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Oceans at Risk, say Scientists...

 

Leaping Clymene dolphins

 

...while Indian pelagic fisheries seem to thrive

 
The future of marine life in the oceans is bleak and marine degradation is happening at an unprecedented rate, if we believe a report released by the International Program on the State of the Ocean in concert with the International Union for Conservation of Nature, in April this year, at a workshop held at the University of Oxford, London.
 
We now face losing marine species and entire marine ecosystems, such as coral reefs, within a single generation, the report said. Corals were particularly at risk from the bleaching effect caused by rising sea temperatures and from acidification, which deprive the tiny organisms of the calcium carbonate they need to build their homes.
 
The key points underlying this conclusion, according to this report, are: 
 
1. Human actions have resulted in warming and acidification of    the oceans    and are now causing increased hypoxia.
   
2. The magnitude of the cumulative impacts on the ocean is greater than previously    understood. Interactions between different impacts can be negatively synergistic (negative impact greater than sum of individual stressors) or they can be antagonistic (lowering the effects of individual impacts).
 
3. Timelines for action are shrinking. 
The longer the delay in reducing emissions the higher the annual reduction rate will have to be and the greater the financial cost. Delays will mean increased environmental damage with greater socioeconomic impacts, costs of mitigation and adaptation measures.
 
4. Ecosystem collapse is occurring as a result of both current and emerging stressors. 
Stressors include chemical pollutants, agriculture run-off, sediment loads and over-extraction of many components of food webs which singly and together severely impair the functioning of ecosystems.
 
5. The threat of extinction to marine species is rapidly increasing. 
The main causes of extinctions of marine species to date are overexploitation and habitat loss. However climate change is an increasing threat to species, as evidenced by the recent IUCN Red List Assessment of reef‐forming corals. Some other species ranges have already extended or shifted pole-wards and into deeper cooler waters; this may not be possible for some species to achieve, potentially leading to reduced habitats and more extinctions.
 
In India too, the impact of climate change on fish species has been perceived with extension of range of some species. Analyzing data on sea surface temperature (SST) and other parameters from a variety of global sources, scientists found warming of the sea surface along the entire Indian coast. The SST increased by 0.2 deg C along the northwest, southwest and northeast coasts and by 0.3 deg C along the southeast coast during the 45-year period from 1960 to 2005. 
 
The oil sardine and the Indian mackerel accounted for 21 percent of the marine fish catch in 2006. These small pelagics, especially the oil sardine, have been known for restricted distribution – between 8 and 14 deg N latitude and 75 and 77 deg East longitude (Malabar upwelling zone, along the southwest coast of India) where the annual average SST ranges from 27 to 29 deg C. Until 1985, almost the entire catch was from the Malabar upwelling zone; there was little or no catch from latitudes north of 14 deg N. During the last two decades, however, catches from latitude 14 - 20 deg N are increasing. In 2006, catches in this area accounted for about 15 percent of the all-India oil sardine catch.
 
The higher the SST, the better the oil sardine catch. The surface waters of the Indian seas are warming by 0.04 deg C per decade. Since the waters in latitudes north of 14 deg N are warming, the oil sardine and Indian mackerel are moving to northern latitudes. It is seen that catches from the Malabar upwelling zone have not gone down. So, in effect, sardines are extending northward, not shifting northward. The Indian mackerel is also found to be extending northward in a similar way.
 
According to CMFRI, the catch of oil sardines along the coast of Tamil Nadu has gone up dramatically. The presence of the species in new areas is a bonus for coastal fishing communities.  Besides exploring northern waters, the Indian mackerel has also been descending deeper as well. The fish normally occupies surface and subsurface waters. During 1985-89, only 2 percent of the mackerel catch was from bottom trawlers, the remainder was caught by pelagic gear such as drift gillnet. During 2003-2007, however, an estimated 15 percent of the mackerel has been caught by bottom trawlers along the Indian coast. It appears that with the warming of sub-surface waters, the mackerel has been extending deeper and downward as well.
 
Communities of humans living along the coasts of developing and poor countries, and their dependence on marine resources don’t figure anywhere in this workshop largely dominated by concerns for conserving ecosystems and marine life. There are large swathes of unregulated fisheries thriving along the coasts of our oceans. Their sustainable management is as urgent as the concerns for bleaching corals and mass extinctions. Let us hope that strategies for adaptation to climate change will include enhancements to livelihoods and economic outputs as well as the safety of ecosystems, and holistically move towards conserving marine life, the oceans and enhancing livelihoods of coastal communities.
(Sources: Summary of the conclusions and recommendations of the international Earth system expert workshop on ocean stresses and impacts, IPSO IUCN WCPA; Bay of Bengal News: March - June 2008)