We analysed data from 29,798 clean-ups around the world to uncover some of the worst litter hotspots

Shutterstock

Lauren Roman, CSIRO; Britta Denise Hardesty, CSIRO, and Chris Wilcox, CSIROCoastal litter is a big environmental problem. But how does this litter differ around the world, and why? In the first global analysis of its kind, we set out to answer those questions using data collected by thousands of citizen scientists.

Our analysis, released today, discovered litter hotspots on every inhabited continent, including Australia. This finding busts two persistent myths: that most of the world’s plastic pollution comes from just a few major rivers, and that countries in the Global South are largely to blame for the marine plastic problem.

Single-use plastics formed the majority of litter in this study. And in general, litter hotspots were associated with socioeconomic factors such as a concentration of built infrastructure, less national wealth, and a high level of lighting at night.

Our insights reveal the complex patterns driving coastal pollution, and suggest there is no “one size fits all” solution to cleaning up the world’s oceans. In fact, the best solution is to stop the waste problem long before it reaches the sea.

This study analyses the data collected by hundreds of thousands of citizen scientists conducting clean-ups worldwide.
Copyright PADI AWARE

A complex picture

We are scientists from the CSIRO’s Marine Debris Research team. Our study involved working closely with Ocean Conservancy and the PADI AWARE Foundation, which together hold the world’s most comprehensive litter data sets gathered by citizen scientists.

We analysed hundreds of thousands of items from 22,508 clean-ups on land (at beaches and the edge of rivers and lakes) as well as 7,290 seafloor clean-ups. The clean-ups spanned 116 and 118 countries, respectively, and involved participants recording counts for each item collected.

The analysis showed a huge diversity in the location and scale of plastic pollution hotspots. They were not limited to single countries or rivers – instead, the hotspots occurred in all inhabited continents and across many countries. In many places, litter patterns between neighbouring locations were vastly different.

---

Read more:
For decades, scientists puzzled over the plastic ‘missing’ from our oceans – but now it’s been found

---

Most litter comprised single-use items: cigarette butts, fishing line, food wrappers, and plastic bottles and bags.

In general, places with more overall litter tended to have:

• more built infrastructure
• less national wealth
• bright lighting at night (which indicated urban density).

Cities and other dense urban areas around the world were linked with hotspots of “convenience” single-use plastic items, such as plastic bags, food wrappers, drink bottles, take-away containers, straws, plastic cutlery and lids. These hotspots are represented in the infographic below.

---

---

However, not all litter items followed this pattern. For example, cigarette butts followed a regional pattern and were more common in Southern Europe and North Africa.

Fishing line was most abundant in wealthier countries where recreational fishing is a popular pastime. Hotspots included Australia, the United Kingdom and the United States.

Clusters of hotspots were often associated with partially enclosed bays, seas and lakes. These included areas such as the Mediterranean Sea, the Bay of Bengal, the South China and Philippine seas, the Gulf of Mexico, the Caribbean Sea, Lake Malawi and the Great Lakes of North America.

Plastic accumulation in these areas is likely due to factors such as high local littering combined with relatively contained bodies of water.

Plastic bottle hotspots were more common in tropical countries such as Costa Rica and Jamaica, among others. Plastic food wrappers were abundant in the island nations of Southeast Asia, particularly around Indonesia and the Philippines.

---

Read more:
It might be the world’s biggest ocean, but the mighty Pacific is in peril

---

Australia contained several global hotspots for fishing line waste.
Shutterstock

Cleaning up our coasts

Ultimately, our study reveals the diversity and complexity of the plastic pollution issue. We hope it helps governments make waste policy decisions based on sound scientific evidence.

The findings suggest programs to tackle ocean litter should be rolled out at the grassroots level, or within one part of a country, as well as nationally.

In Australia, for example, Zoos Victoria’s Seal The Loop program aims to tackle localised fishing line waste at locations where the pastime is common. The program includes fishing line bins placed on piers and at boat ramps to encourage responsible waste disposal.

And in Malawi and 15 other countries in southern Africa, national bans on plastic bags target this locally problematic item.

Our analysis shows much non-degradable waste found in the environment comes from pre-packaged food and beverages. So regulations specifically addressing this type of packaging can be useful.

In Australia, for example, Hobart is aiming to become the first Australian city to ban single-use plastic takeaway food packaging, as part of an ambitious goal of zero-waste to landfill by 2030.

Other strategies known to change litter behaviour include recycling incentives such as container deposit schemes, particularly in lower socioeconomic areas where littering is highest, as well as education campaigns. And levies on plastic items could also help stop litter entering the environment.

