April 20, 2009 -- Nearly 25 percent of land around the world is in bad shape and getting worse, according to a new study, and human activities are to blame. It's the first study to directly measure the extent of human-induced global land degradation. The phenomenon describes a decline in the quality of soil and vegetation that the land can't recover from on its own. Land degradation can have severe economic and environmental consequences, said David Dent, a Netherlands-based environmental scientist with ISRIC-World Soil Information, a soil research and education organization. "Once it's gone, it's awfully hard to get it back again," Dent said. "It's bad news for water. It's bad news for food production. And it's bad news for forests. It's bad news." Related Content:
The only previous attempt to assess the scope of global land degradation was in 1991, when researchers from ISRIC compiled the knowledge of experts from around the world to produce a somewhat subjective map of where land was in decline. That study, called the Global Assessment of Human-Induced Soil Degradation (GLASOD), suggested that 15 percent of the planet's land was degraded. But Dent wanted a more accurate -- and more recent -- count. "The United Nations Convention to Combat Desertification has used this as its raison d'etre to tell the world what a terrible state the world was in," Dent told Discovery News. He thought, "We can do better." In search of cold, hard numbers, Dent and colleagues tapped into a trove of NASA satellite data. Since 1981, a succession of satellites has taken regular measurements of solar radiation that is reflected into space from the Earth's surface. Chlorophyll, the green pigment in plants, absorbs near infrared wavelengths but it reflects red ones. So, by looking in the satellite data at the ratio of red to infrared wavelengths emitted in a given region, scientists can calculate how much vegetation is there. The team broke the world's landmasses into millions of 8-kilometer (4.9-mile) squares. For each square, they plotted what the value of the red-to-infrared ratio was every two weeks over the last 25 years. To make sure they were looking only at human-caused land degradation, the researchers made adjustments for other factors that might affect the numbers, such as global warming, volcanic eruptions and droughts. Get More NewsSpiders, Scorpions Among World's Oldest CreaturesMany creepy crawlies have been on Earth much longer than previously believed.Blood-Sucking Vampire Bats Sing DuetsWhite-winged vampire bats "harmonize" with separated roost mates.Oldest Hebrew Writing Possibly FoundAncient inscriptions on a 3,000-year-old pottery shard could make history.Rare, Prehistoric-Age Reptile Found in N.Z.A tuatara has been spotted on the New Zealand mainland for the first time in 200 years.Iceman Has No Living RelativesOetzi, the 5,300 year-old frozen mummy, left no living genetic legacy.SLIDE SHOW: Landscapes of TerrorWhat makes a place feel scary? There are scientific explanations.It's Official: People Are Warming the PolesHumans are conclusively to blame for polar warming, say scientists.Eight-Armed Animal Preceded DinosaursWhat may be one of Earth's first animals was no bigger than a coaster and had eight arms.Phoenicians Live on in People's GenesOne in 17 Mediterranean men may be descended from ancient Phoenicians.Pesticides, Fertilizers Linked to Frog DeclineA pesticide is found to promote parasites among amphibians.Hubble Telescope Taking Photos AgainThe Hubble Space Telescope is once again snapping stunning photos of the universe.Andean Mummy Hairs Show Hallucinogen UseScientists find direct evidence of hallucinogenic drug use among ancient Andeans.Opals on Mars Reveal Planet's Long Wet PastOpals found on Mars suggest the planet has been wet for much longer. |
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