Remote Sensing Aids Water Monitors, Farmers

 

MADISON, Wisconsin, January 16, 2003 (ENS) - Remote sensing using satellites could help monitor water quality and crop fertilization, according to two teams of scientists. University of Wisconsin-Madison researchers and their cooperators have developed a method of assessing the water quality of

Wisconsin's lakes from space. Using images captured 438 miles above the earth, they have completed the first satellite based inventory of the clarity of

the largest 8,000 lakes in the state.

"Our research aims to integrate satellite data into the state's day to day lake management programs," said Thomas Lillesand, who led the effort as

director of UW-Madison's Environmental Remote Sensing Center. "This won't eliminate the need for conventional water quality monitoring, but it will greatly increase the benefits of ground based sampling." The researchers hope to monitor lake clarity over time to learn "where lake management activities might be most useful, and which lakes will be most subject to change in the future due to such factors as changes in land use and climate," Lillesand added.

The new statewide water clarity map, daily satellite images of  Wisconsin, and an electronic gallery of Landsat images of Wisconsin lakes are viewable online at: http://www.ersc.wisc.edu

Today's wheat growers also face many environmental challenges, including the use of fertilizer. Growers need to apply enough nitrogen based fertilizer to achieve the highest possible crop yields without over-applying - a situation that could lead to serious environmental effects. In wheat, a critical factor comes down to timing in order to determine how efficiently plants will use nitrogen fertilizer. Current methods for determining the optimum timing of nitrogen fertilizer application can be difficult, expensive and time consuming. To assist wheat growers, scientists at North Carolina State University have developed a technique to time nitrogen fertilizer applications using remote sensing, including aerial photography and satellite imagery. "This is one of the first applications of remote sensing technology for nitrogen management available to growers," said Michael Flowers, project scientist. "With the ability to cover large areas in a quick and efficient manner, this remote sensing technique will assist growers in making difficult nitrogen management decisions that affect profitability and environmental stewardship."

In this 2000-2001 study, scientists used remote sensing in the form of infrared aerial photographs to determine when early nitrogen fertilizer applications were required. By relating the infrared reflectance of the crop canopy to wheat tiller density, the scientists were able to differentiate wheat fields that would benefit from early nitrogen fertilizer applications compared to wheat fields that would benefit from standard nitrogen fertilizer applications. The remote  sensing technique was found to accurately time nitrogen fertilizer applications 86 percent of the time across all field locations. The results of the study appear in the January/February 2003 issue of "Agronomy Journal," available online at: http://agron.scijournals

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Climate Records Show Global Warming Could Influence Asian Monsoon"

(Source: Univ of Arizona, 1/22/03)

 

More than half the world's population depends on the Asian monsoon to bring much needed moisture for agriculture and basic human needs. But   the yearly rains can also bring peril. Surging flood waters from last  summer's monsoon killed more than 800 people in India, Nepal,  and  Bangladesh, displacing millions of others.

Scientists have observed that the Asian monsoon has been gaining strength during the past few centuries, possibly due to rising global  temperatures. The intergovernmental Panel on Climate Change concluded in 1994 that global warming could intensify the monsoon and increase  monsoon variability.  But recent research showing a link between the climate of the North  Atlantic Ocean and Asian monsoon suggests that abrupt climate changes could actually sap the strength of future monsoons, according to a University of Arizona geoscientist.  "If the North Atlantic should cool without warning, as some scientists suggest it might, one of the results could be a weakened monsoon and  less water for all the people that depend on it," says Jonathan Overpeck, a professor of geosciences and director of the UA

Institute for the Study of Planet Earth. Overpeck, along with Anil K. Gupta from the Indian Institute of  Technology in Kharagpur and David M. Anderson from the  National

