<text>/* Written 11:42 am Feb 23, 1991 by nsundt in cdp:en.climate *//* ---------- "U.S. WESTERN DROUGHT" ---------- */ DROUGHT IN THE U.S. WEST UPDATE #1 February 23, 1991 by Nick Sundt Washington, D.C. NATIONAL OVERVIEW >From the very beginning of the en.climate conference in 1988, I have periodically posted information on the Western drought. Though I've posted very little on the issue since last Spring, the severity of the situation has reached the point where feel compelled once again to post the followingupdate. I'll start at the national level, and with a glance back over the last five years. In 1987, drought conditions rapidly developed in portions of the United States; by the end of October, about 17 percent of the U.S. was in severe or extreme drought. Where normally one would expect to see considerable improvement in conditions during the winter and spring, this did not occur in late 1987 or early 1988. Instead there was only a small and partial recovery and by the end of January 1988, about 12 percent of the country still was in extreme or severe drought. As many of you know, 1988 saw extensive drought in the U.S., with about 36 percent of the country in severe or extreme drought by the end of July 1988. Again, where a large recovery was expected by early 1989, drought conditions moderated only partially. By the beginning of April 1989, about 20 percent of the nation still was in severe or extreme drought. As in previous years, conditions worsened in the summer and again there was only a very small recovery by the end of the year. The year 1990 also was very dry. Though the peak area covered by the drought conditions was not as high as in 1989 or 1988, there was no widespread recovery. The area of the country covered by drought never dropped below about 20 percent of the U.S. By the end of January 1991, roughly 18 percent of the nation was in extreme or severe drought. During this time, the distribution of the conditions changed. Generally speaking, the drought has become more and more concentrated in the Western States. Much of the attention has focused on California, where the California Basin has experienced the driest October through January period since 1895. Making the situation particularly serious for California is the fact that this is the fifth year of drought in a row. Never before has the state seen such severe conditions. But the drought conditions overlie much more than just California. As of January 19, 1991, extreme or severe conditions covered central and eastern Oregon, the east side of the Cascades in Washington state, much of southern and eastern Idaho, much of Wyoming, and North Dakota, and parts of Montana, Colorado, Utah, Nevada and a small part of Arizona. In January 1991, much of the Far West received for the second straight month less than 50 percent of normal precipitation. This is the time of year when these states ordinarily receive most of their precipitation. The mountain snowpack in most areas is below normal, frequently less than 70 percent of normal. Consequently, Spring and Summer Streamflows forecasts (as of 1 February 1991) in most of the West are far below average. Average or above average streamflows are mostly confined to an area running from north central Montana to Western Washington. Southern Colorado and Northern New Mexico also may see average or above average streamflows. The prospects that heavy rain in the next few months will make up for the deficit are slim. The chances that many of the areas in southern Oregon, California, and Nevada will reach normal seasonal totals by the end of the rainy season range from 0 percent in Medford, Oregon (based on 42 years of data) to 20 percent in Long Beach, California (based on 88 years of data). In short, we will see another year of severe conditions in the U.S. West. I will follow this paper up with additional statements during the next few weeks. These will explore some of the consequences of the drought for the Western states, and will include more detailed information on California. Taken as a whole, the information will provide a very sobering picture -- one with many interesting implications in the context of climate change.Sundt, Nick. U.S. WESTERN DROUGHT. ECONET: List Owner davep@acsu.buffalo.edu. From: cdp!tgray@LABREA.STANFORD.EDU. Posted Sat, 23 Feb 91 15:16:47 PST on BITNET. </text>
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<text>DROUGHT AFFLICTS BISON IN HENERY MOUNTAINSHIGH COUNTRY NEWS - DECEMBER 31, 1991A third of Utah's wild bison herd won't make it through the winter. Four years of drought have forced Utah's wildlife agency to issue 115 special bison hunting permits in addition to the usual 65.The herd in the Henry Mountains of Utah is the only free roaming, huntable herd in the United States. For 27 of the last 40 years, a limited number of hunters have been allowed to kill these trophy animals in "once-in-a-lifetime" hunts.It was no different this year until wildlife officers counted the herd and checked the quality of their desert range. The biologists expected to find 350 animals, but they counted almost 600. The bison had stripped their summer and their winter range, looking for food on drought-ravaged land.Fifty years ago, the Utah Division of Wildlife Resources transplanted 18 Yellowstone bison near Robbers Roost and the Dirty Devil River in southern Utah, an area so remote that it was one of the 1ast places in the continental United States to be explored and mapped. The herd gradually moved west until it settled in the Henry Mountains.This small mountain range rises above the desert plateaus between Capitol Reef National Park and Lake Powell. Its highest peak, Mount Ellen, has an altitude of 11,615 feet. The bison range from the scree-covered peak to the lowlands of Apple Brush Flat