Climate Change and Rangelands: Responding Rationally to Uncertainty By Joel R. Brown and Jim Thorpe

ccording to most estimates, rangeland ecosys- have a dominant infl uence on productivity, stability, and tems occupy about 50% of the earth’s terrestrial profi tability. surface. By itself, this estimate implies range- The interaction between scientists and managers is are important to humans, but their impor- critical to understanding and managing the relationships Atance extends far beyond their global . Globally, critical to healthy rangeland . While scientists rangelands provide about 70% of the forage for domestic uncover new relationships governing behavior, . For many societies, livestock are critical to sur- managers are ultimately responsible for implementing prac- vival. Rangelands also provide a host of ecosystem services tices to ensure continued heath of the systems they manage. technology or other types cannot provide. Among the One of the most important scientifi c contributions of the most important of these services is regulation, or past decade is an enhanced understanding of earth’s climate the ability to sequester and store greenhouse gases such as system and human impacts on climate. Through a collab- carbon dioxide. orative effort, scientists have communicated the links The ability of any rangeland to provide any ecosystem between humans and climate. Policy makers and the public service is dependent, primarily, upon the rangeland’s condi- are generally aware that humans have an infl uence on tion. Degraded rangelands are poor providers of ecosystem climate—an infl uence that is likely to increase in the services, regardless of the commodity. In crop or immediate future. There is a recent consensus on the need ecosystems, managers can overcome inherent biophysical for humans to mitigate their effects on climate and adapt to limitations with additions of , fertilizer, cultivation, or likely climatic shifts. new species. Rangeland managers typically lack those Rangeland managers are certainly not strangers to the options. In general, management is concentrated on affect- vagaries of changing climate; if not aware of long-term, ing changes in and through the application human-induced climatic change, then, certainly they are of disturbances, such as fi re or . The primary input aware of short-term weather variability. Weather events for rangeland managers is intellectual capital, whether it is infl uence and profoundly change entire societies. Historians in the form of livestock management practices based on often point to the North American winter of 1886–1887, research conducted at a nearby experiment station, experi- when extremely harsh weather marked an end to the era of ence handed down across generations, or other forms of open ranges, and caused reorganization of the livestock local knowledge. Because rangeland managers have a lim- industry. Widespread losses of livestock to low temperatures ited ability to manage inputs, they are more dependent on and heavy snow crippled the industry, with effects cascading environmental conditions. In particular, rainfall (amount into a larger fi nancial disaster ultimately affecting the entire and timing) governs rangelands, and managers’ success or country. failure is determined by their ability to respond to, rather The effects of climate change are still making history. than create, conditions. Any change to the environment Media reports of famine and political strife, due to regional affecting rainfall, or how soils and process water, will droughts in developing countries, are becoming more

