Chapter 1.6 – Interoceanic Passages

Authors: Dr. Jean-Paul Rodrigue and Dr. Theo Notteboom

Maritime transportation evolves over a global maritime space with its own constraints, such as the profile of continental masses and the detours and passages it creates.

1. Global Maritime Routes and Chokepoints

Maritime routes are corridors of a few kilometers in width connecting economic regions and overcoming land transport discontinuities. They are part of a continuum subject to geostrategic considerations. Transoceanic maritime corridors are a function of obligatory points of passage, which are almost all strategic places, physical constraints such as coasts, winds, marine currents, depth, reefs, or ice, and political boundaries where sovereignty may impede circulation. When possible, interoceanic canals are built to improve the connectivity of shipping networks.

International maritime shipping routes are forced to pass through specific locations corresponding to passages, capes, and straits. These routes are generally located between major markets such as Western Europe, North America, and East Asia, where an active system of commercial trade is in place. The importance of these large markets is structuring the exchanges of semi-finished and finished goods. Also, major routes involve flows of raw materials, namely minerals, grains, food products, and petroleum. The location of strategic oil and mineral resources shapes maritime routes for bulks since they represent the most transported commodities.

The most important strategic maritime passages are known as chokepoints (or bottlenecks) due to the following:

  • Capacity constraints. Chokepoints tend to be shallow and narrow, impairing navigation and imposing capacity limits on ships. For interoceanic canals such as Panama and Suez, the capacity must, in effect, be managed with appointment and pricing systems.
  • Potential for disruptions or closure. Disruption of trade flows through any of these routes could significantly impact the world economy. Many chokepoints are next to politically unstable countries, increasing the risk of compromising their access and use, such as through piracy. Closures are a rare instance that has only taken place in war situations as one proponent prevented another from accessing and using the chokepoint (e.g. Gibraltar and Suez during World War II). Closure of a maritime chokepoint in the current global economy, even if temporary, would have important economic consequences with the disruption of trade flows and even the interruption of some supply chains (e.g. oil). These potential risks and impacts are commonly used to justify using military naval assets to protect sea lanes, even if such benefits are difficult to demonstrate.

Changes in the technical and operational characteristics of interoceanic canals and passages can substantially impact global trade patterns. The Panama Canal, the Suez Canal, the Strait of Malacca, and the Strait of Hormuz account for the world’s four most important interoceanic passages. This is partly because of the chokepoints they create for global freight circulation and partly because of the economic activities and resources they grant more efficient access. Their continuous availability for global maritime trade is challenging because the global trade system relies on their use. Yet, they have shaped global trade with the ongoing setting up of rings of circulation comprised of maritime and land corridors, notably in the northern hemisphere.

In addition to the interoceanic canals, “dry canals” have been constructed or are under consideration. They are called dry canals because they replicate the role of regular canals, implying that they are relatively short overland corridors of rail, road, and pipeline infrastructures connecting two ports where cargo is transshipped. Several dry canals started as portage routes and were either discontinued as they lost their capability to compete or, in contrast, complemented by a canal, such as the Panama Canal, which has road, rail, and pipeline complementarity to the canal’s traffic. The main disadvantage of dry canals is the load break at both ends, which adds costs and delays, as well as limited economies of scale on the overland route. Still, they represent routing options that can stimulate national imports and exports and the development of logistical activities. Such imprint on regional development is much less evident in passages since they are simply transit points.

2. The Suez Canal

The Suez Canal is an artificial waterway of about 190 km in length running across the Isthmus of Suez in northeastern Egypt, connecting the Mediterranean Sea with the Gulf of Suez, an arm of the Red Sea. The Suez Canal has no locks because the Mediterranean Sea and the Gulf of Suez have roughly the same water level, making Suez the world’s longest canal without locks. It acts as a shortcut for ships between European and American ports and ports located in southern Asia, eastern Africa, and Oceania. Because of obvious geographical considerations, the maritime route from Europe to the Indian and Pacific oceans must round the Cape of Good Hope at the southernmost point of the African continent. There are alternatives to the Suez Canal, but they involve either very long detours (Cape Route) or limited capacity (Eurasian landbridge). For instance, using the Cape Route instead of the Suez Canal can extend the shipping time between Europe and Asia by an extra week.

