Thanks to Yale e360 for this interview that helps us understand the dynamics and differences between mature forests and newly planted forests in terms of carbon sequestration:

Why Keeping Mature Forests Intact Is Key to the Climate Fight

Preserving mature forests can play a vital role in removing CO2 from the atmosphere, says policy scientist William Moomaw. In an e360 interview, he talks about the importance of existing forests and why the push to cut them for fuel to generate electricity is misguided.

A mature forest in the Berkshire Hills in western Massachusetts. LIZA DALY/FLICKR

William Moomaw has had a distinguished career as a physical chemist and environmental scientist, helping found the Center for International Environment and Resource Policy at Tufts University’s Fletcher School and serving as lead author on five reports of the Intergovernmental Panel on Climate Change (IPCC). In recent years, Moomaw has turned his attention to working on natural solutions to climate change and has become a leading proponent of what he calls “proforestation” — leaving older and middle-aged forests intact because of their superior carbon-sequestration abilities.

While Moomaw lauds intensifying efforts to plant billions of young trees, he says that preserving existing mature forests will have an even more profound effect on slowing global warming in the coming decades, since immature trees sequester far less CO2 than older ones. In an interview with Yale Environment 360, Moomaw explains the benefits of proforestation, discusses the policy changes that would lead to the preservation of existing forests, and sharply criticizes the recent trend of converting forests in the Southeastern U.S. to wood pellets that can be burned to produce electricity in Europe and elsewhere.

An area of clearcut forest in the Tar-Pamlico River basin in northeastern North Carolina. DOGWOOD ALLIANCE

“The most effective thing that we can do is to allow trees that are already planted, that are already growing, to continue growing to reach their full ecological potential, to store carbon, and develop a forest that has its full complement of environmental services,” said Moomaw. “Cutting trees to burn them is not a way to get there.”

Yale Environment 360: How do you define proforestation?

William Moomaw: So I began looking at some of the data and some of the papers that had come out recently, and I found that if we managed our forests and grasslands in a different way they could be sequestering twice as much carbon dioxide from the atmosphere as they currently do. One paper found in multi-aged forests around the world of all types, that half of the carbon is stored in the largest one-percent diameter trees. So I began thinking about this, and I realized that the most effective thing that we can do is to allow trees that are already planted, that are already growing, to continue growing to reach their ecological potential, to store carbon, and develop a forest that has its full complement of environmental services.

We needed a name for that, so I began thinking about names. I actually sat down and went to Google and searched for prefixes, found a whole bunch of them, and the one that I settled on was pro. Proforestation. It’s not that we shouldn’t do afforestation [planting new trees] and we shouldn’t do reforestation. We should. But recognize that their contribution will be farther in the future, which is important. But in order to meet our climate goals, we have to have greater sequestration by natural systems now. So that entails protecting the carbon stocks that we already have in forests, or at least a large enough fraction of them that they matter. We have to protect wetlands, which are actually storing an amount of carbon in the United States that equals what’s in our standing forests. We need to protect and improve the carbon sequestration by agricultural soils and grazing lands.

It’s taken a very long time for people to focus on something besides reducing emissions of carbon dioxide and other greenhouse gases. And to recognize that even though we’re putting almost 11 billion tons of carbon into the atmosphere every year, the increase is only 4.7 billion tons. So where is the rest going? It’s going into plants on land and plants in the ocean. And the largest single place that’s removing carbon dioxide [from the atmosphere] on an annual basis is forests. Even what we think of as mature forests are still accumulating carbon because carbon makes up about roughly half of the dry weight of wood, but it is also in the soils. Even older forests continue to accumulate carbon in the soils. In fact there are forests where there’s more carbon in the soils than there is in the standing trees. As trees get older, they absorb more carbon every year, and because they are bigger they store more carbon.

Read the whole interview here.