This Saturday September 18, Ocean Conservancy is holding its annual International Coastal Cleanup – come along if you can and if COVID restrictions allow. You’ll be helping your local environment and collecting data to inform tomorrow’s waste management policies.

Land-based clean-ups were conducted across 116 countries. Please join us for the next one.
Rafeed Hussain Ocean Conservancy

---

The authors would like to acknowledge the tireless volunteers from the International Coastal Cleanup and Dive Against Debris, and collaborators; Ocean Conservancy’s Dr George H. Leonard and Nicholas Mallos, and PADI AWARE Foundation’s Hannah Pragnell-Raasch and Ian Campbell.

Lauren Roman, Postdoctoral Researcher, Oceans and Atmosphere, CSIRO; Britta Denise Hardesty, Senior Principal Research Scientist, Oceans and Atmosphere, CSIRO, and Chris Wilcox, Senior Principal Research Scientist, CSIRO

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Advertisement

Seafloor currents sweep microplastics into deep-sea hotspots of ocean life

A rockfish hides in a red tree coral in the deep sea.
Geofflos

Ian Kane, University of Manchester and Michael Clare, National Oceanography Centre

What if the “great ocean garbage patches” were just the tip of the iceberg? While more than ten million tonnes of plastic waste enters the sea each year, we actually see just 1% of it – the portion that floats on the ocean surface. What happens to the missing 99% has been unclear for a while.

Plastic debris is gradually broken down into smaller and smaller fragments in the ocean, until it forms particles smaller than 5mm, known as microplastics. Our new research shows that powerful currents sweep these microplastics along the seafloor into large “drifts”, which concentrate them in astounding quantities. We found up to 1.9 million pieces of microplastic in a 5cm-thick layer covering just one square metre – the highest levels of microplastics yet recorded on the ocean floor.

While microplastics have been found on the seafloor worldwide, scientists weren’t sure how they got there and how they spread. We thought that microplastics would separate out according to how big or dense they were, in a similar manner to natural sediment. But plastics are different – some float, but more than half of them sink.

---

Read more:
Pristine Antarctic fjords contain similar levels of microplastics to open oceans near big civilisations

---

Plastics which once floated can sink as they become coated in algae, or if bound up with other sticky minerals and organic matter. Recent research has shown that rivers transport microplastics to the ocean too, and laboratory experiments revealed that giant underwater avalanches of sediment can transport these tiny particles along deep-sea canyons to greater depths.

We’ve now discovered how a global network of deep-sea currents transports microplastics, creating plastic hotspots within vast sediment drifts. By catching a ride on these currents, microplastics may be accumulating where deep-sea life is abundant.

Once plastic debris has broken down and sinks to the ocean floor, currents sweep the particles into vast drifts.
Ian Kane, Author provided

From bedroom floors to the seafloor

We surveyed an area of the Mediterranean off the western coast of Italy, known as the Tyrrhenian Sea, and studied the bottom currents that flow near the seafloor. These currents are driven by differences in water salinity and temperature as part of a system of ocean circulation that spans the globe. Seafloor drifts of sediment can be many kilometres across and hundreds of metres high, forming where these currents lose their strength.

We analysed sediment samples from the seafloor taken at depths of several hundred metres. To avoid disturbing the surface layer of sediment, we used samples taken with box-cores, which are like big cookie cutters. In the laboratory, we separated microplastics from the sediment and counted them under microscopes, analysing them using infra-red spectroscopy to find out what kinds of plastic polymer types were there.

A microplastic fibre seen under a microscope.
Ian Kane, Author provided

Most microplastics found on the seafloor are fibres from clothes and textiles. These are particularly insidious, as they can be eaten and absorbed by organisms. Although microplastics on their own are often non-toxic, studies show the build-up of toxins on their surfaces can harm organisms if ingested.

These deep ocean currents also carry oxygenated water and nutrients, meaning that the seafloor hotspots where microplastics accumulate may also be home to important ecosystems such as deep-sea coral reefs that have evolved to depend on these flows, but are now receiving huge quantities of microplastics instead.

What was once a hidden problem has now been uncovered – natural currents and the flow of plastic waste into the ocean are turning parts of the seafloor into repositories for microplastics. The cheap plastic goods we take for granted eventually end up somewhere. The clothes that may only last weeks in your wardrobe linger for decades to centuries on the seafloor, potentially harming the unique and poorly understood creatures that live there.

