Why Are Trees So Important In Fighting Climate Change?

Much has been written about trees, the last one I remember reading is Robin Wall Kimmerer’s explanation in Braiding Sweetgrass on how trees are connected and communicate. Historically, word after word has been inked onto paper to tell others how trees scientifically work. Other people have taken it further and put those words into verses because a tree’s value goes beyond science and could only be approached by poetry. There is, after all, something so incredibly poetic about these wonderful plants. That is why so many dared turn verses into paragraphs, trying to give them a little bit more space in the pages, and therefore attempted to encompass their majesty in the form of novels. They have dug for the essence of trees, trying to find their truth in abstraction, by accommodating them in the shapes of metaphors or sporadic appearances as the meeting point of two characters, as the totem of childhood of another, or perhaps as symbols of life itself, as is the case with the Lisbon sisters in The Virgin Suicides, who cling to one in desperation, but finally perish, as do the trees.

The lyric power of trees emanates from an inner force that creates a sort of halo that is perceivable only with the heart–the beauty of their leaves and branches and outlines, the selfless comfort they transmit when they give us their shade so selflessly, the protection they offer to anyone seeking shelter. They create a sense of community among humanity, replicating that tree unity Wall Kimmerer discusses in her book among people, for if the trees are connected, human beings shall mirror them. But it doesn’t stop there. Trees have existed for almost 400 million years, and some of the longest living organisms on earth are trees, which means their connection powers aren’t limited to roots and community, but extend throughout time, welding the past into the present, and granting the present with a glimpse of the future.

WHAT IS CURRENTLY HAPPENING WITH FORESTS?

Lyricism, peace, or magnificence underlie the significance of trees. Maybe these three are in fact a consequence of the last. Or perhaps poets and novelists have escaped the fact that they might originate from what they have tried to escape with language: science. Trees are vital for the planet because they give us oxygen, they stabilize soil, ameliorate climate change, filter the water we drink and conserve it, store carbon, and provide habitat for wildlife. They also have a positive effect on mental health. Therefore, it is probably their absolute altruism and their role as givers of life, that has earned them a perpetual spot in literature and art.

There are currently around 3.04 trillion trees in the world, of which approximately 1.3 trillion exist in tropical and subtropical forests, 0.74 in boreal regions, and 0.66 trillion in temperate regions. Based on T.W. Crowther’s article, an estimated 15 billion trees are cut down each year due to deforestation and demand for farmland. The net loss falls to about 10 billion, because around 5 billion trees a year are grown. Take a deep breath and read those numbers again and analyze how you feel about this fact after reading this post, because they are going to look much worse then. It has been stated that warming due to land cover change could explain as much as 18% of current global warming trends. Human activities have led to the loss of 45.8% of the world’s trees, according to a study. Since the start of civilization, approximately 3 trillion trees have been cut. These numbers are astronomical, and it is precisely because they are crucial to the existence of this planet.

In 2018, more than 3.6 million hectares of tropical rainforest were destroyed, according to satellite analysis. Beef, chocolate, and palm oil were identified as the main causes. Brazil, the Democratic Republic of the Congo, and Indonesia represented the highest losses, while Ghana and Ivory Coast recorded the biggest percentage increases in rainforest destruction, led by gold mining and cocoa farming. Even indigenous lands who had so far been untouched by deforestation, were invaded.

WHY ARE TREES SO IMPORTANT FOR THE ENVIRONMENT?

AIR

When carbon dioxide concentration goes up, temperature increases too, that is why Co2 has been talked about for years in reference to climate change. Reducing and capturing carbon dioxide emissions has been a longtime priority to care for our environment, although many efforts and promises have fallen short of our expectations. Increasing temperatures mean extreme heat waves, decreased food availability, loss of biodiversity, loss of ecosystems and species, water scarcity, and sea level rises, all of which we are already experiencing, even if we try to ignore it.

Reducing carbon dioxide emissions is imperative to revert climate change, something we can help with as individuals, although the bigger impacts are far beyond our responsibility, as it depends on whole industries and the government. The importance of this reduction was notable during the pandemic, when limitations in various sectors drastically reduced air pollution and greenhouse gas emissions.

However, nature-based solutions provide up to 37% of the reduction in emissions that are needed by 2030 to keep global temperature rises under 2 degrees Celsius, which would demand conserving, restoring, and improving the management of land to increase carbon storage. To conserve forests (and reduce gas emissions), a very important thing we can do is switch to a plant-based diet. A research by the University of Oxford found that plant-based diets require 76% less farmland than diets that include animal products. This is mainly because animals take a lot of land just to exist, but they also need land to grow the food that will feed those animals (70% of the soybeans grown in the U.S. are used for animal feed). You can read more about this here.

