Turning the Tide on Trawls

Bottom trawling, a fishing method that tows heavy, weighted nets and trawl doors along the seabed to catch demersal species, does more than destroy and flatten benthic habitats: by repeatedly resuspending carbon-rich sediments, it accelerates remineralization and weakens the ocean’s role as a carbon sink. Against this backdrop, the International Court of Justice’s Advisory Opinion on Obligations of States in Respect of Climate Change of 23 July 2025 (ICJ AO) is significant: the Court frames states’ climate duties as binding obligations of due diligence, and integrates precaution into that standard (paras 246, 293-294). Critically, the Opinion’s scope covers the “climate system and other parts of the environment.” (para 246). While the Advisory Opinion stops short of prescribing sector-specific tools, it crystallizes binding duties of due diligence, prevention, precaution, and cooperation that apply to the “climate system and other parts of the environment” and operate alongside the law of the sea (ICJ AO paras 94-100, 246, 293-294, 339-345, 457(B)-(D)). Within that architecture, excluding bottom-towed gear in carbon-dense seabeds and Marine Protected Areas is a proportionate way for coastal states to discharge those duties where science shows a serious risk to sedimentary-carbon stores.

In the European regional context, the General Court has upheld area based restrictions on bottom gears in both deep sea closures (joined cases T-681/22 and T-781/22, 11 June 2025) and Marine Protected Area (MPA) measures (T-265/23 VDK v Commission, 21 May 2025), confirming that EU institutions may adopt robust gear controls where science identifies vulnerable habitats and serious risk to the marine environment. This practice illustrates the kind of proportionate response that fits the ICJ’s framework and lowers litigation risk for states that choose to protect seabed carbon and sensitive habitats.

This article aims to demonstrate how the United Nations Convention on the Law of the Sea (UNCLOS) and the International Tribunal for the Law of the Sea’s Advisory Opinion on Climate Change and International Law of 21 May 2024 (ITLOS AO) and regional approaches by the EU and ECtHR complement the ICJ AO’s findings towards developing a global authority for protecting carbon-rich seabeds and a proportional no-trawl rule in carbon-dense areas.

The ICJ’s Findings

The ICJ AO reframes climate protection as a set of binding obligations grounded in multiple sources of international law (here, here, here). In brief: states must exercise due diligence to prevent significant climate harm (paras 132-139, 273-281, 409-410), act with precaution amid scientific uncertainty (paras 158, 293-294), and co-operate in good faith, including with capabilities sensitivity (paras 301-308; 290-292). Compliance with climate treaties does not exhaust or displace obligations under general international law (lex specialis discussion, paras 162-171; relationship of treaty/custom, paras 309-315). Read in this light, protecting carbon sinks, including carbon-rich seabed sediments, sits within states’ required conduct, as the AO’s material scope covers the “climate system and other parts of the environment” (paras 94-100) and its operative clause spells out customary obligations to prevent significant harm and co-operate (operative para 457(B)-(C)).

Three of the AO’s aspects are particularly relevant for ocean policy. First, due diligence is described as a means-oriented and evolutive obligation, calibrated to each state’s capacity and to the best available science, and framed as a stringent duty to do its utmost (paras 273-281, 246, 409-410; operative para 457(B)). This supports adopting stronger protective measures where risk is high and credible alternatives exist. Second, precaution is integrated into that standard: where there is a serious risk of harm, states need not wait for precise quantification before acting (paras 158, 293-294), which is central when sediment-carbon effects are contested in magnitude but clear in direction. Third, cooperation and parallel regimes: the Court confirms that these climate obligations coexist with other regimes, including the law of the sea, and engages UNCLOS Article 192’s duty to “protect and preserve the marine environment” (paras 339-354; operative para 457(D)). Institutionally, this means coastal states can regulate activities in their waters, while regional fisheries bodies (and Union institutions in the EU context) can coordinate broader measures.

The post proceeds to examine how these obligations clarified by the ICJ can be implemented through ocean-law tools—specifically, whether targeted exclusions of bottom-contact gear in carbon-dense MPAs and other sensitive areas can be understood as a proportionate way to discharge due diligence and precaution duties.

