasoline.
Trees help us save energy.
- Trees properly placed around buildings can reduce air conditioning needs by 30 percent and can save 20–50 percent in energy used for heating.
- The average Cincinnati community tree saves the average household $56 annually in cooling costs by reducing electricity use. More than 85,000 Cincinnati community trees save residents $4.8 million.
- Carefully positioned trees can reduce a household's energy consumption for heating and cooling by up to 25 percent. Computer models devised by the U.S. Department of Energy predict that the proper placement of only three trees can save an average household between $100 and $250 in energy costs annually.
Trees benefit wildlife.
- Trees provide vital wildlife habitat.
- In British Columbia, Canada, more than 80 wildlife species depend on trees.
- Trees and forests provide important species range. Many animals have a range of hundreds of square miles. The mountain lion of North America, for instance, has a range of nearly 400 square miles.
Trees help reduce crime.
- In Baltimore, a 10 percent increase in tree canopy corresponded to a 12 percent decrease in crime.
- Among minor crimes, there is less graffiti, vandalism and littering in outdoor spaces with trees as a part of the natural landscape than in comparable plant-less spaces.
- Chicago public housing residents with nearby trees and natural landscapes reported 25 percent fewer acts of domestic aggression and violence.
Trees are a good investment of our public dollars
- Every dollar spent on planting and caring for a community tree yields benefits that are two to five times that investment—benefits that include cleaner air, lower energy costs, improved water quality and storm water control and increased property values.
- In Indianapolis, each dollar invested in the city's community trees yielded $5.55 in benefits.
- In New York City, it has been calculated that community trees provide $5.60 in benefits for every dollar spent on tree planting and care.
- In Cincinnati, the return on a $1 investment in the city's community trees is $4.44.
- The mature street trees in Beverly Hills, California, are worth $450 million.
- A cost-benefit analysis of the Berkeley, California tree canopy indicated that each camphor tree had an annual net benefit to the city and its residents of nearly $12,500, each shamel ash showed a $9,600 annual net benefit, and each London planetree had an annual net benefit of more than $8,700 per tree.
Trees increase our property values.
- In Portland, Oregon, homes with street trees sold for $7,130 more, on average, and 1.7 days more quickly.
- Neighboring houses within 100 feet of street trees sold for $1,688 more, on average.
- The sale premium of having street trees was the same as adding 129 square feet of finished space.
- In Fulton County (Atlanta), Georgia, mature trees positively influenced home sale prices. Homes sold for nearly $105,000 more in neighborhoods with mature trees.
Of course, before you start planting, you want to make sure it's the right tree in the right place. Also remember to take good care of it!
Click here to find out what your town is doing to celebrate Arbor Day. Note that some states observe Arbor Day on different dates depending on the best tree-planting times in the area.
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By Bob Jacobs
Hanako, a female Asian elephant, lived in a tiny concrete enclosure at Japan's Inokashira Park Zoo for more than 60 years, often in chains, with no stimulation. In the wild, elephants live in herds, with close family ties. Hanako was solitary for the last decade of her life.
