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San Diego Coastal Marshes May Become Important Tools To Battle Climate Change

Wetlands in the San Dieguito Lagoon near the Del Mar Fairgrounds on Nov. 17, 2020.
Erik Anderson
Wetlands in the San Dieguito Lagoon near the Del Mar Fairgrounds on Nov. 17, 2020.
San Diego researchers and environmentalists are taking a close look at a pocket habitat that may become an important tool as the climate changes.

Matthew Costa stepped gingerly into a little pocket wetland near the Del Mar Fairgrounds. The squishy salt marsh is more than just a patch of habitat in the intertidal zone.

“Just watch out,” said Costa, a postdoctoral researcher at the Scripps Institution of Oceanography, as he warned a helper. “Watch out for birds.”

Endangered ridgeway rails like hiding in the pickleweed that covers the soft, moist ground nestled between train tracks and a busy Del Mar street.


Costa stopped at the water’s edge and walked inland

“I think this is a good spot. It's 15 meters,” Costa said.

San Diego Coastal Marshes May Become Important Tools To Battle Climate Change Tuesday, December 1, 2020

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He is here hoping to unlock information about this salty marsh. Information that cannot be seen by the thousands of people who pass by each day.

“We’ve got all these plants here, underneath there’s sort of a real muddy layer of sediment. There are lot of snails and creatures living on the mud,” Costa said as he picked up a small ball of dirt.


He uncrated his tools. He pulled out a long, silver tube with a wide fin on one side. The device looks a bit like a stubby sword. Costa placed it upright and leaned in, pushing the metal cylinder into the ground.

When he can not push anymore, he used a slide hammer to help him sink the tube even deeper.

Once the tool is completely seated in the soft, wet dirt, Costa gently pulled the device back out of the ground.

A quick twist revealed a core sample, roughly seven centimeters across, and 48 centimeters long.

“So there is our sediment sample,” Costa said as he runs a finger the length of the core. “As I said, we’re looking at this as a kind of time machine. We’re looking down in the sediment. We’re kind of looking back in time. So, this sediment accumulated maybe hundreds of years ago and built up over time to where we have the plants living today.”

Costa pulled samples and labeled them. Later in the lab, he will measure how much carbon is stored there.

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“It’s an effort to try and catalog the amount of blue carbon that’s currently stored in our San Diego coastal wetlands and ecosystems,” said Cory Pukini of the conservation group Wildcoast.

The plants in the salt marsh grow fast, sucking a lot of carbon dioxide out of the air and some of that carbon gets trapped as plants die and new ones grow over them. It makes the wetlands a carbon sink, as some researchers call it.

Unfortunately, this wet terrain near the ocean is not as common as it used to be: 90% of the region’s coastal wetlands have been swallowed up by urbanization or dredged for recreation. But conservationists are optimistic.

“So as you see behind me, there are a lot of these opportunity parcels that we like to call them,” Pukini said. “These orphan wetlands that are in and around a lot of the currently existing wetlands in San Diego County that have the potential to be restored to enhance their capabilities to draw that carbon out of the atmosphere.”

The research by the Scripps Center for Climate Change Impacts and Adaptation will give conservationists a better idea of how efficient the salt marsh terrain is at storing carbon.

“We’re seeing if we can ecologically enhance them to create this ecological uplift so that we can sequester more carbon using these natural solutions to draw carbon out of the atmosphere,” Pukini said.

Doing that could help slow the pace of global warming because the carbon in the atmosphere contributes to a warmer climate.

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“We’re looking at areas like Batiquitos Lagoon, up in Carlsbad, the Kendall Frost marsh in Mission Bay, here at San Dieguito lagoon, Famosa Slough. And a number of other coastal wetlands here and throughout the region,” said Wildcoast Associate Director Zach Plopper.

This research will help increase understanding of the ecosystems and habitats that are in the nearshore area.

Salt marsh near the Del Mar Fairgrounds in the San Dieguito Lagoon on Nov. 17, 2020.
Erik Anderson
Salt marsh near the Del Mar Fairgrounds in the San Dieguito Lagoon on Nov. 17, 2020.

“With an understanding of how much carbon is stored in our local wetlands it really makes San Diego a leader of natural climate solutions,” Plopper said.

Wildcoast has led efforts to understand these blue carbon habitats which are near the ocean and are particularly good at capturing and storing carbon.

“The salt marsh and seagrass that we have here in San Diego County are these blue carbon ecosystems,” Plopper said. “They sequester and store more carbon than any other ecosystem on the planet.”

Which makes the terrain both a hedge against global warming and a buffer against rising sea levels.

That is why the research project is focused on measuring the impact the habitat has already had.

There is hope that mapping out the terrain’s past will help gauge a salt marsh’s ecological value in the future.

San Diego Coastal Marshes May Become Important Tools To Battle Climate Change
Listen to this story by Erik Anderson.

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