Of all the ecosystems needing care, estuaries arguably deserve one of the top spots. Found where rivers and streams converge with the sea, they play a vital role in the balance and conservation of fresh- and salt-water ecosystems. Usually surrounded by land and secluded from high winds, they provide fertile ground for thousands of species to grow and thrive. “Estuaries are the most productive part of the ocean,” says Mr Leung. “The brackish water system is home to different habitats, from mudflats and mangroves to seagrass beds and oyster reefs, all of which are nursery grounds for fishery resources.”
Despite their ecological importance, scientists’ knowledge about estuaries remains patchy. Very little is known about the state of urbanised estuaries in Africa and South America, and information from South-east Asia and Oceania are uneven, making for an incomplete picture of global estuarine health. The GEM study, led by Mr Leung and four other scientists from Australia, the UK, the US and mainland China, aims to map the health of estuaries worldwide by measuring levels of contamination by microplastics, pharmaceuticals, and heavy metals, and assessing their ecological risks.
The project includes training programmes for researchers on data collection and sharing and seeks to develop a simple, standardised way of collecting and analysing samples to ensure comparable results. GEM aims to identify estuaries that require attention, recommend control measures for priority pollutants and share best practices to tackle estuarine pollution. GEM is now calling for scientists worldwide to collect samples from riverbeds and estuaries, aiming to publish its results towards the end of 2024.