Can carbon sequestration be increased in secondary forests?

More than 30 years ago, two young scientists at the Smithsonian Tropical Research Institute set aside 50 hectares of an isolated island in the Panama Canal for a bold new experiment. Stephen Hubbell and Robin Foster wanted to understand why tropical forests housed vastly more biological diversity than their temperate counterparts. Hubbell, Foster and a team of University of Panama interns counted, identified and mapped almost a quarter million trees on that plot in 1980. They then left the patch of forest alone for five years. When they conducted the same census in 1985, they found that the old-growth forest had changed radically. Their discoveries sparked a cascade of change in global forest science.

The Barro Colorado Island site is now the flagship in a 51-plot global network. ForestGEO censuses some 5 million trees that represent 10,000 species, or more than 20 percent of the world’s tree biodiversity. The plots are in 22 countries and monitored by scientists from 75 partner organizations. Crucially, they use the same methodology developed on BCI, which means forests can be compared with the same set of standards. "The findings have revolutionized our understanding of how forests are put together and how they are changing," says Stuart Davies, the director of ForestGEO.

The networks have produced more than 700 peer-reviewed scientific articles. But Davies says ForestGEO’s accomplishments can also be viewed through a number of the lessons learned.

1. Big questions need large scales

A 50-hectare plot would normally be considered larger than necessary in a temperate forest where most species can be monitored at a smaller scale. BCI’s large plot was necessary to encompass the great diversity of tree species in tropical forests. Otherwise, many small trees and rare species might not have been included.

2. Global models need long-term monitoring and global standards

"No forest on earth is immune from the impact from humans," says Davies. One reason the ForestGEO network is successful is due to global demand for understanding forest change and policies to deal with a shifting climate. "Only through precise long-term and standardized monitoring of the forests will science be able to inform policy on the effective management of our planet," says Davies.

3. Trees are only part of the forest

Numerous biological processes determine forest dynamics. While plot work initially focused on trees, now plot protocols monitor soil, environmental conditions, animal populations and microbial activity. This has helped scientists detect patterns that would otherwise be impossible to recognize, says Davies.

4. Science is needed for policymakers

"Forests play a critical role in the global environment," says Davies. "Are forests losing diversity? Are they storing more or less carbon?" Only through standardized, long-term monitoring will scientists be able to deliver results to strengthen the scientific basis for decision-making.

5. ForestGEO provides local education globally

Hundreds of students and volunteers have gathered plot data, allowing ForestGEO to develop training and educational opportunities for countless local collaborators. "Many of our earliest scholars are now in important positions in science," says Davies.

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Asner Wright Hall Muller Winter Potvin
Turner Detto Hubell Rubinoff Davies