Keep Forests as Forests: the Importance of Forests as Carbon Sinks

An Often Overlooked Solution to the Climate Problem

Published in

The Climate Series

10 min readJun 18, 2018

Hiking alongside my brother and father in the Ecola Forest Reserve on the Oregon coast!

“What we are doing to the forests of the world is but a mirror reflection of what we are doing to ourselves and to one another.” -Mahatma Gandhi

Background. The Earth is presently in the midst of a pressing global crisis, as record-breaking levels of human carbon dioxide emissions threaten the well-being of Earth’s ecosystems, civilizations, climate, and of humanity itself.
The Earth’s climate is governed by the balance of energy entering the Earth and leaving it. The temperature of the planet remains relatively stable when the energy leaving the Earth equals the energy entering it. However, this is currently not the case: much more energy remains in the planet than leaves it.
This imbalance is the result of the build-up of greenhouse gases in the atmosphere. Some gases, like oxygen, are transparent to both incoming solar radiation and outgoing infrared radiation (from the Earth’s surface), which keeps the Earth’s energy balance stable, as energy cycles from the Sun to the Earth, and then back out into space. However, greenhouse gases (like carbon dioxide, methane, and water vapor) work differently. Although they are transparent to incoming solar radiation — letting energy in from the sun — they absorb infrared radiation from the Earth’s surface. Thus, they trap heat in the lower levels of the atmosphere, warming the planet beyond what it should be. This leads to what is called “the greenhouse effect,” the primary cause for anthropogenic global climate change.
Arguably the most important greenhouse gas contributing to climate change is carbon dioxide. In addition to fueling climate change, high CO2 levels negatively affect air quality and human health.
Carbon dioxide has been emitted for millennia by natural sources: plants decomposing, respiration, and release from the oceans. The carbon released by natural sources roughly equals the carbon absorbed by natural sources, so the Earth’s energy balance has remained relatively constant (although natural events, like ice ages and interglacials, have caused CO2 fluctuations throughout history).
However, human carbon emissions have offset this natural balance, keeping heat trapped in the atmosphere without providing a mechanism to absorb greenhouse gases. The safe level of atmospheric CO2 is around 350 parts per million.

The atmospheric CO2 level is currently above 410 parts per million, the highest it has been in the history of Homo sapiens existing on Earth.

In 2015, 195 countries signed the Paris Climate Agreement, agreeing to keep the anthropogenic temperature rise in the twenty-first century under 2 degrees Celsius above pre-industrial levels. (The U.S. initially signed, but Trump withdrew a year and a half later.)

Background: Carbon Sinks

A major way to reduce climate change, then, is to increase the number — and absorptive capacity — of systems absorbing carbon dioxide from the atmosphere and storing it. Natural systems that do so are called carbon sinks. Technically speaking, a carbon sink is any system that absorbs more carbon than it releases. Carbon sinks exist in contrast to carbon sources, which release more carbon than they absorb.

The three largest natural sinks, in order of absorptive capacity, are: 1) oceans 2) plants, and 3) soil. (While the world’s oceans have long been praised for their capacity for carbon absorption, CO2 has begun to alter the chemistry of the seawater — through ocean acidification — which damages marine ecosystems.)

Plants take up carbon dioxide through photosynthesis, releasing glucose and oxygen, which humans breathe, and then release CO2 through respiration. (It is important to note that most of the atmospheric CO2 is not from cellular respiration: rather, it is carbon being introduced into the atmosphere for the first time, from human activity.) As trees grow, they allocate carbon to their trunks, limbs, roots, and leaves. When leaves or branches fall and decompose, or trees die, stored carbon is released to the atmosphere or transferred to the soil.

Thus, forests, especially older forests, are famously effective carbon sinks, pulling vast amounts of carbon out of the atmosphere and storing it at a large scale.

In fact, in 2011, U.S. forests alone offset 14% of annual CO2 emissions from our national economy. Globally, this number increases to 25%.