and the canyons of Tarantula Mesa. They roam across 600 square miles.The herd usually summers on the hillsides of Mount Ellen and Mount Pennell. But this summer the bison spent August and September on their winter range, eating the scarce grasses between the sagebrush down to stubble."Usually there's four-to-six-inch-high grass for the herd to winter on. Right now there's nothing," said Jim Karpowitz, the regional big game manager. "If we have a severe winter, some of the animals could starve. We're trying to avoid this with a bigger harvest."The drought has put the buffalo in a no-win situation. Southern Utah needs snow this winter to put moisture back into the parched desen If it doesn't snow, the drought could continue next summer."Drought is the main reason for taking so many buffalo," Karpowitz explained, "but we also have an agreement with the BLM to limit the herd to 250."Grazing rights on the Henry Mountains have long been allocated to local ranchers. Bison, which eat the same things as cattle, are competition for an already scarce resourceΓÇö grass. Under the 1982 agreement that limited the bison herd to 250 head, piflon and juniper forests were cleared to create more forage for the cattle and bison.The long drought forced cattlemen to take their livestock off the range earlier this year, and wildlife officials fear another year of drought will kill the better grasses and do long-term damage to the bison's habitat.Karpowitz points out that bison are hardy animals that have pulled through droughts before. "But," he adds, "the long-range future of the buffalo herd in the Henry Mountains depends on improving their habitat."Habitat improvement in southern Utah means clearing some of the pinyon and juniper forests that cover the hillsides by dragging a massive chain across the ground to uproot the trees. Last summer wilderness groups protested the practice.Karpowitz says without hesitation that selective chainings create grassy oases for wildlife and cattle. The agency had plans for limited chainings in the Henry Mountains, but several environmental groups, including the Sierra Club, appealed the plan, stopping projects for the next several years.Karpowitz warns: 'Without any habitat improvement there will be less wildlife, and livestock peopb can expect less forage for livestock. There will be less of everything for everybody."ΓÇöVicky Osborn Vicky Osborn is an associate news producer at KUTV, Salt Lake City, Utah.Osborn, Vicky. "Drought Afflicts Bison in Henry Mountains." High Country News. 31 December 1990. Page 7.</text>
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<text>zzzzzzzzzzzzTHE ASSOCIATED PRESSWASHINGTON ΓÇö The California drought may make a dent in this year's U.S. cotton and rice production, the Agriculture Department said Wednesday.Because of the drought, California farmers may not plant as much cotton and rice as they indicated in a recent survey, a department report said."The state is the second largest producer of both crops," it said. "Growers there are enduring one of the state's longest and most severe droughts. And this year has been among the driest ever."According to the recent survey, farmers nationally said they intend to plant 4 percent more corn, l percent more soybeans, 2 percent more rice, 18 percent more cotton, 19 percent more sorghum, and 36 percent more sunflowers than they did last year.However, spring wheat plantings were indicated to decline 13 percent from 1990, reflecting farmers' outlook for prices and costs of production. Burdened by large U.S. and global supplies, wheat price have been depressed."Among California livestock producers, those with forage-based operations will be hit the hardest," the report said. "Output of many field and forage crops will be down sharply and prices will rise."But the report added: "Still, the state's production of fruit and vegetables is expected to be near normal because some water will be diverted from field crops, and many growers depend on groundwater and water from the Colorado River Basin."Also, despite the California drought, U.S. supplies of an major livestock products are expected to increase in 1991, the report said. Beef and pork output is forecast to rise 2 percent each, while milk and egg production are each expected to increase about 1 percent."Lower feed costs and recession-muted demand will dampen livestock prices, especially in the first half of the year," the report said.Associated Press. "Drought Trims Rice, Cotton." Associated Press story in Albuquerque Journal. 24 February 1991. G7.</text>
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<text>zzzzzzzzzzzzTHE ASSOCIATED PRESSEDWARDS AIR FORCE BASE, Calif.ΓÇö A huge crack has closed a runway on the 44-square-mile Rogers Dry Lake, just five miles from the famous clay runway used by space shuttles and experimental aircraft, officials said.Apparently caused by California's five-year drought and ground water pumping, the half-mile-long, 12-feet-deep crack may be the largest such fissure ever found in the state, said U.S. Geological Survey spokesman Devin Galloway.The Air Force said it was concerned the problem could spread. The lake bed is crucial to the base because its clay surface provides long, wide runways suited to landings from many directions."Just because the fissure happened on one runway doesn't mean it won't happen on another runway," said Larry Plews, a civilian Air Force engineer who oversees the runways.The crack, discovered about two weeks ago, runs generally north and south at the southern end of the lake bed, cutting through runway 7-25.Assistant airfield manager Mel Marmet said another runway, 17-35, a 7.5 mile strip that is the base's longest, was put out of service last year by drought-caused crumbling.The surrounding Antelope Valley has recently been plagued by fissures apparently caused by the pumping of too much groundwater.Associated Press. "Drought Causes Crack in Edwards Runway." Associated Press story in Albuquerque Journal. 16 February 1991. E8.</text>
