How Trees Help Us Breathe
How Do Trees Help Us Breathe?
Trees are an effective public health resource that not only improve environmental health but the health of individuals and communities as well. By filtering the air and releasing oxygen, trees play a major role in keeping local air breathable, particularly in cities where pollution can be concentrated. In the worst of cases, poor air quality can restrict people from spending time outdoors or result in long-term health conditions like asthma or other diseases. Reducing the amount of pollution that’s released into the air is an important way to manage air quality, but planting and maintaining lots of tree-filled green space is just as important to the health of our communities.
How Do Trees Prevent Pollution From Spreading?
The impact of air pollution can be seen as a function of population, emission sources, and the condition of the environment. Trees and green space can be most effective in managing and mitigating the amount of air pollution when they’re planted in areas where the emissions are released and where a lot of people live. The more emissions that can be reduced and absorbed near their sources, the less pollution there will be to disburse across the city and into the atmosphere. Here, we’ll go over how pollution moves through the air and how trees can prevent that movement, as well as how they filter the air and produce oxygen for us all to enjoy.
What’s in the Air?
The earth’s atmosphere is mostly made of nitrogen (about 78%) that has been generated by volcanic activity over the planet’s history, oxygen (about 21%), which is produced by trees, algae, and other living organisms, and about 0.93% argon from the decay of potassium in the air, crust, and core of the Earth. This makes up 99.93% of the breaths we take, while the remaining 0.07% variably contains other elements (including carbon and carbon dioxide), pollen, fungal spores, and water vapor.
Most urban areas have some degree of air pollution from cars, factories, energy production, construction, and other aspects of the built environment. Since air is uncontained and moves freely around the world, some of this pollution remains close to where it’s produced, while some drifts around the region and throughout the atmosphere more broadly. The more pollution that’s released in a given area, the more it can concentrate and become dangerous to our health.
Pollutants in the air are tiny and can be difficult to avoid. Heavy metals released during engine combustion are practically unavoidable in an urban environment. When we breathe in polluted air, it can result in health issues like lung disease, heart disease, asthma, and other respiratory or circulatory complications. Young children, older people, and individuals with existing illnesses are most at risk. When we breathe in pollutants, they travel into our lungs and circulatory system, and while our bodies might be able to filter out some of the contaminants, they can have a seriously negative impact on our health.
Air Quality
One way we can avoid these risks is by paying attention to the air quality index. On especially warm days, the toxic pollutants in the air can be transformed by sunlight’s strong UV rays into smog or ozone, a dense form of atmospheric gas that traps heat and raises temperatures in addition to creating toxic air when it forms too near the ground in the zone that we live and breathe.
Checking the city’s current air quality index, especially in the warmest months of the year, is a great way to stay on top of how polluted the air is on any given day. Most weather report resources will include this metric to keep individuals, especially those at higher risk, informed on the air quality in the area. When ozone or particulate matter is especially high, air quality index groups will offer advisories to help people know how to manage the poor quality air. On those days, it’s usually recommended to limit time outdoors or to wear a mask, and in general, it’s recommended to try to avoid driving during rush hour and avoid burning waste or yard litter.
What Is Particulate Matter?
Particulate matter refers to the tiny airborne particles such as soot and smoke, dust from construction, and exhaust from cars that we may breathe in and that can cause health problems. Particulate matter, or PM, is very light and falls slowly, drifting around in the air for a while before reaching the ground. These particles are weighed in microns and are often shown as PM2.5 or PM10. PM2.5 are fine, inhalable particles that can cause the most damage since they can penetrate deeper into the lungs and be more easily absorbed into the bloodstream. Many of us have become intimately familiar with PM2.5 in recent years (including this summer) due to an increase in wildfires in both the U.S. and Canada. PM10 particles are also harmful, but since their particles are larger, they might be filtered out more effectively by our immune systems. PM is measured by governmental, private, and non-profit agencies to monitor, reduce, and regulate their presence in an effort to improve health outcomes in relation to air pollution. For example, the US Clean Air Act has been an important tool for air pollution governance.
Areas with consistently high PM concentrations tend to have more health issues and hospitalizations than areas with less pollution. It’s uncertain which particulates are most dangerous, but it’s easier to control single pollutants by their point sources than the aggregate amount of different types of particulate matter, as well as ozone, in the air. Reductions have been achieved by advances in production and cleanup technology, like removing lead from gasoline or the use of catalytic converters in cars, where the dangerous substances are removed from potential sources before they enter the atmosphere.
Every location will be different in its PM concentration based on the sources of pollution, the layout and geography of the city or region, and the amount of green space and trees present.
