Gulf of Aden
The Gulf of Aden is a funnel-shaped body of water situated between the African and Arabian tectonic plates, linking the Red Sea to the Arabian Sea and ultimately the Indian Ocean. Bordered by Yemen, Somalia, and Djibouti, it features a rich biodiversity and offers diverse coastal ecosystems, including rocky shores, sandy beaches, and mangrove areas. The gulf's significant depth, which ranges from 2,867 feet to 16,500 feet, is influenced by the nearby Great Rift Valley. This region is also known for its seasonal monsoons, which affect water salinity and nutrient availability, supporting a variety of marine life, including endangered sea turtles and a diverse array of coral species.
Despite its ecological richness, the Gulf of Aden faces serious environmental pressures from human activities, including pollution from coastal industries and unsustainable fishing practices. Initiatives like the Jeddah Convention and the Programme for the Environment of the Red Sea and Gulf of Aden aim to address these challenges through regional cooperation and conservation efforts. The gulf's unique habitats and the marine species they support are crucial for maintaining the ecological balance, emphasizing the importance of sustainable management practices in safeguarding this vital marine ecosystem.
Gulf of Aden
Geographic Location: Middle East.
Summary: The Gulf of Aden is part of a major shipping route for international trade, including oil transportation. Consequently, it faces both rapid economic development and increasing environmental threats.
Tectonically, the funnel-shaped Gulf of Aden is located between the African and Arabian plates, extending the Great Rift Valley. This tropical zone between the southern coast of the Arabian Peninsula and the Horn of Africa, surrounded by the arid coastlines of Yemen, Somalia, and Djibouti, possesses extraordinary biotic richness. In the northwest, it connects with the Red Sea through the Bab-el-Mandeb Strait (Gate of Tears; Mandab Strait). In the east, it opens into the Arabian Sea, a northern part of the Indian Ocean. At its widest point, the Gulf of Aden is 217 miles (349 kilometers) from north to south and stretches about 783 miles (1,260 kilometers) from east to west, covering a total surface area of 158,300 square miles (409,995 square kilometers). In the northwest, it is limited by the Red Sea, more precisely by a line joining Husn Murad and Ras Siyan.
The depth of the Gulf of Aden increases from 2,867 feet (874 meters) in the west to 16,500 feet (5,029 meters) in the east, where the gulf opens into the Indian Ocean. This markedly deep system so close to land is due to the area's conjunction with the regional geographically dominant feature of the Great Rift Valley, of which the Gulf of Aden can be considered an extension. A small part of its water flows underground, moving westward into the saline Lake Assal in Djibouti. A predominantly diurnal tide occurs, with an extreme range of about 10 feet (3 meters) at Aden and Djibouti.
The mountains surrounding the Gulf of Aden reach elevations of more than 8,000 feet (2,438 meters): Shimbiris, in Somalia, is 7,927 feet (2,416 meters) above sea level, and Jabal Thamar, in Yemen, is 8,248 feet (2,514 meters) above sea level. Coastal environments here range from rocky outcrops and sand beaches to muddy inlets and drowned river mouths. Intertidal features include seagrass beds, salt marshes, and mangroves. Hard shell and leatherback turtles are present in some abundance, with nesting grounds ranging from the Bab-el-Mandeb Strait in the west to the island chain of Socotra at the eastern end of the gulf, where it joins with the Arabian Sea. The beaches of Socotra are of particular importance as an egg-laying area for the loggerhead sea turtle (Caretta caretta) population in the northwestern Indian Ocean and Arabian Sea.
Fisheries and Coral
Temperatures vary seasonally between 59 degrees F (15 degrees C) and 82 degrees F (28 degrees C). Additionally, monsoons influence wind patterns, which affect the water exchange between the Red Sea and the Gulf of Aden. During the winter (October to May), the northeast monsoon winds blow into the Gulf of Aden and lead surface water into the Red Sea from the south-southeast. The water inflow into the Red Sea is triggered by high evaporation rates and low precipitation, causing high salinity. During the summer (June to September), the southwest monsoon winds cause intense upwelling of deep, cold, nutrient-rich ocean water along the southern Arabian coastline. Abundant available nutrients inhibit coral growth but allow kelp beds to thrive; hence, coastal fisheries are rich.
