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World Environment Day 2025
On 5 June, we celebrate World Environment Day. Hosted by South Korea and dedicated to ending plastic pollution, the 2025 edition of WED will draw inspiration from nature to showcase real-world solutions that encourage sustainable practices. Satellite data help to monitor environmental impact, including the issue of marine plastic pollution.
Guest feature by Dr. Sunmin Lee, Ph. D. Research Specialist at the Korea Environment Institute.
Aquaculture patterns revealed by Sentinel-2
Off the southern coast of South Korea lies Wando County, a patchwork of 265 islands shaped by a ‘ria coastline’. A ria coastline forms when a river valley becomes submerged by rising sea levels on a geological timescale. Known for its nutrient-rich waters and thriving aquaculture industry, this complex marine landscape transforms into a striking mosaic of floating cages, buoys, and net structures when seen from space.
This Sentinel-2 image, acquired on 6 April 2025, uses high-resolution optical sensors to capture vivid natural colour imagery, revealing fine spatial patterns of human activity at sea. With repeated cloud-free observations, we can monitor the expansion of aquaculture zones, track seasonal changes in marine use, and assess their impact on sensitive coastal ecosystems. By supporting more sustainable and informed marine resource management, our satellite helps World Environment Day achieve its goal of ending plastic pollution.
When fishing gear becomes marine waste
While aquaculture plays a vital role in food security and coastal economies, it also contributes significantly to marine plastic pollution. Between late 2024 and mid-2025, cleanup operations recovered more than 150 tons of discarded fishing gear in Wando, including broken buoys, synthetic nets, and plastic cages.
Once adrift, these materials often fragment into microplastics or become ghost gear that traps marine life and damages seafloor habitats. Plastic waste that originates at sea doesn’t stay there — it moves through the food web, ultimately reaching our tables, water, and even air.
Sentinel-2 imagery helps us observe marine infrastructure and surface debris in visible wavelengths, enabling the identification of hotspots where waste may accumulate and helping to guide focused mitigation efforts.
Tracing human impact at sea from space
Though the ocean surface around Wando may appear calm and untouched, satellite imagery reveals a different reality. The Sentinel-2 scene from 6 April 2025 shows dense clusters of aquaculture installations arranged in neat rows across the coastal waters, vividly captured through natural colour processing. These structures, often invisible to the naked eye at sea level, stand out clearly in high-resolution satellite views.
By examining such images over time, scientists and policymakers can assess the scale and spread of marine infrastructure, identify abandoned or unmanaged zones, and understand the cumulative footprint of aquaculture. These observations are essential for balancing the needs of the marine industry with the imperative of protecting ocean ecosystems. Learn more about World Environment Day here