Oceanic and Atmospheric Administration's Paleoclimatology  Program in Boulder, Colo., used sediments from the floor of the Arabian sea near  Oman to reconstruct monsoon strength in the region for the past 10,000  years. Their work appears in the January 23 issue of Nature. The researchers used fossils of the plankton G. bulloides to estimate  wind intensity. During a monsoon, the seasonal reversal of  winds brings moisture from the ocean onto land. The winds also blow  surface  waters off shore, Overpeck says, causing an upwelling of  colder, nutrient-rich water where the microscopic marine animals can thrive.  By counting the levels G.  bulloides present in different  layers of the sediment and using radiocarbon dating, the scientists were able to approximate monsoon strength from 10,500 years ago on up to the present. The resulting record showed a natural variation in the monsoon from one century to the next.   "We have new evidence that the strength of Asian monsoon varies substantially on century to millennial time scales," Overpeck  says.  "We need to understand this if we're going to ensure human  and  ecological sustainability in the Tibet, China, India, and the rest of  Southeast Asia." Earlier studies by Overpeck and other scientists on the last  ice age  -- 80,000 to 10,000 years ago -- suggested a possible link  between  monsoon variations and changes in North Atlantic climate.  To see if this same link persisted in the current  interglacial period,  the researchers compared the Arabian sediment record to iceberg debris that had settled into the floor of the North Atlantic ocean  over the same time period. The tiny iron-stained grains found in the sediment  provide a record of temperatures in the region spanning from  Greenland south to the British Isles.  The records revealed seven intervals of weakened monsoon coinciding with cold spells in the North Atlantic region. The most  intense  monsoons occurred at times when the North Atlantic was warmest.  "It is satisfying because we now find this same hypothesized  link  operating through many oscillations in the last 10,000  years,"   Overpeck says, "but this also leads us to scary  implications." Ocean circulation patterns in the North Atlantic play a key  role in  global climate, working like a conveyor belt to bring warmth from the tropics to northern latitudes in Europe, Overpeck says.  "Heat and salt drive the circulation of the world's oceans,"  he explains. "If you somehow disrupt the ability of this conveyor to work, you disrupt the ability to transport heat to the north." Climate reconstructions show that large influxes of  freshwater from  melting ice disrupted the conveyor in the past, resulting in rapid cooling of the North Atlantic. One such event, 8,200 years  ago,  correlates to a weak monsoon period evidenced in the researchers'  record. The Intergovernmental Panel on Climate Change predicts global  temperatures will rise 3 to 10 degrees Fahrenheit by the end  of the  century. This could cause large-scale melting of the  Greenland ice sheet, resulting in a surge of freshwater that could possibly  slow  down North Atlantic circulation. Even without such a dramatic event, Overpeck notes, global warming brings other changes, such as increases in rainfall, that could disrupt circulation patterns. "The North Atlantic is freshening right now in ways we don't  fully  understand," Overpeck says. "In the past, this possibility  concerned  Europeans the most, but now those dependent on monsoon rains also have a good reason to worry."  While researchers aren't sure on the exact causes of the link  between  the North Atlantic and the Asian monsoon, earlier research showed the amount of snow on the Tibetan plateau may play a critical  role,  Overpeck says. As the land warms in the spring, the air rises above the land causing a pressure gradient that drives the monsoon.  "More snow on the plateau in spring or early summer uses up  all the sun's heating because it has to be melted and evaporated before the land can warm," Overpeck says. "So the more snow you have in winter, the weaker the monsoon the following summer."

The authors speculate that when the North Atlantic is cold, areas downwind like the Tibetan plateau stay cold longer, allowing  more snow  to persist and setting up a weakened monsoon.  "The monsoon snow-cover link may lead to a stronger or more variable monsoon in the coming century as the northern hemisphere continues to

warm faster than the tropics," says Anderson, who is also a research scientist with the Institute of Arctic and Alpine Research at  the University of Colorado, Boulder. "This may last until a time when the conveyor abruptly weakens, leading to an abrupt weakening in the monsoon." Other studies show that changes in the amount of sunlight  correlate to variations in both the North Atlantic climate and the Asian monsoon. The researchers aren't certain if the sun affects each system directly   or if solar radiation influences the North Atlantic circulation, which in turn impacts the monsoon.  "More research is needed to identify the role of solar  variability,  and the remote influence of the north Atlantic climate," Anderson says. In an earlier study, the authors found evidence from  sediments in the same region showing an increase in  monsoon strength in the past 400  years. Their work was published in the July 26, 2002 issue of  Science.  "The monsoon has strengthened significantly -- and in an

unprecedented  way -- over the last couple centuries," Overpeck says. "It  appears  that at least some of this must be the result of human-caused  global  warming."

