Anne Krantz and a Big Tree volunteer at a winning cottonwood tree

Last winter, the idea of planting a trillion trees to offset climate change caused by carbon dioxide (CO2) emissions from burning fossil fuels, suddenly went viral. The source of the captivating idea was a research article in the July 2019 journal Science by a group of scientists from ETH-Zurich in Switzerland.[i] Using mapping techniques, the scientists calculate that there is available space on the planet to plant 2.22 billion acres of trees. Since the concept of planting trees to avoid dangerous climate change is not new, I was surprised at the media attention – it was picked up by the press worldwide.

The BBC explained it like this: “Once these trees matured, they could pull down around 200 gigatons of carbon dioxide, some two-thirds of extra carbon from human activities put into the atmosphere since the industrial revolution.”[ii] Even President Trump endorsed the idea, according to the New York Times. “At the World Economic Forum last month, President Trump drew applause when he announced the United States would join the Forum’s initiative to plant one trillion trees to fight climate change.”[iii] I quickly jumped on board with the idea as well. What better way to showcase our inventory of Big Trees, highlight their many benefits, and encourage people to save them?

But the idea is not that simple, and scientists worldwide challenged this research for a multitude of reasons – calculation errors, omissions of CO2 capture from oceans and soils, while others didn’t like the locations suggested for planting. A Dartmouth study in Science News, June 2015, pointed out that snow reflection of the sun’s rays and heat is important to cooling the planet, suggesting “that some wooded areas may be more valuable without trees, allowing the cleared landscape to reflect rather than absorb the sun's energy. In other words, it's better to have snow-covered ground act as a natural mirror if you want to use some forest lands to cool the climate.” So maybe it is not bad as we thought to cut trees to make ski trails!

More significantly, it was also argued that this method does not address the underlying problem of the continuous release of additional CO2 by burning fossil fuels; as argued in the New York Times.[iv] The author dismisses the tree planting campaign as a diversion from the real problem of pumping fossil fuels buried in the ground for energy. In other words, bailing out a sinking ship without fixing the hole. The problem is like trying to put the genie back in a bottle; we don’t know how to put the CO2 back in the ground without using more energy in the process. Only trees know how to do that. The supporters of tree planting say this is a way to buy time until we can gently wean ourselves off fossil fuels. But it admittedly takes 50 – 100 years for the trees to grow big enough to be real storehouses of carbon.

Whether planting trees can mitigate fossil fuel use is not something volunteers are going to solve. While letting the scientists and academics figure this out, Natural Resources Stewards and Big Tree Team members can promote saving our Big Trees and the planting of new trees. There is no question that trees perform a miracle. They efficiently capture the sun’s energy by photosynthesis which combines CO2 and water to make glucose that trees use to grow, or store, and release the byproduct oxygen into the air. The glucose is stored in roots over the winter. In the spring it is transported up the tree, adding a new growth ring and swelling the buds that the tree formed the previous fall.

The growth ring in the trunk is a new layer of wood  - or stored carbon  - that make the tree’s rigid, strong trunks. Note that the chemical composition of wood varies from species to species, but is approximately 50% carbon. This amazing conversion of sunlight to carbon that can be stored in the plant happens with no energy cost to the tree. All they need to perform their photosynthesis miracle is provided by their environment; air, water, soil, nutrients and space.

There have been debates about whether old growth trees or saplings capture and store more carbon, but the answer to this choice is “Yes”. Tree sprouts need space to get started and to grow. Some species need space in sun to sprout – the pioneer species like birch, white pine, pitch pine, pin choke cherry, while others such as sugar maple prefer some shade to thrive. When they become tall in 20 -30 years, they are storing a measurable amount of carbon. The Nature Conservancy explains that an 18” diameter red oak tree stores 1,600 lbs. of carbon equal to 3 tons of CO2.[v] That is equal to a 50 mile round trip daily commute for 30 weeks.

We need native species saplings planted now in our community landscapes, and to let undeveloped forest lands in NH naturally regenerate with sound forest management practices to ensure that trees can grow to reach their peak carbon storage potential in the decades to come. Big Trees are a historic link to our past, indispensable carbon sinks, and unsurpassed engineering marvels. Simply said, trees help us out and are a lovely addition to our landscapes.


Former NH Big Tree Program Volunteer & Natural Resources Steward