Trees, only a partial solution to climate change
All ideas are born out of human necessity and desire. So does necessity or desire drive one of the bright and shiny new ideas recently gaining traction on the climate-change stage — tree planting? Is this idea based more on the desire for an easy answer, or does it fulfill a real need? Policymakers and corporate entities have finally discovered the relationship between greenhouse gas emissions and carbon sequestration. Chatter about the Trillion Tree Plan is filtering through the halls of Congress. However, the current set of policymakers in Washington DC are not known for their science and math skills, so perhaps we should look more closely at the numbers.
For starters, planting trees is good. Trees capture carbon from the atmosphere, primarily as CO2, and they use photosynthesis to turn that carbon into biomass. Also, excess carbon, beyond what the trees need, is exuded into the soils where microbes fix the carbon as humus. This process provides a win-win situation; sequestration captures carbon above ground and enriches the soils below. In an era of rising greenhouse gas emissions, forests play a significant role in sequestering carbon, thus reducing global temperature rise.
Trees and forests are part of the solution for controlling greenhouse gases in a changing environment. But the real question is, how much of a role can tree planting realistically play? Understanding the facts is essential before jumping on the bandwagon. Too often, planting trees is an excuse to avoid making difficult choices around reducing fossil-fuel emissions. Believing we can plant our way out of the oncoming climate change disaster is essentially an abdication of responsibility.
Where shall we plant these trees?
According to the U.S. Forest Service, forests comprise 33 percent of the total U.S. land area or about 750 million acres. The positive side of this is U.S. forests sequester about 15 percent of the 6.4 billion metric tons of greenhouse gasses emitted in the USA each year. So, this sequestration amounts to approximately one-sixth of total fossil-fuel emissions.
Therefore, as a total solution, we would need to plant enough trees to increase current forest carbon capture by a factor of six. This solution provides a very straightforward calculation. We need a total of 4.5 billion acres of forest to take care of the emissions problem completely. Now we come to our first clash with reality. The total amount of land available in the USA is 2.3 billion acres. We need twice as much land as we actually have.
Another way to look at the Trillion Tree Plan is through actual tree numbers. The estimated number of trees in the USA is 300 billion (trees greater than one inch in diameter). These 300 billion trees sequester one-sixth of the country’s total annual carbon emissions, so complete sequestration of excess atmospheric carbon would require about two trillion trees. The current plan for one trillion new trees only presents a 50-percent solution to the carbon emissions problem. Still, a trillion new trees represent an admirable goal.
But there is always a catch. The forested land needed for these trillion trees is just about the total size of the USA. As nice a fit as this is, planting the USA’s entire surface area with trees seems to stretch the boundaries of realism.
So the simple basic facts about available space cast serious doubt on the Trillion Tree Plan, making it more of a political symbol than a real plan. But ignoring this space problem, the devil is still in the details, and planting a trillion trees requires someone actually putting them in the ground.
At the end of 2019, the National Forest Foundation was pleased to announce they had planted five million trees during the year, representing almost a 100 percent increase over 2018. This tree planting program was an impressive effort. But planting at a rate of five million trees per year requires 200,000 years of work to reach the one-trillion-tree goal.
Other more optimistic studies have asserted that Americans plant 1.6 billion trees each year. Planting at this more optimistic rate decreases the amount of time needed, and the last of the trillion trees will be planted in the year 2645.
Now for the bad news
Even if you don’t live in California, you have probably noticed it is burning — again. Of course, this is less than a year after Australia lit up like a torch. Also, let’s don’t forget about the vast areas of the Amazon rain forest, which seem to go up in smoke on an annual basis. Siberia is now in on the action with Arctic wildfires emitting more CO2 in the first part of 2020 than they emitted during the previous year.
The sad fact is: forests burn. So, gains in forest sequestration are sometimes offset by greenhouse gas emissions from forest fires. On a global scale, wildfires emit about 8 billion tons of CO2 annually. This activity occurs against a backdrop where total global CO2 emissions in 2019 were 33 billion tons. At first glance, forest fires account for 25% of all carbon emissions. However, their real net-contribution is lower due to regrowth in the burned areas.
The environmental toll of large forest fires is significant. California wildfires alone released 68 million tons of CO2 into the atmosphere during 2018. These fires accounted for 15 percent (approximately one-sixth) of the State’s total emissions that year. The State’s forests are increasingly carbon-neutral, sequestering as much CO2 as they release, because of the wildfires.
The rise of tree-planting as a primary solution to climate change exemplifies a lack of scientific understanding. Forests have a positive role in carbon sequestration and climate change management. However, tree planting as a solution to global warming is not a real plan. Instead, it is a political talking point to avoid making actual policy addressing climate change. Our forests are sources and sinks of carbon, and without proper management, tree planting may eventually release more carbon than it sequesters.
The next time you hear a politician tell you we will plant our way out of climate change, give them five Pinocchios.
US Forest Facts and Historical trends (US Forest Service)
Our Impact in 2019: 5 million trees, 18,000 acres, and so much more(National Forest Foundation)
The world’s 3 trillion trees, mapped (By Chris Mooney; Washington Post)
U.S. Forest Facts on Forestland (By Steve Nix; ThoughtCo.)
How Wildfires Can Affect Climate Change (and Vice Versa) (By Bob Berwyn; InsideClimate News)
Global CO2 emissions in 2019 (Source IEA)
New Analysis Shows 2018 California Wildfires Emitted as Much Carbon Dioxide as an Entire Year’s Worth of Electricity (Source: U.S. Department of the Interior)