The first canal between the Nile River Delta and the Red Sea was excavated around the 13th century BC. Its purpose was to expand trade between the Mediterranean and the Middle East, which became significant by 100 AD. During the next 1,000 years, the canal was neglected, but Egyptian and Roman rulers modified it at different times. Restoration efforts were abandoned in the 8th century AD as the Roman Empire collapsed and the Mediterranean trade dropped. Transshipping the goods across the Isthmus and to the Nile was judged more profitable than supporting the maintenance of a canal. This situation endured until the nineteenth century, when powerful maritime interests saw the need to make a Mediterranean – Red Sea connection again a reality.

The Suez Canal was constructed between 1859 and 1869 by French and Egyptian interests, spearheaded by Ferdinand de Lesseps, with a cost of about 100 million dollars. The opening of the Suez Canal in 1869 brought forward a new era of European influence in Pacific Asia. The journey from Asia to Europe was considerably shortened, saving 6,500 km from the circum-African route. In 1874, Great Britain bought the shares of the Suez Canal Company and became its sole owner. According to the Convention of Constantinople, signed in 1888, the canal was to be open to vessels of all nations in times of peace or war. However, Great Britain claimed the need to control the area to maintain its maritime power and colonial interests (namely, South Asia). In 1936, it acquired the right to maintain defense forces along the Suez Canal, which became strategically important during World War II in upholding Asia-Europe supply routes for the Allies.

The second half of the 20th century saw renewed geopolitical instability in the region with the end of colonialism and the emergence of Middle Eastern nationalism. In 1954, Egypt and Great Britain signed an agreement that superseded the 1936 treaty and provided for the gradual withdrawal of all British troops from the zone. All the British troops were gone by June 1956 as Egypt nationalized the canal. This triggered issues with Israel, as Israeli ships were not permitted to cross the canal. This threat was also extended to France and Britain, the former owners of the canal, because they refused to help finance the Aswan High Dam project, as initially promised. Israel, France, and Britain invaded Egypt in 1956. Egypt responded by sinking ships in the canal, effectively closing it between 1956 and 1957. An agreement about the usage of the canal was then reached.

However, geopolitical problems persisted as tensions between Israel and neighboring Arab nations increased in the 1960s. The Six Days War between Israel and Egypt and the subsequent invasion of the Sinai Peninsula by Israel caused the closure of the Suez Canal between 1967 and 1975. The closure was so sudden and unexpected that several ships were stranded in the canal. The canal became the cease-fire line and saw hostilities again during the Yom Kippur War of 1973. The closure of the Suez Canal significantly destabilized international transportation and favored the development of ever-larger tankers to use the long circum-Africa route. The canal was finally re-opened in 1975 as Egypt agreed to let Israel use it. Significant improvements were made between 1976 and 1980, mainly the widening of the canal to accommodate very large crude carriers (VLCC) of about 200,000 tons, supporting petroleum trade between Europe and the Middle East. The current capacity of the canal at 240,000 tons means that ultra-large crude carriers (ULCC; tankers of more than 300,000 tons) cannot pass through the Canal when fully loaded. A common practice is to unload a share of Mediterranean-bound ships and use the Sumed pipeline to transit the overload.

With additional deepening and widening projects, the depth of the canal reached 22.5 meters in 2001 and 23.5 meters in 2008. In 2014, a new expansion project increased the capacity to about 100 transits per day took place. The New Suez Canal was inaugurated in August 2015 at a cost of over 8 billion dollars, and the depth was expanded to 24 meters (78 feet). This expansion included a new 35 km section enabling the canal to transit ships in both directions at once. The expanded Suez Canal has draft limitations similar to those of the Strait of Malacca, which helped improve the continuity of maritime shipping on Asia – Europe trades. The canal has the capacity to accommodate up to 25,000 ships per year (about 78 per day) and roughly accounts for 15% of the global maritime trade and 30% of the container trade. Transits and tonnage have steadily been increasing. A rail line also runs parallel to the canal.

