After 40 Years, New Carbon Sequestration Study Confirms the Value of Trees

Supersized corporate tree-planting pledges can easily grab the media spotlight, only to wilt away when the program fails to meet expectations. To ensure success, businesses need to invest in careful planning, implantation and follow-up. The additional expense is well worth the effort, as demonstrated by a new model for assessing the carbon sequestration capability of trees and other plants. 

For carbon sequestration, trees and plants are 31 percent more important than previously thought

When scientists estimate the ability of plants to sequester carbon on a global scale, many of them rely on a model initially developed 40 years ago.

Under the 1980s model, the carbon sequestration attributed to plants stands at 120 petagrams globally. For some perspective on the size of that figure, consider that each petagram represents the amount of carbon dioxide emitted from about 238 million gas-powered passenger cars.

In contrast, the new carbon sequestration model yields a result of 157 petagrams, or 31 percent more carbon sequestered by trees and other plants.

The new model was developed by a team of researchers from Cornell University, supported by the Oak Ridge National Laboratory of the U.S. Department of Energy. “Understanding how much carbon can be stored in land ecosystems, especially in forests with their large accumulations of biomass in wood, is essential to making predictions of future climate change,” Oak Ridge emphasized in a news update on the findings.

Oak Ridge says the model presents not just a larger estimate of carbon sequestration, but a more accurate estimate as well. It focuses on an easily trackable compound called carbonyl sulfide as an alternative to the more challenging task of measuring carbon directly. The research team also deployed information from the global LeafWeb photosynthesis database, a shared service established by Oak Ridge. 

Another improvement involves the use of precise data from environmental monitoring towers on the ground. In contrast, the 1980s model deploys satellite observations from above, where clouds can interfere with information-gathering. 

A renewed emphasis on rainforest protection

Because cloud interference is especially common in tropical regions, the use of ground-based monitoring equipment has especially significant implications for an improved understanding of the carbon sequestration potential of rainforests.

“Pan-tropical rainforests accounted for the biggest difference between previous estimates and the new figures, a finding that was corroborated by ground measurements,” Oak Ridge reported. “The discovery suggests that rainforests are a more important natural carbon sink than previously estimated using satellite data.”

That finding supports the Rainforest Alliance and other conservation organizations that have drawn the connection between tropical forest loss and global warming. The Rainforest Alliance works with local communities in tropical regions, and both large and small businesses, in collaborative efforts to implement sustainable forest conservation strategies.

Letting nature take its course

The emphasis on collaboration and stakeholder engagement can help corporate tree-planting programs avoid the reputational tarnish that can result when local communities are not part of the planning process.

Loss of biodiversity is another factor that should make business leaders wary. The World Economic Forum, for example, faced criticism that its “One Trillion Trees” program lends support to commercial forest management practices and fails to protect natural habitats.

In terms of both biodiversity protection and carbon sequestration, business leaders may find that a more economical and beneficial alternative is to simply preserve the land, and let nature take care of itself.

In a newly published study in Nature, a multinational research team makes a compelling case for investing in natural reforestation, rather than focusing on planting trees by hand.

“Tree planting in degraded landscapes is a popular but costly forest restoration method that often results in less biodiverse forests when compared to natural regeneration techniques under similar conditions,” the researchers observe. “Using manual techniques in degraded landscapes can be expensive. It can also be less effective in terms of native biodiversity recovery and keeping water systems functioning well,” they added, citing studies that show a 56 percent higher rate of biodiversity in natural regeneration projects compared to manual tree-planting.

Within tropical regions, the researchers estimate that suitable sites for natural reforestation cover a total of 215 million hectares, an area about the size of Mexico. (One hectare is about the size of 2.5 football fields.) 

The study included tropical regions in South and Central America, Southeast Asia, Malaysia, India, and Africa. Among these regions, the researchers recommend that reforestation efforts prioritize Brazil, Indonesia, China, Mexico and Colombia, a group of nations that collectively account for 52 percent of the estimated potential for carbon sequestration.

Trust, but verify

The cost savings of natural reforestation is an attractive factor. The researchers cite expenses of $105 and up per hectare for manual planting in tropical regions, compared to just $12 and up for natural reforestation.

Still, before businesses rush pell-mell into natural reforestation, the researchers indicate that simply setting aside land for conservation does not necessarily result in a satisfactory outcome.

The figure of 215 million hectares represents degraded sites that meet certain conditions supporting natural regeneration, including the availability of surrounding or nearby forests and the organic carbon content of the soil. Accordingly, the researchers indicate that areas where the land has been severely and extensively degraded are not suitable candidates for natural reforestation.

Overall, the science provides additional support to businesses that invest in natural carbon sequestration efforts. Corporate initiatives can make a significant contribution when they are guided by a flexible, knowledge-based approach that engages local stakeholders, takes advantage of natural reforestation where available, and incorporates manual tree planting where necessary.