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<text>From: tgray@IGC.ORG (Tom Gray)Newsgroups: sci.environmentSubject: NEWS: Drought Rept Summary [long]Message-ID: <9108310156.AA25987@cdp.igc.org>Date: 31 Aug 91 01:56:45 GMTSender: daemon@ucbvax.BERKELEY.EDULines: 282/* Written 5:20 pm Aug 30, 1991 by pacinst in cdp:en.climate *//* ---------- "Executive Summary of Report LONG" ---------- */On August 1st, the Pacific Institute release a report on the impacts of the California Drought. By popular request, here is an abbreviated version of the published Executive Summary. I have included only the more critical sections, but in the interests of keeping it short, I have deleted several sections. All sections HEADINGS were left in to let you know what it contains; those of you interested in more detail can either order the whole report, or contact me for more information. The full report is 66 pages long.Peter Gleick, Director, Global Environment Program----------------------------------------------------THE SOCIETAL AND ENVIRONMENTAL COSTS OF THE CONTINUING CALIFORNIA DROUGHT:A Report from the Pacific Institute for Studies in Development, Environment, and Security, 1681 Shattuck Avenue, Suite H, Berkeley, California. 415 843-9550.["pacinst" on EcoNet]EXECUTIVE SUMMARY Since 1987, the State of California has been in the grip of a severe drought. Water availability throughout the State has been far lower than normal for each of the last five years when measured in any of a variety of ways: total precipitation, runoff, ground-water overdraft, or reservoir storage. The current drought is comparable in severity to the drought of the late 1920s and early 1930s, considered to be the worst drought on record, and there is no guarantee that next year will be any wetter. The California Department of Water Resources has classified four of the last five years as "critically dry", while the fifth was classified as "dry". Based on the information collected for this report, we believe that the greatest impacts are currently falling on the environment, and that, moreover, many of the ecological effects may be irreversible. In addition, California will see substantial economic costs, totaling roughly $3 billion, as a result of decreased hydroelectric potential. Limited portions of the agricultural sector are also bearing heavy costs, although the effect on California's overall farm income will be relatively small. While urban areas have suffered shortages, they have been manageable in most cases and have not caused major economic dislocations. The additional rainfall that the State received in March of this year helped to avert much more serious impacts in the municipal and industrial sectors, but only modestly improved the condition of ecosystems and the water supply for agriculture. The drought is not over. Without doubt, another dry year would result in much more severe situation than California has experienced thus far. Reservoir reserves have been drawn down to extremely low levels, some fisheries populations have been brought to the verge of extinction, if indeed they have not already been pushed over the edge, and ground-water reserves have been severely depleted in many agricultural regions. Presented below is a summary of what we currently know about the impacts of the drought. Summary of ImpactsNatural Ecosystems Human activities have made natural ecosystems more vulnerable to droughts than they would otherwise be, and, consequently, the current drought has had severe impacts on a wide range of California's ecological resources. Given the poor condition of the most threatened species, the greatest concern is that some species may not be able to recover once the drought is over. Among the effects observed as of July 1991 are: The coho and chinook salmon catch off the coast of California has declined from a record 14.8 million pounds in 1988 (reflecting the success of the year class raised in the wet year of 1986) to only 4.4 million pounds in 1990. The current estimate for 1991 is 2.5 million pounds. The winter-run chinook salmon, already classified as a threatened species, has reached such low numbers that it is threatened with extinction. The population of striped bass in the San Francisco Bay/Delta has been declining since the beginning of the current drought in 1987. In 1990, the index of larval abundance was the lowest ever recorded. While the decline of the striped bass may have many causes, the striped bass index shows a strong correlation with Delta outflow. The herring fishery in Tomales Bay has been destroyed, at least temporarily, due to low freshwater inflows and consequent increases in salinity. It is possible that this herring population will not recover. Waterfowl populations in California have been declining dramatically over the last decade for many reasons. The drought is exacerbating these losses by reducing the quantity and quality of wetlands habitat in the Central Valley. Tree mortality has been extremely high in large areas of the Sierra Nevada. In some forest areas, 30 to 80 percent of the trees are dead or dying. A wide range of endangered and threatened plant and animal species are directly threatened by low water conditions, including: nesting and wintering bald eagles in the Santa Ynez basin; the ten listed species of native annual and short-lived herbs; the threatened giant garter snake, which depends on seasonal and permanent sloughs and creeks; and almost all of the nine species of endangered butterflies, which are experiencing severe population declines because of drought-induced