Bottom trawling, a common but controversial commercial fishing technique, has been discovered to release substantial amounts of carbon dioxide into the ocean and atmosphere. A new study published this week reveals bottom trawling’s large contribution to global carbon emissions, sparking calls for greater regulation and reform of the fishing industry.
What is Bottom Trawling?
Bottom trawling, also called seabed or benthic trawling, is a fishing method that involves dragging heavy nets across the seafloor to catch species like cod, sole, and plaice. The nets are held open by large, weighted beams and equipped with rollers and chains that plow through the sediment on the ocean floor.
This technique is used extensively around the world, accounting for up to 40% of global wild catches. Bottom trawling is popular because it can catch large volumes of fish in a short period of time. However, it has long been criticized by conservationists for its severe environmental impacts.
Dragging equipment across the seabed damages marine ecosystems by:
- Crushing, burying, and exposing marine organisms and habitats
- Reducing structural complexity and biodiversity
- Impairing seafloor integrity and food availability
- Releasing carbon stored in seafloor sediments
These effects reduce the ocean’s ability to regulate climate and support fisheries. Many countries have implemented restrictions on bottom trawling to mitigate ecological damage, but the practice remains widespread due to high commercial demand for groundfish like cod and sole.
Study Finds Major Carbon Emissions from Bottom Trawling
This week, a research team led by scientists at the National Oceanography Centre published a study revealing that bottom trawling emits far more carbon dioxide into the ocean and atmosphere than previously estimated.
Analyzing sediment samples from trawled and untrawled areas off the UK coast, the researchers found trawling disturbs carbon stored in seafloor sediment, releasing it into the marine environment. They calculated bottom trawling in their North Sea study area emits 6.8 million tons of CO2 annually, which is equivalent to the yearly carbon footprint of nearly 1 million cars.
“Our research shows bottom trawling is a far bigger contributor to carbon emissions than we previously recognized,” said lead author Pippa Moore. “It needs to be considered and accounted for in climate models and calculations of national carbon budgets.”
|Annual CO2 Released (million tons)
|Study Area Bottom Trawling
|Yearly Carbon Footprint of 1 Million Cars
The authors emphasize bottom trawling likely releases 10s to 100s of millions of tons of CO2 globally each year. When scaled up, they estimate carbon emissions from bottom trawling worldwide represents up to 5-20% of the total carbon footprint of global commercial fishing – a startling figure.
“Considering the vast scale of bottom trawling around the world, it’s clear we’ve uncovered an enormous yet overlooked source of carbon emissions further accelerating climate change,” said Moore.
Calls to Reform Destructive Fishing
Publication of this study has intensified demands from scientists and advocacy groups to reform industrial fishing and restrict harmful methods like bottom trawling.
Many experts argue this new evidence shows bottom trawling’s climate impacts are far too big to ignore, and tougher regulations or even bans are warranted to mitigate CO2 emissions and protect marine ecosystems.
Conservation organization Blue Ventures called on governments to recognize bottom trawling as a major source of CO2 pollution and take steps to reduce trawling capacity and effort. Others like Greenpeace advocate transitioning from industrial trawling to more sustainable fishing techniques like hook and line or pot/trap fishing.
Many predict this study will lead to growing public pressure and policy action around reforming commercial fishing as part of strategies to slow climate change and ocean decline. Reducing bottom trawling has now clearly become an important piece in the puzzle.
However, transitioning away from bottom trawling will be economically and politically challenging. The fishing industry argues tighter restrictions on trawling would threaten jobs and global food supply, a contention experts debate. As one fisheries economist notes, balancing these complex tradeoffs will require nuanced policy solutions.
What Happens Next?
In the wake of this study, immediate next steps will likely involve conducting more research to refine global estimates of carbon emissions from seabed trawling. Integrating these CO2 contributions into models and carbon budgets will also be critical for properly accounting for bottom trawling’s climate impacts.
We can also expect growing activism and policy proposals aimed at reforming commercial fishing to be less destructive and carbon intensive. However there are complex social, economic, and political barriers that have long impeded transforming industrial fishing. It remains unclear if regulators will enact bold enough policy changes quickly enough to adequately address the climate and conservation issues highlighted by this new bottom trawling research.
Over the longer term, this study will hopefully accelerate momentum towards fishing more sustainably and protecting marine ecosystems vital for supporting livelihoods and regulating climate. How rapidly the fishing industry and global community choose to respond to these troubling findings will impact whether bottom trawling continues exacerbating or starts mitigating environmental decline. Addressing the global environmental costs now visible may compel much needed reform of destructive industrial fishing practices.
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