Located between the Persian Gulf and the Gulf of Oman, the Strait of Hormuz is one of the world's most critical energy transit corridors. Approximately one-fifth of the global oil supply passes through it, making it a classic energy chokepoint. When shipping flows freely, this strait underpins the stable functioning of the global economy and energy markets. However, since tensions escalated this year, it has not only disrupted oil supply and prices — it has also set off a chain of environmental risks.
The Vital Energy Artery: The Strait of Hormuz as a Strategic Chokepoint
The Strait of Hormuz (Strait of Hormuz) borders Iran to the north and Oman and the United Arab Emirates (UAE) to the south, connecting the Persian Gulf to the Arabian Sea. Its waters are deep enough for the world's largest oil tankers to pass through, making it the primary transit route for oil and natural gas from the Middle East. According to the U.S. Energy Information Administration (EIA), approximately 20 million barrels of oil and crude oil products passed through the Strait of Hormuz every day in 2025, with an annual trade value of around US$600 billion. This oil does not come from Iran alone — it also originates from neighboring Gulf states such as Kuwait, Qatar, Saudi Arabia, and the UAE. About 20% of the world's natural gas also passes through the Strait of Hormuz, the vast majority from Qatar. In 2024, approximately 9.3 billion cubic metres of natural gas per day came from Qatar and 700 million cubic metres from the UAE.
Yet the entrances and exits of the Strait of Hormuz span only 50 km, with the narrowest point measuring just 33 km. This exceptionally narrow passage has become the strategic chokepoint of global energy. In wartime, deploying just a small number of mines or missiles is enough to achieve a complete blockade. The energy crisis of 2026 was triggered by exactly this kind of shipping disruption caused by elevated geopolitical risk.
Is the Strait of Hormuz an International Strait?
Under the United Nations Convention on the Law of the Sea (UNCLOS), an international strait generally refers to a waterway located within the high seas or an exclusive economic zone, or connecting the high seas with an exclusive economic zone, and is subject to the rights of transit passage and innocent passage.
However, the United States and Iran hold fundamentally different views on the Strait of Hormuz. The U.S. regards it as an international waterway through which any vessel enjoys the right of "transit passage," free from the control of coastal states. Iran, on the other hand, considers it part of its territorial waters, asserting the right to determine whether a given vessel's passage is "innocent." Accordingly, the U.S. maintains that Iran has no authority to levy tolls on the Strait of Hormuz, while Iran views any U.S. naval blockade near Iranian ports as a serious violation of Iranian sovereignty.
These divergent interpretations of navigational rights and sovereignty have escalated into military standoffs, sanctions, and shipping disruptions, further compounding uncertainty in international shipping and energy supply.
Oil Spills Could Disrupt the Entire Marine Ecosystem
Regardless of how the U.S. and Iran interpret the legal status of the Strait of Hormuz, the damage wrought by the conflict is far broader than most imagine. Situated between the cool waters of the Gulf of Oman and the warm waters of the Persian Gulf, the Strait of Hormuz holds ecological significance no less profound than its political importance.
The waters surrounding the Strait of Hormuz are rich in biological habitats. Currents from the Gulf of Oman deliver nutrients and larvae that sustain plankton and coral reef growth, while deeper upwellings attract reef fish and seasonally migrating Whale Sharks. Sea turtles nest in the Strait of Hormuz; the Musandam Governorate — a peninsula that juts northward into the strait and belongs to Oman — is a tourism destination for diving and dolphin watching. The Omani coast is habitat to the critically endangered Arabian humpback whale, while dugongs and sea snakes also inhabit the surrounding waters.
During the conflict, a number of oil tankers and merchant vessels have been attacked or seized, and scientists fear that any oil spill event could cause irreversible damage to the surrounding wildlife and ecosystems.
"Many compounds in crude oil affect cardiac function and the respiratory system. Prolonged exposure to petroleum can trigger excessive stress responses, which in turn suppress immune function, making animals more vulnerable to environmental pressures and infection," said Martin Grosell, Professor in the Department of Marine Biology and Ecology at the University of Miami. Beyond that, crude oil disrupts animals' nervous systems, impairing their senses and information-processing abilities, and weakening their innate navigational skills and their capacity to orient correctly within their environment — affecting how they respond to predators and prey. Research on the 2010 Gulf of Mexico oil spill also demonstrated that exposure to oil reduces fish reproduction. In other words, crude oil's harm to individual animals reverberates throughout the entire ecological chain.
The offshore islands between Iran and the UAE serve as nesting grounds for Green Sea Turtles and Hawksbill Turtles. "There is extensive documentation of sea turtle mass mortality caused by oil spills in UAE waters — they essentially die from the oil and are then washed ashore," said Aaron Bartholomew, Professor of Biology at the American University of Sharjah, UAE.
Rerouting Increases Carbon Emissions and Raises Supply Chain Costs
Soaring oil prices and rising carbon emissions are also among the key concerns surrounding the blockade of the Strait of Hormuz. With the entire Middle East shipping route paralysed, vessels are diverting around the Cape of Good Hope in Africa or taking longer routes across the Pacific, adding to shipping time, carbon emissions, and global supply chain costs.
Because ships are travelling much longer routes, shipping companies are compelled to deploy more vessels or increase sailing speeds — both of which increase fuel consumption and carbon emissions. For manufacturers and retailers, even without changing their own operations, shipping remains a link in their supply chain, contributing to increased Scope 3 carbon emissions in their greenhouse gas inventories (see note).
According to earlier research on the Red Sea crisis, vessel rerouting increased greenhouse gas emissions by at least 46% and economic costs by 51%. Compared to the Red Sea crisis, the detour options around the Strait of Hormuz are far more limited. While the specific figures for each conflict may differ, both reflect the same underlying problem: when geopolitical conflicts disrupt global shipping, they not only increase fuel consumption, supply chain costs, and carbon emissions — they further destabilise energy markets and amplify climate risk.
Note: Scope 3 refers to other indirect greenhouse gas emissions — those generated by an organisation's activities but arising from emission sources not owned or controlled by the organisation, such as leasing, outsourced operations, employee commuting, business travel, and upstream and downstream transportation and distribution.
References
- BBC, Why the Strait of Hormuz matters so much in the Iran war
- The Conversation, Strait of Hormuz: Why the US and Iran are sailing in very different legal waters
- CNN, The stunning underwater world that's at risk as the Iran war drags on
- Conflict and Environment Observatory, Three days of Operation Epic Fury: a rapid overview of environmental harm in Iran and the region
- ORF Middle East, Climate Change: The Silent Casualty of War
- ScienceDirect, Geopolitical disruptions and maritime transitions: Environmental and economic costs of rerouting
- Net Zero Compare, From Red Sea to Hormuz: What Rerouted Shipping Means for Emissions
- The UN, United Nations Convention on the Law of the Sea
- Environmental Protection Administration, Executive Yuan, Guidelines for Greenhouse Gas Emission Inventory Operations
※ This article is reproduced from the Delta Electronics Foundation Low-Carbon Living Blog: 〈從能源瓶頸到生態衝擊：荷姆茲海峽衝突的連鎖效應〉, co-produced with BlueTrend.