Carbon and Why It Matters Legally

The only reason carbon science appears here is that it goes directly to the states’ legal duties. Bottom trawling in carbon-rich seabeds is not just an ecological problem; it interferes with an important climate-regulating function. When trawls disturb fine, organic-rich surface sediments and damage the animals that normally mix and bury this material, more carbon is converted quickly into dissolved inorganic carbon (DIC) instead of being stored in the seabed. Part of that DIC remains in coastal waters for years, contributing to acidification and reducing their capacity to absorb future CO₂.

For our argument, two elements are sufficient and well supported: the direction of impact is clear (disturbance lowers sedimentary carbon stocks and increases DIC), and the risk is concentrated in identifiable, carbon-dense areas. That is enough to trigger the precautionary and due diligence obligations under the law of the sea and general international environmental law. In such areas, states can reasonably justify restricting or prohibiting bottom trawling because lighter measures are unlikely to secure comparable protection of sedimentary carbon.

Using UNCLOS and EU Practice to Develop Concrete Rules

If disturbance of carbon-rich seabed sediments undermines a recognized ecological and climate-regulating function, the issue no longer sits only in the realm of fisheries management. It directly engages states’ existing obligations to protect the marine environment. That is where UNCLOS becomes relevant in a straightforward and defensible way.

Part XII of UNCLOS provides the basic framework. Article 192 lays down the general obligation of all states to “protect and preserve the marine environment”. Article 193 affirms coastal States’ sovereign right to exploit their natural resources but expressly subjects that right to the duty to protect and preserve the marine environment. Article 194, read with subsequent provisions, requires states to take “all measures… necessary to prevent, reduce and control pollution of the marine environment” and other forms of degradation from activities under their jurisdiction or control, including those conducted at sea and on the seabed. Taken together, these provisions do not prescribe any fisheries measure, but they clearly authorize, and, where a serious risk is shown, support the adoption of restrictions or prohibitions on destructive gear where such activities endanger key marine functions, including the integrity of carbon-rich sediments.

Recent advisory jurisprudence reinforces this trajectory. The ITLOS AO interpreted anthropogenic greenhouse gas emissions as “pollution of the marine environment” and articulated corresponding due diligence obligations under UNCLOS Part XII. The ICJ’s Advisory Opinion further underlined states’ precautionary and cooperation duties in responding to climate-related harms affecting the oceans. Although both opinions are formally non-binding, they are highly persuasive in clarifying how existing treaty obligations must be read, considering contemporary scientific knowledge. Read together with UNCLOS Part XII, they support a simple proposition: where credible evidence indicates that a given activity poses a serious risk to marine sinks and stores, such as carbon-dense shelf sediments, states are expected to adopt effective measures to prevent or minimise that harm. Targeted limits or bans on bottom trawling in identified hotspots fall comfortably within that expectation.

At the regional level, EU law offers a concrete illustration of how these obligations can be operationalized. Under the Common Fisheries Policy, Article 11 of Regulation 1380/2013 empowers Member states (and the Commission, through joint recommendations) to adopt fisheries measures necessary to ensure compliance with EU environmental law, including obligations under the Habitats and Birds Directives and the Marine Strategy Framework Directive. Building on this, the European Commission’s 2023 Marine Action Plan calls for the phase-out of mobile bottom fishing in all MPAs by 2030, effectively using Article 11 of Regulation 1380/2013 as the legal vehicle for gear restrictions in sensitive sites. Commission guidance and staff working documents further detail how Article 11 can be employed to design site-specific measures aligned with conservation and ecosystem objectives.

State practice is beginning to follow. Greece has announced bans on bottom trawling in newly designated national marine parks and a phased prohibition across all MPAs by 2030, with boundaries and implementing steps subject to public consultation and formal governmental endorsement. This emerging pattern shows that restricting bottom trawling in biodiversity- and carbon-rich areas is not a speculative or radical use of legal tools. It is a plausible, legally grounded response that fits within UNCLOS Part XII as interpreted in light of current advisory opinions, and within the EU’s own framework for meeting its marine environmental obligations.

