Scientists Use AI to Map Global Seagrass Extent for First Time

Scientists have produced the first high-resolution map of seagrass ecosystems worldwide, using satellite imagery and artificial intelligence to identify nearly 150,000 square kilometres of these vital marine meadows. The research, led by Arizona State University and published in Nature, found that 70 percent of global seagrass cover is concentrated off just five countries, yet only 21 percent falls within marine protected areas. The map also revealed that almost 80 percent of seagrass loss occurred outside protected zones, underscoring the need for targeted conservation of ecosystems that store carbon and shield coastlines.

 

Mapping Seagrass for the First Time

 

The research represents the first accurate global map of seagrass meadows. Scientists at Arizona State University used satellite imagery and artificial intelligence to map seagrass cover. They studied two distinct periods, spanning 2019 to 2020 and 2023 to 2024. The team identified 148,506 square kilometres of seagrass globally, an area larger than England. The majority of this cover was found to lie in subtidal areas below the low tide line.

The project aimed to fill a significant gap in marine science knowledge. The lead researcher said the goal was to map seagrass in a highly accurate manner. This would show where seagrass exists and where there is potential to protect it. Such precise mapping had not previously been achieved at a global scale. The resulting data provides a foundation for informed conservation and coastal management decisions.

 

The Ecological Importance of Seagrass

 

Seagrasses occupy a unique and valuable position in marine ecosystems. They are the only flowering plant species in the ocean and form vast meadows in shallow waters. These meadows serve as habitats for many marine species across the world's coasts. They also function as crucial carbon sinks with remarkable efficiency. Seagrass can absorb carbon dioxide up to 35 times faster than terrestrial forests.

Beyond carbon storage, seagrass provides several other environmental benefits. The meadows protect coastlines from erosion and wave action. They also filter pollutants from the surrounding water, improving water quality. Despite these functions, seagrass ecosystems face numerous threats. These include marine heat waves, hurricanes, disease, coastal development and sediment runoff from agriculture and industry.

 

The AI-Driven Methodology

 

The mapping relied on training an artificial intelligence model to detect seagrass. The team had previously attempted to map seagrass alongside coral reefs. However, they realised that mapping seagrass required different techniques altogether. This prompted them to train a deep-learning model to identify seagrass from satellite images. Seagrass had long been overlooked partly because it lacks the visual prominence of coral reefs.

Ground-truthing was essential to ensure the accuracy of the model. Partners and collaborators around the world helped corroborate the data on the ground. They used research dives and underwater cameras to verify seagrass locations. This field data was then used to train the model on satellite images from the same sites. The trained model subsequently analysed satellite data across four years to build the map.

 

Read more: Fugro Wins Saipem Survey Contract for UK's First CO2 Storage Pipeline

 

Findings on Distribution and Loss

 

The map revealed a striking concentration of seagrass in a handful of countries. The Bahamas emerged as a major habitat for the world's seagrasses. They were joined by the United States, Australia, Indonesia and Cuba as the leading locations. Together these five countries account for close to 70 percent of global cover. This concentration has significant implications for where conservation efforts should focus.

The research also documented notable losses over the study period. The team found that close to 4 percent of seagrass meadow cover was lost across the four years. This amounted to 5,969 square kilometres of seagrass disappearing. An additional 6,220 square kilometres in tropical regions were found to have degraded. These figures highlight the ongoing pressures facing seagrass ecosystems globally.

 

Signs of Recovery and Conservation Potential

 

The findings were not entirely negative, with evidence of recovery in some areas. The maps highlighted locations where restoration efforts were producing results. Improved water quality in South Bay, Los Angeles, aided seagrass recovery there. Similar recovery was observed in Cuba following better water conditions. Researchers described the speed of this recovery as unexpected and encouraging.

These recoveries point to the potential for effective seagrass conservation. The lead researcher noted that seagrass returns quickly when water conditions are good. This rebound occurs when human disturbance is limited and conditions are favourable. Such findings offer hope for the future of seagrass protection. They suggest that targeted improvements in water quality can yield rapid ecological benefits.

 

Implications for Policy and Protection

 

The data carries clear implications for conservation policy. The research found that nearly 80 percent of seagrass loss happened outside marine protected areas. This indicates that existing protected zones do not adequately cover seagrass habitats. With this information, conservationists and policymakers can identify gaps in protection. They could then establish new protected areas targeted specifically at seagrass ecosystems.

The researchers hope the maps will support more data-driven decision-making. The team intends for the data to inform conservation and coastal management choices. Accurate mapping allows resources to be directed where they are most needed. This is particularly valuable given the concentration of seagrass in specific regions. The ultimate aim is to enable better decisions for both coastal management and climate mitigation.