The Shadow Fleet Crisis: When Ocean Conservation Meets Global Security

An unprecedented maritime environmental threat demands urgent, coordinated action.

By Mark J. Spalding, J.D.

In the vast expanse of our global ocean, a new environmental crisis is unfolding that demands immediate attention from the conservation community. This crisis, while still in its early stages, presents a critical opportunity for proactive intervention before it escalates into a catastrophic threat to marine ecosystems worldwide.

More than 700 aging, poorly maintained tankers carrying millions of barrels of oil now operate in the shadows of international law, representing approximately 17% of all international tankers.

Bilateral and multilateral sanctions targeting specific countries, geographic regions, entities, and individuals have created an unintended consequence: the rapid growth of a “global shadow fleet.” This shadow fleet represents not only a significant portion of international shipping but also a growing risk of major spills due to the lack of maintenance, inspection, and insurance.

As someone who has spent decades working on ocean policy, I find this emerging threat both alarming and indicative of how quickly new environmental risks can emerge when geopolitical tensions intersect with maritime vulnerabilities. The shadow fleet problem illustrates the urgent need for innovative conservation approaches that can address hybrid security-environmental challenges transcending traditional boundaries.

The Scope of an Emerging Crisis

The numbers tell a sobering story that demands immediate action. Russia’s shadow fleet has expanded from fewer than 100 vessels in February 2022 to 343 vessels today, with approximately 77% of those vessels sanctioned by Western authorities following Russia’s violation of international law when it invaded Ukraine and violated Ukrainian sovereignty. When we include vessels from Iran, North Korea, and Venezuela operating under various sanctions regimes, the total reaches approximately 1,700 aging vessels—a threefold increase since sanctions were first imposed.

Regular crew changes occur on average about every four to twelve months, and often ships can be resupplied, fueled, and even serviced at the same time. As you may recall, COVID-19 significantly affected the global supply chain. You may not remember the accompanying shipping crew change disruptions. Just 25% of regular crew changes occurred in the period from March through August 2020. Four hundred thousand seafarers were stranded at sea. They could not be landed in ports due to public health restrictions and were unable to return home due to travel limitations and quarantine requirements. The resulting labor shortage and schedule disruptions prompted operators to adopt less regulated employment practices and cut costs on maintenance, inspection, and equipment replacement—contributing to the very conditions that make shadow fleet operations both possible and dangerous.

These vessels average 16.8 years in age, operate without adequate insurance, frequently reject professional navigation assistance, and exist largely outside maritime safety regulations.

Before Russia invaded Ukraine, vessels more than twenty years old comprised just 3% of the global tanker fleet. Their share is expected to rise to 11% by 2025, representing what experts call “a ticking time bomb” for marine environments worldwide.

Understanding Vessel Sanctions

Vessels enter the shadow fleet through various pathways, often beginning with the sanctioning of their owners, operators, or the cargo they carry. Sanctions are typically imposed when vessels are found to be transporting goods from sanctioned countries, particularly oil and petroleum products that fund destabilizing activities. U.S. persons are generally prohibited from engaging in transactions with blocked persons, as well as transactions involving Iranian-origin petroleum, petroleum products, and petrochemical products. In addition, non-U.S. persons are prohibited from causing or conspiring to cause U.S. persons to wittingly or unwittingly violate U.S. sanctions, as well as engaging in conduct that evades U.S. sanctions.

The enforcement of these sanctions has been substantial and accelerating. For example, in December 2024, February 2025, March 2025, and April 2025, the U.S. Department of the Treasury’s Office of Foreign Assets Control (OFAC) sanctioned a total of 86 individuals and entities in more than 25 countries and identified 85 tankers as blocked property involved in the shipment and sale of millions of barrels of Iranian oil. In February 2025, March 2025, and April 2025, the Department of State sanctioned a total of 16 entities and identified 13 tankers as blocked property.

Violations of Iran sanctions could result in civil enforcement actions or criminal penalties for persons or transactions subject to U.S. jurisdiction. OFAC has pursued civil enforcement actions against several shipping and logistics companies, some resulting in significant monetary penalties, for violations of U.S. sanctions. For example, in January 2022, April 2024, and December 2024, OFAC took enforcement action against non-U.S. persons in Asia and Europe for conduct involving evasive shipping practices in the Iranian petrochemical industry.

The pattern is clear: aging vessels, poor maintenance, rejected safety protocols, and environmental incidents that coastal states must clean up at their own expense, all while operating outside traditional oversight systems.

A Conservation Community Awakening

The ghost fleet is not operating entirely unmonitored. There are organizations working to highlight the breadth and depth of the present and potential harm to the ocean and coasts from an aging, poorly maintained, secretively operating fleet of ships carrying millions of gallons of oil.