Despite upwelling water and sandy shorelines, the gulf's coral reefs are surprisingly diverse, especially around the Socotra archipelago, albeit not as splendid as the reef systems in the Red Sea. Altogether, 194 species of corals have been recorded along the Saudi Arabian coast. Other habitat types include seagrass beds, limited mangrove communities, salt marshes, and salt flats. Seagrass diversity is relatively high compared with that of surrounding areas, constituting productive ecosystems that provide feeding grounds for green turtles and many species of sea cucumbers. Turtles are caught and eaten opportunistically throughout the region, so all the marine turtles of the region are considered to be threatened, and both the green and hawksbill turtles are declared endangered species. Among the mollusks, cuttlefish and dried sea cucumbers are the main exports. Commercially important invertebrates include rock and deep-sea lobster species. Due to temperature conditions and high salinity levels, the diversity of mangroves is low.
Economic and Military History
Periplus Maris Erythraei (Circumnavigation of the Red Sea) was written in the mid-first century by an Egyptian Greek author. The text is an important source of information about ancient Roman trade in the Red Sea, including the Gulf of Aden. The port of Aden was an important shipping hub of the medieval world. Records from the tenth century note that the city was a busy port linking Red Sea ports with India during the ninth century. The opening of the Suez Canal in 1869 between Port Said and Port Tawfiq, Egypt, linked the Mediterranean Sea with the Gulf of Suez and the Red Sea, including the Gulf of Aden.
All shipping routes from the Mediterranean Sea to the Indian Ocean still use the Suez Canal and, thus, the Gulf of Aden. In 2008 the US Navy reported that approximately 21,000 vessels passed through the Gulf of Aden annually. Thousands of vessels pass through the gulf each year. About 11 percent of the world’s petroleum passes through the Gulf of Aden each day. Main port cities are Aden, Yemen; Djibouti City, Djibouti; and Zeila, Berbera, and Boosaaso, Somalia.
The Gulf of Aden falls within the area patrolled by the US Navy’s Fifth Fleet. The US Navy considers the Strait of Bab-el-Mandeb to be one of three critical choke points in the area it patrols, along with the Strait of Hormuz and the Suez Canal. On October 12, 2000, the USS Cole was bombed by suicide terrorists affiliated with al-Qaeda. The attack ripped a hole in the side of the Navy Destroyer as it refueled at the port of Aden. The bombing killed 17 US Navy personnel.
In the 2000s piracy in the Gulf of Aden increased. Pirates from Somalia perpetrated thousands of attacks on cargo ships passing through the Gulf of Aden and the Indian Ocean, and reduced international trade by about 1.9 percent each year between 2000 and 2010. NATO’s efforts to combat piracy in the Gulf of Aden and other international waters in the Middle East include Operation Ocean Shield (OOS) and the NATO Shipping Centre, the organization’s point of contact with merchant shipping. Increased international naval patrols and private security led to a decline in piracy. In 2022, the International Chamber of Commerce (ICC) Commercial Crime Services reported that worldwide incidents of maritime piracy totaled fifty-eight, the lowest number since 1994. The ICC further advised that although no reports of piracy had occurred in the Gulf of Aden had been reduced, the threat of piracy remained.
Environmental Stress and Response
Most of the coastal areas and the waters of the region are considered to be biologically intact, but increasing anthropogenic activities introduce new threats. Power plants and desalination plants, refineries, and chemical plants along the coastline leak their effluents—including oil, organic pollutants, heavy metals, heated brine, and cooling water—into the gulf, often in uncontrolled fashion. Pressures on the marine ecosystems include increased salinity and particularly chlorine and thermal pollution.
