| Goodbye Baiji
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| Date and Time |
- | Dec. 15th, 2006, 12:32 pm | |
| Current Mood |
- |  sad | |
| Current Music |
- | budgies in conference in next room | |
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 | Human activity in China's Yangtze river is causing the region's dolphins to go extinct — and more species will follow if fishing is not regulated, conservationists have warned.
Scientists on an expedition in China claimed this week that the freshwater baiji (Lipotes vexillifer), also called the river dolphin, should be declared 'functionally extinct' in the river. This means that even if a tiny handful of individuals still remains, their numbers will not be enough for them to bounce back. The creature does not live anywhere else — making it the first cetacean to be driven to extinction by humans.
"There's no hope to save them," says August Pfluger, chief executive of the Baiji.org foundation, which has just completed a six-week survey of the Yangtze during which they found no baijis.
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What's more, another Yangtze mammal, the finless porpoise (Neophocaena phocaenoides), is also heading the same way, Pfluger says. "In the 1980s there were thousands and thousands," he says. "In the 1990s there were around 6,000, according to surveys. Now there are around 400. The population is declining at an alarming speed."
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The Yangtze basin, which winds for 1,750 kilometres and ends at Shanghai, is the most densely populated place on the planet — around 400 million people live along its banks. "The habitat is so degraded that it's very difficult for large animals to survive," says [Rob] Shore.
In the short term, he suggests that remaining dolphin species and other mammals should be taken from the river and put into lakes to safeguard them until the river can be restored. "It's not an ultimate solution but it might have to be the way forward," he says.
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| Sinking in the Earth
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| Date and Time |
- | Jun. 3rd, 2006, 01:41 pm | |
| Current Mood |
- |  enthralled | |
| Current Music |
- | lake singing to dilly | |
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| Deep within Earth, halfway to its center in an area where Earth's core meets its mantle, lies a massive folded slab of rock that once was the ocean floor, reports a team of researchers (including one from Arizona State University) in the current issue of Nature. (Image courtesy of Arizona State University)
The slab, which sank beneath North America some 50 million years ago, holds important clues as to the behavior and composition of the deep interior of Earth and it could help explain how surface features such as volcanos and earthquakes form, the researchers say.
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"In this one location we see quite strong evidence for whole mantle circulation," said Garnero, an ASU seismologist. "Slabs descending deep into the mantle are thought to drive the convective system found within Earth. They are dense and fall into the mantle. But they are connected to the outer shell that includes the oceanic crust."
"It's like a carpet sliding off the dining room table," Garnero added. "If it is more than half way off, it just goes taking everything with it."
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Using the method, the researchers found the subducted slab is composed of essentially the same minerals as the surrounding mantle, but its temperature is about 700 degrees Celsius cooler. This temperature difference affects the location of a "phase transition," where the crystal structure of the mantle rock compresses to a more compact form due to increasing pressure and temperature with depth. Seismic energy reflected by this phase transition revealed an abrupt step in the phase boundary about 60 miles (100 kilometers) high.
The researchers also saw evidence of hot plume-like structures at the edge of the slab, indicating possible upwelling of hot material from the base of the mantle as the spreading slab pushes into it.
"Since there is a conservation of mass in the mantle, something must return as the slab sinks into the Earth," Garnero said. "This return flow can include plumes of hot material that gives rise to volcanism."
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| Where's George Pays Off
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| Date and Time |
- | Jan. 27th, 2006, 08:12 am | |
| Current Mood |
- |  groggy | |
| Current Music |
- | space heater | |
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| Using a popular internet game that traces the travels of dollar bills, scientists have unveiled statistical laws of human travel in the United States, and developed a mathematical description that can be used to model the spread of infectious disease in this country. This model is considered a breakthrough in the field.
"We were confident that we could learn a lot from the data collected at the www.wheresgeorge.com bill-tracking website, but the results turned out far beyond our expectations," said Lars Hufnagel, a post-doctoral fellow at the Kavli Institute for Theoretical Physics at the University of California, Santa Barbara and co-author of an article describing the research in the January 26 issue of the journal Nature.
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Historical pandemics, like the 14th-century plague, moved slowly in waves across geographical areas, because in the Middle Ages people could typically only travel a few kilometers a day. The speed with which epidemics could spread was thus kept in check. It took the plague three years to move up the European continent, south to north, with an average rate of spread of about two kilometers a day.
"But today people move great distances in short time periods, as well as short distances, and they use variable means of transportation," said Hufnagel. "Thus we can expect that future pandemics will spread according to other rules, and more quickly. The rapid worldwide spread of SARS (severe acute respiratory syndrome) has already demonstrated this."
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"Since we can't track people with tracking devices, like we do animals, we needed to get data that provided us with millions of movements of individuals," explained Hufnagel. Scientists are already familiar with similar scaling laws from physical and biological systems. "What is amazing about these particular scaling laws is the fact that they are determined by two universal parameters only. This result surprised us all."
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