Hanako, an Asian elephant kept at Japan's Inokashira Park Zoo; and Kiska, an orca that lives at Marineland Canada. One image depicts Kiska's damaged teeth. Elephants in Japan (left image), Ontario Captive Animal Watch (right image), CC BY-ND
Affecting Health and Altering Behavior<p>It is easy to observe the overall health and psychological consequences of life in captivity for these animals. Many captive elephants suffer from arthritis, obesity or skin problems. Both <a href="https://doi.org/10.11609/JoTT.o2620.1826-36" target="_blank">elephants</a> and orcas often have severe dental problems. Captive orcas are plagued by <a href="https://doi.org/10.1016/j.jveb.2019.05.005" target="_blank">pneumonia, kidney disease, gastrointestinal illnesses and infections</a>.</p><p>Many animals <a href="https://doi.org/10.1016/j.neubiorev.2017.09.010" target="_blank">try to cope</a> with captivity by adopting abnormal behaviors. Some develop "<a href="https://doi.org/10.1016/j.applanim.2017.05.003" target="_blank" rel="noopener noreferrer">stereotypies</a>," which are repetitive, purposeless habits such as constantly bobbing their heads, swaying incessantly or chewing on the bars of their cages. Others, especially big cats, pace their enclosures. Elephants rub or break their tusks.</p>
Changing Brain Structure<p>Neuroscientific research indicates that living in an impoverished, stressful captive environment <a href="https://doi.org/10.1016/j.jveb.2019.05.005" target="_blank" rel="noopener noreferrer">physically damages the brain</a>. These changes have been documented in many <a href="https://doi.org/10.1002/cne.903270108" target="_blank" rel="noopener noreferrer">species</a>, including rodents, rabbits, cats and <a href="https://doi.org/10.1006/nimg.2001.0917" target="_blank" rel="noopener noreferrer">humans</a>.</p><p>Although researchers have directly studied some animal brains, most of what we know comes from observing animal behavior, analyzing stress hormone levels in the blood and applying knowledge gained from a half-century of neuroscience research. Laboratory research also suggests that mammals in a zoo or aquarium have compromised brain function.</p>
This illustration shows differences in the brain's cerebral cortex in animals held in impoverished (captive) and enriched (natural) environments. Impoverishment results in thinning of the cortex, a decreased blood supply, less support for neurons and decreased connectivity among neurons. Arnold B. Scheibel, CC BY-ND<p>Subsisting in confined, barren quarters that lack intellectual stimulation or appropriate social contact seems to <a href="https://doi.org/10.1590/S0001-37652001000200006" target="_blank" rel="noopener noreferrer">thin the cerebral cortex</a> – the part of the brain involved in voluntary movement and higher cognitive function, including memory, planning and decision-making.</p><p>There are other consequences. Capillaries shrink, depriving the brain of the oxygen-rich blood it needs to survive. Neurons become smaller, and their dendrites – the branches that form connections with other neurons – become less complex, impairing communication within the brain. As a result, the cortical neurons in captive animals <a href="https://doi.org/10.1002/cne.901230110" target="_blank">process information less efficiently</a> than those living in <a href="https://doi.org/10.1002/dev.420020208" target="_blank">enriched, more natural environments</a>.</p>
An actual cortical neuron in a wild African elephant living in its natural habitat compared with a hypothesized cortical neuron from a captive elephant. Bob Jacobs, CC BY-ND<p>Brain health is also affected by living in small quarters that <a href="https://doi.org/10.3233/BPL-160040" target="_blank">don't allow for needed exercise</a>. Physical activity increases the flow of blood to the brain, which requires large amounts of oxygen. Exercise increases the production of new connections and <a href="http://dx.doi.org/10.1126/science.aaw2622" target="_blank">enhances cognitive abilities</a>.</p><p>In their native habits these animals must move to survive, covering great distances to forage or find a mate. Elephants typically travel anywhere from <a href="https://www.elephantsforafrica.org/elephant-facts/#:%7E:text=How%20far%20do%20elephants%20walk,km%20on%20a%20daily%20basis." target="_blank">15 to 120 miles per day</a>. In a zoo, they average <a href="https://doi.org/10.1371/journal.pone.0150331" target="_blank" rel="noopener noreferrer">three miles daily</a>, often walking back and forth in small enclosures. One free orca studied in Canada swam <a href="https://doi.org/10.1007/s00300-010-0958-x" target="_blank" rel="noopener noreferrer">up to 156 miles a day</a>; meanwhile, an average orca tank is about 10,000 times smaller than its <a href="https://www.cascadiaresearch.org/projects/killer-whales/using-dtags-study-acoustics-and-behavior-southern" target="_blank" rel="noopener noreferrer">natural home range</a>.</p>