Spilled hydrocarbons smother corals. Drilling mud from oil exploitation can suffocate reefs and disrupt their growth. In 1997–98, reefs were affected by the worldwide coral bleaching event. Furthermore, corals have been mined for the manufacture of cement and lime, as well as for use as jewelry. Chlorinated and organophosphorus pesticides, insecticides, and herbicides, introduced into the marine environment by agricultural runoff, cause eutrophication. Further pressure on corals comes from a natural vector: the population of crown of thorns starfish (Acanthaster planci), for which hard corals are the main sustenance. The crown of thorns is known to thrive when its predators are overfished or displaced by habitat disruption. This has occurred periodically in the Gulf of Aden region.
The problems of pollution and sewage call for sustainable management measures in the industrial and agricultural sectors, but no regulations exist in the fishery sector to ensure sustainable reproduction. Currently, blast fishing with homemade explosives composed of fertilizer, fuel, and fuse caps inserted into empty beer bottles causes massive damage to corals. When the reef structure has been weakened, it is much more vulnerable to wave action, and the reef becomes unable to protect the coastline. Another destructive fishing method involves the use of cyanide to stun fish, allowing fishers to collect them and sell them to the live-fish trade. Monitoring could prevent overfishing of shark and ray, as well as numerous by-catch varieties. Declines in catches have been reported for diverse species, including Indian mackerel, shark, cuttlefish, shrimp, and Trochus.
To organize effective regional cooperation, the Programme for the Environment of the Red Sea and Gulf of Aden (PERSGA) was initiated in 1974 by the Arab League Educational, Cultural and Scientific Organization (ALECSO) and the United Nations Environment Programme (UNEP). In 1982, the Regional Convention for the Conservation of the Red Sea and Gulf of Aden Environment—the Jeddah Convention—was adopted by the neighboring nations of Egypt, Djibouti, Jordan, Eritrea, Palestine, Saudi Arabia, Somalia, Sudan, and Yemen. It was complemented by relevant provisions of various internationally recognized Law of the Seas bodies and covenants.
The Jeddah Convention and its associated protocols through 2006 include a range of features aimed at preventing and mitigating such threats as oil spill pollution and other features that promote conservation of biological diversity. This latter goal is supported by the ongoing development of protected areas in the Red Sea and Gulf of Aden. An overall Strategic Action Plan was implemented in 1999 as a coordinated effort by PERSGA, UNEP, and related regional and global bodies. This plan strives to strengthen administrative structures and regional cooperation; to reduce navigation risks and maritime pollution; and to support sustainable use of living marine resources, habitat and biodiversity conservation, development of a network of marine protected areas, and management of an integrated coastal zone.
Further Reading
Casson, Lionel. The Periplus Maris Erythraei: Text with Introduction, Translation, and Commentary. Princeton: Princeton UP, 1989. eBook Academic Collection (EBSCOhost). Web. 23 Dec. 2015.
Feidi, Izzat H. “Mechanism for Fisheries Management in the Red Sea and Gulf of Aden.” Arab Agricultural Statistics Yearbook 2012, no. 1 (2012). Print.
“Global Piracy and Armed Robbery Incidents at Lowest Level in Decades.” International Chamber of Commerce , 7 Dec. 2022, iccwbo.org/media-wall/news-speeches/global-piracy-and-armed-robbery-incidents-at-lowest-level-in-decades/. Accessed 6 Feb. 2023.
Groombridge, B. and M. D. Jenkins, eds. The Diversity of the Seas: A Regional Approach. WCMC Biodiversity Series No. 4. Cambridge: World Conservation Press, 1996. Print.
Jeffreys, Elizabeth, and Ruth Gertwagen. Shipping, Trade and Crusade in the Medieval Mediterranean. Farnham: Ashgate, 2012. eBook Academic Collection (EBSCOhost). Web. 23 Dec. 2015.
Margariti, Roxani Eleni. Aden & the Indian Ocean Trade: 150 Years in the Life of a Medieval Arabian Port. U of North Carolina P, 2007. eBook Collection (EBSCOhost). Web. 23 Dec. 2015.
Morewood, Steve. “Suez: The Canal before the Crisis.” History Today 56.11 (2006): 38. History Reference Center. Web. 23 Dec. 2015.
Vogt, H. “Coral Reefs and Coral Bleaching in the Region, Reefs in the Red Sea and Gulf of Aden.” Al Sanbouk 12, no. 1 (2000). Print.