A The Aral Sea gets almost all its water from the Amu and Syr rivers. Over millennium the Amu’s course has drifted away from the sea, causing it to shrink. But the lake always rebounded as the Amu shifted back again. Today heavy irrigation for crops such as cotton and rice siphons off much of the two rivers, severely cutting flow into their deltas and thus into the sea. Evaporation vastly outpaces any rainfall, snowmelt or groundwater supply, reducing water volume and raising salinity. The Soviet Union hid the sea’s demise for decades until 1985, when leader Mikhail Gorbachev revealed the great environmental and human tragedy. By the late 1980s the sea’s level had dropped so much that the water had separated into two distinct bodies: the Small Aral (north) and the Large Aral (south). By 2007 the south had split into a deep western basin, a shallow eastern basin and a small, isolated gulf. The Large Aral’s volume had dropped from 708 to only 75 cubic kilometers (km3), and salinity had risen from 14 to more than 100 grams per liter (g/1). The 1991 dissolution of the Soviet Union divided the lake between newly formed Kazakhstan and Uzbekistan, ending a grand Soviet plan to channel in water from distant Siberian rivers and establishing competition for the dwindling resource.

B Desiccation of the Aral Sea has wrought severe consequences. Greatly reduced river flows ended the spring floods that sustained wetlands with freshwater and enriched sediment. Fish species in the lakes dropped from 32 to 6 because of rising salinity and loss of spawning and feeding grounds (most survived in the river deltas). Commercial fisheries, which caught 40,000 metric tons of fish in 1960, were gone by the mid-1980s; more than 60,000 related jobs were lost. The most common
remaining lake occupant was the Black Sea flounder, a saltwater fish introduced in the 1970s, but by 2003 it had disappeared from the southern lakes because salinity was more than 70 g/1, double that of a typical ocean. Shipping on the Aral also ceased because the water receded many kilometers from the major ports of Aralsk to the north and Moynak in the south; keeping increasingly long channels open to the cities became too costly. Groundwater levels dropped with falling lake levels, intensifying desertification.

C The receding sea has exposed and dried 54,000 square kilometers of seabed, which is choked with salt and in some places laced with pesticides and other agricultural chemicals deposited by runoff from area farming. Strong windstorms blow salt, dust and contaminants as far as 500 km. Winds from the north and northeast drive the most severe storms, seriously impacting the Amu delta to the south—the most densely settled and most economically and ecologically important area in the region. Afrbome sodium bicarbonate, sodium chloride and sodium sulfate kill or retard the growth of natural vegetation and crops—a cruel irony given that irrigating those crops starves the sea. Health experts say the local population suffers from high levels of respiratory illnesses, throat and esophageal cancer, and digestive disorders caused by breathing and ingesting salt-laden air and water. Liver and kidney ailments, as well as eye problems, are common. The loss of fish has also greatly reduced dietary variety, worsening malnutrition and anemia, particularly in pregnant women.

D Returning the entire Aral Sea to its 1960s state is unrealistic. The annual inflow from the Syr and Amu rivers would have to be quadrupled from the recent average of 13 km3. The only means would be to curtail irrigation, which accounts for 92 percent of water withdrawals. Yet four of the five former Soviet republics in the Aral Sea basin (Kazakhstan is the exception) intend to expand irrigation, mainly to feed growing populations. Switching to less water- intensive crops, such as replacing cotton with winter wheat, could help, but the two primary irrigating nations, Uzbekistan and Turkmenistan, intend to keep cotton to earn foreign currency. The extensive irrigation canals could be greatly improved; many are simply cuts through sand, and they allow enormous quantities of water to seep away. Modernizing the entire system could save 12 km3 a year but would cost at least $16 billion. The basin states do not have the money or the political will. Kazakhstan has nonetheless tried to partially restore the northern Aral.

E We expect salinities in the Small Aral to settle at three to 14 g/1, depending on location. At these levels many more indigenous species should return, although the saltwater kambala would disappear from most places. Further restoration is possible. For example, if irrigation improvements raised the average annual inflow from the Syr to 4.5 km3, which is entirely feasible, the lake’s level could stabilize at about 47 meters. This change would bring the shoreline to within eight kilometers of Aralsk, the former major port city, close enough to allow recovery of an earlier channel that connected the city to the receding waters. The channel would give large commercial fishing vessels access to the sea, and shipping could restart. Marshlands and fish populations would improve even more because of a further reduction in salinity. Outflow to the southern lakes could also increase, helping then restoration. Such a plan would require a much longer and higher dike, as well as reconstruction of the gate facility, and it is not clear that Kazakhstan has the means or desire to pursue it. The country is, however, now discussing more modest proposals to bring water closer to Aralsk.

