SCIENCE IN THE NEWS in VOA Special English.
I'm Bob Doughty.
And I'm Faith Lapidus. This week, we will tell about one explanation
for many trees dying in the western United States. We will tell about a project to make
electronic maps of soil in Africa. And,
we tell how one kind of caterpillar can trick another insect.
have found that trees are dying at an increasing rate in the western United
States. The scientists say they believe
the tree deaths were partly a result of warmer and drier weather conditions linked
to climate change.
team of eleven researchers reported their findings last month in Science
magazine. The researchers work for the
United States Geological Survey, the Forest Service and several
studied trees in seventy-six long-term forests in six American states and the
Canadian province of British Columbia. The
thirty-year study is said to be the largest ever investigation of North America's
old growth forests.
researchers say they were concerned by the findings. The trees they observed were dying two times
as fast as trees were thirty years ago. Additionally, the increased death rate was
higher than the rate of new tree growth.
findings are similar to those of other recent observations and studies,
including one involving bark beetles.
That study blamed the insect for the destruction of more than one million
hectares of pine forest.
The new study found increasing
death rates of several kinds of forests, like pine, fir and hemlock. The higher rates were observed among trees of
different ages and sizes.
The elevation of the forests was not considered
important. Trees high in the mountains
were dying at about the same rate as those closer to sea level.
The researchers investigated other
possible causes of the tree deaths like insects, fires and air pollution. They also look at issues like operations to
clear forests, and increasing competition among trees. Yet the researchers say none of these are as likely
to blame for the tree deaths as climate change.
Nathan Stephenson was a
lead writer of the report. He says
temperatures have increased in the areas where forests are found. Since the nineteen seventies, temperatures
have increased almost half a degree Celsius in each ten-year period.
Stephenson says summers are becoming longer and hotter in the western United
States. This makes trees weaker and
decreases their ability to survive insect attacks and forest fires.
The researchers say the long-term effects
of the increased death rates are hard to predict. However, they say, there could be fewer
forests in the future.
Forests are important to the environment
because they take in carbon dioxide and release another gas -- oxygen. This process removes carbon from the
atmosphere. However, carbon is released when
trees die or burn. If trees take in less
carbon dioxide, scientists say, it could increase the effects of climate change.
Some researchers say new measures
may be needed to keep the forests alive. Mister Stephenson says one of the best answers
is to reduce the amount of pollution that people produce.
soil keeps many farmers in Africa from growing good crops. Low soil fertility has slowed agricultural
production in parts of the continent for years. The United Nations says that one-third of the people south of the Sahara
Desert suffer from hunger.
But a newly announced project promises help for the
situation. A not-for-profit agency is
working toward developing soil maps and making them available on the
Internet. The agency is called the International
Center for Tropical Agriculture. It
plans to describe the soil in forty-two nations in sub-Saharan Africa.
When the project is
completed, farmers will be able to get information that will help them decide
what to plant and how to care for their land. In the past, it often has been hard to get complete information about soil
conditions. Maps for the purpose
exist. But they are in paper form and
often not widely available.
Tropical Soil Biology and Fertility Institute in Kenya will supervise the
project. Institute director Nteranya
Sanginga says supervision, or management, of soil in sub-Saharan Africa must
improve. He said the improvements are
needed if the area is to reduce poverty and feed growing populations. He said the improvements also are needed to
fight the effects of climate change.
from the African Soil Information Service will study earth samples and rate
them. The researchers will also use
satellite technology to create images showing the nutrients and wetness of the samples. The images also will show the amount of
organic material in the soil.
also will study chemical and physical qualities of the soil with a method
called infrared spectroscopy. The method
can quickly judge the soil's ability to hold water and take-in nutrients. Project information manager Peter Okoth says
a majority of farmers may have the information on-line in three years.
Bill and Melinda Gates Foundation and the Alliance for a Green Revolution in
Africa have given eighteen million dollars to collect the information. The money will be provided over four
years. Project partners include the
Earth Institute at Columbia University in the United States
you ever wondered what it would be like to be treated like an important leader? A European butterfly species has found a way
to make that wish come true.
Insect experts say ants communicate mainly through
touch and chemical signaling. But
scientists now believe that the leader of an ant community, the queen ant,
makes sounds that set her apart from other ants. Because of the sounds, worker ants feed and
protect the queen ant.
scientists say they found that one kind of caterpillar has ways to reproduce a
sound that the worker ants think is their queen. The caterpillars grow to become Maculinea rebeli, also known as the
Rebel's Large Blue butterfly.
The caterpillars also
release chemicals that trick the ants into bringing them to their communities,
or colonies. Once inside, the
caterpillars make the sounds of the queen ant.
The ants feed and care for them during a period when they are
inactive. After eleven to twelve months,
the caterpillars form pupae and become butterflies.
technology made it possible for the scientists to record the queen and worker
ant sounds. The sound the caterpillar
makes was also recorded. When played
back to the worker ants, they reacted the same way to the caterpillar sounds as
they did to the queen ant sounds. They
gathered around a device making the sounds and did not move for hours.
queen ant and the caterpillar sound very different to the human ear. However, scientists say similarities in what
they called resonant frequency were found through sound tests.
An international team of researchers carried out the
study. The researchers come from
Britain's Centre for Ecology and Hydrology, the University of Oxford and
Italy's University of Turin. The
findings were reported last month in Science magazine.
Thomas is a professor at the University of Oxford. He found that ants will rescue a caterpillar
they believe to be the queen when their ant colony is threatened.
research showed the worker ants would do this before protecting their
young. The ants have even been observed
using ant larvae to feed a caterpillar when food supplies are low.
Barbero from the University of Turin was the lead writer of the report. She says the findings show that sounds are
more important in the communication between ants than scientists had thought.
Rebel's Large Blue butterfly has become endangered because of changes to its
environment. Currently, it is only found
in grassy areas within the mountains of Europe.
The scientists believe their findings will help in
designing new methods to protect the endangered insects. Scientists are also interested in discovering
whether other species have developed ways to use a similar kind of trickery to
This SCIENCE IN
THE NEWS program was written by Jerilyn Watson and Brianna Blake, who was also
our producer. I'm Faith Lapidus.
Bob Doughty. Read and listen to our
programs at voaspecialenglish.com. Join
us again next week for more news about science in Special English on the Voice