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The Economist / Environment

Aerodynamics: Blowin' in the wind
28 11 2008 Flapping flags may shed light on how fish school and birds flock OFTEN it pays not to be leader of the pack—just ask a racing cyclist or a Formula One driver. Conserving energy by following the leader, a trick known as slipstreaming, can give a rider or driver that extra bit of juice to pull ahead at the very last moment. In the natural world, however, bodies are more likely to be flexible, like a fish’s, rather than rigid, like a car’s. In these systems, as a recent paper in Physical Review Letters reports, it is the leader that enjoys a significant dynamic advantage over the followers. Jun Zhang of New York University came to this conclusion obliquely, by examining one of life’s burning questions: why is it that flags flutter in a breeze? Flags are good analogues of birds and fish because all three change their shape as they move through a fluid. In 2000 Dr Zhang did some experiments to study the motion of thin silk filaments (standing in for flags) in flowing films of liquid dishwashing soap (standing in for the breeze). ...

Conservation: Tuna in trouble
28 11 2008 Anger that the catch will still be too big ACCORDING to conservationists it is a disaster for the bluefin tuna, but as far as the European Commission is concerned it is a landmark decision to try to conserve their stocks. These are the opposing views of the outcome of a meeting this week in Morocco to set the allowable annual catch of the species, the population of which has tumbled because of overfishing, mainly by European fleets. The organisation responsible for looking after tuna in the north-east Atlantic and the Mediterranean Sea, the International Commission for the Conservation of Atlantic Tunas (ICCAT), agreed to reduce the total allowable catch of bluefin in these areas from 28,500 this year to 22,000 tonnes next and to 19,950 tonnes in 2010, to give a total cut over two years of 30%. But this was considerably short of what many scientists—including some experts appointed by ICCAT—say is necessary. They wanted the catch to be limited to 15,000 tonnes. Some countries, including Spain, had wanted the fishery suspended altogether. ...

Green.view: Sub-subprime
25 11 2008 Greener thinking for the poorest cities WORLD HABITAT DAY last month was marked by a prize rewarding smart urban planning - supposedly in the “greening” of cities. This year top honours went to Nanjing in China, with commendations for Kigali in Rwanda, Ciudad Juarez in Mexico, Shaoxing and Zhangjiagang also in China, and Bugulma in Russia. The day struggled for media attention. Some in Habitat, the United Nations agency tasked with improving the planet’s urban fabric, fretted that they had been outshone by the International Year of the Potato. “We’re not bums and needles like UNICEF,” sighed a Habitat official. “We’re policy, and policy, for most people, is like watching paint dry.” Yet the facts tell a far more dramatic story—one that could soon shove grey and diminutive Habitat towards the front of the UN system and make it an increasingly important player in green politics. ...

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