290 • Department of Energy, U.S. Global Resources U.S. Department of Energy Secretary of Energy Deputy Secretary Federal Energy Regulatory Commission ChiefofStaff Office of the Under Secretary For Nuclear Security/ Administrator for National Nuclear Security Administration Office of the Under Secretary Office of the Under Secretary for Science Associate Administrator for Management and Administration Advanced Research Projects Agency-Energy General Counsel Chief Financial Officer Chief Information Officer Chief Human Capital Officer Management Public Affairs Assistant Secretary for Congressional and Intergovernmental Affairs Assistant Secretary for Policy and International Affairs Health, Safety and Security Inspector General Economic Impact and Diversity Hearing and Appeals Intelligence and Counterintelligence Developmental Staff and Support Offices Energy Information Administration Bonneville Power Administration Southwestern Power Administration Western Area Power Administration Deputy Administrator for Defense Programs Deputy Administrator for Defense Nuclear Nonproliferation Deputy Administrator for Naval Reactors Deputy Under Secretary for Counterterrorism Associate Administrator for Defense Nuclear Security Associate Administrator for Emergency Operations Associate Administrator for Infrastructure and Environment Associate Administrator for Management and Administration Assistant Secretary for Energy Efficiency and Renewable Energy Assistant Secretary for Environmental Management Assistant Secretary for Fossil Energy Assistant Secretary for Nuclear Energy Assistant Secretary for Electricity Delivery and Energy Reliability Civilian Radioactive Waste Management Legacy Management Office of Science Advance Scientific Computing Research Basic Energy Sciences Biological and Environmental Research Fusion Energy Science High Energy Physics Nuclear Physics Workforce Development for Teachers and Scientists Southeastern Power Administration After the end of the Cold War in 1990, the Depart - ment of Energy deemphasized production of new nuclear weapons and shifted some support totheoret- ical research: particle acceleration experiments at the Department of Energy’s Fermi National Accelera- tor Laboratory, SLAC National Accelerator Labora- tory, and other national laboratories. During the Bill Clinton administration, the Department of Energy proposed numerous regulations for disposal of haz- ardous wastes (such as plutonium). Under the free market ideology of President George W. Bush,the De- partment of Energy promoted extraction of oil and nonrenewable energy resources from federal lands in the West and in Alaska. Howard Bromberg Web Site U.S. Department of Energy http://www.energy.gov/ See also: American Mining Congress; American Pe- troleum Institute; Atomic Energy Acts; Atomic En- ergy Commission; Biofuels; Biotechnology; Depart- ment ofAgriculture, U.S.;Department ofthe Interior, U.S.; Department of Transportation, U.S.; Energy economics; Energy politics; Energy storage; Gasoline and other petroleum fuels; Manufacturing, energy use in; Nuclear Energy Institute; Oil embargo and en- ergy crises of 1973 and 1979; Organization of Arab Pe- troleum Exporting Countries; Organization of Petro- leum Exporting Countries; Solar energy. Department of the Interior, U.S. Category: Organizations, agencies, and programs Date: Established 1849 The U.S. Department of the Interior is the federal agency entrusted with conserving much of the nation’s natural resources. These resources include federal for- ests and grazing land; national parks; water and irri- gation; oil, gas, and coal; American Indian lands; and fish and wildlife. Background The Department of the Interior is part of the execu - tive branch of the U.S. government. The secretary of the interior is a member of the president’s cabinet, confirmed by the Senate. The three original execu - tive departments of the federal government estab- lished in 1789 were Foreign Affairs, War, and Trea- sury. Given the limited role intended for the federal government in internal affairs, there wasno executive department to handle general domestic management. As the range of federal responsibilities emerged, Con- gress established the Department of the Interior on March 3, 1849, to assume various domestic duties of the federal government. Impact on Resource Use In the second half of the nineteenth century, the De- partment of the Interior conducted a wide range of domestic activities, such as controlling American In- dian affairs, managing federal lands, paying federal pensions, granting patents, conducting the census, constructing the infrastructure for the District of Co- lumbia, surveying the Western territories, and over- seeing federal monetary and land grants to hospitals and colleges. As a result, the Department of the Inte- rior received the unofficial title of “Department of Ev- erything Else.” As Congress created additional de- partments to assume these manifold tasks, the chief purpose of the Department of the Interior came into view: tomanage andconserve the natural resources of the nation. The principal work of the modern Department of the Interior is performed by eight bureaus. Perhaps the best way to understand the crucial role the De- partment of the Interior plays in administering the nation’s resources is to outline the functions of its ma- jor divisions. The Bureau of Land Management man- ages more than 100 million hectares of federal lands, much of which is leased for cattle grazing and ranch- ing, lumber logging, coal and mineral mining, and oil and gas drilling. These leases raise as much as $23 bil- lion annually for the federal government and account for about 30 percent of the nation’s energy produc- tion. The National Park Service manages 33 million hectares, comprising 391 federal parks, monuments, and cultural sites. The Fish and Wildlife Service man- ages about 40 million hectares of wildlife refuges to conserve and foster marine and animal life. The Bu- reau of Indian Affairs manages 27 million hectares of American Indian tribal and reservation lands. The Bureau of Reclamation manages 479 dams and 348 reservoirs, which provide water to much of the West. The U.S. Geological Survey conducts geological and topographical research. Global Resources Department of the Interior, U.S. • 291 In total, the Department of the Interior plays a cru- cial role in conserving federal lands, forests, and parks; irrigating and supplying fresh water; protecting ma- rine and land wildlife; and leasing lands for material, mineral, and energy production. With jurisdiction over such a wealth of resources, the Department of the Interior has been prone to scandal. In 1929, Depart - ment of the Interior secretary Albert Falls was con - victed of bribery in the Teapot Dome scandal. In the administration of President George W. Bush, Depart- ment of the Interior officials often seemed ambiva- lent aboutthe naturaltreasures that they were obliged to protect. In a December, 2008, report, Department of the Interior inspector general Earl Devaney found unethical, wasteful, and corrupt behavior in the Min- erals Management Service and other divisions of the Bush administration’s Department of the Interior. Howard Bromberg 292 • Department of the Interior, U.S. Global Resources U.S. Department of the Interior SECRETARY DEPUTY SECRETARY INSPECTOR GENERAL SOLICITOR NATIONAL BUSINESS CENTER NATIONAL PARK SERVICE OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT U.S. FISH AND WILDLIFE SERVICE MINERALS MANAGEMENT SERVICE BUREAU OF INDIAN AFFAIRS U.S. GEOLOGICAL SURVEY BUREAU OF LAND MANAGEMENT BUREAU OF RECLAMATION ASSISTANT SECRETARY POLICY, MANAGEMENT, AND BUDGET AND CHIEF FINANCIAL OFFICER ASSISTANT SECRETARY FISH AND WILDLIFE AND PARKS ASSISTANT SECRETARY WATER AND SCIENCE ASSISTANT SECRETARY LAND AND MINERALS MANAGEMENT ASSISTANT SECRETARY INDIAN AFFAIRS OFFICE OF SPECIAL TRUSTEE FOR AMERICAN INDIANS Web Site U.S. Department of the Interior http://www.doi.gov/ See also: Bureau of Land Management, U.S.; Bureau of Mines, U.S.; Bureau of Reclamation, U.S.; Depart- ment of Agriculture, U.S.; Department of Energy, U.S.; Department of Transportation, U.S.; Forest Ser- vice, U.S.; National Park Service; National Parks Act, Canadian; Public lands; U.S. Geological Survey. Department of Transportation, U.S. Category: Organizations, agencies, and programs Date: Established 1966 The Department of Transportation worksto provide ef- ficient, economic, safe, and environmentally sound national transportation systems on land, in the air, over U.S. waters, and through underground pipelines. In this role, it regulates the transport of resources throughout the country. It is one of the departments of the federal government that reports directly to the presi- dent of the United States. Background On March 2, 1966, President Lyndon B. Johnson pro- posed the structure for a new executive department pertaining to federal aspects of transportation. On October 15, 1966, Congress established the Depart- ment of Transportation. More than thirty existing agencies with some ninety thousand employees were brought together in creating the Department of Trans- portation. Impact on Resource Use The transportation systems of the nation are intricately linked to the resources of the nation and the world. Most physical resources—anything from timber to gasoline to crushed stone—are transported from pro- ducer to consumer through parts of the national trans- portation system. The transportation industry is itself a major consumer of many resources, and the Depart- ment ofTransportation assistsin efforts toreduce pol- lution and destruction of natural ecosystems and to in- creasethe efficiency ofthe industry’s