The Wetlands Are Drowning

The chairmaker's bulrush is a common wetlands plant in the Americas, and it has a problem. The bulrush lives in a place where it is always at risk of being drowned. Shoot shoots like straws to suck down oxygen to the roots. The bulrush raises the ground on which it grows. The plant builds its roots near the surface, where they trap the muck that flows into the marsh. The bulrush isn't smothered as the whole system stands a little taller.

"If the water gets deep, they have an effect on the plants," says Pat Megonigal, an ecologist who directs the Global Change Research Wetland. They have been doing it here for 4,000 years.

For a long time, researchers have wondered if that skill could help the plants build their way out of climate change. As sea levels rise, so does the risk that the plants will drown. Increased levels of carbon dioxide in the atmosphere are a boon to the plants, providing more fuel for photosynthesis and helping them build bigger roots. The marathon has been happening in a single marsh in Maryland on the bay for 30 years. The wetlands are losing because of the two forces of sea rise and plant growth.

Some of the more optimistic assumptions about how coastal areas might adapt to rising seas have been upended by those findings. Wetlands are an important part of the ecology of the land and sea. They punch above their weight in terms of carbon storage, packing it away in dense soils that exceed those found in tropical forests. The fate of those areas is uncertain because of climate change. By the end of the century, it's estimated that climate change will cause 20 to 50 percent of those ecosystems to be lost. The ability of wetlands to raise themselves above rising waters is a key factor that will determine whether they can persist where they are or migrate inland.

Wow. Matthew Kirwan is an ecologist at the Virginia Institute of Marine Science who studies how coastal landscapes evolve.