Will planting more trees stop global warming?

By Niki Morock, Meteorologist

I have always preferred to exercise outside. I walk on the sidewalks and greenways and hike in the woods. The fresh air and nature’s music – the sounds of the wind through the trees, the birds, running water, etc. – keep me grounded and happy.

Reedy Creek
Trees line a muddy Reedy Creek running through Umstead State Park in Raleigh, NC.

This weekend while walking with my friend at Umstead State Park, I heard a loud, unmistakable popping and cracking, and I looked to our right just in time to see an old, dead tree come crashing down. Believe it or not, that was the second time in a year we have witnessed a tree fall in the woods. If we see one more, I might start to think it has something to do with us.

That moment was a reminder that trees don’t live forever. It was also just part of a thread of tree-themed conversation items that has run through my life in the last month. A larger part is a question I have been asked a few times in recent weeks: will planting more trees stop global warming?

The answer seems simple. After all, we learned in grade school that trees turn carbon dioxide into oxygen, right? Unfortunately, the issue is really not simple at all.

I don’t claim to be a forestry expert or a climatologist. I’m an operational and broadcast type of meteorologist. Still, that doesn’t mean I don’t enjoy reading and researching answers to questions like this one. Over the last couple of days, I have done just that, and trying to find a succinct answer has lead me down rabbit hole after rabbit hole.

It seems – like so many other aspects of weather, climate, environment, and nature – not only is the answer complicated, but all the things we need to consider to be able to answer it are not necessarily completely understood.

If you ask the Arbor Day Foundation, planting trees fights climate change. Period. Its website even tells you which side of your house to plant trees for the biggest benefit if your goal is an energy-efficient home. It says that neighborhoods with tree-lined streets are several degrees cooler than neighborhoods without, and it lists other reasons to plant trees. Of course, what else would you expect from an organization with the goal of planting trees?

An article by Thinkprogress titled “Reforestation Doesn’t Fight Climate Change Unless It’s Done Right,” inspires a bit more deep thought on the subject. The author points out that while reforestation is generally a good idea, planting in the wrong places may actually do more harm than good.  For example, planting more trees in areas that tend to have a good deal of snow such as Canada’s boreal forests, will decrease the earth’s albedo, which is a measure of a planet’s reflectivity. Snow reflects more of the sun’s radiation – earth’s largest source of heat – back to space than trees do. Decreasing the amount of solar radiation reflected would lead to more warming.

An article on Eos, the news website of the American Geophysical Union, makes the same point and talks about afforestation, which is planting forests where none have existed. There’s another interesting idea that has its own pros and cons and if undertaken, must be done so in an intelligent, thoughtful, and well-researched manner. One point to consider is the trees planted should be native to the area and helpful in creating and protecting biodiversity.

One last article that I read was from the International Union for Conservation of Nature. By looking at three case studies in the American Northwest, it explains a little further how reforestation isn’t just about planting trees. I’ll admit, there isn’t much about climate change in this one, but it was interesting nonetheless.

NASA is currently assimilating satellite data into computer models to show how carbon dioxide moves in the atmosphere and changes seasonally. The better those models are, the better we will understand where the carbon dioxide in the atmosphere comes from and goes to, and in the long run, that may help determine just how much planting the right kinds of trees in the right places might help mitigate a warming climate.

 

I really do suggest reading the following linked articles if you want more detail.

Arbor Day Foundation

https://www.arborday.org/trees/climatechange/treeshelp.cfm

Think Progress

https://thinkprogress.org/planting-trees-climate-change-solution-3e5b6979561f

American Geophysical Union

https://eos.org/research-spotlights/can-tree-planting-really-help-mitigate-climate-change

International Union for Conservation of Nature

https://www.iucn.org/content/forest-landscape-restoration-more-planting-trees-three-case-studies-united-states

NASA carbon cycle video and story

https://www.nasa.gov/feature/goddard/2016/eye-popping-view-of-co2-critical-step-for-carbon-cycle-science

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