losses of host plants. Agriculture Undoubtedly, the drought has reduced California's agricultural income over what it might have been in 1990 and 1991, although it is has not been the disaster that some expected. Certain agricultural sectors and individual farmers have been hard hit by cutbacks in water deliveries. But we also find that the California agricultural community as a whole has experienced manageable losses, in part because the agricultural sector was in a strong financial position before the drought began and because it has been buffered by ground-water availability and the ability of farmers to alter planting patterns. Until 1990, agricultural water deliveries were not affected by the drought, and no significant economic impacts were observed. In 1990, some water deliveries were reduced, but overall impacts were minimal. Strong demand for California farm products has kept both prices and revenue high. Gross cash receipts in 1990 reached an all-time high. Greater agricultural impacts will occur in 1991, but it is too early to quantify these effects. A preliminary estimate by the California Department of Water Resources puts direct losses at roughly $400 million in cash receipts out of an estimated $18 billion total. In addition to these direct losses, there could be substantial indirect costs throughout the State. The statewide averages hide local effects. Some agricultural communities have been hard hit, including the southern San Joaquin Valley, where ground-water supplies are scarce, and the Central Coast region, where there is extensive dryland agriculture and a high dependence on ground water and precipitation. Ground-water storage in the San Joaquin Valley has declined dramatically since the onset of the drought, and will decline even more in 1991. Between 1987 and early 1991, ground-water levels in Tulare County had dropped by over 30 feet and 3.3 million acre-feet. In Madera County ground-water levels has dropped by over 25 feet and 1.4 million acre-feet. Should the drought persist, the decreased availability of ground water will have major impacts on the agricultural sector. Livestock and Grazing [section not included here]Energy The drought in California has affected both the supply of and demand for energy. California is highly dependent on hydroelectricity production -- about one-third of all electricity produced in-state is hydro -- and the drought has greatly reduced hydroelectric generation. As a result, more fossil fuels have been purchased and burned by California utilities. Electricity used for ground-water pumping has also risen with the increased demand for ground water by the agricultural sector. Because the cost of generating electricity with natural gas is higher than the cost of producing hydroelectricity, the drought has led to a direct increase in electricity costs to California ratepayers. We estimate that the first four years of the drought (1987 to 1990) cost California ratepayers an extra $2.4 billion. Hydroelectricity production in 1991 will also be well below average, and the additional costs to ratepayers this year may exceed $500 million. The burning of extra fossil fuels has also increased air pollution. We estimate that the added fossil fuel combustion has increased California's utility emissions of carbon dioxide, the principal gas responsible for the greenhouse effect, by over 25 percent from levels emitted during a normal water year.Forestry and Fire The five years of the drought have had an enormous impact on the forests of California. Trees have become highly susceptible to both disease and pest infestation. There has already been a significant die-back of trees throughout the State, particularly in the Sierra Nevada, while many more trees are sick or infested. In addition, dead and downed trees have created substantial amounts of dry fuel that greatly increases the risk of intense and destructive forest fires. The California Department of Forestry estimates that 12 billion board feet of merchantable timber has been lost on State lands; over 5 billion of that in 1990 alone. The U.S. Forest Service estimates that 10 percent of the trees in 18 National Forests have been killed by the drought and related insect infestations. On the approximately 6.5 million acres managed by the U.S. Forest Service for commercial lumber, 2.6 billion board feet of timber was killed by the drought in 1990. Estimates for August 1989 and August 1988 were each approximately 1 billion board feet. Of the 2.6 billion board feet of dead trees in U.S. National Forests as of August 1990, the Forest Service estimates that only 1.6 billion will be salvaged -- about 800 million board feet each in 1990 and 1991. The drought has led to greater expenditures for fire protection, fire control staffing, and operational expenses. State and Federal emergency expenditures for fire suppression and fighting exceeded $100 million in 1990. These expenditures are over and above the regular costs of maintaining fire-fighting equipment and personnel.Recreation and Tourism [section not included here]Municipal and Industrial Users [section not included here] The Drought as an Analogue of Climate Change Given the current concern over global warming, the question of whether this drought is a manifestation of "global climatic change" invariably arises. While the drought could be associated with larger scale changes in the climate, we are unlikely to know for several more years. Nevertheless, if the drought is merely an extreme of the current climate rather than a manifestation of anthropogenically induced climate change, it may still serve as an analogue of a future climate that is more severe than that of the present. The drought does not provide any information on the effects of increases in global and regional