F The Large Aral faces a difficult future; it continues to shrink rapidly. Only a long, narrow channel connects the shallow eastern basin and the deeper western basin, and this could close altogether. If countries along the Amu make no changes, we estimate that at current rates of groundwater in and evaporation out, an isolated eastern basin would stabilize at an area of 4,300 square kilometers (km2). But it would average only 2.5 meters deep. Salinity would exceed 100 g/1, possibly reaching 200 g/1; the only creatures that could live in it would be brine shrimp and bacteria. The western basin’s fate depends on ground- water inflow, estimates for which are uncertain. Someone has noted numerous fresh- water springs on the western cliffs. The most reliable calculations indicate that the basin would settle at about 2,100 km2. The lake would still be relatively deep, reaching 37 meters in spots, but salinity would rise well above 100 g/1.

A On Mars, signs of wetness keep pouring in: deeply carved river valleys, vast deltas and widespread remnants of evaporating seas have convinced many experts that liquid water may have covered large parts of the Red Planet for a billion years or more. But most efforts to explain how Martian climate ever permitted such clement conditions come up dry. Bitterly cold and parched today, Mars needed a potent greenhouse atmosphere to sustain its watery past. A thick layer of heat-trapping carbon dioxide from volcanoes probably shrouded the young planet, but climate models indicate time and again that C02 alone could not have kept the surface above freezing.

B Now, inspired by the surprising discovery that sulfur minerals are pervasive in the Martian soil, scientists are beginning to suspect that C02 had a warm-up partner: sulfur dioxide (S02). Like C02, S02 is a common gas emitted when volcanoes erupt, a frequent occurrence on Mars when it was still young. A hundredth or even a thousandth of a percent S02 in Mars's early atmosphere could have provided the extra boost of greenhouse warming that the Red Planet needed to stay wet, explains geochemist Daniel p. Schrag of Harvard University.

C That may not sound like much, but for many gases, even minuscule concentrations are hard to maintain. On our home planet, S02 provides no significant long-term warmth because it combines almost instantly with oxygen in the atmosphere to form sulfate, a type of salt. Early Mars would have been virtually free of atmospheric oxygen, though, so S02 would have stuck around much longer.

D "When you take away oxygen, it's a profound change, and the atmosphere works really differently," Schrag remarks. According to Schrag and his colleagues, that difference also implies that S02 would have played a starring role in the Martian water cycle—thus resolving another climate conundrum, namely, a lack of certain rocks.

E Schrag's team contends that on early Mars, much of the S02 would have combined with airborne water droplets and fallen as sulfurous acid rain, rather than transforming into a salt as on Earth. The resulting acidity would have inhibited the formation of thick layers of limestone and other carbonate rocks. Researchers assumed Mars would be chock-full of carbonate rocks because their formation is such a fundamental consequence of the humid, C02-rich atmosphere. Over millions of years, this rock-forming process has sequestered enough of the carbon dioxide spewed from earthly volcanoes to limit the buildup of the gas in the atmosphere. stifling this C02-sequestration step on early Mars would have forced more of the gas to accumulate in the atmosphere—another way S02 could have boosted greenhouse warming, Schrag suggests.

F Some scientists doubt that S02 was really up to these climatic tasks . Even in an oxygen-free atmosphere, S02 is still extremely fragile; the sun's ultraviolet radiation splits apart S02 molecules quite readily, points out James F. Kasting, an atmospheric chemist at Pennsylvania state University. In Easting's computer models of Earth's early climate, which is often compared with that of early Mars, this photochemical destruction capped S02 concentrations at one thousandth as much as Schrag and his colleagues describe. "There may be ways to make this idea work," Kasting says. "But it would take some detailed modeling to convince skeptics, including me, that it is actually feasible."

G Schrag admits that the details are uncertain, but he cites estimates by other researchers who suggest that early Martian volcanoes could have spewed enough S02 to keep pace with the S02 destroyed photochemically. Previous findings also indicate that a thick C02 atmosphere would have effectively scattered the most destructive wavelengths of ultraviolet radiation—yet another example of an apparently mutually beneficial partnership between C02 and S02 on early Mars.

