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Ocean Trawling: An Overlooked Climate and Nature Risk?

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15 December 2022

The world’s oceans are estimated to have absorbed 30% of anthropogenic emissions since the industrial revolution making marine sediments the largest sink of organic carbon on the planet. However, it was recently reported ocean trawling emissions could release up to 1 Gigaton of carbon – almost 3% of global greenhouse gas emissions (39.6 Gigatons). Policy changes may come after COP15 with regards to marine protected areas, potentially extending beyond national jurisdiction, so investors exposed to food retailers, pet foods, supplements or animal feed may need to start preparing for this now.

Some have compared ocean trawling emissions to the size of the aviation sector, though this is hotly debated by academics. However, analysis by FAIRR shows trawling emissions are not currently factored into national or corporate accounting. They could be inaccurately reporting emissions and unable to meet climate and biodiversity goals in future, with implications for investors. Despite net zero commitments and attention to biodiversity, ocean trawling is a topic which has escaped attention up to now.

According to the UK National Atmospheric Emissions Inventory Helpdesk (by email):

“Currently, carbon dioxide fluxes (i.e. sequestration or emissions) from sea, lake and river beds (also referred to as ‘blue carbon’) are not included in the UK national atmospheric emissions inventory. This is primarily driven by the omission of a methodology for estimating these in the IPCC guidelines.”

“The UK can and does estimate emissions and sinks from sources not included in the IPCC guidelines where suitable data and methodologies are identified.”

Most carbon stored in the seabed is in sediments and sits within the Exclusive Economic Zones (EEZs) of countries, providing states with the power to protect them from disruption. However, only 2% are currently located within protected areas where seafloor disturbance is not permitted. Policymakers may begin to address these risks in future ocean policy frameworks. As an example, under the Global Biodiversity Framework to be agreed at COP15, Target 3 proposed to protect 30% of global land and seas, whilst Target 5 calls for ensuring harvesting, trade and use of wild species is sustainable, legal, and safe.

Trawling emissions are neglected

Emissions from trawling seem to be currently neglected in emissions reported by companies. Skretting, the world’s largest producer of feeds for farmed fish, cites vegetable proteins as the largest contributor of emissions within its fish-feed due to land use change and tillage practices (such as ploughing). Trawling is analogous with tillage; it releases carbon from a store, and some fish species cited as being used in feed, for example, sand eels are commonly caught through trawling. Feed producers Cargill and Biomar also state in their annual reporting that sand eels make up 10.9%, and 2.8% of the forage fish used in their feed respectively. Despite this, companies cite the low carbon footprint of marine ingredients, and although this may be true as a generalisation across ingredients, this could be misleading without recognition of trawling emissions. The emissions impact of trawling needs to be accounted for in life-cycle assessments of marine products and currently this does not seem to be the case in reporting from key feed producers. As these emissions factors are likely to be updated once better data is available the carbon footprint from these activities could increase significantly and possibly undermines the accuracy of current TCFD disclosures.

As explained by the NAEI Helpdesk, cited above, calculating emissions from underwater terrain is hindered by complexity, such as “a) the high uncertainty in estimates for CO2 fluxes… b) the challenge in understanding what proportion of these fluxes are anthropogenic… c) the question of territorial boundaries, noting that UK fishing vessels operate outside UK waters, and non-UK fishing vessels operate within UK waters; and, d) reporting systems for inventory reporting do not provide a framework for reporting such fluxes”. These methodological issues may be addressed over time, for example in the next IPCC report.

Like land-based agricultural systems, the aquaculture industry does not have a clear roadmap to reach 1.5˚C. However, increased data accuracy is needed before an effective roadmap can be designed. More cohesion is needed from the sector to give investors’ confidence that climate ambitions will be reached. To draw a parallel with terrestrial farming, efforts toward no-till agriculture could extend into no-till fisheries too. In other words, if we farmed terrestrial land by scraping the surface off the Earth’s surface, it would likely be considered unacceptable

Biodiversity and social emissions of trawling

In addition to emissions, the action of trawling equipment results in severe damage to animal and plant life on the seabed. This varies depending on trawling intensity and sediment type, with trawling impacts ranging between 28-85% in parts of the European continental shelf. Habitats with muddy sediment, like the Mediterranean, tend to experience high trawling pressure with areas off Portugal’s coast and the Mediterranean Sea having the largest trawling footprints. This directly damages organisms and their habitats, alongside the plumes of sediment released from disturbance of the seabed . This particularly impacts coral habitats where trawling equipment damages reefs, with settling sediment inhibiting the feeding of corals and sponges, along with many other cause and effect impacts of dredging on corals.

Corals are of key ecological as well as economic importance acting as a key carbon store and coastal defence but also a nursery for many commercially fished species and a key tourist attraction for many countries. For example, the Mesoamerican Reef which runs from the Yucatan peninsula in Mexico south to Honduras, provides services estimated by the Inter-American Development Bank to have an economic value of over US$4.5 billion annually.

Aside from emissions and biodiversity impacts, trawling is associated with social impacts. Last year, for example, a report by Changing Markets and Greenpeace Africa found the aquaculture and animal feed industry was responsible for taking half a million tonnes of wild-caught fish from the coasts of West Africa with devastating impacts for local communities. In Chile, in 2017, the Government has taken measures to prevent bottom trawling – in recognition of the negative impacts.

FAIRR’s engagement on salmon aquafeed found companies are increasingly focused on reducing greenhouse gas emissions, and disclosures around emissions, but not focused on other risks related to biodiversity. None of the companies in this engagement was able to present investors with a holistic, nature-based approach to reducing impacts on the environment. The trade-offs between a feed basket’s carbon and biodiversity footprints are highly nuanced and complex.

Will policies change in future?

Furthermore, the fishing industry – including trawling – is propped up by subsidies which may change in future. A WTO agreement was reached this year aimed at limiting subsidies which promote illegal, unreported and unregulated fishing (IUU), as well as fishing over-depleted stocks and in unregulated high seas. However, the agreement failed to limit subsidies directed at reducing the operating costs of fishers such as fuel: these being the subsidies which incentivise overfishing, fishery expansion and favour larger vessels.

If subsidies indirectly promote overfishing and unsustainable management of fisheries, they can undermine their own goals, with potential fishery collapse leading to higher prices of marine sourced food and job losses, with the collapse of Atlantic cod stocks in Newfoundland in the 1990s as a prime example. Moving away from capacity-enhancing subsidies towards those that promote better fishery management may provide better returns for governments. For example, improving the monitoring of unreported and unregulated fishing may improve catch rates – representing a possible redirection of government subsidies that can support the fishing industry whilst also protecting fish stocks.

Overall, accounting for the true carbon cost of bottom trawling could lead to a significant rise in current estimates of fisheries emissions. This will have implications not only for the fishing industry’s climate ambitions but will also cascade into the aquaculture industry given the need for wild fish in the feed supply chain. Ocean trawling may pose an overlooked material risk that will need to be addressed to achieve climate and biodiversity goals.