temperature, changes in climatic variability, the hydrologic effects of sea level rise, or a host of other issues. But it does illustrate the impacts of decreased precipitation and runoff, one possible change that might accompany global warming. More importantly, however, the drought is indicative of our society's ability to adapt to climatic variations and the vulnerability of California to long-term shifts in hydrology and water availability. The impacts of the current drought suggest that the California economy can withstand five years of reduced water supply, but that we are running up against severe limits and facing difficult choices. Specifically, ground-water supplies and reservoir storage, which so far have buffered the impacts in the agricultural sector, have been heavily depleted and will be of limited value if the drought continues. Many threatened wildlife populations are so strained by five consecutive years of drought that their ability to recover is being questioned. If the drought were indicative of long-term changes in the State's water supply, it would imply fundamental changes in the State's economy and environment. Although an imperfect analogue to global warming, the drought highlights the vulnerability of the economy and the environment of California to variations in climate. The worry, however, is that climatic changes would be even more extreme than the drought we are currently experiencing. Moreover, our response to the drought suggests that we will tend to discount the future and adopt the easiest responses first. On the positive side, the drought has forced California to re-analyze its water policies and has spurred an important debate about vulnerability, tradeoffs, and priorities. In this sense, the drought may provide the impetus to plan for and to adapt to global warming.*******************************************************************Tom Gray Second Wind, Inc.EcoNet/PeaceNet: cdp:tgray {standard disclaimer applies}Internet: tgray@igc.org 7 Davis SquareBITNET: tgray%igc.org@stanford Somerville, MA 02144UUCP: uunet!pyramid!cdp!tgray (617) 776-8520</text>
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<text>From: tgray@IGC.ORG (Tom Gray)Newsgroups: sci.environmentSubject: Droughts & Flooding RainsMessage-ID: <9110240157.AA12243@cdp.igc.org>Date: 24 Oct 91 01:57:09 GMTArticle-I.D.: cdp.9110240157.AA12243Sender: daemon@ucbvax.BERKELEY.EDULines: 433/* Written 2:49 pm Oct 18, 1991 by envcenwa in cdp:en.climate *//* ---------- "Droughts & Flooding Rains" ---------- */Cc: conf!data.farmnet conf!en.agriculture conf!en.climate conf!oz.greenhouse________________________________________________________________The following article has been taken from "Environment" magazine - a publication of the Environment Centre of Western Australia. "Environment" is a quarterly publication that acts as a forum for the discussion of environmental issues in WA and its region. If you are interested in subscribing then send us your details and $12 (one years subscription) or $20 (two years) to: Environment Magazine PO Box 7375 Cloisters Square Perth, WA 6850Alternatively you can e-mail us and give details and receive an invoice with your first issue. If you would like to contribue an article/letter please e-mail. Jeff Bryant. ________________________________________________________________ Date: Sept 1991Vol. 13 No. 2Title: DROUGHTS AND FLOODING RAINSAuthor: Miko Kirschbuam and Theo NabbenThe climatic changes associated with global warming are likely to have a dramatic influence on farming. How farmers are to enable their farms to cope given the inherent unpredictability of those changes must be considered very carefully and as soon as possible, particularly if long-term sustainable farming practises are to be adopted. Miko Kirschbuam has worked as a research officer for the Global Change Program of the Australian Conservation Foundation. He has also written on this same subject for the South Australian agricultural journal, Acres. Theo is the rural liaison officer for the WA branch of the Australian Conservation Foundation. In recent years, public awareness has grown of the potential of significant global warming as a result of a build-up of trace gases such as carbon dioxide in the atmosphere. This global warming is commonly referred to as the Greenhouse Effect. Concern about the Greenhouse Effect is not new and has been discussed in the scientific community for over hundred years. Agriculture is most vulnerable In the possible effects of the Greenhouse Effect, agriculture is particularly vulnerable. There are directly damaging effects, such as heat waves, cyclone damage, increased erosion potential due to heavier rainfalls and others, as well as the special problems associated with having to deal with change and uncertainty itself. temperature The most certain change is an increase in temperature. It will affect crops that have specific vernalisation requirements such as stone and pome fruits and might necessitate a shift to species or cultivars with different temperature requirements. This is a major problem for fruit trees due to their long life spans, and fruit growing areas that are only just cool enough to allow flowering to be initiated will be likely to be facing difficulties and only be able to survive as fruit growing regions if they can switch to fruits with lower chill requirements. A 3oC mean temperature rise would see Manjimup with temperatures similar to those Geraldton currently has, and be clearly above the chilling requirements of its deciduous fruit industry. Increasing temperature will also mean a greater incidence of heat waves. Perennial plants and summer crops will be most at risk. On the positive side, higher winter temperatures may increase productivity in regions that are currently of low