A new study by researchers at Yale University found that smaller ponds generate disproportionately higher concentrations of global greenhouse gas emissions from inland waters. Although ponds less than a quarter of an acre in size make up only 8.6% of the surface area of the world’s lakes and ponds, they account for 15.1% of carbon dioxide emissions and 40.6% of diffusive methane emissions, the study concluded.

By combining recent estimates on the global number of lakes and ponds with a compilation of greenhouse gas concentration measurements taken from 427 lakes and ponds, the researchers determined that carbon dioxide and methane concentrations were greatest in smaller ponds and decreased as the ponds and lakes grew larger.

The rationale for this imbalance, according the researchers, is related to the capacity of smaller ponds to collect higher concentrations of terrestrial carbon compared to larger-sized water bodies. With shallower waters, gases produced at the bottom of smaller ponds also can more easily reach the surface.

Meredith Holgerson, the study’s lead author, said the findings warrant additional research to more accurately estimate the number of tiny ponds around the world and are important to quantifying the global carbon cycle and making predictions about future stocks and flows of carbon.