JJuneune 22008008 3 frequent, and more disturbing. However, news reports Explanation of the terminology used in Inter- seldom convey the complex relationship between human governmental Panel on Climate Change reports societies and their environment. The drought of 2000 in Mongolia, close on the heels of a harsh winter, resulted in Terminology Probability widespread livestock deaths, rising meat prices, and devas- Virtually certain >99% tated rural economies. The combination of harsh winter and Extremely likely >95% drought, called “dzuds” by Mongolians, is often cited as a major factor in power shifts among dominant political par- Very likely >90% ties. The sequence of drought–famine–social unrest–political Likely >66% upheaval is currently being played out in eastern Africa and is affecting millions of people and destabilizing entire More likely than not >50% . Furthermore, these destabilizing droughts could About as likely as not 33–66% encompass multiple decades. Once this sequence of events is Unlikely <33% underway, droughts are often forgotten, yet whole societies are forever changed. Even in developed countries with established political projected changes is explained in the sidebar. Some of the systems and stabilizing infrastructure, climatic change can general changes in ecosystems globally are as follows: be devastating. Australian range scientists and pastoralists are familiar with drought, and have an enviable history of • Warming will be greatest over land, and at high northern coping with its effects. In the past, droughts impacted latitudes; it will be least over the southern oceans and parts agricultural economic sectors while having minimal effects of the North Atlantic on the larger economy. However, a current decade-long • Contraction of snow cover, increases in thaw depth over drought, which qualifi es as the worst drought in a century, permafrost regions, and decrease in sea extent is affecting other economic sectors and causing considerable • Very likely increase in frequency of hot extremes, heat political consternation. Some groups are proposing that waves, and heavy events Australia’s population might already exceed the carrying • Likely increase in tropical cyclone intensity capacity needed to maintain their desired quality of • Poleward shift in extra tropical storm tracks given the prospect of a drought-plagued future. • Very likely precipitation increases in high latitudes and The effects of climate change must be considered across likely decreases in most subtropical regions multiple scales. The examples above generally describe how • High confidence that river runoff and water availability the effect of climate change extends beyond local or - will increase at high latitudes and decrease in dry regions al boundaries to contribute to change at national scales. in midlatitudes and tropics As technical sophistication improves our ability to observe • High confidence that many semiarid regions (Mediter- our world, and observations encompass longer time frames, ranean basin, western , southern Africa, the global nature of climate change becomes more obvious. and northeast ) will see decreases in water availability Local effects (reduced precipitation, increased temperatures) can lead to , which can cascade into regional Although these projections are informative and provide desertifi cation. We now know that regional desertifi cation valuable insights into important potential changes and their can cause increased wind erosion and dust that can be effects on ecosystem behavior, more detailed projections transported by upper atmospheric winds where it can affect are necessary to formulate regionally and locally appropriate global weather patterns and impact human health. responses. Both the IPCC and the USGCRP have devoted Although numerous examples of the impacts of climate signifi cant effort to predict likely climate scenarios that can change can be informative upon post hoc analysis, the real be used by policy makers and land mangers. Some of those challenge that remains is developing tools that predict cli- predictions are as follows: mate changes and us in developing adaptive responses to impending change. The increasing sophistication of global Africa climate models is allowing scientists to make reasonable • By 2020, between 75 and 250 million people could be inferences about potential changes in regional and local cli- affected by diminishing availability of water mates. The work of the Intergovernmental Panel on Climate • By 2020, yields from -fed could be reduced Change (IPCC), through the Assessment Reports, and the by up to 50%, greatly affecting security United States Global Change Research Program (USGCPR), • By the end of the 21st century, sea-level rise is projected to through the National Assessment Report, provide relevant affect low-lying coastal areas; adaptation costs could projections of changes in climate and offer interpretations of amount to 5–10% of Gross Domestic Product how those changes might affect human activities. An expla- • By 2080, an increase of 5–8% of arid and semiarid nation of the terminology used to describe the likelihood of conditions