productivity due to cold winter temperatures. Slower maturing varieties of plants may be more suitable under warmer temperatures since they are less likely to "bolt" to maturity, thereby reducing potential yields. Higher temperatures in winter could also reduce post-natal lambing losses in sheep. Disease problems are likely to become more prevalent, as warmer regions generally are more prone to diseases. Similarly, insect pests may become more of a problem, as the higher metabolic rate of many insects and diseases will allow faster growth and multiplication. Many pest species are also killed by frost. The disappearance of frost would, therefore, also allow many pests to extend into regions from which they are currently excluded by frost. rainfall Warmer air can hold more water, and in a warmer world, surface water is likely to evaporate faster. This means that the hydrological cycle is likely to intensify with more rainfall and faster evaporation rates, at least in globally averaged terms. Most Greenhouse models suggest that, in general terms, summer rainfall will increase so that water availability to crops in regions reliant on summer rainfall may not change very much; winter rainfall, however, is likely to decrease sharply. However, our current models are not reliable enough to predict with any certainty which regions may experience what changes, but it seems certain that there will be both winners and losers in the distribution of changes in temperature and rainfall. Since rainfall intensity is almost certain to increase, problems such as erosion and flooding are very likely to increase. Reduced rainfall will affect the recharge of aquifers, groundwater level and possible salinity problems in some areas. It will also have important implications for farmer reliance on farm dams, and mean that farmers may need to invest in expanding their farm management practises to more variable rainfall regimes. Extreme events Cyclones are generally expected to increase in both their frequency and intensity and are likely to occur in regions further south. There are, however, still major uncertainties about the physics of cyclones so that this change cannot yet be predicted with certainty. Other extreme events, such as prolonged dry spells, long spells at temperatures above or below their averages or increased non-cyclonic wind speeds may or may not change in their frequency. Current models cannot yet make any reliable predictions on any of these questions, and there is no simple reason to assume that their incidence should change. On the other hand, if it gets warmer and the variability about the new average remains the same, it would, nonetheless, mean that the incidence of damaging high temperatures would increase. the carbon dioxide fertilisation Effect Growth of plants is dependant on the uptake of carbon dioxide from the atmosphere. The pre-industrial concentration of carbon dioxide was about 280 ppmv; it has increased to over 350 ppmv by now, and is currently increasing further at a rate of about 1.5 ppmv per year. This should increase the ease with which plants can take up carbon dioxide in the process of photosynthesis. Plant physiological studies support that contention, but it is not clear yet to what extent growth enhancements will be expressed in plants growing under natural conditions when other factors, especially phosphorus nutrition, may be limiting growth. There are likely to be differences between the ways in which different species respond to increases in carbon dioxide concentration. With ample water supply, it is likely that plants using the C3 photosythetic pathway such as wheat, legumes and most tree species may grow better, whereas growth in plants using the C4 pathway, such as maize and sorghum, may not be increased. Under water-limited conditions, both types of plants should be similarly stimulated. the CO2 fertilisation effect should be particularly important at higher temperature, and could thereby to some extent counteract the negative effects of the Greenhouse Effect. However the absence of dramatic yield improvements up to now should make us cautious about expecting major improvements to eventuate in the near future. There is also the possiblity that plants which adapt gradually to warming temperatures may not respond favourably to the fertilisation effect. It is unlikely to be able to compensate for the negative aspects of the Greenhouse Effect. Change and uncertainty Potentially the most serious threat imposed by the Greenhouse Effect is change and uncertainty itself. Agriculture is heavily dependant on the expectation that next year's weather will be predictable. A particular crop species, for example, is chosen because it is expected to grow best under the environmental conditions expected for the coming season. This is particularly important for long-lived plants like trees. Tree varieties must be chosen that respond well not only in the next year, but over the next decades. Uncertainty in future rainfall is bound to increase as we do not yet have any clear understanding of how changes in global temperature may affect local weather patterns and rainfall distributions. Changes in temperature may further compound the difficulties, as it is again not clear how global changes in temperature will be expressed at the local level. All models of climate change clearly predict there to be significant regional differences in the extent of global warming, with some regions experiencing less than the global average. We cannot yet predict what regions will experience more and what regions less warming. Computer models are continuously being refined to develop more reliable regional predictions. However, the complexity of the global climate system may be such that we will never be able to predict these local