Besides restraining the main causes of gas emissions, actively capturing, and storing existing Co2 is just as important. And here come the trees! Trees clean the air and provide us with the most precious gift: oxygen. They absorb harmful pollutants and gases like carbon dioxide, carbon monoxide, sulfur dioxide, and nitrogen dioxide, through their leaves and bark by photosynthesis, which is released as clean oxygen through respiration, stored in tree leaves and branches that later fall to the ground and decay into soil, and is stored belowground in roots and soil organic matter with the help of microbes. This last one is thought to represent 50-70% of the carbon bound in soil, which comes from tree roots and fungi that grow on them. Fungi exchange minerals for sugars and store carbon deep in the soil. On average, a tree will absorb 10 kg of carbon dioxide per year for the first 20 years, but this numbers will increase as the tree gets older, reaching up to 40 kg.  When trees die and decompose, little carbon is released.

Trees are therefore crucial to reduce the effects of climate change, and this is one of the reasons why deforestation takes such a big toll on the environment.

Water

Trees also play a very relevant role in saving water and preventing water pollution, as well as capturing rainwater and reducing the risk of natural disasters, like floods. It doesn’t come as a surprise that the increasing deforestation levels bring along an increasing frequency of floods, which you probably experienced yourself, or seen on the news. Because of transpiration, interception, evaporation, infiltration, and groundwater recharge, trees can store or recycle significant amounts of water downwind, providing a positive impact on the local catchment, thus moderating floods.

Their roots act like filters by removing pollutants and slowing down the absorption of water into the soil, which helps prevent waterslide erosion and flooding. In water-rich areas, fast growing, high water-consuming tree species will reduce flood risk, whereas in water-limited areas, slow growing, low water-consuming tree species can increase infiltration and help moderate flooding.  A 100-foot-tall tree can take about 11,000 gallons of water from the soil and release it into the air again, as oxygen and water vapor, in a single growing season.

Trees are also immense contributors in the preservation of soil. Far reaching roots hold soil in place and prevent erosion. By absorbing and storing rainwater, they reduce runoff and sediment deposit after storms, as well as helping the groundwater supply recharge and prevent the transportation of chemicals into streams.

Tree roots also act as filters for harmful chemicals and pollutants from storm runoff that ends up in lakes, rivers, and streams. Some 180 million people in over 68,000 communities rely on these forested lands to capture and filter their drinking water. Even major cities in the United States rely on water from agency lands, like Los Angeles, Portland, Denver, and Atlanta, which receive a significant portion of their water supply from national forests.

Tree root architecture is also extremely important for the hydraulic redistribution of water in soils because it improves dry-season transpiration and photosynthesis by facilitating upward and downward flows, at the same time they transport rainwater downward to levels where it can’t easily be evaporated.

The same research paper from Science Direct, explains that forests offer solutions to water availability and cooling, because by evapo-transpiring, trees recharge atmospheric moisture, and thereby contribute to rainfall both locally and in more distant locations. Moreover, their microbial flora and biogenic volatile organic compounds can promote rainfall because trees enhance soil infiltration and improve groundwater recharge. Rainfall that is filtered through forested catchments delivers purified ground and surface water.

Forests are great regulators of water supplies. To begin with, they capture fog and cloud water, which draws additional moisture out of the atmosphere. High altitude forests have this ability of intercepting fog and cloud droplets, which means losing these types of forests have negative effects on water availability. When these are removed, the atmospheric moisture in clouds move to other locations, which represents a loss to local, downstream water supply.

The effects of trees on water are too broad, from recycling precipitation and transport it to other places, to triggering rainfall, transporting atmospheric moisture toward continental interiors, cooling temperatures, producing clouds that deflect radiation from terrestrial surfaces, intercepting fog, and clouds to draw additional moisture out of the atmosphere, facilitating infiltration and groundwater recharge, and moderating floods by dispersing water.

Biodiversity

Trees are the home of many a species, including insects, plants, fungi, bats, owls, moss, mammals, birds, lichen, and many other animals, as well as being a source of food for them. Many animals, like koalas or giraffes, eat leaves from trees; monkeys and birds eat fruits and flowers from them. Leaf-covered branches serve as protection for lots of animals, including squirrels, who use them to hide from predators.

An oak tree hosts 532 species of caterpillars, 147 species of birds, 120 species of mammals, and 60 species of reptiles and amphibians. It has been estimated that a total of 2.3 million living species depend on one single tree. Even dead trees provide vital habitat for more than 1,000 species of wildlife.