Before its expansion in 2015, the canal could only handle unidirectional traffic, with crossings organized into convoys of about 10 to 15 ships. Three convoys per day, two southbound and one northbound, were organized, with a transit time of about 17 hours. After the 2015 expansion, two simultaneous convoys per day were organized since a longer section of the canal became bi-directional. Missing a convoy can incur supplementary delays to the point that, on occasion, maritime shipping companies (particularly for containers) would skip a port call to ensure on-time arrival at the Suez Canal to be part of a daily convoy. The growing ship size transiting the canal can involve risks, such as the grounding of a 20,000 TEU containership in 2021, which blocked the canal for six days.

In mid-2021, the Suez Canal Authority (SCA) announced plans to widen and deepen the Canal. An 18.6-mile stretch between the city of Suez, where the canal meets the Red Sea, and the Great Bitter Lake will be widened by 131 feet (40 meters) and deepened from 66 feet to 72 feet. The plan also includes the construction of a 10-kilometer stretch of an additional lane linked to the 2015 extension. The expansion is expected to be completed in 2023.

The transit rates are established by the Suez Canal Authority (SCA) and are computed to keep the canal transit fees attractive to shippers. In the fiscal year 2014, Egypt earned USD 5.3 billion in canal fees, making it the country’s third-largest revenue generator after tourism and remittances from expatriate workers. Container ships account for just under half of the Canal’s traffic and a slightly higher percentage of its net tonnage and revenues. The average canal transit fee (at 90% vessel utilization) amounts to 102 USD per TEU for a vessel of 1,000 TEU, down to 56 USD per TEU for the largest container vessels. The Far East – Europe trade constitutes about 75% of the traffic handled by Suez. In recent years, services to the North American East Coast from Asia and transiting through the Suez Canal have increased to account for more than 15% of the traffic it handles. The canal area has also become a major transshipment cluster.

3. The Panama Canal

The Panama Canal joins the Atlantic and Pacific oceans for 82 kilometers across the Isthmus of Panama, running from Cristobal on Limon Bay, an arm of the Caribbean Sea, to Balboa, on the Gulf of Panama. Since its expansion in 2016, it has involved two lock systems that can be used simultaneously. The old locks, completed in 1914, can handle ships with a draft of 12.2 meters (40 feet), a width of 32 meters (106 feet), and a length of 294 meters (965 feet). The expanded locks, completed in 2016, can handle ships with a draft of 15.2 meters (50 feet), a width of 49 meters (160 feet), and a length of 366 meters (1200 feet).

The construction of the Panama Canal and subsequent expansion rank among the greatest engineering works of the 20th century as the canal replaces a long detour around South America, thus improving global trade connectivity. The Panama Canal is particularly important to the United States as it enables quicker linkage between the East and the West coast, saving about 13,000 km (from 21,000 km to 8,000 km) on a maritime journey.

The Panama Canal is composed of three main elements, the Gatun Locks (operational in 1914) and Agua Clara Locks (operational in 2016), giving access to the Atlantic Ocean, the Culebra Cut (Gaillard) crossing the continental divide, and the Miraflores and Pedro Miguel Locks (1914) and Cocoli Locks (also part of the 2016 expansion) accessing the Pacific Ocean. The canal handles about 5% of the global seaborne trade and about 12% of the American international seaborne trade. Besides, close to 70% of the Panama Canal traffic either originates or is bound to the United States.

Interest in establishing a short route between the Atlantic and Pacific began with the exploration of Central America in the early 16th century. In 1534, the Spanish surveyed the Panama region in order to construct a canal, but the project never came into existence due to acute technical constraints. Overland portage routes were used instead, initially as paths through the isthmus, but in 1855 the completion of the Panama Railway provided a faster and higher capacity link. The United States became interested in building a canal when gold was discovered in California in 1848, which incited large westward population flows. A possible path through Nicaragua was also surveyed. However, in 1878 the French Geographical Society of Paris signed a treaty with Columbia (then the owner of the Province of Panama) to construct a canal. From 1879 to 1899, the French Canal Company (Compagnie Universelle du Canal Interoceanique), under the initiative of Ferdinand de Lesseps (who was the key driver behind the construction of the Suez Canal in 1869), undertook construction after capitalizing on 1 billion francs from 800,000 private investors. However, the ambitious project failed mainly due to financial problems, tropical diseases (an estimated 25,000 workers died), and the technical difficulties of building a sea-level canal where it could not be realistically done. The resulting financial collapse of the company was estimated to be the largest of the 19th century.

