The Mediterranean Sea's Pollution: A Historical Perspective

The Mediterranean Sea is one of the most polluted marine areas in the world, with an estimated 730 tonnes of plastic waste entering its waters every day. The sea's semi-enclosed shape, coupled with its high rates of urbanisation, population growth, tourism, industrial activity, and fishing, has made it particularly susceptible to pollution. The first scientific studies on plastic pollution in the Mediterranean Sea were published in the 1980s, and since then, it has become a hotspot for plastic and microplastic pollution, with plastic accounting for 95 to 100% of total floating litter. Initiatives to combat marine plastic pollution in the Mediterranean have been implemented, but the complex governance of this issue and the increasing levels of plastic production pose significant challenges.

Plastic pollution

The presence of plastic pollution in the Mediterranean was first documented in the 1980s, with research focusing on an area southwest of Malta. Since then, the problem has intensified due to various factors. The Mediterranean's densely populated coasts and high tourism contribute significantly to plastic waste generation. Additionally, the region's economic models, particularly in the tourism industry, have been associated with a "take-make-waste" approach, exacerbating the issue.

The impact of plastic pollution in the Mediterranean is widespread and detrimental. Plastic debris affects marine life through ingestion, entanglement, and suffocation, with 134 Mediterranean species known to have ingested plastic, including sea turtles, seabirds, and marine mammals. Microplastics, which make up a significant portion of the pollution, act as vectors for other harmful pollutants, threatening human health and accumulating within marine food chains.

The accumulation of plastic pollution in the Mediterranean is a complex issue. The sea's semi-enclosed morphology and the transboundary nature of plastic waste generation across surrounding countries make it highly vulnerable to microplastic pollution. Additionally, the increasing levels of plastic production and the challenges of governance and responsibility at different levels hinder effective solutions.

Initiatives to address plastic pollution in the Mediterranean Sea are being implemented at various levels. The Regional Plan on Marine Litter Management (RPML), adopted by the Contracting Parties to the Barcelona Convention in 2013, is a legally binding instrument aimed at preventing, reducing, and removing marine litter using environmentally sound techniques. Additionally, organizations like the WWF are advocating for tighter measures, pushing for a UN treaty to eliminate plastic leakage and working with local stakeholders to increase the recycling of plastic waste.

Population growth and tourism

The Mediterranean's semi-enclosed basin geometry and oceanic circulation patterns make it a natural trap for marine litter, particularly plastics. An estimated 0.57 million metric tons of plastic enter the Mediterranean annually, with half originating from coastal zones and the other half from rivers and maritime routing. The dense population and tourism activities, driven by a "take-make-waste" economic model, are the primary sources of this plastic pollution.

Tourism, while vital to the region's economy, has adverse environmental impacts. The uncontrolled development of the tourism sector contributes to environmental degradation and poses challenges to sustainability. Intense tourism demand can increase pollution levels, and the associated human activities harm biodiversity and fragile ecosystems. The Mediterranean's coastal tourism industry faces pressure from rising tourist arrivals, with an annual increase of 13% recorded in North Africa and Europe. This influx of tourists exacerbates pollution, waste management issues, and habitat destruction.

The relationship between tourism and environmental pollution is complex. While tourism generates economic growth and employment opportunities, it also strains natural resources. Tourism activities contribute to climate change, resource depletion, water and air pollution, and plastic pollution. The social and economic importance of tourism in the Mediterranean makes balancing environmental sustainability and economic development challenging.

To address these issues, spatial management planning is necessary to control land use and occupation changes. Implementing effective policies at local and regional levels and ensuring cooperation among Mediterranean countries are crucial to combat pollution effectively.

Industrial and urban waste discharge

The Mediterranean Sea is one of the most polluted marine areas in the world, heavily impacted by human activity. Industrial and urban waste discharge is a significant contributor to this.

Urban wastewater treatment plants contribute to about 90% of nitrogen discharges, with the remaining 10% attributed to industrial discharges. The raw effluent discharged from sewage outfalls often includes domestic wastewaters, and in some cases, liquid waste from industry and other human activities. For example, Malta's sewage network collects both domestic and industrial waste.

The Urban Waste Water Treatment Directive (UWWTD, 1991) of the EU prescribes the required level of treatment before discharge into marine waters. However, only 77% of Mediterranean coastal cities are served by sewage treatment plants, with 23% discharging untreated wastewaters directly into the marine environment. This untreated waste discharge is a primary cause of water pollution and can lead to significant harm to aquatic life, promoting harmful algal blooms and poisoning fish and other marine species with antibiotics and heavy metals.

