SCIENCE
NEWS
This Week
groove and then retracts several times
within half a second.
To measure tongue extension, Muchhala
encouraged bats to sip sugar water from
drinking straws. He started with test tubes
but switched when the small, agile bats
plunged in up to their shoulders. Other local
nectar bats reached down 4 cm. The new
species more than doubled that depth,
Muchhala reports in the Dec. 7 Nature. “I
was amazed,” he says.
By studying newly identified museum
specimens, Muchhala found that the prodigious tongue attaches within a tube of tissue that originates in the bat’s chest between
the sternum and the heart and extends to
the back of the mouth. Circular muscles
within the tongue tighten to rapidly
increase its length.
Some of the pollen grains that Muchhala collected from the bats’ fur came from
Centropogon nigricans, a pale-green, trum-pet-shaped flower. Nectar collects at the
bottom of these blossoms, which average
about the length of the tube-lipped bat’s
tongue extension.
When Muchhala videotaped such flowers, day and night, for more than a week,
bats were the only visitors. He never found
the flower’s pollen on other bat species, so
he proposes that only tube-lipped bats pollinate that flower.
Other tropical plants cater to single pollinators, notes Scott Mori of the New York
Botanical Garden. Those flowers tend to be
more specialized than their pollinators,
which will visit other flowers after their private nectar reserves have been depleted.
Bat systematist Nancy Simmons of the
American Museum of Natural History in
New York City welcomes the report of the
new tongue structure as “a fabulous discovery.” She says that anteaters are the only other
animals that she knows to have tongues in
their chests. Other observers have reported
that scaly anteaters extend their tongues
about 50 percent of their body length.
The anteaters’ supertongues probe ant
nests, which present a problem similar
to that posed by deep flowers. Simmons
says that the anteaters and bats independently evolved tongues that met that
challenge. —S. MILIUS
Dim Harvest
Asian air pollution
has limited rice yields
Thick clouds of air pollution over southern
Asia and increased concentrations of greenhouse gases in the atmosphere worldwide
have restricted rice harvests in India for the
past 2 decades, a new analysis suggests.
Aerosols, such as volcanic ash and industrial soot, typically cool Earth’s surface by
reflecting some solar radiation back into
space. This phenomenon somewhat counteracts the planet-warming effect of
increased concentrations of gases such as
carbon dioxide, says V. Ram Ramanathan,
a climate scientist at the Scripps Institution of Oceanography in La Jolla, Calif.
However, after reviewing crop records
LONG DRINK A tube-lipped nectar bat from Ecuador sticks out its tongue to drink from a
glass cylinder. Between sips, the lower part of the tongue will retract into a sheath that runs
from the back of the bat’s mouth down into its chest (inset diagram).
and past research, Ramanathan and his colleagues suggest that the cooling action of
the so-called Asian brown cloud that hangs
over much of India hasn’t countered global
warming’s negative consequences on rice
harvests. For one thing, the cooling effect
occurs at the wrong time of day, they say.
Increased concentrations of greenhouse
gases raise nighttime temperatures, says
Ramanathan. But air pollution blocks radiation only in the daytime, he notes.
In previous studies, each 1°C increase in
average nighttime temperature decreased
rice yield in the Philippines about 10 percent (SN: 7/10/04, p. 29), and in India, the
air pollution was shown to reduce rice yields
between 6 and 17 percent.
Beyond their cooling action, thick clouds
of high-altitude pollution tend to stifle precipitation. The abundance of small particles in the atmosphere results in water
droplets that are too tiny to fall as rain (SN:
3/11/00, p. 164). Furthermore, says
Ramanathan, the clouds of pollution
decrease evaporation at ground level and
thereby reduce the amount of water vapor
available to form rain.
The reduction in rainfall both decreases
rice yield per acre and cuts the number of
acres that can be farmed. “This shows that
air pollution isn’t just an urban problem,”
says Ramanathan.
He and his colleagues have analyzed
India’s rice harvests since 1966. They report
in an upcoming Proceedings of the National
Academy of Sciences that after improvements in agricultural techniques sparked
dramatic yield increases in the mid-1960s,
the annual growth of yields dropped to
around 3 percent in the mid-1980s and has
been stagnant since 2000. Although factors such as soil degradation and falling
rice prices may have played a role in this
decline, air pollution and greenhouse gases
have contributed substantially, the researchers contend.
If the Asian brown cloud hadn’t been present over India, increased precipitation would
have boosted rice harvests by 10.6 percent
each year between 1985 and 1998, the scientists say.
Rice yields would have been another
3.8 percent higher if atmospheric concentrations of greenhouse gases had
remained stable during those years, says
Ramanathan.
The new findings “combine several
aspects of climate change and give a better
idea of how crop yields might change in the
future,” says Lew Ziska, a plant physiologist with the Agricultural Research Service
in Beltsville, Md. “When you look at climate
change, it’s not just about warming.”
Says Peter Timmer, an agricultural economist at the Washington, D.C.–based Center for Global Development, “Brown-cloud
pollution has already cost India millions of
tons of food production.” —S. PERKINS
M. COOPER; (INSET) MUCHHALA