Fundamental Rights and Proportionality in the EU and ECHR

Because a carbon-first no trawl rule regulates how people fish, it inevitably engages fundamental rights. In the European regional systems, the proportionality criterion of the EU Charter of Fundamental Rights (CFR) and the property framework of the European Convention on Human Rights (ECHR) give insight as to how this issue could be approached for a global carbon-first no trawl rule.

A prohibition on bottom-towed gear restricts the freedom to conduct a business (EU Charter of Fundamental Rights Article 16) and may affect property/possessions interests (Charter Article 17; ECHR Protocol No. 1 Article 1 (A1P1)). But the Charter’s general limitation clause (Article 52(1)) allows restrictions laid down by law that are necessary and proportionate in pursuit of objectives of general interest, here, a high level of environmental protection (Charter Article 37) and the Union’s precautionary environmental policy (Treaty on the Functioning of the European Union Article 191(2)).

The EU courts’ precautionary line accepts protective measures where risk is plausibly evidenced, even amid scientific uncertainty, so long as institutions examine the science carefully and act consistently with the objective pursued. In Afton (C-343/09), the Court of Justice held that, under the precautionary principle, the EU legislature may adopt protective limits without waiting for full scientific proof, so long as it (i) conducts a comprehensive, best-available-science assessment and (ii) chooses a measure not manifestly inappropriate for the protective aim (paras 60-62, 41-42, 46-50). Applying proportionality, the Court of Justice accepted the limits despite contested technical evidence, noting they were not manifestly disproportionate (paras 68-69). That logic readily extends to excluding bottom-contact gears in carbon- and habitat-sensitive areas: the risk is plausibly evidenced (sediment-carbon loss, DIC increase), authorities can document the science and alternatives considered, and spatial closures are targeted, reviewable, and consistent to protect the marine environment and climate sinks.

Recent judgments confirm that area-based closures to bottom gears can be a necessary tool, and institutions enjoy discretion to choose scientifically advised methodologies for identifying vulnerable zones. On 11 June 2025, the General Court dismissed challenges to the 2022 deep-sea closures (joined cases T-681/22 and T-781/22), rejecting claims that the Commission had to fine-tune measures gear-by-gear. In parallel, the Commission’s Marine Action Plan (2023) calls to phase out mobile bottom fishing in all MPAs by 2030, providing a policy baseline against which “necessity” can be assessed. Where less-restrictive tweaks cannot protect seabed carbon/habitats, a no-trawl rule in defined zones is justified.

Finally, the ECHR’s property case-law consistently affords a wide margin for environmental restrictions: Fredin v Sweden upheld the withdrawal of an extractive license on environmental grounds; Posti and Rahko v Finland accepted fishing restrictions where authorities pursued conservation aims and maintained a fair balance. These strands support the view that spatial gear bans, properly reasoned and time-bounded, strike a proportionate balance between economic interests and environmental/climate imperatives.

Read against existing EU and ECHR case law on precaution, proportionality, and control of use, a carefully designed no trawl rule, adopted by law, grounded in best available science, targeted to mapped carbon and habitat hotspots, reviewed at set intervals, and paired with transition support, fits within Article 52(1) CFR and A1P1 ECHR and provides a secure basis to protect the marine environment and the ocean carbon sink. The same reasoning could guide a global no-trawl rule.

Conclusion

After the Advisory Opinion, treating seabed-carbon protection as a decorative add-on is hard to defend. The ICJ’s account of due diligence, precaution, and cooperation, reinforced by the 2024 ITLOS AO and UNCLOS Part XII, puts states on clear notice that they must take reasonable measures to protect sinks and stores where serious risk is shown, even if the exact tonnage is disputed. In the EU, Article 11 of the Charter of Fundamental Rights and recent General Court judgments offer a ready-made route to exclude bottom-towed gear from carbon-dense MPAs and vulnerable sediments, framed against the Commission’s 2030 phase-out objective.

What remains is not a gap in authority, but a gap in implementation. Drawing credible maps, phasing in closures, enforcing them in practice, and funding fair transitions for affected fleets are all choices that fit comfortably within the legal framework the courts have sketched. A carbon-first no-trawl rule in defined high-risk areas is therefore best read not as overreach, but as an appropriately cautious response to the obligations the law has already made visible.