H Kasting maintains that an S02 climate feedback could not have made early Mars as warm as Earth, but he does allow for the possibility that S02 concentrations may have remained high enough to keep the planet partly defrosted, with perhaps enough rainfall to form river valleys. Over that point, Schrag does not quibble. "Our hypothesis doesn't depend at all on whether there was a big ocean, a few lakes or just a few little puddles," he says. " Warm doesn't mean warm like the Amazon. It could mean warm like Iceland— just warm enough to create those river valleys . " with S02, it only takes a little. If sulfur dioxide warmed early Mars, as a new hypothesis suggests, minerals called sulfites would have formed in standing water at the surface. No sulfites have yet turned up, possibly because no one was looking for them. The next-generation rover, the Mars Science Laboratory, is well equipped for the search. Scheduled to launch in 2009, the rover (shown here in an artist's conception) will be the first to carry an x-ray diffractometer, which can scan and identify the crystal structure of any mineral it encounters.

When Janos Vargha, a biologist from the Hungarian Academy of Sciences, began a new career as a writer with a small monthly nature magazine called Buvar, it was 9 years after the story behind the fall of the Berlin Wall had started to unfold. During his early research, he went to a beauty spot on the river Danube outside Budapest known as the Danube Bend to interview local officials about plans to build a small park on the site of an ancient Hungarian capital.

One official mentioned that passing this tree-lined curve in the river, a popular tourism spot for Hungarians was monotonous. Also, it was to be submerged by a giant hydroelectric dam in secret by a much-feared state agency known simply as the Water Management.

Vargha investigated and learned that the Nagymaros dam (pronounced “nosh-marosh”) would cause pollution, destroy underground water reserves, dry out wetlands and wreck the unique ecosystem of central Europe’s longest river. Unfortunately, nobody objected. “Of course, I wrote an article. But there was a director of the Water Management on the magazine’s editorial board. The last time, he went to the printers and stopped the presses, the article was never published. I was frustrated and angry, but I was ultimately interested in why they cared to ban my article,” he remembers today.

He found that the Nagymaros dam was part of a joint project with neighbouring Czechoslovakia to produce hydroelectricity, irrigate farms and enhance navigation. They would build two dams and re-engineer the Danube for 200 kilometres where it created the border between them. “The Russians were working together, too. They wanted to take their big ships from the Black Sea right up the Danube to the border with Austria.”

Vargha was soon under vigorous investigation, and some of his articles got past the censors. He gathered supporters for some years, but he was one of only a few people who believed the dam should be stopped. He was hardly surprised when the Water Management refused to debate the project in public. After a public meeting, the bureaucrats had pulled out at the last minute. Vargha knew he had to take the next step. “We decided it wasn’t enough to talk and write, so we set up an organization, the Danube Circle. We announced that we didn’t agree with censorship. We would act as if we were living in a democracy.” he says.

The Danube Circle was illegal and the secret publications it produced turned out to be samizdat leaflets. In an extraordinary act of defiance, it gathered 10,000 signatures for a petition objecting to the dam and made links with environmentalists in the west, inviting them to Budapest for a press conference.

The Hungarian government enforced a news blackout on the dam, but articles about the Danube Circle began to be published and appear in the western media. In 1985, the Circle and Vargha, a public spokesman, won the Right Livelihood award known as the alternative Nobel prize. Officials told Vargha he should not take the prize but he ignored them. The following year when Austrian environmentalists joined a protest in Budapest, they were met with tear gas and batons. Then the Politburo had Vargha taken from his new job as editor of the Hungarian version of Scientific American.

The dam became a focus for opposition to the hated regime. Communists tried to hold back the waters in the Danube and resist the will of the people. Vargha says, “Opposing the state directly was still hard.” “Objecting to the dam was less of a hazard, but it was still considered a resistance to the state.”

Under increasing pressure from the anti-dam movement, the Hungarian Communist Party was divided. Vargha says, “Reformists found that the dam was not very popular and economical. It would be cheaper to generate electricity by burning coal or nuclear power.” “But hardliners were standing for Stalinist ideas of large dams which mean symbols of progress.” Environmental issues seemed to be a weak point of east European communism in its final years. During the 1970s under the support of the Young Communist Leagues, a host of environmental groups had been founded. Party officials saw them as a harmless product of youthful idealism created by Boy Scouts and natural history societies.

Green idealism steadily became a focal point for political opposition. In Czechoslovakia, the human rights of Charter 77 took up environmentalism. The green-minded people of both Poland and Estonia participated in the Friends of the Earth International to protest against air pollution. Bulgarian environmentalists built a resistance group, called Ecoglasnost, which held huge rallies in 1989. Big water engineering projects were potent symbols of the old Stalinism.