Peatlands Harness Leaf Chemistry to Lock Up Billions of Tons of Carbon

Peatlands, dominated by Sphagnum mosses, are waterlogged, acidic environments covering just three percent of the planet’s land surface. These ecosystems represent an enormous global carbon sink, sequestering more carbon dioxide (CO2) than all other organisms combined.

In a recent study published in New Phytologist, an international team combined analyses of photosynthesis and leaf surface chemistry to reveal how Sphagnum mosses capture such large amounts of CO2. “This is really important for understanding the carbon cycle and carbon storage,” said Anna Di Palma, a researcher at the Italian National Research Council and coauthor of the study. “If we know how it works, we can also do some predictive studies concerning the future of peatlands in view of climatic changes, for example.”

Sequestration Secrets Lie in Leaf Chemistry

Having been isolated from other mosses for roughly 350 million years, Sphagnum species are highly unusual, noted botanist Brent Mishler of the University of California, Berkeley, who was not involved in the study. “They’re not at all like regular mosses,” he said. “They’re ecosystem engineers, meaning they can literally raise the water table where they are all by themselves—in other words, they create a bog by just starting somewhere. They’re not reacting to the water environment; they’re affecting it.”

These plants act like sponges, retaining more than 20 times their own weight in water. “In general, for an aquatic plant, they have difficulties sequestering CO2 because carbon diffuses about 10,000 times slower through water than through air,” Mishler explained. “So they need special mechanisms to cope with this carbon limitation; even with abundant sunlight, they cannot obtain sufficient CO2.”

To understand how Sphagnum mosses achieve high carbon sequestration under waterlogged conditions, Di Palma and colleagues investigated the plants’ cell surface chemistry—a factor that had previously been overlooked. Although surface chemistry has been studied for ion exchange, acidification, and pollutant binding, its influence on photosynthetic performance and carbon assimilation had not been examined.

The researchers discovered that species with higher densities of reactive chemical groups—such as carboxyls and phosphoryls—on their leaf cell surfaces fixed CO2 more efficiently. “What it is showing is how active the cell surfaces are, and how they can assimilate not only CO2 but also other ions like hydrogen,” Mishler commented.

Sphagnum palustre, a generalist that thrives across diverse ecological conditions, maintained stable photosynthesis and CO2 assimilation over the full pH range. In contrast, other species exhibited more specialized performance. “Other things were surprising because I expected that some other species would perform well, but it was strongly dependent on pH conditions,” Di Palma noted.

Combating Climate Change by Bolstering Bogs

Carbon sequestration is not merely about incorporating CO2 into cells; the carbon must be stored long‑term. Unlike short‑lived forests, the acidic conditions of peat bogs inhibit decomposition, allowing plant material to remain locked away for millennia. “The reason why peat really has just a huge amount of the stored carbon in the world is because for thousands of years you have basically no decomposition, and so it preserves the material in a semi‑stable way for a long time,” Mishler explained.

These fragile ecosystems face increasing threats from climate change and intensive peat mining, which is conducted for fuel and agriculture. The exploitation converts peat from a carbon sink into a carbon source. “Peat mining companies are removing thousands of years’ worth of peat using large machines similar to coal strip mining, then burning it,” he said. “So they are releasing thousands of years of carbon accumulation.”

Because peatlands have a disproportionate impact on the global carbon cycle, their destruction can trigger a positive feedback loop that accelerates global warming, Mishler noted. “If it gets hotter, then the peat starts to decompose, even if you’re not mining it,” he added. “Even in completely undisturbed peatlands that have not been messed with at all, the peat is shrinking.”

Di Palma highlighted that the findings provide strategies for protecting and enhancing peatlands, such as cultivating species like S. palustre that can fix carbon across a broad pH range. Laboratory‑grown clones maintain the same cell‑surface chemistry as wild specimens, indicating that “if you want to cultivate peat moss in a photobioreactor and transplant it in nature to restore peatlands or preserve a specific peatland, you can,” she explained.

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