Forests play a crucial role in offsetting climate change, and keeping carbon concentrations at a level to meet the Paris Agreement’s goals. Even if we were to stop emitting greenhouse gases today, we are committed to warming from previous emissions for hundreds of years. In fact, 30% of anthropogenic CO2 will remain in the atmosphere 900 years from now. Thus, to prevent future climate change, it is not enough to reduce our greenhouse gas emissions — we must expand our forests, and their capacity to remove carbon from the atmosphere.

When the Europeans reached North America, forests stretched from the East Coast to Kansas — it is said that a squirrel could travel from Boston to the Mississippi river without once touching the ground. Since then, much of the country’s forested land (especially in the East) has been converted to farmland. Today, less than 1% of “Frontier Forests” — contiguous, virgin forests with all the species intact — exist in the lower 48 states.

Deforestation is currently the biggest threat to our natural carbon sinks. The current deforestation rate equates to losing about 27 soccer fields per minute. If deforestation continues at this rate, in a century, there will be no rainforests left on Earth. Deforestation contributes to between 15 and 17% of annual global greenhouse emissions.

Not only does deforestation eliminate crucial carbon sinks (trees), but the leading driver of deforestation is clearing land for agriculture — which emits more CO2 than any other industry, except for the energy sector.

Forest soils are generally moist, but when sun-blocking trees are cut down, they quickly dry out. Trees also moderate high daytime and low nighttime temperatures, so cleared land is more susceptible to temperature extremes. (In a second part to this essay, I will discuss other benefits of forests, like flood control, water and air purification, watershed protection, and erosion reduction!) Trees cool the air by turning water from the soil into moisture in the air, perpetuating the water cycle. Without them, once-forested lands can quickly become barren deserts, and temperatures can rise. In fact, if the tropics were deforested completely, it is estimated that the global temperature would increase by 0.7 degrees Celsius. Additionally, deforestation triggers drops in rainfall and later rainy seasons, the effects of which we’ve already seen in the Amazon and the Congo basin.

Ironically, although most forests are cleared for agriculture, deforestation actually hurts agricultural productivity, as crops falter under longer dry seasons and more extreme temperatures.

Forest degradation occurs when a forest’s condition is compromised, reducing its capacity to act as a carbon sink. Forests can be degraded by commercial logging, land pollution, air pollution, acid rain, pests, and diseases — the latter five of which are amplified by climate change (pests and pathogens thrive in hotter, moister climates!) In the U.S., many ecologically complex, biodiverse forests are converted to single-species tree plantations to boost wood production. These highly-managed monocultures not only fall short in biodiversity and ecological functioning, but store less carbon than the original forests.

Commercial logging — cutting down trees to produce timber and pulp — supplies the world’s markets for furniture, paper, and construction, and is a major contributor to forest loss. Logging rates in the U.S. are the highest in the world, and the U.S. is the world’s largest producer and consumer of wood products. The Forest Service is currently proposing to increase national forest logging to 1980 levels, which could increase emissions by 6 percent.

Unsurprisingly, climate policy in the U.S. has largely focused on reducing fossil fuel emissions without recognizing the importance of forest conservation as a climate strategy.

Rather, the U.S. government has continually argued for an increase in our markets for wood, paper, and biofuel to bolster economic growth. But, as the Dogwood Alliance — a forest protection group — writes: “Treating forests as an unlimited, renewable, extractable commodity that can support infinite growth in the forest products industry is an outdated business model.”

Policymakers have even advocated logging as a climate solution, pointing to the fact that the U.S. South has recently become the largest exporter of wood pellets to Europe. Because pellets are burned to generate electricity in place of coal, they are purportedly more environmentally-friendly. However, this is not the case: burning wood for electricity releases 50% more CO2 than coal per unit of electricity generated.

Some advocate logging to use wood for bioenergy — renewable energy made from biological sources — as an alternative to fossil fuels. Although biofuels are supposedly carbon neutral — neither increasing nor decreasing the amount of carbon in the atmosphere — logging in order to produce biofuel releases carbon, and eliminates crucial carbon sinks (trees). Logging diminishes the capacity of U.S. forests as carbon sinks by at least 35 percent.

