Resources & Climate

Acid Test: Global Greenhouse Emissions and Indian Ocean Ecosystems

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This spotlight highlights Chapter 8, “Environmental Pressures in the Indian Ocean,” in the newly-published Indian Ocean Rising: Maritime Security and Policy Challenges.

The Indian Ocean represents one of the richest environments in the world. It is home to 35,000 marine species and biological diversity equal to or greater than any of the seven seas.  It is also one of the most valuable ecosystems on the planet, providing food, resources, and livelihoods to hundreds of millions of people across the region.  But oceans and coastal regions are coming under mounting environmental pressures worldwide. These growing stresses include habitat destruction and land-based and marine pollution, over-fishing, and especially the increasing impacts of global warming. Significant portions of the Indian Ocean, particularly its vital fisheries and unparalleled coral reefs, figure among the most vulnerable ecosystems on Earth to rising greenhouse gas emissions and climate change, endangering the food security and economic wellbeing of populations around the Indian Ocean littoral.

Coastal and marine environments deliver indispensable ecosystem goods and services, supplying food, fuel, and materials, and regulating hydrological cycles and nutrient flows. Fisheries constitute perhaps the most commonly known of the ocean’s natural resources. According to the FAO, Indian Ocean marine capture fisheries supplied 11.3 million tonnes of fish in 2010, about 14.6 percent of the world catch. Fisheries contribute substantially to many regional economies.  In Indonesia, for example, fishing and fish farming employ nearly 6 million people.    Equally importantly, fisheries furnish a crucial food source for communities around Indian Ocean.  On average, the populations of Egypt, Malaysia, Mozambique, Seychelles, Singapore, Tanzania, and Thailand obtain 20 percent or more of their animal protein from fish. The inhabitants of Bangladesh, Comoros, Indonesia, Maldives, and Sri Lanka get more than half of the animal protein in their diets from fish.

Many of the natural goods and services afforded by marine environments, though, are harder to quantify and value. Their worth in regulating climate, filtering pollutants, providing habitat, cycling nutrients, protecting shorelines, etc., is not directly monetized or traded in markets.  Available analyses, however, suggest these services can be very valuable indeed.  Globally, ocean ecosystems have been calculated to provide natural resources and services worth some $21 trillion annually.  Coral reefs alone account for $3.75 trillion, equivalent to more than $6,000 yearly per hectare.1  Reefs are often labeled the “rain forests” of the ocean for their biodiversity, food production, and habitat value, but nearly half of their assessed economic benefit resides in their recreational role.  Indeed, many Indian Ocean nations depend considerably upon their marine resources, including coral reefs, for tourism revenues.  Tourism earns 28 percent of GDP and 60 percent of foreign exchange receipts in the Maldives. In the Seychelles it engages 30 percent of the labor force and accounts for 70 percent of hard currency earnings. Less well known, much of Egypt’s roughly $11 billion in annual tourism also draws heavily on the endowments of the Indian Ocean.  Surveys indicate that water sports (particularly snorkeling and diving in the renowned coral reefs of the Red Sea) represents one of the top attractions luring foreign travelers to Egypt, and as much as 90 percent of the country’s new investment in tourist infrastructure in recent years concentrated in coastal resorts, mostly on the Red Sea.   

But coastal and marine ecosystems are among the most vulnerable of all environments to global climate change.  As humanity’s emissions of greenhouse gases have grown, the oceans have absorbed increasing amounts of added carbon dioxide from the atmosphere.  Since the beginning of the Industrial Revolution, the cumulative ocean uptake amounts to some 25 to 30 percent of humanity’s total CO2 emissions.  The absorbed carbon dioxide in turn alters the ocean’s chemistry, rendering it more acidic (measured by a lower pH value).  From preindustrial levels, the surface ocean pH has already fallen by 0.1 units. If greenhouse emissions continue unabated, pH levels will tumble a further 0.2 to 0.3 points over the 21st century, a change 30 to 100 times greater than seen in the past and at a rate unprecedented in the geological record. By the same token, as climate change warms global average temperatures, the oceans are also absorbing heat from the atmosphere, raising surface ocean temperatures.2

Warmer water temperatures and acidifying oceans can degrade the ecology of coral reefs and threaten the artisanal and commercial fisheries that nourish many seaboard communities.  Coral bleaching – together with pollution, coral mining for construction materials, and other stresses – has already destroyed or critically endangers two-thirds of the Indian Ocean’s 12,070 km2 of coral reefs.  Fisheries, too, may be increasingly at risk.  Studies suggest that, to keep pace with projected food requirements, world fish production might have to rise by half from current levels by mid-century.  Yet according to some analyses, climate change impacts could engender large-scale shifts in potential catch distributions.  Indian Ocean fisheries are projected to see marked increases in maximum catch potential relative to 2005 levels in much of the Arabian Sea and East African waters, among other areas, while catch potentials may plummet by 30 to 50 percent or more in the Red Sea, Persian Gulf, and Indonesian waters and some areas of the open ocean.  Catch potentials within the Indonesian EEZ, for example, are projected to slip more than 20 percent by 2055, the largest drop for any country.  Such a significant shuffle of fishing potential could dramatically alter fisheries politics across the region.3

Several regional and international agreements exist to promote the sustainable management of the Indian Ocean’s resources, from the FAO’s 1995 Code of Conduct for Responsible Fisheries to UNEP’s Regional Seas programs.  So too, most coastal states have also established national legislation to manage their marine resources.  Ultimately, however, such actions alone cannot hold back the tide. Only broader global action to control continuing greenhouse gas emissions can curb the warming and acidification of the oceans.


1  Robert Costanza et al., “The value of the world’s ecosystem services and natural capital,” Nature 387 (253) 1997.

2  Scott C. Doney, “The Growing Human Footprint on Coastal and Open-Ocean Biogeochemistry,” Science 328 (1510) 2010; Bärbel Hönisch et al., “The Geological Record of Ocean Acidification,” Science 335 (1058) 2012.

3  William W.L. Cheung et al., “Large-scale redistribution of maximum fisheries catch potential in the global ocean under climate change,” Global Change Biology (2009).

Photo Credit: Jim and Becca Wicks via Wikimedia

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