Disrupting Brain Chemistry and Killing Cells<p>Living in enclosures that restrict or prevent normal behavior creates chronic frustration and boredom. In the wild, an animal's stress-response system helps it escape from danger. But captivity traps animals with <a href="https://doi.org/10.1073/pnas.1215502109" target="_blank">almost no control</a> over their environment.</p><p>These situations foster <a href="https://doi.org/10.1037/rev0000033" target="_blank">learned helplessness</a>, negatively impacting the <a href="https://doi.org/10.1155/2016/6391686" target="_blank" rel="noopener noreferrer">hippocampus</a>, which handles memory functions, and the <a href="https://doi.org/10.1016/j.neuropharm.2011.02.024" target="_blank" rel="noopener noreferrer">amygdala</a>, which processes emotions. Prolonged stress <a href="https://doi.org/10.3109/10253899609001092" target="_blank" rel="noopener noreferrer">elevates stress hormones</a> and <a href="https://doi.org/10.1523/JNEUROSCI.10-09-02897.1990" target="_blank" rel="noopener noreferrer">damages or even kills neurons</a> in both brain regions. It also disrupts the <a href="https://doi.org/10.1016/j.neubiorev.2005.03.021" target="_blank" rel="noopener noreferrer">delicate balance of serotonin</a>, a neurotransmitter that stabilizes mood, among other functions.</p><p>In humans, <a href="https://doi.org/10.1006/nimg.2001.0917" target="_blank" rel="noopener noreferrer">deprivation</a> can trigger <a href="https://doi.org/10.3389/fnins.2018.00367" target="_blank" rel="noopener noreferrer">psychiatric issues</a>, including depression, anxiety, <a href="https://doi.org/10.3389/fnins.2018.00367" target="_blank" rel="noopener noreferrer">mood disorders</a> or <a href="https://doi.org/10.1177/1073858409333072" target="_blank" rel="noopener noreferrer">post-traumatic stress disorder</a>. <a href="https://doi.org/10.1007/s00429-010-0288-3" target="_blank" rel="noopener noreferrer">Elephants</a>, <a href="https://doi.org/10.1371/journal.pbio.0050139" target="_blank" rel="noopener noreferrer">orcas</a> and other animals with large brains are likely to react in similar ways to life in a severely stressful environment.</p>
Damaged Wiring<p>Captivity can damage the brain's complex circuitry, including the basal ganglia. This group of neurons communicates with the cerebral cortex along two networks: a direct pathway that enhances movement and behavior, and an indirect pathway that inhibits them.</p><p>The repetitive, <a href="http://dx.doi.org/10.1016/j.bbr.2014.05.057" target="_blank">stereotypic behaviors</a> that many animals adopt in captivity are caused by an imbalance of two neurotransmitters, dopamine and <a href="https://doi.org/10.1016/j.neubiorev.2010.02.004" target="_blank" rel="noopener noreferrer">serotonin</a>. This impairs the indirect pathway's ability to modulate movement, a condition documented in species from chickens, cows, sheep and horses to primates and big cats.</p>
The cerebral cortex, hippocampus and amygdala are physically altered by captivity, along with brain circuitry that involves the basal ganglia. Bob Jacobs, CC BY-ND<p>Evolution has constructed animal brains to be exquisitely responsive to their environment. Those reactions can affect neural function by <a href="https://www.penguinrandomhouse.com/books/311787/behave-by-robert-m-sapolsky/" target="_blank">turning different genes on or off</a>. Living in inappropriate or abusive circumstance alters biochemical processes: It disrupts the synthesis of proteins that build connections between brain cells and the neurotransmitters that facilitate communication among them.</p><p>There is strong evidence that <a href="https://doi.org/10.1523/JNEUROSCI.0577-11.2011" target="_blank">enrichment</a>, social contact and appropriate space in more natural habitats are <a href="https://doi.org/10.1111/j.1748-1090.2003.tb02071.x" target="_blank" rel="noopener noreferrer">necessary</a> for long-lived animals with large brains such as <a href="https://doi.org/10.1371/journal.pone.0152490" target="_blank" rel="noopener noreferrer">elephants</a> and <a href="https://doi.org/10.1080/13880292.2017.1309858" target="_blank" rel="noopener noreferrer">cetaceans</a>. Better conditions <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5543669/" target="_blank" rel="noopener noreferrer">reduce disturbing sterotypical behaviors</a>, improve connections in the brain, and <a href="https://doi.org/10.1038/cdd.2009.193" target="_blank" rel="noopener noreferrer">trigger neurochemical changes</a> that enhance learning and memory.</p>