The Spanish-American War of 1898 gave an incentive to build a canal due to the long repositioning of American ships between the Atlantic and Pacific oceans. It was only in the twentieth century that the Panama Canal project would become a reality. As a province of Colombia, the United States was unsuccessful in securing a concession for a canal in Panama. However, in 1903, the Panamanian Revolution, supported by the United States, resulted in the independence of Panama. In that same year, the United States and the new state of Panama signed the Hay-Bunau-Varilla Treaty. With this treaty, the United States guaranteed the independence of Panama and secured a perpetual lease on a 16-km (10 miles) strip for the canal, over which the United States had complete sovereignty. Panama, in return, got a monetary compensation of $10 million and an inflation-indexed annual compensation.

The Panama Canal was constructed between 1904 and 1914 by American engineers at the cost of $387 million (including the $10 million compensation to Panama and $40 million to purchase the previous project from the French Canal Company). In 1906, President Theodore Roosevelt, mainly credited for the achievement, placed the construction of the canal under the authority of the U.S. Army Corps of Engineers. The Soo Locks linking Lake Huron to Lake Superior, which at the time were the most heavily used in the world, became the engineering template for Panama’s locks. The construction of the Gatun Dam enabled the creation of an artificial lake (Lake Gatun), which reduced the need for excavation (higher water levels) as well as providing a large reservoir of water to supply the locks. A total of 70,000 people worked on the project, and about 5,600 died in the process, mainly because of tropical diseases. The work was completed in 1914 and involved excavating 143 million cubic meters of earth and sanitizing the entire canal area, which was infested with mosquitoes that spread yellow fever and malaria.

Since its completion in 1914, more than 1.14 million vessels have transited the canal, carrying 13.94 billion tons of cargo (as of 2020). It is synonymous with a standard in maritime transport related to capacity, the Panamax standard, which equals 65,000 deadweight tons, a draft of 12 meters, and a capacity of about 4,500 TEUs depending on the load configuration (about 5,200 TEU if most of the containers are empty). About 14,000 ships transit the canal every year, with an average of 35 ships per day. There are two major components in the transit time for the Panama Canal. The canal transit time (CTT) is the average time it takes for a ship to cross the canal from its entry point in Balboa to its exit in Colon (or vice-versa). The time spent in Panama Canal waters (PCWT) includes the transit time in addition to the time spent waiting for a transit slot to become available. However, the canal has the optimal capacity to handle 50 ships per day. Using the canal requires an average transit time of about 16.5 hours if the passage has been reserved in advance. With no reservations, the transit takes an average of 35 hours due to the additional time spent waiting for a transit slot. Containers, grains, and petroleum account for the dominant share of the cargo transited. The introduction of super-tankers at the beginning of the 1950s forced the reconsideration of its strategic importance as economies of scale in petroleum shipping are limited by the size of the canal.

Under the control of the United States until 1979, its administration was entrusted to the State of Panama by the Panama Canal Treaty of 1977 (also called the Carter-Torrijos Treaty). In December 1999, the canal was reverted to Panama under the jurisdiction of the Panama Canal Authority. The authority generates revenue by collecting tolls on all ships crossing the canal and is responsible for the operation and maintenance of the facility. A loaded ship pays about $2.57 per net ton, and the average toll is about $45,000. For container ships, the toll (as of 2011) was $74 per TEU of capacity on laden containers and $65.60 per TEU of capacity on ships with empty containers. In 2008, $1.32 billion in tolls were collected, of which 54% was generated by container shipping.