4 RRangelandsangelands Asia • Higher winter temperatures will very likely reduce snow- • By 2050, freshwater availability throughout most of Asia pack and peak runoff and shift peak flows earlier in spring is projected to decrease in both the Rocky and Sierra Mountains • Climate change, associated with rapid urbanization, in- • Water management for control, fish runs, and dustrialization, and economic development will compound will become more complicated pressure on natural • Increased chances of summer drought will likely increase • Changes in the hydrologic cycle are projected to increase frequency and intensity on both range and forest human morbidity and mortality due to diarrheal diseases lands • could be favored by changes in wildfire Australia regimes and precipitation and temperature changes • By 2020, significant loss of in coastal and near coastal tropical environments Southwestern United States and • By 2030, water supply and security problems will intensify Rangelands in southern and eastern Australia • Increases of about 3–4° F by the 2030s and 8–11° F by the • By 2030, agricultural productivity is projected to decline 2090s over southern and eastern Australia due to increased • Rainfall for the region is likely to become more highly incidence of drought variable and with increases occurring primarily during the winter Latin and • Reduced snowpack and increased peak flows during late • Increases in temperature and decreases in water winter and spring availability are projected to lead to replacement of tropical • An increase in the number of extremely wet or dry years, forest by in eastern Amazonia. There will be a increasing the chance of multiyear drought or more frequent and intense likely shift from semiarid to arid vegetation • Increases in the amount of , , and • Risk of significant biodiversity loss throughout the at the expense of vegetation tropics • Decreases in crop yields in some areas, with soybean yields Great of the United States projected to increase in temperate areas • Temperatures are forecast to increase 5–12°F over the next • Loss of is projected to significantly affect water century, with the greatest increase in the western portion availability for food production of the region • A greater number of heat events (>3 consecutive days North American rangelands, because they are among over 90°F), increasing stress on humans and livestock the most studied on the planet, could have the most cer- • Although increases in precipitation are forecast, greater tainty with regard to predicted responses to climate change. increases in are likely to result in The USGCRP Assessment used two common and reliable reduced soil moisture availability models (Hadley Model and Canadian Model) to predict • Increased CO content in the atmosphere could favor climatic changes during the 21st Century. Although the 2 (C3) over grasses (C4) models differ slightly in their predictions, general trends • Increased climate variability will favor invasive and weedy were similar. The USGCRP then conducted a series of species workshops in the late 1990s to analyze the potential effects of climate changes and develop response scenarios. We Given the benefi t of history, combined with our expand- slightly altered the defi nitions of regions used by USGCRP ing understanding of the effects of climate change and to better refl ect rangeland ecosystems and their use and climate variability on rangelands, and subsequently human management patterns. societies, we can make inferences on how to manage rangelands in the future. We asked authors from around the Northwestern United States Rangelands world to address how rangelands might respond to a chang- • Average temperatures will likely increase about 2°F by the ing climate and discuss possible management options. 2030s and 5°F by the 2050s, with increases occurring both Management options might be in the form of mitigation or in the summer and winter adaptation. Mitigation refers to how rangelands can be • Average precipitation could increase in and managed to reduce the effects of human activity on climate the southern Great Basin, primarily in the winter, with no through carbon sequestration. Sequestration is the increased change or decreases in summer storage of carbon in the soil and vegetation through the • California’s Mediterranean climatic patterns are unlikely management of naturally occurring processes: photosynthe- to change sis, humifi cation, and aggregation. Adaptation, on the other • Increasing temperatures will likely raise stream tempera- hand, assumes that climate change will occur and focuses tures primarily on how can change to

JJuneune 22008008 5 reduce the impact of those changes. This issue of Rangelands clearly the most important issue of this century…climate contains a series of eight articles addressing different aspects change. of rangelands and climate change. The fi rst (de Steiguer et al.) examines how rangelands can be managed to miti- Additional Reading gate, or lessen the impact of, climate change. The remaining articles provide insights into how climate change might Gore, A. 2006. An inconvenient truth: the planetary emergency of global warming and what we can do about it. New York, NY, affect rangeland ecosystems on a regional scales and how USA: Rodale Books. 327 p. current management can respond to maintain the fl ow of Havstad, K., M. Peters, D. P. C. Skaggs, R. Brown, J. Bestel- ecosystem services and the integrity of these valuable lands. meyer, B. Fredrickson, E. Herrick, and J. Wright. 2007. In organizing this special issue, we felt publishing only one Ecological services to and from rangelands of the United States. article on mitigation is appropriate, given the limited capac- 64:261–268. ity of managed rangelands to mitigate climate change and Lund, H. G. 2007. Accounting for the world’s rangelands. the potentially large impact of climate change on rangeland Rangelands 29(1):3–10. ecological processes and management. National Assessment Synthesis Team, US Global Change We have taken pains to ensure that the articles are read- Research Program. 2000. Climate change impacts on the able and relevant. In order to improve the readability of the United States: the potential consequences of climate variability articles, we have limited citations within the text. However, and change. New York, NY, USA: Cambridge University Press. 155 p. because the fi eld of climate change and predictions about United Nations Environment Program Intergovernmen- impact are fraught with uncertainty, it is important that tal Panel on Climate Change. 2007. Climate change 2007: interested readers have access to the full range of literature impacts, adaptation and vulnerability. New York, NY, USA: upon which the authors have relied to make their con- Cambridge University Press. 103 p. clusions. The articles with full citations are posted at http:// www.rangelands.org/climatechange.shtml. All of the articles in this special issue were peer-reviewed and we thank the Authors are Rangeland Scientist, USDA–NRCS, Jornada reviewers for their efforts. We sincerely hope this issue Experimental Range, MSC 3JER, PO Box 30003, New Mexico stimulates some thought within the rangeland management State University, Las Cruces, NM 88003-0003, USA, community (managers, technical advisors, policy makers) [email protected] (Brown); and Rancher, Newkirk, NM about the numerous possibilities for responding to what is 88431, USA (Thorpe).

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