A global study led by the Smithsonian’s National Zoo and Conservation Biology Institute (NZCBI) and the Smithsonian Tropical Research Institute (STRI) has revealed a major gap in how carbon markets value coffee farms.
While many programs promote planting new shade trees to generate carbon credits, they often fail to recognize the vast carbon storage and biodiversity benefits provided by mature shade trees already thriving in traditional agroforestry systems.
The research, published in Communications Earth & Environment, analyzed 67 studies from across the world’s coffee regions.
The findings show that coffee farms currently store about 482 million metric tons of carbon in aboveground biomass.
However, if all shade-grown farms were converted to sun-grown monocultures, the resulting tree loss could release 174–221 million metric tons of carbon, far outweighing the estimated 82–87 million metric tons that could be gained through global tree-planting initiatives on sun farms.
This imbalance points to a troubling incentive problem: carbon credit systems often reward planting new trees but not protecting existing ones. As a result, farmers may be pushed toward replacing older, carbon-dense trees with younger species that generate credits but store far less carbon.
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Beyond climate impacts, the study highlights biodiversity risks. Shade-grown farms with diverse native tree canopies support roughly four times more bird species than monoculture systems.
This forms the basis of the Smithsonian’s Bird Friendly certification, which connects producers to premium markets while protecting wildlife habitat.
The researchers argue that carbon payment frameworks must shift to reward conservation of mature shade trees, not just new plantings.
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Ruth Bennett, senior author and ecologist at NZCBI, explained that planting on degraded farms is important, but it cannot replace the loss of older shade systems.
The team is also developing tools like the Shade Catalog to help farmers select tree species that balance productivity, carbon storage, and biodiversity. Without reforms, they caution, tree-planting efforts risk undermining climate and conservation goals instead of advancing them.
