3. Desert Ecosystems

Studying Desert Ecosystems

2013 February 12. NASA Satellite Data Find Freshwater Losses in Middle East. NASA RELEASE 13-049. Excerpt:  A new study using data from a pair of gravity-measuring NASA satellites finds that large parts of the arid Middle East region lost freshwater reserves rapidly during the past decade. ...during a seven-year period beginning in 2003, parts of Turkey, Syria, Iraq and Iran along the Tigris and Euphrates river basins lost 117 million acre feet (144 cubic kilometers) of its total stored freshwater. That is almost the amount of water in the Dead Sea. The researchers attribute about 60 percent of the loss to pumping of groundwater from underground reservoirs. ...NASA's twin Gravity Recovery and Climate Experiment (GRACE) satellites, are essential. GRACE is providing a global picture of water storage trends and is invaluable when hydrologic observations are not routinely collected or shared beyond political boundaries. "GRACE data show an alarming rate of decrease in total water storage in the Tigris and Euphrates river basins, which currently have the second fastest rate of groundwater storage loss on Earth, after India," said Jay Famiglietti, principle investigator of the study and a hydrologist and professor at UC Irvine. "The rate was especially striking after the 2007 drought. Meanwhile, demand for freshwater continues to rise, and the region does not coordinate its water management because of different interpretations of international laws." ...The team calculated about one-fifth of the observed water losses resulted from soil drying up and snowpack shrinking, partly in response to the 2007 drought. Loss of surface water from lakes and reservoirs accounted for about another fifth of the losses. The majority of the water lost ...was due to reductions in groundwater. ..."The Middle East just does not have that much water to begin with, and it's a part of the world that will be experiencing less rainfall with climate change," said Famiglietti. "Those dry areas are getting dryer. ...Study co-author Matt Rodell of Goddard added it is important to remember groundwater is being extracted unsustainably in parts of the United States, as well. "Groundwater is like your savings account," Rodell said. "It's okay to draw it down when you need it, but if it's not replenished, eventually it will be gone."....

2010 October 19.  VIDEO: Protected areas in Kuwait and their potential long-term role in adaptation to climate change.  Rio Conventions' Pavilion.  Video Description: Dr. Samira Omar Asem, whose work studying the desert ecosystem of Kuwait following the 1990-1991 Iraq war is featured in Ecosystem Change chapter 3, presents more recent research on the Sabah Al Ahmad Nature Reserve.

2010 July 17. After Oil Spills, Hidden Damage Can Last For Years. By Justin Gillis and Leslie Kaufman, The New York Times.Excerpt: Only 20 years ago, the conventional wisdom was that oil spills did almost all their damage in the first weeks, as fresh oil loaded with toxic substances hit wildlife and marsh grasses, washed onto beaches and killed fish and turtles in the deep sea.
…But disasters like the Valdez in 1989, the Ixtoc 1 in Mexico in 1979, the Amoco Cadiz in France in 1978 and two Cape Cod spills, including the Bouchard 65 barge in 1974 — all studied over decades with the improved techniques of modern chemistry and biology — have allowed scientists to paint a more complex portrait of what happens after a spill.
…[E]ven before the spill, the land was under enormous environmental stress, largely due to human activity. Dams on the Mississippi River and its tributaries have slowed the flow of sediment to the marshes, and global warming has caused sea level to rise.
…Oil spills produce a powerful impulse to clean up the oil and restore as much of the environment as possible. But that impulse can itself be a source of destruction.
…The lesson, scientists say, is not that people should never try to clean up an oil spill. It is possible to do too little as well as too much. But the calculation of how much to do is tricky, demanding deep scientific understanding of an area’s ecology. Applying supposed common sense has repeatedly led to mistakes.
…Already in Louisiana, battles have erupted between the Army Corps of Engineers and local residents, led by Gov. Bobby Jindal, over proposals to build sand and rock barriers to block the oil from coming into the marshes. The corps has been cautious on approval permits and recently rejected a plan to build a rock barrier outside Barataria Bay, arguing that such structures would change water-flow patterns to the possible detriment of the marsh ecology.