Additionally, logging accounts for 85% of emissions from U.S. forests, more than five times that from tree mortality, land conversion, fire, and insects combined.

Loggers also clear trees to build roads for access to more remote forests, leading to further deforestation. Multiple scientific reports have concluded that an increase in carbon storage and removal by forests (not just tropical, but also in boreal and temperate regions) is critical to achieving the goals set forth in the Paris Agreement. Article 5 of the Paris Agreement focuses on forests as a climate strategy.

If we stopped deforestation, restored degraded forests, and protected existing forests, we could offset annual emissions by 75 percent in the next half-century.

Solutions: Forest Protection & Sustainable Forest Management

At this point, you may be asking — with a Lorax-ean voice of concern — how we can speak for the trees: what we can do to conserve forests, one of the most important pieces in the climate mitigation puzzle.

First and foremost, committing to stopping deforestation (not only of tropical forests, but also in boreal and temperate regions) is key. Currently, global treaties like the Convention on International Trade in Endangered Species and U.N. REDD (Reducing Emissions from Deforestation and Forest Degradation in Indigenous Countries) Programme and U.S.-specific laws like the Wilderness Act and Roadless Rule protect forests and species indigenous to them. As international markets for forest products are largely interdependent, global collaboration in crafting conservation policy is key.

In 2016, Norway banned deforestation altogether. In the five preceding years, Norway paid Brazil $1 billion for completing an agreement between the two to reduce deforestation in the Amazon.

Protecting mature, old-growth forests — like Alaska’s Tongass National Forest — from logging is especially important, as these forests hold the highest densities of carbon. Additionally, allowing young forests to mature (rather than logging them early on) increases their carbon absorptive capacity. Halting the conversion of natural forests to tree plantations is also crucial for heightening carbon storage.

As previously stated, the most common driver of deforestation is clearing land for agriculture.

Much of the U.S.’ once-forested land that has been converted to agriculture is unable to be reforested, as depleted, dry soil prevents it from being able to support forests and produce the same biodiversity it once did.

Similarly, forests degraded by logging, pollution, and other sources may lose their capacity to act as carbon sinks. For land that has not been depleted, reforestation — replanting forests where they were located historically — can restore the land’s net primary productivity and capacity to store carbon.

Reducing carbon debts from logging doesn’t have to be all or nothing — logging can be done in a more sustainable manner. Clearcut logging is the most detrimental method, in which virtually all standing trees in an area are uniformly cut down. Because it removes seed sources, clearcut logging is highly disruptive to biodiversity, and prevents the natural regrowth of endemic species.

A more sustainable alternative is selective logging — cutting down only one or two species of trees, generally high-value species, while leaving the rest intact. Although by no means perfect, selective logging maintains a greater degree of diversity — in tree age, size, and species—than clearcutting, and is more resistant to insects and disease. Replacing older, harvested trees with younger trees in these areas can help maintain carbon stocks. Better yet is Reduced Impact Logging (RIL), a collection of timber harvesting techniques designed to reduce environmental impacts on forest stands, soil, and water quality.

So: What Can I Do?

Rely less on forest products: use less paper; reuse paper; print less; print double-sided; clean with cloth towels instead of paper towels and napkins; order less with paper packaging; buy less new furniture; use less rubber products — as a general rule, consume less. Look for products with a Forest Stewardship Council (FSC) logo. Buy makeup made from palm oil that is deforestation-free. Eat organic, locally grown food, which reduces the clearing of forested land for agriculture. Eat less meat and fewer animal products — animal agriculture is the leading driver of deforestation!

Write your congressperson in support of forest protection policy. Speak up against attempts to log old-growth forests, like Canada’s Boreal Forest. Support forest conservation efforts, like that of the World Wildlife Fund, the National Forest Foundation, Greenpeace, and the Nature Conservancy. If you have money to spend on forest product consumption, consider donating to forest conservation.