This is SCIENCE IN THE NEWS in VOA Special English. I'm Bob Doughty.
And I'm Faith Lapidus. Do forests prevent major floods? A United Nations report says no.
Building houses powered by the sun ... but what happens when it rains?
And, later, we tell about a possible new way for many people with diabetes to take their daily insulin.
|A deadly landslide after Hurricane Stan hit Guatemala|
People often blame the destruction of forests when rains lead to severe flooding. Such blame followed recent floods in Central America and East Asia, for example. But a new report disputes this idea.
It says there is no scientific evidence to link severe floods to the loss of forests. The report is the work of the United Nations Food and Agriculture Organization and the Center for International Forestry Research.
Patrick Durst is a forestry official for the F.A.O. office in Bangkok. He says government officials, aid groups and the media are often quick to blame flooding on deforestation caused by small farmers and tree cutters. He says such ideas have, in the past, led some governments to force poor farmers from their lands and away from forests. Mister Durst calls such actions misguided.
The new report says forests can help to reduce the flow of rainwater, or runoff, that causes floods in local areas. However, it says there is no evidence that the loss of trees is a major cause of severe widespread flooding. The report came out this month in the same week as major flooding caused by a powerful storm in Central America.
The report says the flood-reducing effects of forests depend heavily on the structure and depth of the soil. The amount of water in the soil is another influence. Even at the local level, the report says, the effects do not depend just on the presence of trees.
David Kaimowitz is director-general of the Center for International Forestry Research. He says planting trees and protecting forests can be good for the environment in many ways. But, he adds, preventing large floods is not one of them.
Mister Kaimowitz notes that thick forests were more plentiful a century ago. But he says the rate of what he calls "major flooding events" has remained the same over the past one hundred twenty years.
Economic and human losses from floods have increased over the years, however. The report says that is mainly because more people live and work in areas where floods are common.
Pal Singh of the World Agroforestry Center says people need to stop blaming floods on those who live and work in and around forests. He says people should instead consider the effects of many different land-use issues. In some cases, he says, these issues can include poor methods of tree removal.
The report says people have believed since the nineteenth century that forests prevent floods by capturing heavy rainfalls. But it says major floods blamed on deforestation almost always happen after many days of rains. The water then has nowhere to go but into rivers, which flood quickly.
Here are some other things said in the new report from the United Nations:
There can be a political interest not to dispute the traditional beliefs about forests and flooding. Governments can act to ban the removal of trees. Such policies give the appearance of strong action. But the effect is to force poor farmers from their lands and leave many people unemployed. International agencies might also have an interest because the traditional beliefs lead to aid for reforestation projects.
David Kaimowitz at the Center for International Forestry Research says: "Politicians and policymakers should stop chasing quick fixes for flood-related problems."
You are listening to SCIENCE IN THE NEWS in VOA Special English.
The United States Department of Energy held the Solar Decathlon earlier this month. The event is a chance to see which team from a college or university can build the best solar-powered house.
Eighteen houses powered by energy from the sun formed a "solar village" on the National Mall here in Washington. Hundreds of students traveled from around the country as well as Puerto Rico, Canada and Spain. They built their houses on the grassy open space between the Capitol building and the Washington Monument.
The teams were made up of students who want to be engineers, scientists and architects. Some of them spent almost two years working on their projects.
Each house had to collect as much energy as a family of four would need to heat their home, cook, wash clothes and do other tasks.
The houses had to be energy-efficient. The systems had to waste as little energy as possible.
The teams also designed their homes so that they would be pleasant to live in. Many of the houses in the solar village had gardens or walls that could move to create outdoor living spaces.
Each team competed in ten different competitions to decide the winner.
For most of the eight-day competition, the students faced an additional challenge. Clouds covered the sun, and rain fell on the specially designed roofs of their houses. On a sunny day, these roofs take in the heat of the sun and change it into electrical energy. Tiles on the floors of the houses store additional heat for use when the weather becomes cold.
The more solar panels each house had on its roof and walls, the more energy the house could collect during breaks in the rain. Batteries stored the energy for later use.
The team from the University of Madrid was able to collect enough energy to power a computer and to heat several gallons of water. A gallon is almost four liters. But the students had trouble with another one of the ten events. They could not collect enough energy to win a race of cars powered by solar batteries.
At the end of the week, the rain had not stopped. But it was time to take down the houses. Some of the teams said that they would ship the homes back to their schools and use them for educational purposes. Other teams said they planned to give their houses to victims of Hurricane Katrina.
|2005 winning design|
The team from the University of Colorado won the first Solar Decathlon in two thousand two. And they did it again this time. Cornell University in Ithaca, New York, finished second. California Polytechnic State University finished third.
The Energy Department plans to hold the Solar Decathlon every two years from now on.
There may be an easier way for many people with diabetes to take insulin to control their blood sugar levels. Diabetics who now need daily injections may one day be able to take their insulin by mouth. They would breathe it as a powder into their lungs, through a mouthpiece device.
The inhaled insulin is called Exubera. The drug companies Pfizer, Sanofi-Aventis and Nektar Therapeutics developed it. They say it is generally as effective as the injected form in controlling blood sugar levels. But they say it should not always be used in place of longer-lasting injections of insulin.
Last month, an advisory committee of the United States Food and Drug Administration urged the agency to approve Exubera. The committee voted seven-to-two to support approval for both type one and type two diabetes. The F.D.A. generally follows the advice of its committees, but does not have to.
Some members of the committee expressed concern about possible safety risks, especially to people with lung disease. Smokers would probably not be able to use the inhaled insulin. But there are questions about the safety for people who breathe a lot of tobacco smoke in the air. The drug makers have proposed to study the long-term effects until two thousand nineteen.
SCIENCE IN THE NEWS was written by George Grow and Katherine Gypson. Cynthia Kirk was our producer. Our programs are online at voaspecialenglish.com. I'm Bob Doughty.
And I'm Faith Lapidus. If you have a science question that we might be able to answer on our program, send it to email@example.com. And listen again next week for more news about science in Special English on the Voice of America.