Depending on whether a forest is young, middle-aged, or older, they will attract different species. Even though rainforests cover less than 2% of Earth’s total surface area, they are home to 50% of the planet’s plants and animals, according to The Nature Conservancy.

Deforestation, therefore, removes shelter and food for all these species, creating an ecological imbalance, and posing a risk to many species that are at risk of extinction.

Soil

As if all this wasn’t enough, trees also help prevent soil erosion (and flooding, as mentioned above), by absorbing thousands of liters of storm water and holding soil in place and fighting erosion, which is done by far reaching roots.

Loss of tree because of converting land for other uses promotes soil degradation, which has a negative effect in soil infiltration and water retention capacity, therefore reducing groundwater reserves.

They also have a substantial role in improving soil quality, by increasing its fertility, supplying it with nutrients, maximizing soil formation, increasing aeration and drainage, and optimizing soil health.

Fallen leaves from trees benefit soil, as well as boost compost. By adding autumn leaves, the compost pile will decompose more efficiently, leading to a better end-product. Leaves have a high amount of carbon, which makes soil be dark and earthy, providing spaces for plant roots.

Climate Change

Trees are the most wonderful and natural removers of carbon dioxide from the atmosphere, another reason why they are indispensable to fight climate change. Maintaining low levels of carbon dioxide leads to a reduction of heat, and therefore lowering air temperature. Not only this, but trees also control climate by moderating effects of the sun, rain (as mentioned before), and reducing wind speeds; they cool the air by losing moisture and absorbing heat.  

Forests provide a “carbon sink” that absorbs a net 7.6 billion metric tons of Co2 per year, 1.5 times more carbon than United States’ annual emissions.

Evapotranspiration (evaporation from soil and plant surfaces, and transpiration of water by plants), alone or combined with shading, can help decrease peak summer temperatures by 2–9°F (1–5°C). In parking lots, trees have been shown to reduce asphalt temperatures by 36°F, and car interiors by up to 47°F. A study done by the University of Wisconsin-Madison, shows at least 40% canopy coverage is needed to counteract the warming effect of asphalt.

Earth’s land and ocean surfaces release water vapor to the atmosphere, which is aided by forests and other vegetation through evapotranspiration. The atmospheric moisture that results from this process is circulated by winds across Earth. This precipitation recycling can promote and intensify the redistribution of water across terrestrial surfaces. However, forest loss and degradation reduce evapotranspiration. Large-scale deforestation will reduce rainfall in some regions by as much as 30%. This change in rainfall patterns due to climate change, combined with warming, can affect vegetation, reduce biomass accumulation, drought, die-off and fires. Aerosol particles from fires can scatter solar radiation, disrupt water vapor uplifting, alter regional circulation, and disrupt rainfall patterns.

With the sun’s energy, trees can transpire hundreds of liters of water daily, which represents a cooling power equivalent to 70 kWh for every 100 L of water transpired–enough to power two average household central air-conditioning units per day. Therefore, trees also conserve energy because of their heat-reducing effects. According to the Maryland Department of Natural Resources, a minimum of three strategically placed shade trees can reduce air conditioning costs by 30%. Evergreens, which maintain heir leaves yearlong, will serve as windbreakers to your house and save 1%-50% of energy used for heating.

Forests can remain much cooler during daytime do to shade and the role of evaporation and transpiration in reducing heat. In tropical and temperate regions, they cool the Earth’s surface, whereas at high latitudes, particularly in winter, forests have reduced albedo (the ability of surfaces to reflect sunlight), hence contributing to local warming. Also, through emissions of reactive organic compounds, forests can increase low-level cloud cover and raise reflectivity, providing additional regional and global cooling.

Even during long-lasting heatwaves, trees with deeper roots can maintain this cooling function. This is not restricted to forests. In urban areas, greater tree and vegetation coverage, and fewer impermeable surfaces, tend to exhibit lower temperatures than those blanketed by solid surfaces.

Also, as I mentioned in the section ‘Air’, evapo-transpiration, where water is drawn up through the soil by the roots and evaporates through the leaves, trees control climate, because they cool the air while transforming the water into vapor.

Other benefits of trees

In addition to the incredible positive impact and role that trees have on the environment, they offer additional benefits. For example, medicine and mental health.

Approximately 50,000 plant species are used for medical purposes, and many come from trees. For instance, bark from the red stinkwood tree is used to treat malaria, fever, gonorrhea, insanity, urinary tract ailments, and impotence, and white birch bark extracts have antimicrobial properties.