While stronger monsoons could bring relief to Asia's dry lowlands, scientists aren't certain where increased rains would fall. Data seems to point to Tibet, Overpeck says. The headwaters for all the major rivers in Asia come from the Tibetan Plateau, he notes,  indicating increased potential for flooding if the monsoon continues to

strengthen.  "Either way you look at it, global warming could cause real trouble for the monsoon system of Asia," Overpeck says. "This could generate substantial human suffering and political instability."

 

Mekong yielding diminishing returns

Villagers and environmentalists along the lower Mekong say the fish stocks have decreased dramatically in the past years. Despite the potentially  devastating consequences, no-one else seems much concerned
POONA ANTASEEDA

In Khong Jiam district in Ubon Ratchathani, the Mekong River curves as it  leaves Thailand and enters Laos. Thailand's portion of the Mekong River  leaves national territory at the border village of Woenbuek. The little fishing community has less than 100 families, most of which depend on fish from the Mekong. The village is about half an hour by boat from the Khong Jiam town district. ``I have been fishing the Mekong River for half a century,'' said Buasi  Kaewsai, 60. Talking as he weaved repairs into his fishing net, he recalled that he was in elementary school when he caught his first fish on the Mekong. Buasi said he earns about 200 baht a day from his catch these days, much less than before. Pla nua on or bleekeri cost 70 baht a kilo. Pla jog or  holdier river barb is 90 baht per kilo,'' he said. In Bangkok markets, the fish sell for between 120 baht and 150 baht a kilo. ``I used to catch about six kilogrammes of fish a day,'' he said. ``Now  I  am lucky to catch two kilos.''  Buasi blames the Pak Moon dam for the decline of fish in the river. The dam was built on a tributary of the Mekong, the Mae Moon, which flows into the Mekong upstream from Woenbuek. `Now we catch less fish than before the dam was built. The dam causes unnatural fluctuations in the Mekong's water level,'' he said. ``That's the reason for the declining catch.'' Others say the large dams built along the upper Mekong in the Yunnan province of China have a greater effect. Buasi admits that he does not know how the dams affect the river in terms of its ecology.. ``I know only that there are less fish. If this goes on, we will have no income, and we will end up going to Bangkok in search of
work.''  Wichian Pungpa, a 31 year-old fish trader in Woenbuek district, echoed the old fisherman's worries. He said that in the past he used to buy an average of two tonnes of Mekong fish from both Thai and Laotian fishermen each week. ``Today, I can buy  only one or two tonnes. ``I think in the future there will be even less fish in the Mekong River,''  said the fish trader. The opinions in this fishing village are indicative of the general alarm sounding up and down the Mekong. The Mekong River at  Woenbuek is only 300 metres wide. Thai and Laotian communities on opposite banks of the river share a good relationship.  Laotian fishermen cross the river to buy construction materials and food from the Thai side, after selling their fish to Wichian in Woenbuek. Sunday Perspective has made the river trip from Chiang Khong, Chiang Rai in northern Thailand to Kokpadaek Village in southern Laos. Everywhere, fishermen say the same thing: ``There are less fish in the Mekong River.''  A villager in Kokpadaek said: ``The fish hauls continue to decline. Thirty  years ago we used to haul up to 100 kg of fish daily. By 1996 we caught a  mere three to four kg a day.'' The big picture is mostly out of their control, but villagers in Kokpadaek and elsewhere in Laos are doing what they can to preserve their livelihood as well as the ecology of the river. In 1997, they set up a fish conservation area in a 300-square-metre river pool, with great success (see sidebar). Today, there are 76 fish conservation zones along the Mekong river in the Khong District of southern Laos alone.