2009 November 5. Climate Change, Nitrogen Loss Threaten Plant Life in Arid Desert Soils. NSF Release 09-218. Excerpt: ...As Earth's climate warms, arid soils lose more nitrogen, which could lead to deserts with even less plant life than they sustain today.
Available nitrogen is second only to water as the biggest constraint to biological activity in arid ecosystems, but ecologists have struggled to understand the balance of the input and output of nitrogen in deserts. For the first time, however, researchers have discovered a mechanism that balances the nitrogen budget in deserts: Higher temperatures cause nitrogen to escape as gas from desert soils.
...In the past, researchers focused on biological mechanisms in which soil microbes near the surface produce nitrogen gas that dissipates into the air, but ecologists Jed Sparks and Carmody ("Carrie") McCalley, both at Cornell University and co-authors of the paper, found that non-biological processes are playing a bigger role in nitrogen losses from soil to air.
"This is a way that nitrogen is lost from an ecosystem that people have never accounted for before," said Sparks.  "It allows us to finally understand the dynamics of nitrogen in arid systems."
...Further temperature increases and shifting precipitation patterns due to climate change may lead to more nitrogen losses in arid ecosystems, making their soils even more infertile and unable to support most plant life, according to McCalley. Although some climate models predict more summer rainfall for desert areas, the water, when combined with heat, would greatly increase nitrogen losses, she said.
"We're on a trajectory where plant life in arid ecosystems could cease to do well," said McCalley....

2007 June 28. Likely Spread of Deserts to Fertile Land Requires Quick Response, U.N. Report Says. The New York Times. By Elisabeth Rosenthal. Excerpt: Enough fertile land could turn into desert within the next generation to create an ''environmental crisis of global proportions,'' large-scale migrations and political instability in parts of Africa and Central Asia unless current trends are quickly stemmed, a new United Nations report concludes. ''The costs of desertification are large,'' ...

2007 January 3. Defining Desertification. By Holli Riebeek. NASA Earth Observatory. [This article gives some insight into the origins and significance of the development of NDVI (Normalized Difference Vegetation Index) which the GSS Interpreting Digital Images software helps students to understand. ---Alan Gould]
Botswana, 1984. Cattle roam over grasslands at the edge of the Kalahari Desert. ...A full 77 percent of the country's 576,000 square kilometers is already used for grazing, but even this isn't enough to support the cattle. The grasslands are prone to drought, and the government is forced to import food for them. British biogeographer Stephen Prince is among the scientists that the United Nations Food and Agriculture Organization has asked to assess the health of the rangelands. How is drought impacting the land? Is overgrazing occurring? ...Conditions could vary widely; healthy vegetation could be growing meters away from barren land. "You couldn't measure vegetation change over the entire country with 50 data points." ...Prince stopped by the house of a colleague, John Townshend. ... from NASA Goddard Space Flight Center...remote-sensing ecologist Compton Tucker had developed a new scale, or index, of global vegetation based on satellite data. ...the index could show how much photosynthesis was happening in every 8-by-8-kilometer patch of ground. Displayed as a map, the index revealed the productivity of the grazing land over a broad area over successive 15-day periods. ..."It blew me away that we could see a complete continent at frequent time intervals," Prince says. "It was a career-changing moment." ...the vegetation index would be able to answer even larger questions about Africa's vegetation. ...Prince had seen the effect of devastating drought in Africa's Sahel, a...semi-arid, sparse savanna immediately south of the Sahara Desert. A list of Sahelian countries is a yearbook of famine: Sudan, Chad, Niger, Mali, Mauritania, Ethiopia, Burkina Fasso, and Senegal. A string of dry years leading up to the early 1980s shriveled vegetation throughout the Sahel, causing some people to fear that the Sahara Desert was steadily marching southward, .... Ground studies had produced dramatic pictures of formerly productive lands reduced to apparent desert. Many people extrapolated from these local examples of desertification to propose that the whole Sahel was becoming a desert, but no one had surveyed the entire Sahel. It was far too large a task. ..."When I saw the vegetation index data, I realized that it was exactly the scale we wanted for studying desertification," says Prince. "There is no other way of seeing big enough areas at high enough frequency." ....


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