By: Our Correspondent

Marine plastic – the millions of tonnes of discarded bags, bottles, toys, condoms, rubber ducks and any number of other items that flow into the world’s oceans –is having a phenomenal global impact across the entire ecological system, costing in the trillions of lost revenue according to an exhaustive study published this week in the May edition of the Marine Pollution Bulletin.

The pollution “is evidenced to have implications for human health and wellbeing, linked particularly to fisheries, heritage and charismatic species, and recreation,” according to the report, written by 10 marine scientists from Norway and the United Kingdom. The study, which so far has received little notice, is said to be the first of its kind and is built on the volume of plastics in the oceans in 2011.

On a global scale, according to the report, “it has been estimated that for 2011 marine ecosystem services provided benefits to society approximating US$49.7 trillion per year. Most of the values on which this approximation was calculated were based on maximum sustainable use (actual or hypothetical) of natural (or semi-natural) systems, reflecting functioning biomes with minimal anthropogenic disruption.

“While limitations in its accuracy are acknowledged, this figure is considered to provide sufficient precision for global analysis and an estimate of the decline in its value, due to the presence of marine plastic, can be taken as a first order approximation of an economic cost.

Positing a decline of 1 percent to 5 percent decline in marine ecosystem service delivery because of pollution by marine plastic “equates to an annual loss of US$500 billion to US$2.500 trillion in the value of benefits derived from marine ecosystem services,” the researchers calculate.

With the 2011 stock of plastic in the marine environment having been estimated between 75 and 150 million tonnes, this would equate under 2011 levels of marine plastic pollution and based on 2011 ecosystem services values to each tonne having an annual cost in terms of reduced marine natural capital of between US$3,300 and US$33,000.

“This postulation of an economic cost relates only to the impacts of marine plastic on marine natural capital and as such represents a ‘lower bound’ of the full economic costs of marine plastic,” according to the research. “This figure does, however, illustrate the potential order of magnitude of the impacts.”

An estimated 4.8 million to 12.7 tonnes of plastics entered the marine environment from land-based sources alone in that year, according to an abstract of the study, “and the flux of plastics to the oceans is predicted to increase by an order magnitude within the next decade.

Five gigantic “gyres” of plastic whirled together by ocean currents exist across the world, including the “Great Pacific garbage patch, also described as the Pacific trash vortex in north central Pacific Ocean that is the size of France, Belgium, and Switzerland combined. It has famously been estimated that unless radical steps are taken plastics in the ocean will outweigh the volume of fish by 2050.

While, over time, this plastic may fragment into small pieces, referred to as “microplastics,” the vast majority of it “is expected to persist in the environment in some form over geological time.” Depressingly, “although removing some marine plastic is possible, it is time-intensive, expensive, and inefficient.”

While research on plastic pollution has been growing exponentially over the past decade, according to the researchers, there is poor understanding of the effects and resultant impact on ecosystem services, and in turn its bearing on human wellbeing, society and the economy. It is, however, a global issue

The impacts on birds, fish, mammals, and turtles were subdivided into ingestion and entanglement with a demonstrating that “there is global evidence of impact with medium to high frequency on all subjects, with a medium to high degree of irreversibility. The majority of these impacts are negative with the exception of algae and bacteria. In this case, the plastic increases the range of habitats available for colonization and enables the spread of these species to new areas, thus increasing their range and abundance.

Globally, seafood is the principal source of animal protein and makes up more than 20 percent of food intake by weight for 1.4 billion people, 19 percent of the global population. Marine plastic has the potential to reduce the efficiency and productivity of commercial fisheries and aquaculture through physical entanglement and damage but also by posing a direct risk to fish stocks.

Plastic is frequently ingested by a wide range of marine species, including those directly vital to food provision such as shellfish and fish at all stages of their lifecycle. This plastic can be ingested directly from the environment, or indirectly consumed via plastic contaminated prey

Polymers are typically rich in additives such as plasticizers, biocides, flame retardants, and once in the marine environment can readily concentrate microbial pathogens and toxic persistent organic pollutants such as dichlorodiphenyltrichloroethane and polycyclic aromatic hydrocarbons. These pollutants can accumulate in the tissues of marine animals and biomagnify in higher predators including humans.

“The contamination of the food chain with plastic and associated contaminants puts fish and shellfish stocks, and their prey, at risk of lethal and sub-lethal harm including diminished reproductive success and growth, with capacity for population level impacts.”

That means consumption of marine plastic by humans “will occur when the entirety of a contaminated organism, including the gut, is eaten in such seafood as mussels, oysters, sprats, anchovies. It then may also exacerbate the concentrations of persistent organic pollutants in the flesh of shellfish and fish, posing an additional risk to consumers.”

“Overall, our evidence suggests that the productivity, viability, profitability and safety of the fishing and aquaculture industry is highly vulnerable to the impact of marine plastic, particularly when coupled with broader factors including climate change and over-fishing,” the researchers found. “The high dependency on seafood for nutrition leaves the wellbeing of a significant proportion of the world’s population highly vulnerable to any changes in the quantity, quality and safety of this food source.”

Beyond the immediate ecological impacts documented here, the presence of plastic has the potential to dramatically shift the ecology of marine systems, according to the research. An altered environment and shifts in biodiversity can have potentially wide-reaching and unpredictable secondary societal consequences, not least through impairing the ecosystem resilience and recovery potential in a time of global change.

Plastics are a stressor, which can act in concert with other environmental stressors such as those arising from other pollutants, changing ocean temperatures, ocean acidification, and the over exploitation of marine resources. The cumulative impacts of these stressors may result in marine plastic causing far greater damage than suggested here.

Marine plastic has been linked to increased rates of invasive species and unprecedented rates of species dispersal using man-made flotsam have been documented, including an estimate that marine plastic has doubled organisms’ opportunities for dispersal in the tropics (Barnes, 2002). This additional impact is not included in this analysis, but has clear potential for causing substantial ecological, social, and economic consequences.

“We recognize that the economic cost presented here is an underestimate as there are broader social and economic costs that need to be quantified and included, for example, direct and indirect impacts on the tourism, transport and fisheries sectors as well as on human health,” the researchers say

Second, “the economic cost presented here is an average per tonne of plastic, while in reality the cost per tonne will vary depending on the place of emission, where it moves to and accumulates, its size and type, and the amount already in the ecosystem. Each tonne of marine plastic is therefore likely to have a cost that is either greater or smaller than the average since plastic is not ‘perfectly mixing’. Plastic emissions, accumulation and resultant ecological damage will be spatially heterogeneous and this must be considered in the development and use of any cost per tonne value for plastic.

Third, “since this cost per tonne value is a global average, it is not equivalent to the notion that every future tonne added to this stock will have a similar average cost. It is possible that the damage cost of each marginal tonne will increase, meaning the relationship between the cost per tonne value and increasing amounts of marine plastic is unlikely to be linear. Since we cannot from our current knowledge determine the rate of this increase, a key recommendation for further research is to understand better the marginal damage cost of each additional tonne of marine plastic entering the oceans, so as to be able to calculate future total costs.

A final complication with regard to plastic is that one piece goes through different ‘life stages’, from macro to micro, with accumulation and disassociation of toxins and biological material, and ideally these changes should be incorporated within any cost per tonne value attributed to plastic.”