By Steve Milloy
California can either manage its forests better or watch them burn for another 200 years — according to the New York Times.
All you need to know about California drought and wildfires:
NYT 1994: BEGINNING about 1,100 years ago, what is now California baked in two droughts, the first lasting 220 years and the second 140 years. Each was much more intense than the mere six-year dry spells that afflict modern California from time to time, new studies of past climates show. The findings suggest, in fact, that relatively wet periods like the 20th century have been the exception rather than the rule in California for at least the last 3,500 years, and that mega-droughts are likely to recur.
As there were no SUVs or coal-fired power plants 1,100 years ago, California may want to start thinking now about some serious forest management before nature takes her own devastating course.
The full text of the NYTimes article is below.
BEGINNING about 1,100 years ago, what is now California baked in two droughts, the first lasting 220 years and the second 140 years. Each was much more intense than the mere six-year dry spells that afflict modern California from time to time, new studies of past climates show. The findings suggest, in fact, that relatively wet periods like the 20th century have been the exception rather than the rule in California for at least the last 3,500 years, and that mega-droughts are likely to recur.
The evidence for the big droughts comes from an analysis of the trunks of trees that grew in the dry beds of lakes, swamps and rivers in and adjacent to the Sierra Nevada, but died when the droughts ended and the water levels rose. Immersion in water has preserved the trunks over the centuries.
Dr. Scott Stine, a paleoclimatologist at California State University at Hayward, used radiocarbon dating techniques to determine the age of the trees’ outermost annual growth rings, thereby establishing the ends of drought periods. He then calculated the lengths of the preceding dry spells by counting the rings in each stump.
This method identified droughts lasting from A.D. 892 to A.D. 1112 and from A.D. 1209 to A.D. 1350. Judging by how far the water levels dropped during these periods — as much as 50 feet in some cases — Dr. Stine concluded that the droughts were not only much longer, they were far more severe than either the drought of 1928 to 1934, California’s worst in modern times, or the more recent severe dry spell of 1987 to 1992.
In medieval times the California droughts coincided roughly with a warmer climate in Europe, which allowed the Vikings to colonize Greenland and vineyards to grow in England, and with a severe dry period in South America, which caused the collapse of that continent’s most advanced pre-Inca empire, the rich and powerful state of Tiwanaku, other recent studies have found.
Does Tiwanaku’s fate await modern California?
Dr. Stine, who reported his findings last month in the British journal Nature, says that California, like Tiwanaku, presents “a classic case of people building themselves beyond the carrying capacity of the land,” which is determined not by wet times but by dry ones. “What we’ve done in California is fail to recognize that there are lean times ahead,” said Dr. Stine, “and they are a lot leaner than anything we’ve come up against” in the modern era.
How far ahead that reckoning might lie is, of course, uncertain. But one ominous sign may be that the earth’s climate as a whole is now warming up, whether from natural causes or because of heat-trapping atmospheric gases emitted by industrial society. Any significant global warming would probably cause changes in atmospheric circulation and precipitation patterns, and the new findings suggest that “during much of medieval time the planetary ocean-atmosphere system operated in a mode unlike that of modern time,” Dr. Stine wrote in Nature.
This alteration of the system could well have been caused by a natural global warming, he said. He believes that one long-term effect was to steer storm tracks and rainfall away from California. If this pattern was indeed brought about by a medieval global warming, he said, a future global warming — whether natural or human-induced — might bring back the decades-long droughts of yore.
Dr. Stine’s findings, combined with similar evidence he turned up in Patagonia, strengthen the case of those who believe that the earth experienced a general warming at the time of the Middle Ages, Dr. F. Alayne Street-Perrott, a paleoclimatologist at Oxford University in England, wrote in a commentary accompanying Dr. Stine’s report in Nature. Other experts maintain that the medieval warming was not global but instead affected only some parts of the world.
“I’m not prepared to believe that the whole world was warmer,” said Dr. Malcolm K. Hughes, a paleoclimatologist who directs the Laboratory of Tree Ring Research at the University of Arizona in Tucson. Nor is it possible to say for sure that future global warming would bring back the large-scale droughts of the past. “We’ve not done the work on the actual mechanisms,” he said.
But he said that Dr. Stine’s findings, coupled with similar conclusions that can be drawn from other tree-ring studies by scientists in his laboratory, are a “serious cause for concern.” There appears to be little doubt that the epic dry spells of the past did occur, he said, adding that “what has happened can happen.”
The findings also emphasize the importance of precipitation changes, rather than simply changes in temperature, when weighing the potential impact of future global climate change, Dr. Stine wrote in Nature. Periods of ‘Epic Drought’
The Sierra Nevada, where Dr. Stine conducted his study, is California’s most important area for the collection of water. Runoff from the Sierras provides two-thirds of the state’s surface-water supply for cities and farms. The study involved trees at four places: Mono Lake, Tenaya Lake, the West Walker River and Osgood Swamp. Dr. Stine’s tree-ring analysis found that live trees had covered dry beds of lakes, streams and swamps for overlapping periods of 50, 100, 141 and 220 years and that these “lowstand” periods were clustered in two major dry spells separated by a century-long wet period. “Epic drought,” he wrote in Nature, is “the only plausible explanation for the site-to-site contemporaneity of the stumps.”
