Coral reefs and coastal mangrove forests are frequently the focus of discussions regarding valuable ocean ecosystems that are in danger. Even though seagrass meadows provide a wide range of services to society and store a lot of carbon that warms the climate, they receive very little attention.
Seagrass ecosystems, on the other hand, merit being at the forefront of the global conservation agenda, according to the authors of a new study led by the University of Michigan. It’s the main review to put a dollar value on the many administrations—from storm security to fish territory to carbon capacity—given via seagrasses across the Caribbean, and the numbers are great.
The researchers estimated, based on newly available satellite data, that the Caribbean holds approximately one-third of the carbon stored in seagrasses worldwide and holds up to half of the world’s seagrass meadows by surface area.
According to their estimates, Caribbean seagrasses contribute approximately $255 billion to society annually, including $88.3 billion to carbon storage.
“Our study is the first to show that seagrass beds in the Caribbean are of global importance in their areal extent, in the amount of carbon they store, and in the value of the economic services they provide to society,”
Lead author Bridget Shayka, a doctoral student in the U-M Department of Ecology and Evolutionary Biology.
According to a study that was published online on June 21 in the journal Biology Letters, the ecosystem services that seagrasses provide in the Bahamas alone are worth more than 15 times the country’s GDP in 2020.
According to study lead author Bridget Shayka, a doctoral student in the U-M Department of Ecology and Evolutionary Biology, “our study is the first to show that seagrass beds in the Caribbean are of global importance in their area, in the amount of carbon they store, and in the value of the economic services they provide to society.”
“The findings emphasize the importance of conserving and protecting these ecosystems, which are critical allies in the fight against climate change and are highly threatened and globally important.”
Including these lush undersea meadows in global carbon markets through projects that minimize loss, increase area extent, or restore degraded beds is one way to prioritize seagrass conservation.
There are a number of reasons why the concept of selling “blue carbon” offset credits, which monetize carbon stored in coastal and marine ecosystems, is gaining popularity.
First, many island nations that have already been affected by climate change have large areas of valuable coastal ecosystems that store carbon and provide other services to society. Examples of this include hurricanes that are getting stronger or rising sea levels.
Offset credits for “blue carbon,” which refers specifically to carbon stored in coastal and open-ocean ecosystems, and “green carbon,” which refers more broadly to carbon stored in all natural ecosystems, could be a way for wealthier nations to compensate for their contribution to human-caused climate change while also assisting in the preservation of coastal ecosystems, which are among the most severely degraded in the world.
Coastal development, chemical pollution, recreation, shipping, and climate change are all threats to seagrass meadows.
Senior author and marine ecologist Jacob Allgeier, an associate professor in the University of Michigan Department of Ecology and Evolutionary Biology, stated, “Because seagrass ecosystems are both highly important for carbon storage and sequestration and are highly degraded globally, they represent an important burgeoning market for blue carbon.”
“However, the lack of comprehensive seagrass distribution data has been a fundamental impediment to both evaluating seagrass and promoting it in the blue carbon market up to this point.”
The team led by U-M used brand-new seagrass distribution data from the PlanetScope constellation of small DOVE satellites for their research. Using data from Thalassia testudinum, the predominant seagrass species in the region, they estimated the amount of carbon in plants and sediments and classified Caribbean seagrass ecosystems as either sparse or dense.
Using previously published estimates for the value of services such as food production, nursery habitat for fish and invertebrates, recreation, and carbon storage, the researchers then calculated a conservative economic value for the entire ecosystem services provided by seagrasses in the Caribbean.
The animals that are commercially harvested that are dependent on Caribbean seagrass include grouper, queen conch, and lobster. Manatees, tiger sharks, and green sea turtles all rely on it.
The researchers borrowed $18 per metric ton of carbon dioxide equivalents from California’s cap and trade program to estimate the carbon stored in Caribbean seagrass beds.
The researchers calculated values for individual Caribbean nations in addition to Caribbean-wide estimates:
With 61% of the Caribbean seagrass, the Bahamas provides ecosystem services worth $156 billion annually, including $54 billion for carbon storage.
Cuba has the second-highest coverage of areal seagrass in the Caribbean, accounting for 33% of the total, and receives an annual value of $84.6 billion for all ecosystem services, including $29.3 billion for carbon storage.
The carbon found in seagrasses around Cuba will be worth 27% of the country’s GDP in 2020.
The authors wrote, “Importantly, the degradation of seagrass beds frequently leads to erosion and resuspension of sediment, which can create a positive feedback loop of increased seagrass loss and the release of C stored in sediments.” As a result, “blue carbon finance” is a potential way for the global community to invest in the preservation and protection of these essential ecosystems.
Seagrasses of more than 60 different species thrive in shallow coastal waters all over the world. From land plants that repopulated the oceans 70 to 100 million years ago, they evolved.
Allgeier and colleagues demonstrate in a separate paper that has been accepted for publication in the journal Proceedings of the Royal Society that the construction of artificial reefs in the Caribbean can assist in protecting seagrass ecosystems from the effects of human activity, such as nutrient pollution and overfishing.
Seagrasses store carbon in plant tissues after removing carbon dioxide from the atmosphere through photosynthesis. The decomposition of the seagrasses is slowed by the rapid flooding caused by sediments. Consequently, the top meter of sediment contains more than 90% of the carbon that is stored in seagrass beds.
The new study says that Caribbean seagrasses and the sediments that go with them store an estimated 1.3 billion metric tons of carbon. According to the new study, while that number is significant, it represents only 1.09 percent of the carbon in above- and below-ground woody biomass in the Amazon and 1.12 percent of the carbon in the biomass and soils of temperate forests worldwide.
More information: Bridget F. Shayka et al, The natural capital of seagrass beds in the Caribbean: evaluating their ecosystem services and blue carbon trade potential, Biology Letters (2023). DOI: 10.1098/rsbl.2023.0075