useof resources. Environmental issues that are researched through funding from the Department of Transportation in - clude the safe packaging and transportation of haz - ardous materials and the effects of airline and auto- mobile emissions on air quality. Also studied are the water quality in rivers and oceans (particularly as af- fected by merchant shipping and inland barge trans- portation) and how best to preserve wetlands or wild- life habitats during the construction of highways, airports, and urban transit systems. The Department of Transportation conducts research on the feasibility of electrictransportation regardingboth automobiles and mass transit. The department is the main force in the federal government for developing and coordinating a na- tional transportation system and developing a national policy regarding transportation. Its responsibilities include the development and enforcement of trans- portation safety improvements, the development of international transportation agreements, and the smooth running of accessible transportation for the general public. It coordinates transportation issues with states and cities and provides technical assistance to other levels of government. The department ac- quires equipment and services and disburses federal funding to state and municipal authorities for trans- portation purposes. The Department of Transportation has a number of operating divisions. Each is headed by an adminis- trator who answers directly to the secretary of the De- partment of Transportation, who heads the depart- ment and serves on the president’s cabinet. The divisions are the Federal Motor Carrier Safety Admin- istration, Federal Railroad Administration, Federal Transit Administration, the Pipeline and Hazardous Materials Safety Administration, the Surface Trans- portation Board, the Federal Aviation Administra- tion, the Federal Highway Administration, the Saint Lawrence Seaway Development Corporation, the Na- tional Highway Traffic Safety Administration, the Maritime Administration, and the Research and Spe- cial Programs Administration. In 2003, the Department of Transportation under- went a slight restructuring when two of its divisions, the United States Coast Guard and the Transporta- tion Security Administration, became parts of the De- partment of Homeland Security. Each of the eleven divisions isinvolved in specificaspects of resource and environmental management. The National Highway Traffic Safety Administration, for example, assists in the development and enforcement of national fuel economy standards. The Federal Aviation Adminis - Global Resources Department of Transportation, U.S. • 293 tration assists in studies related to changes in the ozone layer as a result of airline emissions. Dion C. Stewart Web Site U.S. Department of Transportation http://www.dot.gov/new/index.htm See also: National Oceanic and Atmospheric Admin- istration; Transportation, energy use in. Desalination plants and technology Category: Obtaining and using resources Seawater and other salt-containing waters are con- verted into potable water by distillation, reverse osmo- sis, and other processes experimentally, and increas- ingly practically, in regions where water resources are limited or expensive. Background For many years, large ships at sea have used distilla- tion processes to convert seawater into usable water for passengers and crews because it is more economi- cal than carrying enormous quantities of fresh water for drinking, cooking, and cleaning. In desert regions and some areas that have limited suitable fresh water available, distillation and, more recently, membrane processes have been introduced for the conversion of brackish water, industrial effluents, wastewater, and seawater. Large-scale pilot processes have been rare. One notable example is a plant that was built in San Diego in the 1950’s and later shipped tothe U.S. naval base at Guantánamo Bay in Cuba. It can produce 13 million liters of distilled water per day. Because brackish water and various wastewaters contain between 500 and 5,000 parts per million of dissolved solids, and seawater and geothermally pro- duced brines contain up to 50,000 or more, a number of different processing methods have been devel- oped. In addition, the end use of the water may dic- tate the superiority of one method above the others. For many agricultural purposes, water containing a few thousand parts per million can be used, whereas U.S. drinking waterstandards are set at a maximum of 500 (in actuality, many U.S. cities’ water supplies ex - ceed this standard). Distillation Methods Distillation methods were first described by Aristotle, but they had their first practical use aboard English naval vessels in the 1600’s. Since then they have be- come much more complex, but they still involve a high-cost, energy-intensive boiling