The Panama Canal Authority undertook a privatization policy that began with the concessioning of its port terminal facilities. The first private project was Manzanillo International Terminals (MIT), which began operations in 1995. In 1999, Hutchison Port Holdings (HPH) was granted a 25-year concession for the operation of port terminals on both the Atlantic (Port of Cristobal) and Pacific (Port of Balboa) sides of the canal. The rail line between the Atlantic and Pacific sides was reopened in 2002 as a private concession to handle the growing containerized traffic. The Panama Canal Railway Company (a concession to KCS and Mi-Jack Products) supports transshipment activities between the Atlantic and the Pacific sides through doublestack services, allowing for repositioning containers between the maritime facades without transiting through the canal. The railway has a capacity of about 500,000 containers per year, implying that it can support interoceanic container flows but cannot be a substitute for the substantial capacity of the canal that can surpass 50 million TEU per year, depending on the configuration of the transits. The same rationale applies to oil circulation with the trans-Panama pipeline that resumed its operations in 2003, but the additional capacity this pipeline conveys is only about 1 Mb/d.

The continuous growth of global trade since the 1990s has placed additional pressure on the Panama Canal to handle a growing number of ships promptly and predictably. This raised concerns that the existing canal could reach capacity by the second decade of the 21st century. Because of these capacity limits, many shipping companies changed the configuration of their routes. This became increasingly apparent as a growing share of the global containership fleet reached a size beyond the Panama Canal capacity, which came to be known as “post-Panamax” containerships. Through economies of scale, they offer significant operational cost advantages that the old canal could not exploit. The increasing usage of those ships along the Pacific Asia-Suez Canal-Mediterranean routes and the development of the North American rail landbridge created substantial competition for the canal as an intermediate location in global maritime shipping. Thus, there is a range of alternatives to the Panama Canal trade routes, with the North American landbridges being the most salient. However, concerns about the reliability of the landbridge connection incited the setting up of “all-water routes” directly linking Pacific Asia and the American East Coast, particularly in light of the booming China-United States trade relation.

The Panamanian government decided to expand the Panama Canal in 2006. The expansion was a 5.4 billion US dollar project that involved building a new set of locks on both the Atlantic and Pacific sides of the canal, which would accommodate ships up to 12,500 TEU depending on their load configuration. The dredging of access channels and the widening of several sections of the existing canal were also required. This allows Aframax and Suezmax vessels to pass through the canal, thus permitting new opportunities for container shipping services, such as the re-emergence of round-the-world services. Essentially, a new containership class was created to add to the existing Panamax ship class. It was dubbed New-Panamax (or NeoPanamax; NPX). The announcement of the expansion also induced the upgrade of ports and related infrastructures along the North American East Coast since larger containerships were expected to call.

The new locks complement the existing lock systems, creating a two-tier service, one for the very large ships and the other for Panamax, or smaller ships. The outcome allows about 12 ships per day in the new lock system to be added to the existing capacity of about 45 ships per day in the existing locks. However, the additional capacity is constrained because the new locks are unidirectional compared with the existing double locks. The new infrastructures came online in July 2016, after some delays since the expansion was initially expected to be completed in 2014.

Despite being over a century old, the Panama Canal remains a critical bottleneck in global trade. The Panama Canal expansion took place in an environment of notable commercial changes, such as a revision of sourcing strategies and the possibility of building a competing canal in Nicaragua. Further, the latest generation of containerships (such as the Triple E class) has reached sizes beyond the expanded locks. Within the foreseeable future, the expanded Panama Canal will still handle 95% of the global containership capacity. As a global intermediary location, Panama is shifting from being a point of transit toward being a logistics cluster and a trading platform for the Americas.

