FIRST WORLD OCEANS REPORT REVISITED Theme A: Climate change and its impact on the oceans (Third in a series)
22 scientists from around the world—including Silliman University’s Hilconida Calumpong, Ph.D.—submitted to the UN General Assembly in late 2015 their report as the Ad Hoc Working Group on the Regular Process for Global Reporting and Assessment of the State of the Marine Environment, including Socioeconomic Aspects. We wish share some details of the Report.
Fish stock distribution
As seawater temperatures increase, the distribution of many fish stocks and the fisheries that depend upon them is shifting. While the broad pattern is one of stocks moving poleward and deeper in order to stay within waters that meet their temperature preference, the picture is by no means uniform, nor are those shifts happening in concert for the various species. The result is changes in ecosystems occurring at various rates ranging from near zero to very rapid. Increasing water temperatures will also increase metabolic rates, and, in some cases, the range and productivity of some stocks. As ocean climate continues to change, those considerations are increasing concern for food production. Greater uncertainty for fisheries results in social, economic and food security impacts, complicating sustainable management.
Seaweeds and seagrasses
Cold-water seaweeds, in particular kelps, have reproductive regimes that are temperature-sensitive. Increase in seawater temperature affects their reproduction and survival. Kelp die-offs have already been reported along the coasts of Europe, Southern Africa and Southern Australia, with warm-water-tolerant species replacing those that are intolerant of warmer water. The diminished kelp harvest reduces what is available for human food and the supply of substances derived from kelp that are used in industry and pharmaceutical and food preparation. Livelihoods and economies will be affected.
For seagrasses, increased seawater temperatures have been implicated in the occurrence of a wasting disease that decimated seagrass meadows in the north-eastern and north-western parts of the United States. Changes in species distribution and the loss of kelp forest and seagrass beds have resulted in changes in the ways that those two ecosystems provide food, habitats and nursery areas for fish and shellfish, with repercussions on fishing yields and livelihoods.
Because of the acidification of the ocean, impacts on the production by shellfish of their calcium carbonate shells has already been observed periodically at aquaculture facilities, hindering production. As acidification intensifies, this problem will become more widespread, and occur in wild, as well as in cultured stocks. However, acidification is not evenly distributed across areas. In addition, temperature, salinity and other changes will also change shellfish distributions and productivity.
Sea-level rise, due to ocean warming and the melting of land ice, poses a significant threat to coastal systems and low-lying areas around the world, through inundations, the erosion of coastlines and the contamination of freshwater reserves and food crops. Such effects are inevitable as they are consequences of conditions already in place, but they could have devastating effects if options for mitigation are not pursued. Entire communities on low-lying islands have nowhere to retreat to within their islands and have no alternative but to abandon their homes entirely, at a cost they are often ill-placed to bear. Over 150 million people are estimated to live on land that is no more than 1 metre above today’s high-tide levels, and 250million at elevations within five metres of that level. – Excerpted by SU Research and Environmental News Service
Thumbnail photo from www.nasa.gov