For plants in wetlands, sea level rise shows benefits of higher CO2 – Is it increased because of that?

Beneficial effects of increased CO2 on plants disappearing under floods, 33-year field experiment shows

Peer-reviewed publications

SMITHSONIAN

Wetlands around the globe are at risk of drowning due to sea level rise. But for decades, scientists hoped that another facet of climate change – increased carbon dioxide (CO₂)—May trigger further plant growth, enabling coastal wetlands to grow fast enough to overcome sea level rise. They found that helpful side effect is disappearing in a new study published May 18.

“Too much water is a stress, an environmental pressure, on the response of plants to high CO₂“Chunwu Zhu, lead author of the report said in Scientific advance. Zhu, a biologist with Chinese Academy of Sciencesconducted research while working as a PhD student with Smithsonian Center for Environmental Research (SERC).

Conservation of wetlands is crucial to combating climate change and adapting to it. Besides providing habitat, wetlands sequester large amounts of carbon and protect people from some of the harsher effects of climate change, such as hurricanes and hurricanes.

“Although they cover only a small fraction of the Earth’s surface, they provide superior ecosystem services that fundamentally benefit humans,” said corresponding author Pat Megonigal, a biochemist. SERC study, said. “And we appreciate them in part because by protecting a relatively small part of the Earth we can have huge positive impacts on the environment.”

Return of Carbon Dioxide

Research takes place at SERC’s Wetlands Global Change Study, a Megonigal research site that runs on the west coast of Maryland. The wetlands are the site of several future experiments, where scientists simulated the climate of the year 2100. For this study, the researchers relied on an experiment that began in 1987. – currently the world’s longest field experiment on rising levels of CO₂ affect plants. Inside 15 open chambers, scientists increased CO₂ the concentration added 340 parts per million, almost double the CO in the atmosphere₂ 1987 levels. Another 15 chambers act as controls, no additional CO₂. The team focused on 10 chambers containing “C3” plants — a group of plants known to respond strongly to high CO₂ comprises about 85% of all plant species on Earth.

During the first two decades of the trial, plant growth in a higher CO environment₂ blooming chamber. Above ground, plants in high CO₂ chambers grew on average 25% more than plants grown in untreated chambers. The effect is even stronger underground: high CO₂ activates root growth by about 35%. Root growth is especially important for wetland survival, as roots help the wetland build up soil and keep it growing. upward even as sea levels continue to rise.

“Even though the CO is so high₂ contributing to sea level rise, it also enhanced the vertical accretion capacity of the marsh during the early years of the trial,” said Don Cahoon, co-author and study ecologist. US Geological Survey.

But after 2005, the effect diminished and disappeared. For the study’s last 14 years of data, there were no mean differences in plant growth between the high CO plants.₂ and normal compartments.

“CO₂ The effect has always been one of the silver layers of climate change,” said co-author Adam Langley, an ecologist. Villanova University. “Well, at least the plants will grow more. But here we see that they did not. So the silver lining for me just became a little drier. “

The team looked at several possible reasons for the drop: rainfall, temperature, water salinity during the growing season, or the presence of important soil nutrients, such as nitrogen. Only sea level rise shows any connection to plant growth. Once sea levels in wetlands rise 15 cm above where they started in 1987, the benefits of CO are higher₂ disappear.

Lewis Ziska, co-author and plant physiologist at Columbia University Mailman School of Public Health. “A race between what CO₂ can do and what sea level can do”.

Escape from flood

Sea level rise could further slow growth for a very simple reason. As the water rises, the wetlands flood more often. Plants need oxygen as well as CO₂—And plants in wetlands have evolved to get most of their oxygen from the air, not the water.

“Plants are aerobic organisms, breathing oxygen,” says Megonigal. “And that includes their roots. And so they basically face this problem when they put their root system in an oxygen-free environment. “

Some wetlands can still escape drowning. If wetlands cannot be raised higher by land-building, inland migration is another possibility. However, that can only happen if they have enough space. For many communities, allowing wetlands to move in will require a change in how they use and value land.

Meanwhile, Earth’s climate accountants will need to rethink the planet’s carbon budget. Now, scientists know more CO₂ not always stimulating wetland growth as much as they thought, how much carbon wetlands could absorb in the coming decades is even more uncertain.

The study will be published in the journal website after publication. For photos, a prior copy of the article, or to speak with the authors, contact Kristen Goodhue at [email protected].

JOURNEYS

Scientific advance

DOI

10.1126 / sciadv.abn0054

RESEARCH METHODS

Experimental study

RESEARCH SUBJECTS

Do not apply

ARTICLE TITLE

Rapid sea level rise is suppressing the CO2 stimulation of tidal marsh productivity: A 33-year study

ARTICLE PUBLICATION DATE

May 18, 2022

From EurekAlert!