In the period separating the two long droughts, Dr. Stine said, the water in Mono Lake rose to a level higher than any in the last 150 years, suggesting that the California climate was even wetter then than it is today. The last century and a half, Dr. Stine found, has been the third wettest period in the last three millenniums. But, he said, “the vast majority of years during the past 3,500 years have been much drier than what we’ve come to expect to be normal in California.”
The evidence for the medieval drought periods is especially strong, Dr. Hughes said, because the lake basins are closed, with no natural outlets; consequently, their water levels are influenced only by inflow and evaporation, making them ideal gauges of drought. And even though radiocarbon dating is somewhat imprecise, he said, it is good enough “to show two major phases of tree growth and lowstands; there’s no doubt about that.” This, he said, shows that “often, for sure, there have been periods of 100 years or more” that have been “markedly drier” than the 20th century.
The 10th to the 14th centuries, encompassing the prolonged droughts reported by Dr. Stine, saw “dramatic changes” in Western Hemisphere civilizations, Dr. Street-Perrott wrote in Nature, and some have been attributed by archeologists to changes in rainfall. One example is the sudden decline of the Anasazi cliff-dwellers in the American southwest at about the year 1300. Another, even more striking, is the collapse of Tiwanaku.
Tiwanaku was a flourishing empire that lasted seven centuries and reached its zenith near the end of the first millennium A.D. It commanded an area about the size of California, extending from the Andean plateau around Lake Titicaca to the Pacific Coast and covering parts of present-day Bolivia, Chile and Peru.
The empire’s economy was based on intensive agriculture carried out on raised fields: acres of end-to-end rectangular platforms created by digging the dirt from areas between them. The dug-out areas became canals from which silt was taken to provide fertilizer. This highly productive and environmentally sound system dominated Latin American agriculture for centuries. Death of a Civilization
But several lines of evidence, including analyses of fossilized pollen grains and isotopes of oxygen in lake sediments, make it clear that an extended drought afflicted the region starting between A.D. 950 and A.D. 1000 and continuing, with fluctuations, until 1410, concluded a study last year by Charles R. Ortloff, a fluid-mechanics specialist at the FMC Corporate Technology Center at Santa Clara, Calif., and Dr. Alan L. Kolata, an archeologist at the University of Chicago. That period mostly overlaps the one in which the California mega-droughts occurred.
The South American drought was of “horrendous proportions,” said Dr. Kolata, and it destroyed Tiwanaku’s agricultural base. The empire’s cities were abandoned by about 1000. Dr. Kolata believes that the raised fields could no longer support the cities, and archeological evidence shows that the fields were abandoned between 1000 and 1100. The political state collapsed, the population dispersed and, with agriculture no longer possible, the people relied on raising alpacas and llamas.
Tiwanaku’s agricultural system had been able to adjust to the less drastic cycles of drought and inundation that were thought to be normal, but “Tiwanaku agro-engineers were incapable of responding to a drought of unprecedented duration and severity,” Mr. Ortloff and Dr. Kolata wrote in a 1993 paper in The Journal of Archeological Science.
Like Tiwanaku’s engineers, those who draw up California’s water-management plans do so on the basis of what are believed to be normal droughts but in fact are not nearly as severe as what has occurred in the past and can occur again, said Dr. Stine.
“The assumption they’ve made for a long time — that California is subject to droughts of a maximum of seven years — could be harmful in the long run,” he said, because “they have doled out water on that assumption.
“This could be destructive if you get hit with a 9th or a 10th or a 15th year of severe drought.”
In gauging the length and frequency of droughts for planning purposes, California officials rely on a tree-ring study extending back to about 1560. Over that period, the 1928-1934 drought was the longest and worst. The problem, said Dr. Stine, is that the study period includes not only the wet 19th and 20th centuries, but also the even wetter 16th and 17th centuries. “They’re using the wettest period of the last 3,000 years to define the duration and severity of the droughts we can expect in the future,” he said.
Maurice Roos, the chief hydrologist of the California Department of Water Resources, said he had not read Dr. Stine’s report in Nature. But he did acknowledge that a mega-drought of the kind described in the report would probably cause much of the state’s lush irrigated cropland to cease producing. The cities would probably have the money and political power to appropriate enough water to get by, he said, adding, “There will always be some water; there is not going to be no water.” He said he would not expect farming to cease altogether, or cities to be deserted.
Modern California has at least one coping weapon that Tiwanaku did not: the ability to turn sea water into fresh water. The 1987-92 drought did, in fact, prompt Santa Barbara to build a desalinization plant, Mr. Roos said, though he was quick to point out that this solution at present would be “enormously expensive.”
At the very least, Dr. Stine wrote in Nature, a recurrence of the medieval droughts “would be highly disruptive environmentally and economically.” Planning for a mega-drought now, while heads are a little cooler, would help, he says. The planning might include, for example, deciding which crops are to be taken out of production first, what restrictions to place on the pumping of groundwater and how cities are to obtain water.
But in the end, he said, a reprise of the medieval droughts would simply overwhelm California’s efforts to cope. And he said: “We don’t need 200 years of drought to bring us down. At some point, in the 9th year, or the 15th year or the 19th year, the damage is done and it doesn’t matter any more.”