RIVER FEEDS MILLIONS
The Mekong is the largest river in southeast Asia, and the twelfth largest  in the world. An estimated 1,700 species of fish are believed to inhabit the Mekong's waters, including the endangered Mekong giant catfish. Another endangered Mekong species is the freshwater Irrawady dolphin. The Mekong River Commission (MRC) says the Mekong basin supports about 60 million, but no one has estimated the number of people depending on the river directly or indirectly for their income. Fish is by far the greatest  source of protein for most of the 60 million people around the basin. The Mekong supports one of the largest inland fisheries in the world. The total annual catch of the lower areas (Cambodia, Laos, Thailand and Vietnam) alone is conservatively estimated at about 1.8 million tonnes,  worth approximately US$1.4 billion. The Tonle Sap Lake in Cambodia contributes up to 400,000 tonnes a year. But except from the fishermen and a few environmentalists, there is no cry  of alarm along the Mekong about the decline of fish in the river. No organisation or country has gone so far as to study the Mekong's  progressive decline of fish stocks, its causes, or ways to stop it. Chavalit Witdhayanon, an aquatic biologist at the Thai Department of  Fisheries, said there has been no study or research specifically  investigating the  declining stocks of fish in the Mekong river. ``Such research takes time, manpower and a lot of budget,'' said Chavalit, a lecturer at Kasetsart University. Environmentalists say the decline of fish stocks is caused by many factors such as deforestation, riverbank environmental changes, and not least the construction of dams on the upper Mekong in Yunnan. ``Cutting trees affects the Mekong and its tributaries because it reduces fertility, fish food, and fish breeding'' said Chavalit.
Overfishing and the use of modern fishing equipment are partly responsible for the decline of fish in the Mekong River, and fish fry are destroyed by  fishermen who use explosive bombs as well  The increasing human population also depletes the fish stock of the Mekong. Fishing does not stop during the breeding season. Many environmentalists have claimed that dams in China confuse the breeding habits of fish in the river, but no investigation has focused on the types  of fish sensitive to water level changes. Chavalit explained how the fluctuations in the Mekong's water levels _ caused by dams in China _ could affect the number of fish in the Mekong.
``Many fish breed according to seasonal lows and highs in water level. If  the water level changes unusually, they may not lay their eggs. Or if they  do lay eggs the survival rate of the fish fry may be low.  ``All the dams along the Mekong affect the fish,'' he said.. Though no research has been done on the affects of dams on fish in the
Mekong, the usual catch of up to 40 giant catfish a year is now so dramatically less that alarms cannot be ignored.  Chavalit pointed out that the bigger the dams are, the more they impact  fish breeding and nurseries.
The history of the Pak Moon Dam in the Mae Moon _ a tributary of the Mekong _ shows how dams affect fish in rivers. The dam prevents fish from the Mekong from breeding and spawning in the Mae Moon River.

 

DAMS BIGGEST THREAT
Environmentalists in Laos also believe that Chinese dams negatively affect  fisheries downstream the Mekong. They say that fish populations are threated not only by dams but also by  overfishing, destructive fishing, pollution _ factories, household, agricultural _ rapids blasting, destruction of wetlands and floodplain habitats, riverbank erosion, as well as river bank stabilisation projects. ``There are many threats, but dams may be the biggest, as they cause  permanent and long term hydrological changes that have huge ecological implications,'' said a fish conservationist in Laos speaking on anonymity. Chinese dams will cause unusual hydrological conditions which are contrary  to requirements of various fish species and other aquatic animals that have evolved their migrations and spawning behaviour to the natural hydrological conditions of the Mekong, said the scientist. For example, primary food production (algae) in the Mekong River requires photosynthesis. The sun's rays must pass through the water so that algae can grow on rocks in the dry season. Many fish migrate to eat this algae in  the dry season. If there is more water in the dry season, the sun will not be able to easily reach the rocks below, so there will be less algae for fish and other aquatic animals. It is difficult to speculate on fish production over the next ten years, said the fish conservationist. ``China's dams and rapids blasting may continue to cause declines, although  fish will not entirely disapper from the Mekong. ``However, the people must do something to ensure larger quantities of fish in the years to come,'' said the fish conservationist.  The future will depend on whether people are committed to protecting the Mekong or not, he said. ``If the governments of the region support community fish conservation  along the Mekong, there is a chance that fish populations could actually  increase.'' A detailed study by the Mekong-connected governments and concerned  organisations which prescribes preventive measures is imperative to protect  the ecology of the river, unless they intentionally want the fish  populations to decline. If fish populations do continue to decline it will eliminate many riverine jobs, causing people to migrate to the big cities, as Buasi is afraid will  be the only choice for his children.

Bangkok Post, January 26, 2003