Ian Kane, Reader in Geology, University of Manchester and Michael Clare, Principal Researcher in Marine Geoscience, National Oceanography Centre

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Guns, snares and bulldozers: new map reveals hotspots for harm to wildlife

Human activity threatens many species across Africa’s savannahs.
Paul Mulondo/WCS, Author provided

James Allan, The University of Queensland; Christopher O’Bryan, The University of Queensland, and James Watson, The University of Queensland

The biggest killers of wildlife globally are unsustainable hunting and harvesting, and the conversion of huge swathes of natural habitat into farms, housing estates, roads and other industrial activities. There is little doubt that these threats are driving the current mass extinction crisis.

Yet our understanding of where these threats overlap with the locations of sensitive species has been poor. This limits our ability to target conservation efforts to the most important places.

---

Read more:
Earth’s wilderness is vanishing, and just a handful of nations can save it

---

In our new study, published today in Plos Biology, we mapped 15 of the most harmful human threats – including hunting and land clearing – within the locations of 5,457 threatened mammals, birds and amphibians globally.

We found that 1,237 species – a quarter of those assessed – are impacted by threats that cover more than 90% of their distributions. These species include many large, charismatic mammals such as lions and elephants. Most concerningly of all, we identified 395 species that are impacted by threats across 100% of their range.

Mapping the risks

We only mapped threats within a species location if those threats are known to specifically endanger that species. For example, the African lion is threatened by urbanisation, hunting and trapping, so we only quantified the overlap of those specific hazards for this species.

This allowed us to determine the parts of a species’ home range that are impacted by threats and, conversely, the parts that are free of threats and therefore serve as refuges.

We could then identify global hotspots of human impacts on threatened species, as well as “coolspots” where species are largely threat-free.

The fact that so many species face threats across almost all of their range has grave consequences. These species are likely to continue to decline and possibly die out in the impacted parts of their ranges. Completely impacted species certainly face extinction without targeted conservation action.

Conversely, we found more than 1,000 species that were not impacted by human threats at all. Although this is positive news, it is important to note that we have not mapped every possible threat, so our results likely underestimate the true impact. For example, we didn’t account for diseases, which are a major threat to amphibians, or climate change, which is a major threat to virtually all species.

Hotspots and coolspots

We produced the first global map of human impacts on threatened species by combining the parts of each species range that are exposed to threats.
The overwhelmingly dominant global hotspot for human impacts on threatened species is Southeast Asia.

This region contains the top five countries with the most threats to species.
These include Malaysia, Brunei, Singapore, Indonesia and Myanmar.

The most impacted ecosystems include mangroves and tropical forests, which concerningly are home to the greatest diversity of life on Earth.

Hotspots of threats and threatened species richness.
Allan et al. Plos Biol., Author provided

We also created a global map of coolspots by combining the parts of species ranges that are free from human threats. This map identifies the last vestiges of wild places where threatened species have shelter from the ravages of guns, snares and bulldozers. As such, these are crucial conservation strongholds.

Coolspots include parts of the Amazon rainforest, the Andes, the eastern Himalayas, and the forests of Liberia in West Africa.

In many places, coolspots are located near hotspots. This makes sense because in species-rich areas it is likely that many animals are impacted whereas many others are not, due to their varying sensitivity to different threats.

Coolspots of unimpacted species richness.
Allan et al. Plos Biol., Author provided

What next?

There is room for optimism because all the threats we map can be stopped by conservation action. But we need to make sure this action is directed to priority areas, and that it has enough financial and political support.

An obvious first step is to secure threat-free refuges for particular species, via actions such as protected areas, which are paramount for their survival.

---

Read more:
An end to endings: how to stop more Australian species going extinct

---

To ensure the survival of highly impacted species with little or no access to refuges, “active threat management” is needed to open enough viable habitat for them to survive. For example, tiger numbers in Nepal have doubled since 2009, mainly as a result of targeted anti-poaching efforts.

Tackling threats and protecting refuges are complementary approaches that will be most effective if carried out simultaneously. Our study provides information that can help guide these efforts and help to make national and global conservation plans as successful as possible.

---

The authors acknowledge the contributions of Hugh Possingham, Oscar Venter, Moreno Di Marco and Scott Consaul Atkinson to the research on which this article is based.

James Allan, Postdoctoral research fellow, School of Biological Sciences, The University of Queensland; Christopher O’Bryan, PhD Candidate, School of Earth and Environmental Sciences, The University of Queensland, and James Watson, Professor, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.