process, and sub- sequently a cooling process for liquefaction of the steam generated. The original processes required submerged tubes, which became encrusted with chemical deposits. Multistage flash process plants are currently used in which the latent heat of evaporation of the water is captured and reused, and the scaling is diminished by adding chemicals or removing the ions causing the deposits. Newer variations of these pro- cesses are being investigated. Some attempts have been made to couple power generation plants with distillation units, which may provide more desirable economy of operation. Various versions of the multistage flash process are used in many parts of the Middle East and in more than three-quarters of the currently operating sys- tems. Other designs for distillation plants have been proposed, and some have been built. Most of these have used horizontal tube processes witha design that permits multiple stages with vacuum distillation and a gradual reduction of saline content by incorporating steam with the brine. Large installations are currently incorporating this design. Smaller plants have em- ployed a vapor compression procedure for industrial plants and resort hotels, but these are gradually being replaced by reverse osmosis facilities. Solar distillation procedures would appear to offer great future alternatives in the very regions where water is in short supply. If solar energy could be more cheaply and efficiently obtained, and the land area needed made available, the saline water conversion problem would be solved relatively easily. Membrane Methods Although reverse osmosis has been most heavily pro- moted, thereis actually alarge group ofrelated proce- dures that utilize membrane separations to purify water. In ordinary osmosis, such as occurs through cell walls, a semipermeable membrane (one through which only the solvent can flow) allows water to flow from a lessconcentrated solution into a more concen- trated one(thus exhibiting an“osmotic pressure”). In reverse osmosis, pressure is exerted on the more con - centrated solution, overcoming the osmotic pressure and reversing the flow. After the brine (saline water) 294 • Desalination plants and technology Global Resources has been concentrated in this manner, the process is repeated with fresh brine. Among the membranes that have been utilized, most are polyamides and polyimides, which closely re- semble protein structures. Reverse osmosis has been most effective with brackish waters, which do not have the high osmotic pressure of seawater to overcome. However, improved membrane systems have permit- ted construction of larger seawater charged reverse osmosis plants in the 13-million-liters-a-day range. A procedure known as electrodialysis permits an elec- tric field to assist in directing ion flow through mem- branes, which are permeable to either cations or an- ions; some success in using this method with brackish water has been achieved. Pressurization cycles with ion exchangeresins ormembranes havebeen success- ful with low energy requirements, but experiments have failed to find the high-strength materials re- quired to survive the high pressures needed. Ion Exchange Methods Utilizing ion exchange resins in a normal flow-by mode isvery reasonablefor purifying slightlybrackish water. In fact, it is used to soften water in many com- munities with hard-water supplies. Resins that replace metallic ions with positive hydrogen ions, and non- metal ions with negative hydroxide ions, can readily accomplish that limited task, but they are not ade- quate for seawaterconversion. The necessity of regen- erating the exhausted resins with acid or base make designing a continuous process more difficult. Freezing and Solvent Extraction Methods When a solution freezes under equilibrium condi- tions, the solid formed is pure solvent. Therefore, when an iceberg forms, it contains very pure water. It has been proposed that icebergs could be towed to water-short regions. However, mechanical problems, such as providing appropriate freezing chambers and removing brine from the ice surface have prevented these methods from being seriously explored.Solvent extraction procedures have been tried experimen- tally, but solvent use and removal are costly. William J. Wasserman Further Reading Khan, Arshad Hassan. Desalination Processes and Multi- stage Flash Distillation Practice. New York: Elsevier, 1986. Lauer, William C., ed. Desalination of Seawater and Brackish Water. Denver, Colo.: American Water Works Association, 2006. National Research Council of the National Acad- emies. Desalination: A National Perspective. Washing- ton, D.C.: National Academies Press, 2008. Simon, Paul. Tapped Out: The Coming World Crisis in Water and What We Can Do About It. New York: Wel- come Rain, 1998. Spiegler, K. S., and A. D. K. Laird, eds. Principles of De- salination. 