effects. This leaves agriculture in the quandary of having to contend with a changing climate where the nature of change cannot yet be foreseen. Some aspects of change are predictable, and that poses its own costs and challenges. As it gets warmer, regions that were once suitable for, say, winter wheat may become suitable for summer wheat, or a region may change from being suitable for wheat to maize. How do farmers respond? When is the appropriate time for switching from one production system to the other? Do individual farmers have the necessary skills to adapt; do they have the right tools and machinery? How easy is it for a farmer who has grown wheat for twenty years to switch to the production of maize? Some regions may also become totally unproductive; current models predict that winter rainfall may decrease, which together with warmer temperatures, may make much of the areas in South and Western Australia that rely on winter rainfall less productive. If Australia is lucky this loss in production potential may be compensated for by increased productivity in the summer rainfall regions of NSW and Queensland. But much of the human and physical infrastructure in South and Western Australia may be lost to the extent that it is not relocatable. In addition there is likely to be immense human hardship involved in the translocation of farmers once certain areas become unproductive, with the attendant break-down of social networks. To make this transition harder, there will be no clear point at which an area becomes unproductive and there would be likely to be a long period of increasing hardship with decreasing yields before it finally becomes unavoidable to give up unproductive enterprises. In addition to the anticipated gradual change, there is the possibility of sudden shifts from one climate regime to another. Such quick changes have apparently occurred during past episodes of climate change that were associated with the ice ages. influencing the Greenhouse Effect The most important Greenhouse gases are carbon dioxide, methane, nitrous oxide and the chlorofluorocarbons. The relative contribution from each of these gases from Australian sources is shown in Figure 1. Of Australia's carbon dioxide emissions, 2.2% originate from agricultural activities. Agriculture plays a more significant role as a source of methane and nitrous oxide. The fourth major group of greenhouse gases, the CFCs, originate to no significant extent from agricultural activity. It is worth describing what the major sources of Greenhouse gas emissions from agricultural activities are in some detail, and also what scope there is for limiting these emissions. carbon dioxide The emissions of CO2 originating from agricultural activities come predominantly from the operation of farm machinery and the production of fertilisers. In principle, farmers can reduce these emissions by 1. reducing the use of high energy options for farming operations (eg. mustering with horses rather than helicopters; or limiting the amount of chemicals applied by aerial spraying; or simply by minimising the number of cultivation passes over the land.); 2. using biofuels (ethanol, methane) derived from farm produce, and 3. attempting to reduce the use of fertilisers or replacing them with organic sources. Additionally, agriculture can help alleviate the Greenhouse Effect by storing carbon on the farm in the form of either living biomass or organic carbon in the soil. Agricultural activities usually lead to a reduction in the amount of carbon stored on the farm either above or below ground. Tree farming, either in the form of permaculture or just the provision of shelter belts, can store considerable amounts of carbon in the trunks of trees. Frequent cultivation and the burning of stubble, on the other hand, all lower the amount of carbon retained in the soil organic matter, while mulching, zero tillage or use as pasture all tend to lead to a build up of the amount of soil organic matter. Carbon storage on the farm can be quantitatively very significant. A hectare of forest may contain 100 t (or more) of carbon in tree trunks and 100 t of carbon in the soil organic matter. A paddock with wheat, on the other hand, may contain only 5 t of carbon above ground and lose 1% of soil organic matter per year of cultivation. By clearing a 1,000 ha farm, a single farmer may thus cause the immediate release of 100,000 t of carbon into the atmosphere, and cause the loss of another 1,000 t of soil carbon per year. Conversely a switch from annual soil preparation to zero tillage may arrest the carbon loss, and a switch to permaculture may lead to an increase of 2,000 t per year on the 1,000 ha farm. This compares with the average of about 5 t carbon emitted by the average Australian in one year. These figures are, of course, only indicative and would differ between regions, soil types and management systems. methane The major agricultural sources of methane are enteric fermentation in the guts of herbivores, biomass burning and anaerobic organic matter breakdown, mainly in flooded rice paddies. Scope for limiting methane production from cattle lies firstly in a switch in diet in consumers from beef, which produces large amounts of methane per unit of protein to other animal proteins such as from chickens or fish, or to a more vegetarian diet, which would have health in addition to environmental benefits. There is scope for limiting methane production per unit beef produced. Methane production is significantly increased with poorer nutrient content of the type of fodder ingested by the animals. Animals receiving a high-protein diet may release half as much methane per day as animals on a poor diet and may grow twice as fast. Most cattle in Australia unfortunately graze in northern regions of Australia