March 31, 2008
As a native Michigander, I’m a sucker for news about the Great Lakes. (That’s HOMES, remember? Huron, Ontario, Michigan, Erie, and Superior.) Engineers at the U of M Marine Hydronamics Laboratory have now designed a boat without a ballast tank in order to prevent the introduction of non-native species.
A ballast tank is a compartment that sits at the bottom of any large boat. When the boat doesn’t have any cargo, its crew can fill the ballast tank with water to help it stay afloat. The mechanical details on how this works can be found here; but basically, the extra water lowers the boat’s center of gravity and makes it more stable on the water.
Trouble is, these ballast water pools typically harbor lots of aquatic species. Researchers have identified 185 non-native species in the Great Lakes, and guess that most of them got there via cargo ship. The most famous are Zebra mussels, which are native to the Caspian Sea and were first introduced to the Great Lakes in 1988. Since then, they’ve disrupted ecosystems all over the U.S., out-competing local species for food and wreaking havoc in harbors, boats, and power plants.
Those U of M engineers are clever, though. They’ve figured out how to keep a ballast-free boat from sinking. As a press release explains:
Instead of hauling potentially contaminated water across the ocean, then dumping it in a Great Lakes port, a ballast-free ship would create a constant flow of local seawater through a network of large pipes, called trunks, that runs from the bow to the stern, below the waterline.
This design concept has been around since 2001, but only now have its creators built a prototype. When testing their 16-foot, $25,000 wooden scale model (shown above), the engineers found that not only does it work, but propelling it requires 7.3 percent less power than regular ships. That efficiency translates to a savings of $540,000 per ship (which is only slightly less impressive when you consider that a typical vessel costs a whopping $70 million to construct).
March 24, 2008
A decade ago, thanks to the Federal Endangered Species Act, gray wolves were reintroduced into Yellowstone National Park. Conservationists have since used radio collars and overhead surveillance technologies to keep track of the animals’ whereabouts. But at the end of this month, federal support will dissolve—meaning scientists will no longer be able to use the expensive equipment.
But a new, cheaper technology might save the day. “Howlbox,” developed by scientists at the University of Montana in Missoula, is a $1,300 speaker-recorder system that broadcasts digitized wolf howls and then records any real howls that respond to the fakes. The system is pretty sophisticated: a precise frequency analysis of the recordings shows not only how many wolves responded, but which specific ones did.
The Howlbox was tested in one spot in Montana in January. The University of Montana’s pilot project, involving four remote sites in Idaho, is slated for June.
The biggest problem with the box might not be the response from wolves, but from humans. As this NYT article points out:
To the uninitiated, a Howlbox-enhanced forest could sound as if wolves were everywhere—a scary proposition. Montana wildlife officials are braced for a public relations campaign if the project moves forward.
(Flickr, by Hare Guizer)
March 17, 2008
Never in my life have I seen so much news on leaf-cutting ants! Ok, ok, there’s only two findings but that still seems like a lot.
Most ants work in a kind of caste society, dividing labor among morphological subtypes within the colony. In the Atta laevigata leafcutter species, for instance, smaller worker ants take care of fungus growing on decaying leaves inside the colony, while larger workers focus on defending the colony. But all of the ants work on cutting and bringing back fruit pieces, which puzzled scientists Heikki Helantera and Francis Ratnieks. “Fruit is soft and can be cut by smaller workers,” they write in the latest issue of Proceedings of the Royal Society B: Biological Sciences. “Why, therefore, are large workers involved?
It turns out that since fruit (unlike leaves) is three-dimensional, ants with larger mandibles can cut and carry much larger pieces back to the colony than smaller ants. Their results show “how size variation among worker ants enhances division of labour.” Divide and conquer.
Just when your heart’s melted from thinking of all that colonial cooperation, here’s something a bit more scandalous. Ant colonies, like bees, have queens. It was thought that these queens developed from larvae that had been randomly selected, then carefully fed and nurtured by the rest of the colony.