SkyTruth, a nonprofit organization that uses satellite imagery and remote sensing technology to expose environmental threats, has emerged as a crucial technical partner in documenting environmental risks associated with the shadow fleet. Using sophisticated imagery analysis to track pollution incidents that would otherwise go undetected in remote ocean areas, SkyTruth’s ability to combine satellite data with vessel tracking information represents precisely the kind of technical innovation needed to monitor and document environmental violations by vessels designed to operate outside traditional oversight systems. Their satellite monitoring capabilities provided the evidence for the landmark 2024 POLITICO and SourceMaterial investigation, which revealed at least nine oil spills from shadow fleet vessels since 2021, in locations worldwide, including Thailand and Scotland. Greenpeace has highlighted the risks in European waters, even painting “Oil fuels war. People want peace” on shadow vessels conducting dangerous ship-to-ship transfers of oil.

We have a limited window of opportunity to proactively address this emerging crisis before the potential spills, the potential groundings, and the potential sinkings all cause irreversible environmental and economic harm, not to mention tragic loss of life. To date, no organization has taken the lead. This absence of dedicated environmental leadership reflects a broader challenge in ocean conservation. Our field has evolved around relatively stable threats, such as overfishing, pollution, and habitat destruction, all of which can be addressed through established policy frameworks and enforcement. We’re less equipped to address rapidly evolving hybrid threats that blur the lines between environmental protection, maritime security, and international law. The shadow fleet crisis demands expertise in sanctions policy, maritime law, satellite monitoring, and international diplomacy—skill sets that don’t typically overlap in environmental organizations or government agencies.

Thus, it is clear that we need to tap our collective experience and identify ways to build a multi-pronged strategy quickly that can help us address the ghost fleet problem and lay the groundwork for addressing similar hybrid threats in the future.

International Frameworks Under Stress

The United Nations and other multilateral organizations designed to address maritime risks face structural limitations that the shadow fleet crisis exposes starkly. The International Maritime Organization adopted Resolution A.1192(33) in December 2023, targeting “dark fleet” tankers, but as a UN specialized agency, it can only urge member states to act—it lacks enforcement authority. When leading nations like Russia and Iran openly undermine the maritime order, global consensus becomes challenging.

Similarly, the United Nations Convention on the Law of the Sea provides both the legal foundation for ocean governance and the constraints that complicate enforcement. UNCLOS guarantees “innocent passage” through territorial waters, meaning shadow vessels cannot be denied access unless they pose “a concrete and immediate threat”—a standard nearly impossible to meet proactively for environmental protection.

The European Union has emerged as the most proactive force, with the European Maritime Safety Agency operating 20 pollution response vessels and monitoring systems that provide detection and response capabilities most nations lack. The EU’s recent sanctions package targeting 189 shadow fleet vessels represents the most significant coordinated action to date. This European leadership highlights the potential for coordinated international action and the need for all sanctioning nations to follow through on the environmental consequences of their policies.

The Need for Global Ocean Statesmanship

The shadow fleet crisis calls for a new model of international cooperation—one that recognizes the interconnectedness of security, economic, and environmental challenges. The nations that initially imposed sanctions—primarily the United States, European Union, United Kingdom, Canada, and Australia—bear particular responsibility for addressing the environmental consequences of their policies. However, this is not solely their burden; it requires global ocean statesmanship from all maritime nations.

The challenge demands sustained, technical, multilateral cooperation. We need satellite monitoring systems, coordinated enforcement mechanisms, shared intelligence on vessel movements, harmonized legal frameworks, and patient diplomatic engagement with flag states and port authorities. Most fundamentally, we need reliable international partnerships that can sustain long-term environmental protection efforts despite changing political landscapes.

Strategies to Counter the Shadow Fleet Threat

Several promising approaches are emerging to address the shadow fleet crisis:

Enhanced Monitoring and Detection: Advanced satellite technology, artificial intelligence-powered vessel tracking, and collaborative intelligence sharing can identify suspicious vessel behavior and track oil spills in real-time. Organizations like SkyTruth demonstrate how technological innovation can expose environmental violations.

Port State Controls: Coastal nations can refuse entry to suspicious vessels, demand proof of insurance, and require comprehensive documentation of cargo origin. The EU’s approach of denying port access to vessels that turn off their AIS trackers provides a model for other regions.

Financial Pressure: Targeting insurance providers, financiers, and service providers that enable shadow fleet operations can significantly increase operational costs and risks for these vessels. Insurance companies that support the transport of Iranian cargo for the Iranian regime and its proxies are subject to sanctions risk.

Flag State Accountability: Encouraging flag states to participate in information-sharing compacts and maintain higher standards for vessel registration can reduce the availability of “flags of convenience” for shadow fleet operations.

International Legal Frameworks: Developing new international agreements specifically addressing environmental risks from sanctions-evading vessels, building on existing maritime law while closing regulatory gaps.