on very poor fodder. This can be artificially improved by providing non-bloat capsules or urea and molasses licks to animals. This may be already economical in many farming enterprises, and could get a significant further boost due to its environmental benefits. About one third of Australian methane emissions are released during biomass burning. Of that, about 60% originate from grassland fires in Northern Australia and 15% from natural unpreventable bushfires2. The remaining 25% are released as part of agricultural and forestry management, and part could be minimised by phasing out stubble and sugar cane burning. Rice paddies also release significant amounts of methane, and that could be avoided by a switch to dryland rice production. nitrous oxide Nitrous oxide emissions originate largely from agricultural activities, and it is principally activities that involve the turn-over of soil nitrogen. During any process where nitrogen is converted from one chemical form to another, some of the nitrogen escapes into the atmosphere in the form of nitrous oxide. As nitrous oxide is chemically very inert, it may remain in the atmosphere for 150 years before eventually being broken down by photochemical decomposition in the stratosphere. The chemistry of nitrous oxide is still surprisingly poorly understood, and it is not entirely clear what its major sources are. Large amounts of nitrous oxide might be released from nitrogen fertilisers, with estimates of the conversion of fertiliser N to nitrous oxide ranging from 0.01 - 2.0%4. The actual release is believed to depend on a whole range of factors such as fertiliser type, soil moisture and temperature, and farming practise such as the frequency of soil disturbance. Some reductions in nitrous oxide release might be achievable through a switch from organic to inorganic fertilisers or greater reliance on legumes, as that would lower the concentration of inorganic nitrogen in the soil and give less opportunity for the escape of gases. However, while this is plausible, concrete experimental evidence in its support is still not available. Reducing the release of nitrous oxide might only be possible through a reduction in nitrogen turn-over in the soil. As this would be associated with a decline in soil fertility, it would be a costly way to achieve reductions in nitrous oxide release. All in all, the paucity of information about the sources of nitrous oxide release make it difficult to recommend specific steps to reduce its emissions. conclusions Agriculture is reliant on a predictable and more or less benign climate. If the climate changes toward a harsher regime, productivity will decrease. If the climate becomes unpredictable farmers will find it increasingly difficult to make the correct managerial decisions to match species and management to their climatic conditions. A shift in climatic zones may also cause considerable hardship for many individual farmers in one region even if, nationally averaged, the inherent productivity of the country were to remain the same. While being the biggest likely loser out of Greenhouse-induced changes, agriculture is also one of the main contributors. Methane and nitrous oxide, in particular, are chiefly of agricultural origin, and for methane the scope for modification to agricultural practises to minimise its release is significant. The control of nitrous oxide is more difficult, as its most significant sources, and the factors controlling these, are still only very poorly understood. Some steps to limit the emission of Greenhouse gases may be warranted and economic in their own right, such as cessation of stubble burning or conversion to zero tillage regimes. Others may be justified by other environmental concerns, such as a shift to more organic farming methods, especially permaculture, or cessation of the growing of flooded rice because of concerns over rising ground water. Other steps may not be economically attractive to farmers, but they could constitute an important contribution to limiting emissions as a national responsibility. For example, the provision of urea and molasse licks for cattle in the north of Australia would have considerable potential to limit the emission of Greenhouse gases. It may not be economic for individual cattle station managers to use licks, but it might be warranted to support such a move as a nationally supported and financed initiative to combat the Greenhouse Effect. Perhaps a fundamental way that farmers can prepare for the future changes is by preserving their preeminent resource, the land, from further degradation. By protecting our land, water and biological resources and maintaining the biodiversity of ecosystems, farmers will have a broader resource base which can help them adjust to climate change. references 1. Cicerone, R. and Oremland, R.; Biochemical aspects of atmospheric methane; Global Biochem. Cycles 2; 1988. 2. Greene, D., Gavin, G., Armstrong, G., O'Dwyer, A.J., Braddock, P.; Reducing greenhouse gases: options for Australia; Report prepared for the Australian and New Zealand Environment Council; 1990. 3. Mitchell, J.F.B., Manabe, S., Tokioka, T. and Meleshko, V.; Equilibrium climate change; Scientific assessment of climate change (Houghton, J., Seck, M., Moura, A. eds), Intergovernmental panel on climate change, working group I; 1990. 4. Watson, R. Rodhe, H., Oescheger, H. and Siegenthaler, U.; Greenhouse gases and aerosols; Scientific assessment of climate change (Houghton, J., Seck, M., Moura, A. eds), Intergovernmental panel on climate change, working group I; 1990. 5. Wilkenfield, G. and Associates; Greenhouse gas emissions from the Australian energy system: the impact of energy efficiency and substitution; National Energy Research, development and demonstration program; 1990. </text>
