Why We Need Tree Canopies | Part II

Welcome to Part II of "Why We Need Tree Canopies". This portion will go into a bit more depth of CA's current tree situation, benefits of living near green space and what other jurisdictions in the country are doing to mitigate tree loss and increase benefits from expanded tree canopies.

According to a study by the Carnegie Institution for Science, well over 50 million trees throughout California are at risk of dying because of the drought. Furthermore, drought allows bark beetles to thrive, creating more dire conditions for susceptible trees and, as of last spring, the U.S. Forest Services estimated 12 million trees have already died from a mix of both severe drought conditions and this resulting bark beetle infestation. Studies show that the vast majority of the areas affected have been in the San Joaquin Valley and surrounding Central Valley. Governor Brown declared a state of emergency over dying trees and the California Department of Forestry and Fire Protection (CAL FIRE) have focused efforts to remove dead trees in the SJV to eliminate the area’s vulnerability for fire and wildfire outbreaks.

Tree loss and disease from drought.

Tree loss results in increased forest fire susceptibility and severity as well as decreased animal and insect diversity, water resources and carbon sequestration. This imminent increase in fires, dying trees and beetle infestations will only continue to produce more carbon emissions, contributing to poorer air quality and climate change.

While the drought has exacerbated these conditions, an increased population of well-maintained, native and drought-tolerant trees will help mitigate some of these issues and provide substantial benefits to communities that plant these types of trees, increasing the local urban canopy. The USDA’s report Effects of Drought on Forests and Rangelands in the U.S.: A Comprehensive Science Synthesis notes that while native, drought-resistant plants do require some water and will increase a community’s necessary allotment, forests, including urban forests, are naturally resilient and resist effects from drought. Forests also help manage erosion and water runoff, supply and quality.

The San Joaquin Valley is home to many who both suffer greatly from asthma and live in poverty. Tree canopies, as previously mentioned, improve local air quality through CO₂ sequestration, reducing respiratory-related illnesses and deaths. Tree canopies also provide widespread cooling and temperature control. Tree Fresno, a local environmental agency, shares the information that open, cemented areas can be over five degrees Fahrenheit warmer than similar areas with green space. This causes a reduced quality of life. Community members are less able to take advantage of outdoor amenities, exercising or interacting outdoors; people are more likely to suffer from health problems because of high air-pollution levels and daytime temperatures as well as minimized nighttime cooling; energy bills are higher due to a great need for air conditioning; and city resources become more limited.

Tree Fresno is the "regional resource for trees, trail and greenbelts".

To combat these severe results, Tree Fresno has also shown that a single fully-grown tree can have a net cooling effect of 10 single-room air conditioners each running for 20 hours a day and that shade reduces UVB radiation exposure by up to 50 percent. Pacific Gas and Electric Company (PG&E) shares an emissions factor of 457 pounds CO₂ per MWh. This means that 10 500 Watt air conditioning units running for 20 hours a day is 100 kWh, which is about 45.7 pounds of kWh-related CO₂ avoided with every tree planted.

By providing temperature control, the surrounding community is more willing and able to take advantage of outdoor activities and services and less likely to suffer from heat exhaustion and other related illnesses. Health benefits do not stop here. Environmental Health Perspectives recently published a Harvard University study illustrating a link between lower mortality rates as a result from respiratory illnesses and cancer and living near greenery. Living near greenery decreases air pollution and allows for more physical activity and social engagement. The study also found a much lower prevalence of depression in those that lived near greenery.

Additionally, trees reduce road maintenance costs. The Journal of Aboriculture shared a field study conducted in Modesto, CA, which showed that an unshaded street required 6 slurry seals over a period of 30 years and a tree-shaded street only required 2.5 seals over the same time period. This is a 58 percent reduction. So, let us consider the City of Clovis, which has over 120 Million square feet of roads. If the cost for slurry seals are approximately $0.66 per square foot, the City could see potential savings of nearly $80,000,000. Moreover, in its 2014 Regional Transportation Plan, Fresno COG indicated that over $1 Billion needed to be put towards road operations and maintenance projects. Projects may be avoided or have reduced costs with an increase in tree-lined streets.

I also must point out that since the San Joaquin Valley suffers from high unemployment and poverty levels, we need to shed light on the extensive economic benefits provided by expanded and properly maintained tree canopies. Trees provide natural and low-cost energy efficiency benefits to homes and properties protected and shaded by them. Properly placed trees can reduce cooling costs by 30 percent and can even lower heating costs by up to 50 percent. Lower utility bills put more money back into the pockets of the community, which then goes back into the local economy. Tree-lined streets also promote a higher level of business activity and increase home and property values.

Louisville suburb south of Bowman Field

Louisville, Kentucky adopted a Tree Canopy Ordinance and has since formed a nonprofit organization dedicated to expanding the City’s tree canopy. In support of this effort, the City released a study that outlined many of these benefits in detail. As of 2015, Louisville’s canopy covered about 37 percent of the City, which equates to approximately 147 square miles with nearly 6.2 million trees. This canopy provides the community with over 67 million kilowatt hours (kWh) and over $5 million in energy savings each year as well as a $240 million increase in property values citywide. Additional savings have been reported from nearly 7 million pounds of pollutants and 400,000 tons of CO₂ removed from the atmosphere each year and a near 19 billion gallon reduction in storm water runoff each year. The City of Louisville estimates that $330 million in savings will be seen annually from just maintaining the current tree canopy. Expanding the canopy will only increase these savings across all sectors.

Are you impressed by these benefits of tree canopies? Would you like your city to adopt a Tree Canopy Ordinance? Let us know!