How Do Trees Condition the Atmosphere?
While about 70% of the earth’s oxygen comes from plants, algae, and other plant-like organisms in the ocean, just under 30% of the rest of the planet’s oxygen is produced by plants on land, most of which comes from trees. Trees are powerhouses of air filtration and oxygen production, while they also provide cooling services by shading the land and facilitating the water cycle by absorbing groundwater through their roots and transpiring it through their leaves, releasing water vapor into the air.
How Do Trees Make Oxygen?
Trees are often described as the lungs of the earth for their respiration habits. Where we breathe in oxygen and breathe out carbon dioxide, tree leaves take in the carbon dioxide, in addition to other forms of carbon and elements in the air, and release oxygen back out. They do this through photosynthesis—when a tree absorbs a molecule of carbon dioxide, the chlorophyll in the leaves performs the photosynthesis process to break down the compound, using water and carbon to create carbohydrates (made of carbon and hydrogen), with oxygen as a byproduct. As the carbs are used for energy, the carbon is stored in the tree’s roots, trunk, branches, and leaves, while the oxygen gets released as a gas back into the atmosphere, literally creating the healthy air that we need to breathe.
How Do Trees Filter Particulate Matter?
In addition to absorbing carbon and other gases, trees filter the air in another way: they physically block and collect particulate matter that may be floating around within reach. When PM comes into contact with certain tree leaves, it will stick to the leaves and collect as dust, effectively being removed from the air. Some trees work better than others for this—tall trees with sticky leaves like maples and elms are best at this. When it rains, those collected particles then get rinsed off and washed away into soil and sewers.
Scientists measure the ability of trees to capture particulates in the air by collecting leaf samples to weigh and analyze the amount of matter collected on the leaf surface. However, this doesn’t mean that smaller trees that don’t collect as much PM shouldn’t be planted for air quality benefits. Different trees play different roles within the wider ecosystem: tall trees and short trees alike are necessary to fill in vertical spaces. Bushes, vines, and other ground-level plants play their roles as well in providing green cover to capture, process, and store carbon from the air and release oxygen.
Which Trees Produce the Most Oxygen?
While all trees contribute an amount of oxygen into the air, some trees are more productive than others. It comes down to a few factors that put certain species ahead in terms of oxygen productivity. This includes the tree’s size, its leaf size, as well as the season. The bigger a tree is, the more leaves it can put out, and the more leaves a tree has, the more photosynthesis it performs. Tall, mature trees with lots of big, dense leaves will produce the most oxygen. This includes maples, beeches, elms, and fir trees. All of these species are most photosynthetically active during the summer when the sun is strong, the days are long, and they’re growing at the fastest rate.
Where Do Trees Make the Biggest Impact?
Choosing the right tree for any location makes a big difference in its ability to produce the desired effects, whether that’s providing shade or producing oxygen. Some upfront strategic planning will help planting endeavors be more successful. Native trees that are planted in a spot where they will be cared for and will be able to grow to maturity will produce more benefits than invasive trees or young saplings that only get planted but aren’t cared for and die before reaching their full potential.
For Nashville’s urban areas, trees like elms, oaks, bald cypress, and maples are good choices because they grow large, and their bushy canopies will catch particulate matter on their big leaves while absorbing carbon dioxide, producing oxygen, and casting shade. No single tree is a solution, however, to the complex issue of urban pollution and ecosystem management. When it comes to the built environment, where buildings and pavement seem to dominate a city center, it’s important to remember that the majority of Nashville’s green space and tree canopy is located on private property!
Helping Trees Help Everyone
While city governments have responsibilities of their own to pass regulations, plant and maintain street trees, and manage parks, privately held properties can actually make a much larger impact. In Davidson County, 94% of the land is privately owned, which means that homeowners and business owners can make a big difference in the green space and canopy cover in Nashville since the majority of it is located in people’s front and back yards. That’s why the Nashville Tree Conservation Corps’ mission is to support good regulation about tree protections, to inform Nashville residents on the importance of trees, and to actively provide and plant new trees to build up our canopy.
Our tree sale is one of the ways we make trees available to you, the residents of Nashville, so that you can play your part in managing our local canopy. However, you don’t have to be a property owner to further the cause; you can volunteer with us as well! And the foundation of good environmental care is usable information, which is why we publish articles like this to share the actionable strategies we can all use to support our city’s trees. If you haven’t already, subscribe to our newsletter to stay on top of our activities and the educational information we’re putting out so you’re best equipped to know what to do for the trees in your yard and neighborhood.