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Source: International Atomic Energy Agency – IAEA

Sewage outlets such as this cause a deterioration in the quality of sea water, especially in areas important for fishery, in addition to the emission of unpleasant odors. (Photo: M. Kayyal/UNEP-MAP)

The latest report of the Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP), published in coordination with the IAEA, draws on nearly a century’s-worth of data to demonstrate the need for regulating pollution in coastal environments to help reverse the destruction of ecosystems.

Coastal ecosystems play a critical role in the global climate and the carbon cycle, serving as one of nature’s carbon storage reservoirs. As a natural interface between land and sea, they preserve fisheries, facilitate natural processes of nutrient cycling, protect the coasts and even provide recreational spaces for humans. However, urbanization, agriculture and industrialization have released a myriad of harmful contaminants into the coastal environments over many years disrupting the natural balance as well as threatening entire ecosystems, seafood safety and human health.  

According to the Global Pollution Trends: Coastal Ecosystem Assessment for the Past Century report, the number and concentration of many contaminants such as heavy metals, industrial by-products and chemical discharges, hydrocarbons, pesticides and micro-plastics are increasing at an alarming rate. However, the report notes, where restrictions have been introduced, certain strictly regulated contaminants have been decreasing over the last 50 years, illustrating the success of national policies, international agreements and social environmental awareness.

“Pollution is one of main causes of ecosystem destruction. Over the past century, human activities have been disrupting the delicate balance of coastal ecosystems that are most vital to the natural cycle of self-restoration,” said Florence Descroix-Comanducci, Director of the IAEA Environment Laboratories in Monaco. “Together with ten other United Nations organisations, we have mandated independent experts to look into the accumulated data to determine whether national legislation and international agreements have been effective in protecting these precious ecosystems.”

To conduct the assessment, the IAEA-led GESAMP Working Group 39 examined trends in global pollution in coastal environments to reveal the impacts of continued anthropogenic activities. They evaluated over 70 years of research on data reaching back as far as the preindustrial period. The dating of sediments at such timescales can be achieved using radionuclides that are present in the environment, such as 210Pb, 137Cs and Pu isotopes.

In tracing the historical records of pollution, marine experts analysed 37,720 data points from 2355 independent time series research studies from around the world conducted over the past century, of a large number of different contaminant classes including some radionuclides.

The study demonstrated that since the 1950s, a wide array of chemical contaminants have invaded coastal environments. The research findings indicate that in some regions, large and increasing contaminant trends were observed during periods without national legislation and international agreements. The use and production of several of these hazardous substances such as polychlorinated biphenyls (PCBs) were banned for the first time in 1970s. The regulation of other bio-toxic compounds followed. As a result, a substantial decrease of toxic compounds such as dichlorodiphenyltrichloroethane (DDTs), copper, cadmium, zinc, lead, mercury and organic pollutants has been witnessed in some marine areas with the implementation of international agreements, national policies and increasing social environmental awareness.

“As these research findings show, when there is enough monitoring data available, contamination trends play an important role in understanding the underlying causes of coastal deterioration and provide scientifically sound information for decision-making,” said Ana Carolina Ruiz-Fernandez, the chair of this GESAMP Working Group 39.

If left unregulated, these toxic contaminants have tremendous capacity to alter coastal ecosystems, destroy natural habitats and threaten seafood safety and the health of humans relying on the marine biosphere for their wellbeing and socio-economic development.

“In this assessment, we have attempted to provide decision-makers with important current knowledge that can underpin predictive management tools to support decisions of socio-economic consequence. We believe that this study can have a positive impact on policy-making to better protect the coastal environments worldwide,” said David Vousden, GESAMP Chair. “Coastal zone management and protection must be prioritized, and its effectiveness monitored comprehensively in the future as coastal environments are threatened by both complex historic and newly emerging contaminants.”

The research has also revealed an array of other increasing threats to coastal environments. The report calls for further analysis of emerging contaminants such as micro-plastics, excessive nitrogen input from sewage and runoff of chemical fertilizers and organic carbon concentrations that are ubiquitous in coastal areas.


The world trend of polychlorinated biphenyls (PCBs) is a good example of the effectiveness of national policies following the international agreements such as the Stockholm Convention, as mean levels on this graph rise steadily from the 1920s and reach a broad maximum around 1980, in agreement with the PCB banning in many developed countries. Since then, mean world values have been decreasing slowly, but they have not disappeared. (Graph credit: GESAMP WG39).

The GESAMP works to advise the United Nations and its Member States on the scientific aspects of marine environmental protection, with the goal of ensuring sustainable governance of the marine environment. The GESAMP Office is based at the International Maritime Organization, IMO.

Ten GESAMP Sponsoring Organizations with maritime and ocean interests are International Maritime Organization (IMO), Food and Agriculture Organization (FAO), United Nations Educational, Scientific and Cultural Organization – Intergovernmental Oceanographic Commission (UNESCO-IOC), United Nations Industrial Development Organization (UNIDO), World Meteorological Organization (WMO), United Nations (UN), UN Environment Programme (UNEP), UN Development Programme (UNDP), International Seabed Authority (ISA). GESAMP’s principal task is to provide scientific advice concerning the prevention, reduction and control of the degradation of the marine environment to the Sponsoring Agencies.

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