A Model for Institutional Response: Beyond Traditional Approaches

Addressing the environmental crisis of the shadow fleet requires innovative institutional frameworks that bridge the gap between international standard-setting and effective environmental protection. The model that emerges from initiatives like Project Tangaroa demonstrates how multi-stakeholder collaboration can be effectively implemented in practice.

This approach emphasizes several key elements: standardized assessment protocols that allow different nations and organizations to evaluate environmental risks using compatible methodologies; proactive risk management that identifies and addresses potential environmental threats before they become disasters; technical excellence that combines cutting-edge monitoring technology with established maritime expertise; and enforcement mechanisms that operate through coordinated action by willing partners rather than relying on universal consensus.

How does this interconnected approach improve environmental safety? By creating redundant monitoring and response systems, sharing real-time intelligence about vessel movements and environmental risks, and enabling rapid coordinated responses when incidents occur. Instead of relying on individual nations to detect and respond to threats within their waters, this model creates a network effect where environmental protection capabilities are multiplied through cooperation.

What constitutes proactive risk management in this context? It means identifying high-risk vessels before they cause environmental damage, tracking their movements through international waters, assessing their mechanical condition and cargo, and positioning response resources in areas where incidents are most likely to occur. This is fundamentally different from reactive cleanup efforts that begin only after spills have occurred.

Who provides enforcement mechanisms and where? Enforcement operates through coordinated action by participating nations within their respective jurisdictions, port state controls that deny services to high-risk vessels, financial sector cooperation that restricts insurance and financing for shadow fleet operations, and flag state cooperation that removes vessels from registries when environmental or safety violations are detected.

How can the problem be addressed systematically? Through a combination of technological innovation (satellite monitoring, AI-powered risk assessment), legal frameworks (harmonized international standards, bilateral cooperation agreements), economic pressure (sanctions on enablers, insurance requirements), and diplomatic engagement (flag state cooperation, port state coordination). Success requires sustained commitment from multiple stakeholders working in parallel rather than waiting for a comprehensive global agreement.

This model has successfully convened international experts, developed technical standards, and created frameworks that participating nations can adapt to their specific circumstances while maintaining compatibility with broader international efforts. The shadow fleet environmental crisis presents similar challenges but at a much larger scale and with greater urgency.

The Path Forward: A Framework for Accountability

The environmental crisis of the shadow fleet will not resolve itself except through disaster. As sanctions continue and geopolitical tensions persist, the number of aging, poorly maintained vessels will continue to grow, their condition degrading, until a grounding, collision, or equipment failure results in a massive spill and forces a reactive rather than proactive response.

The right framework does not just punish those who transact with the owners of shadow fleet vessels. The right framework holds the actual owners accountable. It applies strict liability principles that make vessel owners financially responsible for environmental damage regardless of their attempts to obscure ownership through shell companies and complex corporate structures. This means piercing the corporate veil to reach ultimate beneficial owners, requiring environmental bonds that cover the full cost of potential cleanup operations, and creating international mechanisms for collecting damages that transcend traditional jurisdictional boundaries.

Furthermore, this framework must establish mandatory environmental insurance requirements that cannot be waived through sanctions evasion, create joint liability among all parties in the shipping chain (owners, operators, charterers, cargo owners, and service providers), and implement asset forfeiture mechanisms that allow states to seize vessels and related assets to fund environmental cleanup when shadow fleet operators cannot be held accountable through traditional legal channels.

The ocean conservation community has the opportunity to help develop appropriate institutional responses. We need frameworks that combine strong precautionary principles with rapid response capabilities and long-term investment in monitoring and enforcement. The work must be carried out nationally, regionally, and globally, utilizing every tool at our disposal.

At The Ocean Foundation, this represents both a defining challenge and an unprecedented opportunity. Our proven Project Tangaroa framework provides a foundation for addressing complex maritime environmental risks through international cooperation, technical innovation, and stakeholder engagement. We are actively exploring how to adapt and scale this approach to address the shadow fleet challenge.

With shadow fleets now comprising 17% of international tankers and documented oil spills already occurring globally, proactive intervention is both urgent and cost-effective compared to reactive cleanup efforts.

The timing is critical. The conservation community has an opportunity to demonstrate that environmental organizations can evolve to address hybrid challenges that governments struggle to coordinate around, but this window will not remain open indefinitely.

The ocean deserves better than crisis-driven, reactive responses to preventable environmental disasters. The shadow fleet threat is still manageable with proactive intervention, innovative institutional approaches, and sustained international cooperation. The choice—like the ocean itself—belongs to all of us, but the time for action is now, before this manageable threat becomes an uncontrollable environmental catastrophe.

---

About the Author

Mark J. Spalding, President of The Ocean Foundation, was part of the group that founded the Shipping Safety Partnership and has responded to shipwrecks, such as the MV Selendang Ayu, and worked on addressing forced labor on ships and chronic noise pollution from shipping. He co-led Project Tangaroa and has authored several publications on sustainability in the maritime domain.