2d ed. New York: AcademicPress, 1980. Web Site National Academies Press Desalination: A National Perspective http://books.nap.edu/ openbook.php?record_id=12184&page=R1 See also: Oceans; Salt; Solar energy; Water. Desertification Category: Geological processes and formations Desertification is the degradation of semiarid lands and includes the reduction in the biological diversity of the ecosystem, the reduction in soil nutrients, and soil erosion. Background Desertification occurs over a period of years, with nu- merous factors interacting to stress the environment. Desertification results when social, political, and eco- nomic forces cause agricultural exploitation beyond the carrying capacity of marginal arid lands.Airborne and waterborne erosion strip vulnerable topsoil, ren- dering the land less productive over time. People liv- ing in areas undergoing desertification have poor harvests and are increasingly unable to feed them- selves. Although desertification can result from natural causes over eons, it can occur in relatively short pe- riods of time, notably as a result of improper land- use management—usually a combination of defor- estation and overgrazing on semiarid grasslands. Nonnative cash crops and monoculture plantations quickly deplete soils, impoverishing the ecosystem and accelerating desertification. In developed coun - tries, boom and bust agricultural practices in arid Global Resources Desertification • 295 lands cause overexpansion during favorable climatic conditions, followed by drought. People living on marginal lands in less developedcountries depend on subsistence agricultural production. Drought causes these people severe hardships, as their crops fail and animal herds die. Sustainable development of semi- arid lands in less developed countries would benefit many impoverished people worldwide. Desertification in the Western Hemisphere In 1806, Zebulon Pike characterized the southern plains as a sandy wasteland, an area later called the “Great American Desert” on maps. Following the Homestead Act of 1862, 65 hectares of shortgrass could be claimed by settlers living and working on the land, and some people thought that to be sufficient incentive to migrate there. Amish and Mennonite set- tlers found the 65 hectares sufficient for their type of agriculture, but the concept of large commercial ranches and farms, coupled with the introduction of machinery, prompted the passage of the Enlarged Homestead Act of 1909, resulting in a land rush. By the time World War I began, wheat was the fa- vored crop in the Great Plains. Previously unculti- vated land throughout Kansas, Colorado, New Mex- ico, Oklahoma, and Texas was plowed and planted with wheat by residents and absentee farmer-specula- tors between the end of World War I and 1930. When a lengthy drought began in 1931, precipitation was spotty, and wheat crops began failing. Fields were abandoned, and the airborne soil erosion which char- acterized the Dust Bowl began. Within the United States, elimination of home- steading, massive purchase of marginal land, large public works projects, and agricultural subsidies helped reclaim marginal desert lands throughout the Great Plains and Southwest. The “New Deal” of Presi- dent Franklin Delano Roosevelt began land reclama- tion using the Soil Conservation Service and the Civil- ian Conservation Corps throughout the Dust Bowl region, sowing sorghum and planting shelterbelts of trees in an effort to limit soil erosion. The introduc- tion of contour plowing limited some of the worst disk-plowing problems for agriculture. The Sahel: Southern Encroachment of the Saharan Desert The African region known as the Sahel, which roughly follows the 15° north parallel, is an example of dry woodland and dry wooded grassland undergo - ing desertification. Its northern border with the Sa - hara Desert receives 150 millimeters of annual rain- fall; its southern border receives 600 millimeters of rain yearly. Between 1931 and 1960 the Sahel experienced greater than normal levels of precipitation, coupled with a doubling in population. During this time, a large part of theSahel was populated by nomadic peo- ples herding small livestock flocks and practicing sub- sistence agriculture. In1970, a period of decades-long drought began. This drought signaled a period of overgrazing by livestock and deforestation to feed cooking fires, two key factors in accelerating desertifi- cation. Starting in 1968, the Sahel began to move southward from its 1931-1960 boundaries. Warmer ocean waters changed rainfall patterns, resulting in less precipitation in the northern Sahel in the late twentieth century. More than 60 percent of foreign aid in the region was expended on road construction, which consumed valuable water resources. Develop- ment of large-scale dams in the Senegal River Valley during the 