Showing posts sorted by date for query FOREST. Sort by relevance Show all posts

Saturday, January 24, 2026

Litter invades the mangroves of tropical countries

A major environmental problem

University of Barcelona

Litter invades the mangroves of tropical countries — image:
Litter, mainly plastic bags, accumulated in the mangrove swamp of the Ranchería River delta (La Guajira, Colombian Caribbean).
view more
Credit: Ostin Garcés – University of Barcelona

Mangroves, typical of tropical and subtropical latitudes, have become veritable natural traps for land- and sea-based waste. The roots of these trees, known as mangroves, have a great capacity to trap litter — from both land and sea — which gradually breaks down until it is buried in the muddy bottom. Now, an article in the journal Environmental Pollution warns that the accumulation of rubbish threatens the environmental balance and biodiversity of these ecosystems, as well as the well-being of nearby local communities that depend on the resources provided by mangroves.

The study analyses, for the first time and on a large scale, the pressure and state of pollution from waste in Colombia’s mangroves. The first two authors of the article are Ostin Garcés-Ordóñez and Miquel Canals, from the UB Chair on Sustainable Blue Economy and the Consolidated Research Group in Marine Geosciences at the Faculty of Earth Sciences of the University of Barcelona. The study’s co-authors are Diana Romero-D’Achiardi, from the José Benito Vives de Andréis Institute of Marine and Coastal Research (INVEMAR, Colombia); and Martin Thiel, from the Smithsonian Environmental Research Center (SERC, United States) and the Catholic University of the North (Chile).

A major environmental problem

The mangroves most affected by rubbish are located near Colombian coastal cities such as Cartagena de Indias, Barranquilla and Riohacha (Caribbean coast), and Bahía Solano, Buenaventura and Tumaco (Pacific coast). “On the outskirts of coastal cities and in rural areas of the Pacific, the situation is exacerbated by the lack of adequate waste collection and treatment services. As a result, nearby mangroves are often used as uncontrolled dumps, although there are also accumulations of waste in the mangroves of marine protected areas, such as those on the island of San Andrés in the Caribbean,” says Ostin Garcés-Ordóñez, who is currently doing a postdoctoral research in the SERC’s MarineGEO programme under the supervision of Martin Thiel.

Much of the rubbish reaches the mangroves via rivers, rainwater and tidal currents. “In addition to natural factors, and beyond the distance from urban centres, the concentration of active sources of pollution in the mangrove environment is a determining factor. The largest amounts of rubbish — especially plastics — accumulate in marginal mangroves, a type of forest that grows on the margins of open bays and lagoons, where they are exposed to the action of the tides,” says Miquel Canals, professor at the UB’s Department of Earth and Ocean Dynamics and director of the UB Chair on Sustainable Blue Economy.

“This type of mangrove is exposed to the action of tides and coastal currents, which carry floating debris towards the coast. Marginal mangroves can be considered large sinks for marine debris, with around 2.5 objects accumulated per square metre,” says Canals.

In coastal mangroves, which occupy riverbanks, streams and floodplains, and in basin mangroves, which form around deep inlets and bays with little tidal influence, the amount of litter is less than 0.4 items per square metre.

Trapped rubbish accumulating on the mangrove floor

Over time, the trapped rubbish degrades and accumulates on the mangrove floor. “Plastics slowly fragment due to the action of the sun, water dynamics and interaction with mangrove organisms, such as crabs, generating increasingly smaller fragments that are progressively buried, further promoting their long-term persistence: this is ‘soil plastic carbon’,” warns Garcés-Ordóñez.

The structure of the roots of the trees that make up mangroves reinforces this process. The powerful stilt roots of the red mangrove (Rhizophora mangle) trap debris, which ends up becoming even more entangled in the mangrove root system due to the action of the tides. Similarly, the aerial roots (pneumatophores) of black mangroves (Avicennia germinans) and white mangroves (Laguncularia racemosa) also retain debris.

Some plastics can also be remobilized and transported by tidal action to nearby coastal bays or lagoons, or even to the open sea, where they tend to accumulate. “The smallest fragments, or microplastics, can enter marine food webs, a process that also poses a risk to wildlife and, ultimately, to the balance of coastal ecosystems,” says Thiel, executive director of SERC’s MarineGEO programme.

Protecting mangroves, an oasis of life and biodiversity

Rubbish that ends up in mangroves can cover much of the soil and roots, thereby affecting the delicate ecological balance, biodiversity and development of local communities. Fish, crustaceans and birds can become entangled in the litter or accidentally ingest fragments — such as microplastics — which can introduce toxins or pathogenic microorganisms into the food chain.

Avoiding single-use plastic packaging for mass-market products would be one of the most urgent measures to mitigate this environmental problem. In addition to promoting the use of reusable and returnable packaging, it is also essential to improve waste management and promote community education in public environmental protection policies.

“Access to basic sanitation and proper management of waste and other types of refuse are fundamental rights for a dignified life, and a key requirement for protecting coastal ecosystems for present and future generations in Colombia and other countries in the region and around the world,” the authors conclude.

Journal

Environmental Pollution

DOI

10.1016/j.envpol.2025.127550

Method of Research

Observational study

Subject of Research

Not applicable

Article Title

Macrolitter trapping in mangroves: Insights from forest structure and local community knowledge

Large accumulations of litter mixed with propagules and organic matter in the marginal mangrove forest of La Virgen marsh (Cartagena, Colombian Caribbean).

Refrigerator remains deposited in the Smith Channel mangrove swamp on the island of San Andrés (Colombian Caribbean).

Waste dump in the community of Francisco Pizarro, located on the banks of the Patía River (Nariño, Colombian Pacific coast).

Rubbish dump within the mangrove forest in the community of Tierra Bomba Island (Cartagena, Colombian Caribbean).