The Panama Canal faces long-term water supply challenges, which remains a risk factor. Severe drought conditions in 2023 forced the Panama Canal to reduce its operational draft from 50 to 44 feet. Due to a strong El Nino climate pattern (La Nina) that brings warmer water currents across the central Pacific, Central America received significantly less rainfall than usual. The resulting lower levels of Gatun Lake, the main reservoir feeding the locks, the Panama Canal Authority was forced to curtail capacity in terms of the number of daily passages. These went from 50 per day under normal and optimal circumstances to 32 per day by the summer and 24 per day by the fall, to a low of 18 per day in early 2024. The same year the government of Panama created the Panama Multimodal Dry Canal legislation that creates a customs distinction between goods in transit and in transshipment. The latter does not enter Panama even if it physically moves overland (e.g. by rail or road) from one port on the Pacific side to another on the Atlantic side. The simplification facilitates overland movements since they are much less subject to the stringent procedures of cargo inspection and clearance by customs. The outcome is an integrated multimodal strategy for the Panama Canal and its associated dry canal. Even if this regulatory change was unrelated to the canal’s capacity issues, it came into effect at a time when the additional flexibility to use the overland route could support the capacity shortage.

4. The Strait of Malacca

The Strait of Malacca is one of the most important strategic passages in the world because it supports the bulk of the maritime trade between Europe and Pacific Asia, which accounts for 50,000 ships per year. About 30% of the world’s trade and 80% of Japan’s, South Korea’s, and Taiwan’s petroleum imports transited through the strait, which involved approximately 16 Mbd in 2016. It is the main passage between the Pacific and the Indian oceans, with the Strait of Sunda (Indonesia) being the closest alternative. It measures about 800 km in length, has a width between 50 and 320 km (2.5 km at its narrowest point), and has a minimum channel depth of 23 meters (about 70 feet). It represents the longest strait in the world used for international navigation and can be transited in about 20 hours.

Historically, the Strait was an important passage point between the Chinese and the Indian worlds and was controlled at different points in time by Javanese and Malaysian kingdoms. From the 14th century, the region came under the control of Arab merchants who established several fortified trading towns, Malacca being the most important commercial center in Southeast Asia. Again, control of the trade route shifted as the European expansion era began in the 16th century. In 1511, Malacca fell to the Portuguese, which marked the beginning of European control over the Strait. In 1867, England took control of the passage with Singapore as the main harbor and other important centers, such as Malacca and Penang, forming the Strait Settlements. This control lasted until the Second World War and the independence of Malaysia in 1957. As the transpacific trade increased considerably after the Second World War, so did the importance of the passage. At the southern end of the Strait of Malacca, Singapore is one of the world’s most important ports and a major oil refining center.

One of the main challenges facing the Strait of Malacca is that it requires some dredging since it is barely deep enough to accommodate ships above 300,000 deadweight tons. Since the Strait is between Malaysia, Indonesia, and Singapore, an agreement about how the dredging costs should be shared and how fees for its usage should be levied is difficult to reach. Political stability and piracy are also major issues for the safety of maritime circulation, especially on the Indonesian side, where the province of Aceh has experienced political instability.

The Strait of Malacca ends up in the South China Sea, another crucial shipping lane and a region subject to contention since oil and natural gas resources are present. The Spratly and Paracel islands are partly claimed by China, Vietnam, Malaysia, Indonesia, Brunei, and the Philippines. The region has proven oil reserves estimated at 7.0 Bb, with oil production accounting for 2.5 Mb/d. With the substantial economic growth in the region, large quantities of oil, liquefied natural gas, and other raw materials (iron ore, coal) are transiting toward East Asia. About 25% of the global shipping fleet transits through the region each year, underlining the importance of the South China Sea as an extension of the Malacca chokepoint. Still, the potential for disruptions of trade routes in the South China Sea must consider the high level of reliance China has on such routes and its limited interest in seeing them compromised. For instance, 80% of China’s oil imports and 50% of its foreign trade transit through the Strait of Malacca, underlining that China is the stakeholder depending the most on reliable and secure navigation through the strait.

