Limits on carbon sequestration in arid blue carbon ecosystems

Area of Science:

• Marine ecology
• Biogeochemistry
• Climate change science

Background:

• Blue carbon (coastal ecosystem carbon) is well-documented in temperate and tropical climates.
• Arid coastal ecosystems, including mangroves, marshes, and seagrasses, are understudied due to environmental stressors.
• Understanding carbon sequestration in these unique environments is crucial for climate mitigation strategies.

Purpose of the Study:

• To quantify whole-ecosystem carbon stocks in diverse arid coastal habitats across the UAE.
• To compare carbon storage across different ecosystem types (mangroves, marshes, seagrasses, microbial mats, sabkha).
• To assess the potential of arid blue carbon ecosystems for national climate policy and reporting.

Main Methods:

• Conducted a comprehensive survey of 58 sites across the United Arab Emirates.
• Measured above- and belowground biomass and soil carbon stocks in various coastal ecosystems.
• Utilized a uniform sampling protocol for country-wide carbon accounting.

Main Results:

• Natural mangroves exhibited the highest carbon stocks in biomass. Planted mangrove stocks increased with age, but with significant variability.
• Soil carbon varied widely (2-367 Mg C/ha), with microbial mats showing substantial carbon pools comparable to vegetated ecosystems.
• UAE mangroves and marshes had lower plant and soil carbon stocks than global averages, attributed to poor carbon preservation conditions.

Conclusions:

• Arid coastal ecosystems, including microbial mats, represent significant blue carbon sinks.
• Lower carbon stocks in UAE ecosystems are linked to environmental conditions like soil redox potential and sediment type.
• This study provides critical data for integrating blue carbon into national climate strategies and conservation efforts.