Seedlings and propagules of the red mangrove growing among rubbish accumulated in their natural habitat in Turbo (Antioquia, Colombian Caribbean).

Deposits of organic material with litter reaching the edge of the mangrove swamp in Turbo Bay (Antioquia, Colombian Caribbean).

Credit

Ostin Garcés – University of Barcelona

Wood, coal, and kitchen fumes: The sources of Sarajevo’s smog have been identified

Paul Scherrer Institute

image:
André Prévôt is a scientist in the PSI Center for Energy and Environmental Sciences. Together with researchers from eight countries, he revealed the sources of Sarajevo’s infamous smog.
view more
Credit: © Paul Scherrer Institute PSI/Markus Fischer

Sarajevo, the 1984 Olympic city, is always good for record-setting – even, unfortunately, when it comes to air pollution. In winter, the skies above the capital of Bosnia and Herzegovina in southeastern Europe are even more heavily polluted with particulate matter than the air in the Chinese capital Beijing. This was shown by the research project SAAERO (Sarajevo Aerosol Experiment), in which researchers from eight countries took part. Besides the Laboratory for Atmospheric Chemistry in the PSI Center for Energy and Environmental Sciences, the University of Nova Gorica, Slovenia, and the Federal Hydrometeorological Institute of Bosnia and Herzegovina played leading roles. At the beginning of 2023, André Prévôt’s team drove through Sarajevo, completing 39 measurement runs within three weeks – through densely populated residential areas on the slopes of the narrow valley, along main traffic arteries, and into the city centre. For this they used PSI’s smog-mobile: a van containing a complete mobile laboratory with state-of-the-art instruments for determining air quality. The results have now been published in the journal Environment International.

“With these mobile measurements we have, for the first time, made it possible to see where particularly high levels of pollution occur,” says Prévôt, who heads the Laboratory for Atmospheric Chemistry at PSI. “In some cases, there are major differences between neighbouring streets.” The researchers were also able to identify the sources: “Heating with solid fuels such as wood and coal in residential areas is the main factor driving up particulate matter concentrations in the evenings,” says Prévôt. Around two-thirds of all measurements exceeded the WHO’s recommended daily limit for particulate matter (PM2.5) of fifteen micrograms per cubic metre. Brief peaks as high as several hundred micrograms per cubic metre were recorded.

Uneven distribution of pollution in the evening

During the day, particulate matter pollution is distributed fairly evenly within the city. In the evenings, concentrations rise sharply in certain districts – especially in residential areas outside the city centre. There, up to 60 percent of the organic particulate matter originates from wood-burning stoves. The PSI team also found high concentrations of polycyclic aromatic hydrocarbons, which are considered carcinogenic.

The air is also polluted in the old town district of Baščaršija in the east of the city. These emissions, however, do not originate from wood heating, but rather from the kitchens of the many restaurants. “Here you always have the smell of grilled meat in your nose,” says PSI team member and study co-author Katja Džepina. There is one advantage for the residents: At night, fresh air flows into the valley from the east, and the levels of pollutants drop faster than in the west.

Sulphur dioxide from old power plants

Another air pollutant is sulphur dioxide. Eighty-one percent of all European emissions of this gas originate in the western Balkans – primarily from old coal-fired power plants dating back to the Soviet era. When the PSI researchers set off from Zurich with their mobile laboratory, sulphur dioxide levels were barely measurable. But as soon as they reached Bosnia and Herzegovina in the Balkans, the levels skyrocketed and remained high, especially in the valleys in and around Sarajevo.

To improve the air quality over Sarajevo, as many buildings as possible would need to be insulated and connected to the gas network. This is not easy everywhere, especially on the hillsides, and therefore a quick solution is not in sight. Along with gas, cleaner pellet heating systems would also be a viable solution.

Thousands of deaths due to air pollutants

This has consequences for health. In an international study published last year in Nature, in which André Prévôt also participated, researchers investigated the toxicity of specific air pollutants. It’s not just the amount of particulate matter that is important; the critical factor is oxidative stress in the lungs, which can trigger respiratory and cardiovascular diseases and lead to premature deaths. Already in this study, Sarajevo was the unenviable leader. Researchers estimate that reducing air pollutants by 50 percent could save 5,000 lives per year in Bosnia and Herzegovina.

André Prévôt recommends making air quality measurements in the western Balkans more consistent by establishing so-called supersites. These are permanent monitoring stations that continuously record air quality data over several years, thus making it possible to compare the measurements. “The region is still inadequately studied,” says Prévôt. In the coming months his team aims to close this gap, at least partially, by analysing additional data from the measurement campaign conducted in early 2023. The researchers want to investigate, among other things, how the concentration of sulphur dioxide changes the chemistry in the atmosphere.

Text: Bernd Müller

PSI’s smog-mobile is a mobile laboratory with state-of-the-art instruments for determining air quality. PSI researchers drove it to Sarajevo to investigate the air pollution there.

Credit

About PSI

The Paul Scherrer Institute PSI develops, builds and operates large, complex research facilities and makes them available to the national and international research community. The institute's own key research priorities are in the fields of future technologies, energy and climate, health innovation and fundamentals of nature. PSI is committed to the training of future generations. Therefore about one quarter of our staff are post-docs, post-graduates or apprentices. Altogether PSI employs 2300 people, thus being the largest research institute in Switzerland. The annual budget amounts to approximately CHF 450 million. PSI is part of the ETH Domain, with the other members being the two Swiss Federal Institutes of Technology, ETH Zurich and EPFL Lausanne, as well as Eawag (Swiss Federal Institute of Aquatic Science and Technology), Empa (Swiss Federal Laboratories for Materials Science and Technology) and WSL (Swiss Federal Institute for Forest, Snow and Landscape Research).