Using the Kra Isthmus in Thailand as a shortcut between the Gulf of Thailand (Pacific Ocean) and the Andaman Sea (Indian Ocean) was considered as early as the 17th century. The Kra Canal project aims to build a 102 km-long canal along the narrowest segment of the Kra Isthmus. By avoiding a detour through the Strait of Malacca, the potential canal could reduce shipping distance by 1,200 km, corresponding to about two to three shipping days in one direction (such figures do not take account of canal transit times). Although the project represents a shortcut, this benefit is relatively marginal, particularly for long-distance shipping routes. The importance of Singapore and Tanjung Pelepas as major transshipment hubs linking Asia-Oceania-Europe trade routes also undermines its viability. Shipping lines using the canal will need to consider the benefits of lower transit times versus the canal tolls. The canal would mainly benefit Thailand, Burma, Cambodia, and Vietnam as they would see more significant shipping time and cost reductions for their maritime trade. China is pursuing this project for commercial and strategic reasons since it will give it an alternative to using the Strait of Malacca.

5. The Strait of Hormuz

The Strait of Hormuz forms a strategic link between the Persian Gulf oil fields, which is a maritime dead-end, the Gulf of Oman, and the Indian Ocean. It has a width between 48 and 80 km, but navigation is limited to two 3 km wide channels, each exclusively used for traffic in one direction (inbound or outbound). With 34,000 transits per year, it is the most significant chokepoint for the maritime circulation of oil. Circulation in and out of the Persian Gulf is highly constrained because the sizable amount of tanker and containership traffic makes navigation difficult along the narrow channels. Besides, islands essential to the control of the strait are contested by Iran and the United Arab Emirates. The strait is deep enough to accommodate all the existing tanker classes.

The security of the strait has often been compromised, and its commercial usage has been contested. Between 1984 and 1987, a “Tanker War” took place between Iran and Iraq, (in the Iran-Iraq War of 1980-1988), where each belligerent began firing on tankers, even neutrals, bound for their respective ports. Shipping in the Persian Gulf dropped by 25%, forcing the intervention of the United States to secure the oil shipping lanes. About 85% of all the petroleum exported from the Persian Gulf transits through the Strait of Hormuz and is bound for Asian markets. Its importance for global oil circulation cannot be overstated. For instance, 75% of all Japanese oil imports transit through the strait. Thus, there are few alternatives to oil exports if the traffic of about 17 million barrels per day going through Hormuz is compromised.

While the Persian Gulf has conventionally been centered on the production and distribution of oil, the growth of container shipping has also expanded its commercial importance. For instance, in 2018, Dubai ranked as the world’s 10th largest container port with a traffic of 15 million TEU, and it can only be accessed through the Strait of Hormuz. It has become a major transshipment hub linking Asian, Middle Eastern, and East African trade routes. Consequently, compromising circulation through the Strait of Hormuz would impair global oil trade as well as commercial trade along Europe / Asia routes.

6. Other Important Passages

The Strait of Bab el-Mandeb (often misspelled as Bab al-Madab) controls access to the Suez Canal, a strategic link between the Indian Ocean and the Red Sea. It literally means the “Gate of Grief” due to difficulties in its navigation. The strait has between 48 and 80 km of width, but navigation is limited to two 3 km wide channels for inbound and outbound traffic. The sizable amount of tanker traffic makes navigation difficult along the narrow channels. Closing this strait would have serious consequences, forcing a detour around the Cape of Good Hope and, in the process, demanding additional tanker space. Like the Strait of Malacca, Bab el-Mandwb is a crucial link in the Europe – Asia trade route. In the Fall of 2023, a major disruption of deepsea shipping services took place as Iranian proxies, the Houthi Mouvement, began attacking transiting ships with missiles, drones, and boarding actions around the Strait of Bab el-Mandeb.

The Oresund Strait is a passage of 115 km between Denmark and Sweden connecting the North Sea and the Baltic, a maritime dead-end. It enables Russia, the Baltic States, Poland, and Germany to access international maritime shipping. The majority of Russian container trade transits through the strait.

