After nearly four decades, the world's longest-running soil warming experiment is revealing a surprising result: even 'stable' carbon in forest soils can break down as temperatures rise, releasing more CO₂ into the atmosphere.
"Microbes are critical components of soil ecosystems because they break down organic matter and recycle elements essential for plant growth," explains Jerry Melillo, a Distinguished Scientist at the Marine Biological Laboratory, who has moved the needle on the world's understanding of climate change over the course of his career. "As warming reshapes these microbial communities, it can speed the loss of carbon from soils."
For the past thirty-seven years, his work has focused on plots in the Harvard Forest in central Massachusetts, where the soil has been artificially heated to 5 °C above the ambient temperatures regardless of the season. Melillo says they chose five degrees for the study as it was at the upper end of global warming projections by the climate modeling community when the soil warming study started.
Global average temperatures have already risen by about 1.1 to 1.4 °C since the Industrial Revolution. How much further they rise, Melillo emphasizes, depends on human choices. "If we dramatically cut CO₂ emissions from fossil fuel burning, or reduce deforestation, the projected increase would be lower," Melillo explains.
