Restoring mangroves could help countries meet their climate goals

Recently, countries all over the world have been struggling to meet their international climate commitments. Nature-based approaches, such as using the potential of mangroves, seagrasses, or salt marshes to sequester carbon provide a promising solution and could help nations significantly reduce their greenhouse gas emissions and mitigate climate change. 

However, due to the complexity of calculating how much carbon wetlands and other coastal ecosystems can sequester and where to implement such strategies in order to maximize the co-benefits for the climate, economy, or flood risk reduction, major coastal countries, including the United States, have largely overlooked such “blue carbon strategies.”

Now, a team of researchers led by Stanford University has quantified the value of Belize’s coastal mangrove forests in terms of how much carbon they can hold, what value they can add to fisheries and tourism, and what protection they can provide against coastal storms and other risks. Their findings could help chart a path to mitigate climate change, while also boosting the economy and making communities safer.

“The U.S. has one of the largest coastlines in the world, and extensive wetlands,” said study lead author Katie Arkema, a senior Earth scientist at the Pacific Northwest National Laboratory, who conducted this research during a fellowship at the Stanford Natural Capital Project. “This paper offers an approach we could use for setting evidence-based climate resilience and economic development goals.”

How the study was conducted

Collaborating with an international team of scientists, as well as Belizean policymakers and stakeholders, Arkema and her colleagues quantified carbon storage and sequestration by using land cover data from Belize and field estimates from Mexico. 

The experts also took into account factors such as coastal flood risk reduction, tourism, and fisheries co-benefits by modeling related services – such as lobster breeding grounds – provided by mangroves under current and future protection, and possible restoration scenarios at different locations.

What the researchers learned 

The analysis revealed that, in some regions, even small amounts of mangrove restoration could have significant benefits for both fisheries and tourism. However, since it takes some time for carbon stocks to accumulate in the soil and biomass, total organic carbon sequestration was found to be initially lower when restoring mangroves than when protecting already existing forests. 

Moreover, the experts discovered that, as mangrove areas increase past a certain point, benefits other than carbon storage begin to decrease. Identifying such inflection points could help policymakers and stakeholders decide how to most effectively balance ecosystem protection with coastal development. At the same time, pinpointing the locations where blue carbon strategies could offer the greatest amounts of co-benefits could help bolster local support.

Belize sets new targets

Based on these findings, Belizean policymakers pledged to protect an additional 46 miles of existing mangroves – thus bringing the national total protected area to 96 square miles – and to restore 15 square miles of mangroves by the end of this decade. If these targets will be met, the mangroves could store millions of tons of additional carbon, while also providing additional benefits, such as boosting lobster fisheries by up to 66 percent, generating mangrove tourism worth several million dollars annually, and reducing the risk of coastal hazards for at least 30 percent more people.

Since this approach addresses both climate and sustainable development goals, it can open new opportunities for financing nature-based solutions in other countries too. In the following months, the Natural Capital Project, the InterAmerican Development Bank, and the Asian Development Bank will collaborate with 10 countries to help translating such nature-based approaches into policy and investment processes. 

“Belize’s example, illustrating the practical ways nature’s many benefits can be spatially quantified and inform a country’s climate policy and investments, are now primed to be scaled around the world with development banks and country leaders,” concluded co-author Mary Ruckelshaus, the executive director of the Stanford Natural Capital Project.

The study is published in the journal Nature Ecology & Evolution.

More about mangroves

Mangroves are tropical trees and shrubs that grow in coastal and estuarine environments. They are an important part of the ecosystem because they help protect coastlines from storm surges, prevent erosion, and provide habitats for a variety of animal and plant species.

Mangroves have several interesting features that allow them to survive in saline, oxygen-poor environments. 

Key characteristics:

Salt Tolerance

Unlike most other types of trees, mangroves are able to tolerate and even thrive in saltwater. They have evolved several mechanisms to deal with high salt levels, including salt excretion through leaves and specialized root structures that limit the amount of salt taken up.

Specialized Root Systems

Mangroves have unique root structures known as pneumatophores, which protrude from the water or soil and allow the trees to breathe in oxygen-poor environments. These roots also stabilize the trees in the loose, shifting sediments of the intertidal zone.

Tidal Adaptations

Mangroves are well-adapted to living in intertidal zones, where water levels can fluctuate dramatically between high and low tides. Their roots help to trap sediments, which builds up the soil and allows the mangroves to keep pace with sea level rise.

There are about 80 different species of mangroves, and they’re typically divided into two major types: the “true mangroves” and “mangrove associates.” True mangroves are species that are exclusively found in mangrove habitats, while mangrove associates can be found in other environments as well.

Mangrove ecosystems are under threat worldwide due to a variety of factors, including coastal development, pollution, and climate change. Despite their ecological importance, mangrove forests have been cleared at an alarming rate. This not only destroys habitats for a multitude of species but also reduces the coastline’s natural protection against storms and erosion. Consequently, efforts to conserve and restore mangrove habitats are vital for both local communities and global biodiversity.

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By Andrei Ionescu, Earth.com Staff Writer

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