The Strait of Gibraltar is a peninsula between the Atlantic and the Mediterranean oceans and represents an obligatory passage point between these two oceans. The strait is about 64 km long and varies in width from 13 to 39 km, organized as two one-way shipping lanes. About 300 vessels transit the strait each day. It has been under British control since its conquest from Spain in 1704 and its formal cession by the Treaty of Utrecht (1713). During the Second World War, Gibraltar blocked access to the Atlantic to the Italian and German fleets of the Mediterranean, which represented a major strategic military stronghold. The Strait has become an important transshipment nexus along major Europe-Mediterranean-Asia shipping routes. More recently, the growth of the trade using the Suez Canal to reach the North American East Coast has provided additional transshipment opportunities around the strait, particularly at the Port of Algeciras on the Spanish side and the Port of Tanger Med on the Morrocan side.

The Strait of Bosporus has a length of 30 km and a width of only 1 km at its narrowest point, linking the Black Sea to the Mediterranean. Its access has been the object of two conflicts, the Crimean War (1854) and the Battle of the Dardanelles (Gallipoli, 1915). Turkey fortified the passage after the Convention of Montreux in 1936, which recognized its control of the Bosporus but granted free passage to any commercial vessel without inspection in peacetime. With the Dardanelles passage, Bosporus forms the only link between the Black Sea and the Mediterranean Ocean. In the current context, the Bosporus represents a passage of growing strategic importance, notably after the fall of the Soviet Union. Ukraine has become a major exporter of grains (sunflower, corn, and wheat) and iron ore, relying on the Strait of Bosporus. Further, the Caspian Sea has vast oil reserves, which must transit through the Black Sea and Bosporus to reach external markets, namely around the Mediterranean. Although pipelines offer an alternative, the cost differentials are advantaging maritime transportation. For instance, the cost of moving oil along the Baku – Ceyhan pipeline ranges between $1 and $2 per barrel, while shipping oil by tankers through the Black Sea costs 20 cents per barrel.

About 50,000 ships, including 5,500 tankers, are transiting through the passage each year, which is getting close to capacity. Due to its sinuosity, the Bosporus is one of the most difficult passages to navigate, particularly for larger ships. Oil transits through the Bosporus have grown substantially in recent years with the exploitation of oil fields around the Caspian Sea, and about 2.4 Mb/d were transited through the passage in 2016. The future growth of petroleum circulation through the Bosporus is thus highly problematic, notably with the risk of collisions and oil spills in Istanbul. In 2002, the Turkish government forbade the use of the passage by large tankers during the night.

The Strait of Magellan separating mainland South America from Tierra del Fuego was crossed in 1520 by the Portuguese explorer Ferdinand Magellan. It has a length of 530 km and a width of 4 to 24 km. It provides a better-protected passage than Cape Horn and the Drake Passage, which is the body of water between South America and Antarctica. It was initially kept secret for more than a century to ensure the supremacy of Portugal and Spain in the Asian trade of spices and silk. With the construction of the Panama Canal in 1916 and later on, the setting up of the North American transcontinental bridge in the 1980s, this passage lost most of its strategic importance, a marginalization reinforced by limited economic activity at the southern tip of South America. Still, it offers an alternative in case of disruptions at the Panama Canal but involves a long detour.

The Cape Good Hope represents the extreme tip of Africa separating the Atlantic and Indian oceans, and it offers no technical limitations of significance to maritime shipping. The early stages of the European maritime expansion in the fifteenth century were oriented towards exploring the west coast of the African continent. After its discovery by the Portuguese in 1488, the cape took the name Good Hope because it offered a maritime passage towards India and Asia, thus the hope of a fortune for those who traversed it. Vasco de Gama got around the cape in 1497 and was the first European to reach India by sea. Afterward, the Cape of Good Hope became an important point of transit in Europe-Asia trade networks, including a coaling station when steamship technology was developed in the 19th century.

The completion of the Suez Canal in 1869 undermined the strategic importance of the Cape Route, particularly following its widening in the 1970s, but the Cape Route remains an important passage. The growth of trade relations between Latin America and East, South, and Southeast Asia has stimulated the growing use of the Cape Route and South Africa as a transshipment hub. This underlines that the Cape Route is no longer focused on European trade, but more of a passage supporting south-to-south trade. Navigation across the cape can be hazardous (it also bears the name “Cape of Storms”), particularly in the winter, due to strong winds and sea currents between the Atlantic and Indian oceans.

Related Topics


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