Habitat Loss
It is a curious situation that the sea, from which life first arose, should now be threatened by the activities of one form of that life.
Rachel Carson
The numbers
- 14.8 million sq. km of the sea floor is trawled each year, more than 100 times the area of forest lost annually
- 75 percent of coral reefs worldwide are at risk from climate change and local threats such as pollution, fishing and coastal development
- 67 percent of wetlands and 65 percent of seagrasses were lost over the past 150 years
- 20 percent of mangrove forests were destroyed since 1980
- 11 percent of carbon in the ocean is found in seagrass beds, despite these habitats only covering 0.1 percent of the sea floor
Coastal habitats — including coral reefs, seagrass beds, and mangroves — are home to 90% of known marine wildlife. They also provide us with the majority of fish catches and play vital roles as buffers against storms and sea level rise, and as stores of carbon.
However, human pressures are increasing on these areas; 45% of the world’s population live on the 5% of land next to the coast. These habitats are being destroyed more rapidly than almost any other.
75% of coral reefs — home to a quarter of marine species despite covering just 1% of the seas — are threatened by local threats (pollution, destructive fishing methods and coastal development) and climate change. According to the World Resources Institute, the worst affected region is Southeast Asia where 95% of reefs are threatened.
One fifth of mangroves were lost in the past three decades — for commercial shrimp farming, agriculture, mining and coastal development — at a rate of 1–2% a year, faster than deforestation. Mangroves play important roles as nurseries for fish and other species, as well as coastline protection. During the 2004 tsunami in Southeast Asia regions buffered by mangroves were less damaged than those without.
Seagrasses also provide important habitat for marine species, and a primary source of food for dugongs and other endangered species. Incredibly, while covering just 0.1% of the seafloor they store 11% of oceanic carbon. Like mangroves and reefs, seagrasses are being lost to coastal development and declining water quality. Since 1980 110 square kilometres have been lost each year, and over the past 100 years almost a third were lost.
Additionally, activities such as bottom-trawling are increasing the pressure on sea-floor ecosystems, which are less adapted than coastal areas to human impacts. It is thought that nearly half the continental shelf area worldwide is trawled each year, much of it repeatedly. Some of the habitats affected are hundreds, if not thousands, of years old.
Read More
- Burke et al 2011 Reefs at Risk Revisited. World Resources Institute
- Danielsen et al 2005 The Asian Tsunami: A Protective Role for Coastal Vegetation. Science 310, 643
- Lotze, et al. 2006 Depletion, Degradation, and Recovery Potential of Estuaries and Coastal Seas. Science 312, 1806
- Marine Conservation Biology Institute and Deep Sea Conservation Coalition. Debunking claims of sustainability: High-seas bottom trawl red herrings. April 2005.
- Morgan et al. Why the world needs a time-out on high-seas bottom trawling. Deep Sea Conservation Coalition. June 2005
- Norse et al 2012 Sustainability of deep-sea fisheries. Marine Policy 36, 307–320
- Watling and Norse 1998. Disturbance of the seabed by mobile fishing gear: A comparison to forest clearcutting. Conservation Biology 12, 1180-1197.
- Waycott et al. 2009 Accelerating loss of seagrasses across the globe threatens coastal ecosystems. Proceedings of the National Academy of Sciences.