Trees are a critical part of the carbon cycle, in which carbon moves between the atmosphere, ocean and land. They remove atmospheric carbon dioxide, incorporating the carbon into their tissues as they grow. Worldwide, forests are a net storehouse, or sink, of carbon, removing one billion to two billion tons from the atmosphere each year. That’s a substantial portion of the roughly 10 billion tons of carbon pumped into the air by fossil-fuel burning and other human activities.

When a forest is damaged, the dead vegetation eventually decomposes, returning the carbon to the atmosphere. The amount can be enormous: a study of damage after Hurricane Katrina in 2005 found that the storm killed or severely damaged 320 million trees across the Gulf Coast, containing about 100 million tons of carbon.

As forests start to recover, the mix of species is often different — in a rain forest like El Yunque, for example, species that thrive in full light tend to take over until the canopy regrows. The trees are also younger and smaller, so the recovering forest stores less carbon.

“Forests take a while to recover,” said Louis Verchot, a researcher with the International Center for Tropical Agriculture in Palmira, Colombia. “And what initially recovers is not always what was there before.”

If this cycle of damage and regrowth — what ecologists call a disturbance regime — occurs more often as extreme storms become more frequent, some forests may never recover completely. Over decades, the reduction in stored carbon would likely become permanen t. More carbon from human activity would remain in the atmosphere to contribute to climate change, or would have to be removed in other ways.

“If the climate warms, do we expect an increase in disturbance regimes?” said Jeffrey Q. Chambers, a geographer at the University of California, Berkeley, who led the Katrina study. “That could work on the ability of those systems to remove CO₂ from the atmosphere.”

Determining how the biomass in damaged forests changes over time is thus crucial to understanding the global carbon balance. But the work is not straightforward, as counting damaged trees in even a modest forest is a practical impossibility. Instead, researchers rely on remote sensing: satellite images to determine the presence or absence of trees, for example, or laser-based airborne measurements of a forest canopy.