Trees also are great contributors to humanity’s mental health. Just picture yourself living in a city made only from brick, asphalt, concrete, and no trees. Would you like to live in a place like that? Both in rural and urban areas, trees impact our mental health positively. Even studies have suggested that they are crucial in maintaining a person’s well-being during isolation. This is the reason why we feel much better about ourselves and the world when we spend time in nature. Forest environments promote lower concentrations of cortisol, lower pulse rate and blood pressure, greater parasympathetic nerve activity, and lower sympathetic nerve activity than city environments. Trees also intercept sound waves and change their behavior, thus reducing sound pollution.

Actions to restore forests and help the environment

Reducing deforestation and forest degradation is vital. Restoring forested land is an urgent matter in our path towards capturing atmospheric carbon and mitigating climate change. According to a study, ecosystems could support an additional 0.9 billion hectares of continuous forest. This would represent a greater than 25% increase in forested area, including more than 200 gigatons of additional carbon at maturity. Such a change has the potential to store an equivalent of 25% of the current atmospheric carbon pool. However, this potential tree coverage will be altered by climate change itself, as the global potential canopy cover may shrink by 223 million hectares by 2050.

There are already tree planting initiatives, like the Bonn Challenge, who want to restore 350 million hectares of degraded and deforested landscape by 2030, which is backed by 48 nations. However, many of these countries have committed to restore less than half the area that could support new forests. Also, as a part of the World Economic Forum, 1t.org aims to conserve, restore and grow one trillion trees by 2030.

Tom Crowther, a professor at ETH Zürich university, who carried out a research that estimated that a worldwide planting program could remove just under one-third of all the emissions from human activities that remain in the atmosphere today, stated that 1 trillion trees could be restored for  $300 billion, the cheapest solution proposed so far. Joseph Poore, an environmental researcher at the Queen’s College, University of Oxford, stated many of the reforestation areas are currently grazed by livestock, reinforcing the fact that livestock and deforestation are strictly linked. He affirms that without freeing up the billions of hectares used to produce meat and milk, this goal is not viable. You can read more about it in my post about plant-based diets and sustainability.

Even though trees play such an essential role in environmental welfare, reforestation efforts should be accompanied by addressing the underlying issues that create a negative environmental situation in the first place: fossil fuels, the meat and dairy industry, air, and water pollution, etc. Tree planting alone won’t fix the climate crisis unless everything else is tackled.

Another challenge that should be prioritized is replacing wood used for common products like toilet paper and packaging, with more environmentally friendly alternatives like cellulose extracted from non-tree sources, such as recycled clothing and paper, waste food and agricultural residues. If these alternatives were used for the packaging supply chain alone, more than 3 billion trees in forests would be saved annually. Some biodiverse and carbon-rich old growth forests are converted to industrial plantations like pine, eucalyptus, and palm oil, which has horrible consequences.

As individuals, we can do a lot, but blame will ultimately fall unto countries, governments, big companies. In 2020, destruction of the Amazon–the world’s largest rainforest–rose 9.5% from a year earlier, to 2.7 million acres (11,088 square kilometers). This meant Brazil missed their own target, established in a climate change law in 2009, of reducing deforestation to 3,900 square kilometers.

An annual investment in tree-planting initiatives of $100 million, could provide as many as 68 million people with significant reductions in PM levels (particulate matter, which is the most damaging air pollutant in most cities, which is emitted from a variety of sources, especially the burning of agricultural residues, fuelwood, and fossil fuels), as well as providing 77 million people with a reduction of 1°C in air temperature.

As I mentioned before, reducing deforestation is crucial, as well as reforesting. A study by TNC estimated that improved forest management could mitigate 267 million metric tons of carbon dioxide per year in the U.S., which is equivalent to taking 57 million cars off the road. This is important because reforestation should be managed by experienced groups. Plantation forests and the use of exotic species can upset the balance of evapotranspiration, impacting negatively on water availability. Reforestation (replanting trees in areas that have been affected) and afforestation (planting new forests across land without trees) can reduce water availability, or impact species richness and ecosystem services. For this reason, they should be done in the correct setting, so that they can have a positive impact in water and energy cycles, and water availability. Mixed species forests may yield healthier, more productive, and more resilient ecosystems, as well as more reliable water-related services. Because of variations in rooting depth, strength and pattern, these different species could help each other through water uptake and infiltration, and erosion control.

All in all, trees are one of the keys to fight climate change, because of their indispensable roles in the environment. Reducing deforestation is a pressing need, for which we need to tackle its origins. Reforestation and afforestation are also as crucial but need to be managed cautiously. We can do a lot personally, but it is also important to vote wisely, push our governments to make this an urgent matter, as well as stop supporting big companies that thrive on deforestation and environmental damage.

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Hi, I’m Melina,

I’m the creator of Sustainable Rookie, and my goal is to share what I learn throughout my sustainability journey, so that I can help other people live a more conscious life.

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