Department of Water Resources
A daily compilation of significant news articles and comment
May 26, 2009
3. Watersheds -
Studies chart humans' huge effect on sea life
The
By Scott LaFee
Humans have been exploiting the oceans for far longer and with more devastating effect than anyone had imagined, scientists report in advance of an international conference on the state of the Earth's oceans and marine life.
Dozens of new studies will be presented tomorrow at the Oceans Past II conference in
Most of these species are now smaller and more rare – and in some cases, threatened with extinction.
“Joni Mitchell once famously sang that 'you don't know what you've got till it's gone.' But when it comes to marine life, in many cases we're only just starting to fully realize what the planet once had,” said Ian Poiner, deputy chief of the Division of Marine Research at the Commonwealth Scientific and Industrial Research Organisation in Australia.
The foundation of the conference is the ongoing History of Marine Animal Populations project, a worldwide effort to assess lost biodiversity using novel sources such as old ship logs, tax accounts, legal documents, photographs and literary texts.
“HMAP's evidence includes old restaurant menus, whalebone buttons, logbooks and lore, paintings and pavements, isotopes and ice,” said Jesse Ausubel at the Alfred P. Sloan Foundation, a primary funder and manager of the project.
As with conventional research, the data gathered by HMAP are rigorously scrutinized. “Everything is cross-checked when possible using multiple sources,” said Andy Rosenberg, a marine scientist at the
“What's important to remember with historical data like this is that there was no incentive back then to misreport. There were no concerns or penalties for reporting big catches, like there might be today. And people knew what others were doing, so there were no secrets.”
Still, the findings are a revelation.
For example, many studies indicate serious human exploitation of the seas began in some parts of the world as early as the Middle Stone Age, 30,000 to 300,000 years ago – 10 times earlier than previously believed.
Latin and Greek texts dating to the second century suggest Romans were already trawling for fish with nets. By A.D. 1000, early European cultures had shifted from consuming declining numbers of local freshwater fish to harvesting marine species.
As fishing techniques and boat technologies improved, people moved farther out to sea. The real revolution, said Maria Lucia De Nicolo of the
Four centuries later, the modern reality is “really quite depressing,” said Poul Holm, a professor of history at Trinity College Dublin in
For example, at the turn of the 17th century, researchers estimate 22,000 to 32,000 southern right whales resided in the Southern Ocean surrounding
A comprehensive whaling ban and rigorous conservation efforts have helped the species rebound to an estimated 3,000 to 8,000 southern right whales in the Southern Hemisphere. However, the whale's cousin, the
The data confront a phenomenon researchers call the “shifting baselines syndrome,” the notion that current levels of sea life reflect past levels.
Case in point: A Scripps Institution of Oceanography study published this year by Loren McClenachan and others documented how much marine life in the
McClenachan, a graduate student at the time, compared photos taken by sport fishermen of their catches at the same dock. Photos from the mid-1950s depict veritable sea monsters, with 13 groups of “trophy” reef fish averaging 43.8 pounds and 6½ feet.
Fifty years later, some species are no longer seen. (Some, such as groupers, had acquired protected status to slow a precipitous decline in numbers.) A 2007 trophy fish was an imitation of its predecessors. The average weight had declined to 5 pounds. The mean length was 1 foot.
“These studies inform us about the factors that changed ocean productivity in the past and may help us develop new methods and targets for preserving and maybe recovering some of what was lost,”
“No one is arguing that we can restore the oceans to their previous pristine state, but if we're going to try to rebuild the seas at all, we need to know what's possible,” he said.
The
Launched in 2000 with private and public funding, the census has generated about 200 scientific books and papers involving hundreds of researchers. The database contains 350,000 records, with a goal of more than 1 million by the end of next year. #
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