Link between northern pollution and African drought and other stories

Link between northern pollution and African

drought and other stories

Adapted by I-han Chou and Kathleen Wong, California Academy of Sciences

Thursday, July 11, 2002


Smoking Gun Link Between Northern Pollution and African Drought


The smokestacks of North American and European factories may have spawned the devastating droughts that killed millions of people in Ethiopia and other parts of the Sahel region of Africa.


Scientists have been puzzled about the source of the 40-year dry spell, among the most severe in recorded history.


Now a global climate model developed by Leon Rotstayn of CSIRO Australia and Ulrike Lohmann of Dalhousie University in Canada appears to link the two phenomena. The cycle works like this: The sulfur spewed from factory chimneys tends to form aerosols that are more proficient than natural clouds at reflecting sunlight back into space. The cooling of the land below drives the tropical rain belt further south, causing droughts in the Sahel. Rain has slowly returned over the past few years, possibly as a result of the cleaner atmosphere from anti-air-pollution laws. The work is to be published in a future issue of the Journal of



Bees Boost Coffee Bean Yields


Birds and bees do it, and bees can help coffee plants do it even better. A new study in the journal Nature reveals that coffee plants, once thought to be largely self-pollinating, are able to produce more beans with the help of bees.


Entomologist David Roubik of the Smithsonian Tropical Research Institute in Panama compared the yield of coffee plants (Coffea arabica) available to insects against those shielded by netting. Conventional wisdom held that pollinating insects do not make a difference to bean production.


But Roubik found that plants visited by African honeybees produced more than 50 percent more beans than covered plants, perhaps because the bees transferred extra large loads of pollen. The find may explain why commercial coffee growers have been experiencing lower yields in newer coffee plantations: Monoculture farm fields aren't hospitable to honeybees.


Lean Times for Rockhopper Penguins


Perhaps one-fourth of the world's rockhopper penguin population has starved to death this year, possibly due to a drastic decline in local food sources. Biologists say that birds from the Falkland Islands colonies didn't have enough energy to leave the islands to hunt for food after molting. The emaciated bodies of at least 2,000 penguins —one-quarter of the colony — were found on Saunders Island in May.


Researcher Andrea Clausen of Falklands Conservation estimates the same number of penguin bodies were eaten or lost at sea. Boom and bust cycles have happened to rockhoppers before; the 1986 population of 2.5 million breeding pairs halved by 1987. Numbers stabilized at about 300,000 five years ago.


Researchers suspect melting Antarctic ice has cooled Falkland waters by up to 2 degrees Celsius. This, in turn, could be disrupting plankton production and forcing fish stocks to dine elsewhere. Biologists worry the dieoff could push rockhoppers, already classified as vulnerable, irreversibly closer to extinction.


Trees Mine Rock for Minerals


Trees don't need a milk mustache to get their essential daily calcium intake. A new study appearing in the journal Nature shows that some trees have developed a way to extract calcium out of solid rock.


Geologist Joel Blum and colleagues at the University of Michigan showed that some tree species spread fungus tendrils onto rock surfaces with their roots. The friendly fungi can then extract the calcium compound apatite from the rock. This allows spruce, fir, and other tree species to colonize poor-quality soils.


The talent may also confer the trees some protection against the effects of acid rain, which dr ains calcium from soil. However, Blum cautions against being too optimistic about forest ecosystems being able to resist this pollution byproduct. He said many other species cannot obtain calcium in this fashion and will still be devastated.


Hybrid Corals Add to Reef Biodiversity


Every summer on just a few special nights, the tropical waters of the Caribbean become the scene of a massive orgy. By the light of the full moon, more than 100 species of coral spawn simultaneously, turning the water oily with eggs and sperm.


Scientists have long wondered how, amidst this chaos, eggs and sperm of the same species are able to find each other and preserve the identity of their species. Now Steven Vollmer and colleagues at Harvard University report in the journal Science that coral crossbreeding does happen.


Genetic testing revealed that one of the three known species of Acropora coral is actually a hybrid of the other two. The hybrid is sterile but, as is the case with many corals, can reproduce itself by cloning. So even without the ability to combine their genes with others, these "immortal mules" are able to contribute to the biodiversity of the reefs.


Jupiter Is Not Alone


Astronomers have discovered a planet much like Jupiter orbiting a star in the constellation Cancer. Roughly the same size as Jupiter, the planet also orbits its sun, 55 Cancri, at a similar distance.


Planet hunters Geoffrey Marcy of the University of California at Berkeley and Paul Butler of the Carnegie Institution of Washington, announced the find while unveiling a batch of 15 new extrasolar planets. One of these, the size of Saturn, is the smallest extrasolar planet yet found. But the "new Jupiter" isn't an identical twin of our big solar system buddy. It's 3.5 to 5 times larger than Jupiter and orbits 55 Cancri about 28 million miles farther away.


Still, the discovery shows astronomers are homing in on solar systems that bear ever more similarity to ours. The team identifies the presence of planets indirectly: by observing the gravitational wobble large planets impose on the orbits of their suns. However, the technique is not sensitive enough to detect a planet as small as Earth.




Copyright 2002 — California Academy of Sciences