What Oregonian doesn’t love trees? We certainly love them here at Metro. Thanks to voter investments, Metro shows our love by planting native trees and shrubs in our parks and natural areas – more than 4 million since 1995.
Now, for the first time we know about how many trees there actually are to love on Earth and just maybe, how planting trees can help save the planet from climate change. But having the data is just one part of solving a far more complex problem.
There are about 3 trillion trees in the world, according to a 2015 study led by researchers from Yale University and published in the prestigious science journal Nature. While that is a lot, the number has actually fallen by about half since the start of modern human civilization, meaning that 10,000 years ago there were twice as many trees. Worse, we continue to lose 10 billion trees each year.
Where do they all go? Conversion to farms, ranches, cities and loss to drought (desertification) are among the biggest contributors to tree loss.
A 2019 study from the Swiss Institute of Integrative Biology suggested that planting 1 trillion trees would dramatically reduce the amount of carbon in the atmosphere and significantly help stop global climate change.
So should we all get busy planting as many trees as possible, as soon as possible?
Well, yes and no. Among their many amazing qualities, trees absorb carbon dioxide and release oxygen. Planting a lot of them would – eventually – absorb a lot of carbon dioxide from the atmosphere.
Although any tree absorbs carbon, forests – with their many interwoven elements – provide many other benefits. They clean our air and water, reduce flooding, and provide habitat for other plants and animals. In cities, trees especially help keep things cool, reducing what is called the Urban Heat Island Effect, where human activities, asphalt and the built environment lead to far hotter temperatures than surrounding rural areas. The planet can surely use a lot more of all that trees provide.
Stopping climate change with a trillion trees however, is more complicated than it might seem.
Forests typically have 100 to 200 trees per acre. One trillion trees would require five to 10 billion acres of land, two to four times the entire area of the United States. Where would all those trees be planted? By whom? Who would pay for them? Who would care for them? What species would be planted? Could they be harvested? Who gets to make these decisions? What else could that money be spent on?
Many experts think the best solution for stopping climate change is keeping fossil carbon like oil, coal, natural gas and old-growth forests in the ground in the first place. They fear a focus on planting trees would distract from efforts to reduce carbon emissions. While trees and forests are wonderful for many reasons, one tree grown in Portland for 10 years stores about the same amount of carbon as 7 gallons of gasoline or reducing one household’s annual electricity use by 1%.
The United States has added 20 million acres of trees – approximately 2 billion individual trees – between 1990 and 2010. But the U.S. and our region still contribute to global deforestation and climate change as an importer of forest products and being the world’s heaviest user of fossil fuels.
So while restoring habitat by planting the right trees in the right place is always a good thing and can certainly make a difference on the regional scale, if you really want to save the planet, be sure to take the bus. Or carpool on the way to the planting project, and turn off the lights before you leave the house.
