Warming oceans will affect the planet's poorest
Photo by Michele Solmi/flickr.
Oct. 23, 2013
As oceans warm and grow more acidic, yields of fish and shellfish will decline. And that will make life very difficult for up to 870 million of the world's poorest people who rely on the sea for food, jobs and income.
By Tim Radford
Climate News Network
LONDON – Greenhouse gas emissions from industry and power generation have begun to trigger ocean changes that will impose huge costs to the poorest people on the planet.
These changes are likely to cascade through marine ecosystems and habitats to the deep ocean itself, and to affect humans along the way, according to a report published this month in the journal Public Library of Science Biology.
"The consequence of these co-occurring changes are massive – everything from species survival, to abundance, to range size, to body size, to species richness, to ecosystem functioning are affected by changes in ocean biogeochemistry," said Camilo Mora, a geography professor at the University of Hawaii and lead author on the paper.
Mora and fellow data analysts made headlines earlier this month by calculating the year in which any given location on Earth was likely to experience dramatic and inexorable climate change: the researchers arrived at a mean date of 2047 (give or take six years on either side) for change, with the first impact in West Papua by 2020.
The new PLOS Biology paper once again takes a global view of change on the blue planet. The researchers calculated the effect of two scenarios for the future: one in which the world rapidly tries to reduce emissions, and the notorious business-as-usual scenario, which will take carbon dioxide concentrations to the unprecedented level of 900 parts per million by 2100.
Then they contemplated the impact on 32 marine habitats and biodiversity hotspots, and then they examined the available data on human dependence on the ocean.
They found that most of the world's ocean surface would feel the heat. Only in the polar regions would there be any increase in productivity or in oxygen levels. Nowhere would there be any cooling, and pH levels would trend towards acidification everywhere.
Chopping the base of the food chain
By 2100 global averages for the upper layer of the ocean would increase by between 1.2° Celsius and 2.6° Celsius. Dissolved oxygen concentrations would on average fall by between 2 percent and 4 percent, and phytoplankton production would diminish by between 4 percent and 10 percent.
Phytoplankton are the base of the ocean food chain; such a reduction would chop overall yield for between 470 and 870 million people who make a precarious and meager living from the sea, they estimated.
"The impact of climate change will be felt from the ocean surface to the sea floor," said Andrew Sweetman, a co-author, now at the International Research Institute of Stavanger, Norway. "It is truly scary to consider how vast these impacts will be. This is one legacy that we as humans should not be allowed to ignore."
Tim Radford is an editor at Climate News Network, a journalism news service delivering news and commentary about climate change for free to media outlets worldwide.
Fishing boats off Zanzibar courtesy Charles Roffey/flickr.
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