thumb|300px|right|China's Critical Sea Lines of Communication. In 2004, over 80 percent of Chinese [[crude oil imports transited the Straits of Malacca, with less than 2 percent transiting the Straits of Lombok. Click to enlarge.
See also: China's String of Pearls]]
Sea Lines of Communication (abbreviated as SLOC) is a term describing the primary maritime routes between ports, used for trade, logistics and naval forces. It is generally used in reference to naval operations to ensure that SLOCs are open, or in times of war, to close them.
The importance of SLOCs in geopolitics was described in Nicholas J. Spykman's America's Strategy in World Politics published in 1942.
In the American Revolutionary War and the Napoleonic Wars, the SLOCs were, for the most part, in the control of the British Navy. When the British lost control of them during the Revolution, the result was the fall of Yorktown and its biggest army and, ultimately, the war. In the Napoleonic era, maintaining belligerence throughout, the British embargoed and blockaded any country associated with Napoleon, which created large economic hardships and dislocations that played a part in people of France becoming disenchanted with Napoleon.
In World War I and World War II, the British and Germans declared mutual blockade and the Kriegsmarine attempted to close the SLOCs from North America to the British Isles with the use of submarines. In each case the Allies succeeded in keeping the sea lanes open. The Germans in each case failed to defeat the British naval blockade of Germany. The United States Navy in World War II successfully closed the SLOCs to Japan, strangling the resource-poor island nation.
Had the Cold War turned hot, Europe would have required resupply and reinforcement from North America. The Soviet Navy could potentially threaten and contest Atlantic SLOCs to support ground offensives in Europe.
Economic Importance of Sea Lines of Communication
Around 70-90 percent of global trade in volume and 70 percent in value is dependent on maritime transport and therefore open Sea Lines of Communication. Maritime transport is of crucial importance to firm interest, as it allows Transnational Corporations to diversify their supply chains, access larger markets and reduce production cost. Because Sea Lines of Communication enable this international linkage and make it profitable, they are a key driver of overall economic growth and stability. Shipping, making use of open SLOC, as a “blue industry” is therefore important to secure economic growth and national interest.
Threats to Economic Effectiveness of Sea Lines of Communication
There prevail challenges to maritime trade along SLOC, for example piracy and maritime terrorism. These can negatively impact global economic stability.
Piracy in the Gulf of Aden
Piracy in the Gulf of Aden had a negative economic impact, because it directly affected shipping along one of the most important SLOC connecting Europe to Asia through the Suez Canal. Piracy attacks reduced bilateral trade value between two countries. As a consequence, the cost of Somali piracy activity between the years 2000 and 2016 is estimated to lie between $1 billion to $25 billion annually. The direct cost of rerouting due to Somali piracy in the Gulf of Aden amounted to $12 billion in 2010. Around 12-15 percent of global trade and 30 percent of global container trade pass through the Suez Canal and through the Red Sea annually.
Firstly, Houthi activity in the Red Sea increased operational costs of shipping companies by 18 percent. Longer routes also required higher expenses due to higher wages, more maintenance and repairs.
Thirdly, the Red Sea Crisis caused disruptions in the financial sector. Increased operational costs of shipping companies reduced dividends and served as a negative signal to investors. Because of this, investors exited the stock market which made stock prices more volatile and disrupted overall financial market stability.
See also
- Choke point
- Indo-Pacific Maritime Surveillance Collaboration
- Line of communication
- String of Pearls (Indian Ocean)