The Mediterranean's semi-enclosed shape and densely populated coasts, with over 150 million inhabitants, make it particularly susceptible to pollution. This is further exacerbated by tourism, which comprises a third of the world's total volume, and industrial activity. These factors, along with specific patterns of oceanic circulation, have made the Mediterranean a natural trap for marine litter, particularly plastics.

Plastics account for 95-100% of total floating litter and more than 50% of seabed litter. It is estimated that 230,000 tons of land-sourced plastic leak into the sea each year, with plastic waste hardly ever leaving the Mediterranean due to its shape and currents. Microplastics, in particular, have become a significant concern, with concentrations exceeding 64 million floating particles per square kilometer in certain locations.

Shipping and maritime traffic

The Mediterranean Sea is a significant maritime trade route, with commercial and passenger traffic contributing to pollution. The Mediterranean fleet is made up of around 8,000 ships, with about 500,000 employees in the maritime transport sector. During the period from 2010 to 2019, maritime trade to and from Mediterranean countries increased by 284 million tonnes. As maritime traffic increases, so does the risk of pollution from shipping accidents and routine operations.

Shipping activities release oil and other chemicals into the sea, and spills can occur accidentally or due to human error or technical failures. While there has been a decrease in major incidents of oil and chemical pollution in recent decades, the Mediterranean remains vulnerable to such events. The impact of international regulations, such as the MARPOL Convention, has been positive in reducing accidental pollution. However, polluting substances continue to be discharged, and the increase in maritime traffic heightens the risk of pollution caused by shipping.

Maritime traffic also contributes to air pollution in the Mediterranean region. Freight traffic generates harmful emissions, including particulate matter, black carbon, nitrogen oxides, and sulphur oxides. The increase in goods flows in the Mediterranean area results in a higher number of ships moving within the basin annually. This increase in traffic flow leads to a consequent rise in polluting emissions.

In addition to chemical and air pollution, shipping activities are a source of noise pollution in the Mediterranean Sea. Noise from human activities at sea, including ship traffic, oil and gas exploration, and industrial construction, travels long distances underwater and can negatively impact marine species and ecosystems. The increase in Mediterranean maritime traffic is expected to exacerbate this issue.

To address the pollution caused by shipping and maritime traffic, several strategies and initiatives have been proposed. The Mediterranean Sea emission control area for sulphur oxides and particles was established by the International Maritime Organization (IMO). The Regional Plan on Marine Litter Management (RPML) in the Mediterranean, adopted in 2013, aims to prevent and reduce marine litter and plastic pollution. The Marine Litter MED II project, funded by the European Union, supports the implementation of the RPML. Additionally, the Mediterranean Strategy for the Prevention of, Preparedness, and Response to Marine Pollution from Ships (2022-2031) sets out Common Strategic Objectives to tackle marine pollution.

Noise pollution

Marine noise pollution (MNP) in the Mediterranean Sea has been caused by a multitude of human activities, including maritime traffic, pile driving, air guns, oil drilling, military activities, wind farm projects, and seismic exploration activities. These noise-generating activities have significantly impacted marine wildlife and their habitats, with the Mediterranean Sea reported to be 2-10 times louder compared to pre-industrial times.

The adverse effects of noise pollution on marine life in the Mediterranean are well-documented. Research has shown that both chronic and acute MNP can cause detectable effects on intra-specific communication, vital processes, physiology, behavioural patterns, health status, and even survival. These impacts can extend beyond individuals to induce population- and ecosystem-wide alterations, especially when functionally important species are affected. For example, noise pollution can disrupt the reproductive success of the Lusitanian toadfish, a species that relies on advertisement calls for mate attraction.

The development of the tourism industry has also contributed to the increase in noise pollution, as it has led to a rise in maritime traffic and coastal urbanization. The Mediterranean is a popular tourist destination, with sun and beach tourism being of major social and economic importance for Mediterranean countries. This has resulted in the intensification of pressure on the environment, leading to changes in environmental quality and the social and cultural state of the Mediterranean coastal region.

To address the issue of noise pollution in the Mediterranean Sea, various measures have been proposed and implemented. In 2021, the EU identified a need to reduce underwater noise pollution in its waters, and several regional, sub-regional, and national activities have been carried out under the MED POL and MAP Programme of Work (PoW) frameworks. Additionally, the "Overview of the Noise Hotspots in the ACCOBAMS Area, Part I – Mediterranean Sea" report identified noise hotspots and their overlap with important cetacean habitats, providing valuable data for future noise reduction strategies.

While curbing the threats of MNP in the Mediterranean Sea is challenging, successful measures will require accurate information on impacts and effective management of MNP as a priority in policy agendas. Risk mitigation strategies and the implementation of noise abatement techniques, such as the proposed low-frequency sound insulation ventilation barrier, can also play a crucial role in reducing noise pollution and minimizing its impacts on marine organisms in the Mediterranean Sea.

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