But that theory’s now been debunked, thanks to DNA fingerprinting done by biologists Bill Hughes and Jacobus Boomsma. Certain males, they found, carried a “royal” gene, making their offspring more likely to become queens. But here’s the rub: the sisters of these royal males have no idea that their offspring is getting the shaft. Their results were published in PNAS on March 13. As Hughes (no relation) told LiveScience: “We think the males with these royal genes have evolved to somehow spread their offspring around more colonies and so escape detection. The rarity of the royal lines is actually an evolutionary strategy by the cheats to escape suppression by the altruistic masses that they exploit.â?
(Flickr, by Charles Lam)
March 10, 2008
Since its construction in 1964, the Glen Canyon Dam in Northern Arizona has depleted the sandy sidebars of the massive Colorado to just one quarter of their original size, leaving archaeological sites vulnerable to wind and destroying the natural habitat of dozens of fish species.
To try to remedy this, last Tuesday, authorities flooded part of the Colorado. The man-made flood—using 300,000 gallons of water per second for about 60 hours—was the third in the Grand Canyon in the past 12 years. The previous two weren’t entirely successful, as The Economist points out:
Floods were sent down the Grand Canyon in 1996 and 2004 and the results were mixed. In 1996 the flood was allowed to go on too long. To start with, all seemed well. The floodwaters built up sandbanks and infused the river with sediment. Eventually, however, the continued flow washed most of the sediment out of the canyon. This problem was avoided in 2004, but unfortunately, on that occasion, the volume of sand available behind the dam was too low to rebuild the sandbanks.
This time there is enough sand behind the dam. And most environmental groups argue that these kinds of floods need to happen more often to ensure that sediment levels remain steady. But there’s an economic downside to the floods: the water used in the flooding will not go through the hydropower turbines in the upper river, costing those power producers about $1 million.
In a month, scientists will be using sonar and surveying tools in the river banks to figure out how well the flood worked. With better models of sandbar formation, they’ll be better equipped to decide whether more frequent flooding is worth the high price tag.
(Flickr, via jackfrench)
March 4, 2008
Tragically, and even despite a phone call reminder from a friend, I forgot to look at the lunar eclipse on February 20 (and won’t get another chance to see one until December 2010). When later perusing this great collection of eclipse photos, I was surprised to see that it glowed red.
During a lunar eclipse, the Earth lies directly between the Moon and the Sun, thus blocking the Sun’s rays from directly hitting the Moon. Some light does hit the Moon, but only after getting refracted through the Earth’s atmosphere. The atmosphere is filled with low levels of volcanic dust. The less dust in the atmosphere, the brighter the Moon looks during an eclipse. Since few large volcanoes have erupted in the last decade, our recent eclipses have all been fairly luminous.
Richard Keen at the University of Colorado, Boulder thinks that these recent low levels of volcanic dust have contributed to global warming—as much as 0.2 degrees Celsius. This theory is extremely controversial, as pointed out in a news article posted today on NewScientist.com.
Most climate scientists, including authors of the mammoth IPCC report, say that the 0.6-degree Celsius rise in Earth’s temperature over the last 50 years is due almost entirely to greenhouse gases released by humans. In fact, if you look back over the last 40 years, volcanic dust levels have actually been higher than the 20 years before that, Susan Solomon of the US National Oceanic and Atmospheric Administration told New Scientist.
Wired blogger John Borland doesn’t put too much stock in Keen’s results:
There’s almost no question that this is going to stir up the climate-change deniers. So, before people get too excited, and claim that all this global warming is happening because we’re just going through a period of low volcanic activity– read the IPCC reports.
I’m less concerned about how the climate change deniers will use Keen’s data. Even if he’s right (and he may be right—the volcanic dust levels have been extremely low since 1995, allowing in lots of extra sunshine that could be heating the oceans, etc.), there’d still be 0.4 degrees of warming to account for. And the human use of fossil fuels would still be the most likely culprit.
(Flickr, by Savannah Grandfather)