1980’s caused population displacement because much of the irrigated land was taken over by large plantations growing cash crops of peanuts, rice, and cotton. Deforestation to expand plantations was widespread in Senegal. Annual rainfall began to increase in the mid-1990’s. Satellite data show that vegetative growth in the Sahel increased beyond what would be expected from observed rainfall. In Niger, where felling of nitrogen- fixing gao acacia trees has stopped, an estimated 49,000 square kilometers of savanna showed in- creased vegetation by 2008. In 2008, the population of the Sahel was estimated at fifty million. Emigration via the port of Dakar toEu- rope, or overland to North Africa, continues to re- duce the population, as does continuing warfare in the Darfur region of Sudan, which claimed an esti- mated 200,000 lives between 2003 and 2008. Defores- tation has been rapid around Darfur refugee camps, as trees have been cut to fuel refugee cooking fires and brick kilns for houses for United Nations aid workers. Mitigation of Desertification Identification of the problems caused by desertifica- tion by national governments and international agen- cies led to concerted efforts to halt and reverse the process during the late twentieth and early twenty- first centuries. Developed nations, including the 296 • Desertification Global Resources United States and Australia, have relied heavily on technology to combat desertification. Ranchers have formed effective organizations to lobby the central governments for aid. Drilling wells, building dams, in - stalling irrigation canals, using chemical fertilizers on depleted soil, using crop-dusting airplanes to limit pest damage, and implementing large-scale reforesta- tion and revegetation programs are some of the meth- ods used to combat desertification. In Australia, ranchers of large areas import feed in drought years and move herds of cattle and sheep out of desert environments to more productive grazing Global Resources Desertification • 297 Equator Tropic of Cancer Tropic of Capricorn Gulf of Guinea Mediterranean Sea Atlantic Ocean Indian Ocean True desert Acute risk of desertification Moderate to great risk Desertification of Africa land. Government-sponsored selective breeding pro - grams produced special cattle breeds—the Belmont Red and the Australian Milking Zebu—better suited to production in arid lands. Less developed countries rarely have the resources to purchase technology. International aid efforts fo- cused on building dams have been found to result in dislocation of hundreds of thousands of people while worsening public health problems like schistosomia- sis andmalaria. Becauseof theseproblems, beginning in the 1990’s, international aid organizations increas- ingly emphasized the need for introducing low tech- nology to combat desertification and permit sustain- able development. Important initial steps included involvement of the local populace to establish sustain- able land-use policies and then to teach agricultural techniques to reclaim land. Natural revegetation, the self-seeding byplants remaining inthe area,is encour- aged, as is the use of direct seeding of crops and plant- ing of trees to limit erosion. Where overgrazing by livestock is removing most of the sparse natural vege- tative covering, reducing and limiting herd size is im- portant. Concentration of landownership accelerates growth of unsustainably large herds and encourages overgrazing. Farmers at the subsistence level own few animals, using them mainly for milk production. Minimizing the use of wood for cooking fuel through the introduction of more efficient cooking stoves and solar cookers has lessened desertification in the Sahel. Other successful low-technology meth- ods include digging shallow basins for planting in eastern Mali and stone line construction to retain water and limit erosion in Burkina Faso. In 1984, after stone lines were completed in Yatenga Province in Burkina Faso, crop yields doubled. In less developed countries where a few landown- ers control large, semiarid plantations utilized for nonsustainable cash crops, such as peanuts and cot- ton, land redistribution to smaller, privately owned farms growing drought-resistant crops for local con- sumption is ideal. However, the World Bank under- went a paradigm shift in the 1980’s that favored com- mercial farmers over small farmers. This accelerated desertification in many arid regions of less developed countries, especially in Africa. Large farmers raise un- sustainable large herds and force poor people onto marginal land. Mitigation ofdesertification becomesdifficult when severe periodic droughts occur. Expansion of agri- culture above subsistence levels is inevitable during good times when crop yields increase. When drought struck the U.S. Great Plains from 1954 to 1957 and again from 1974 to 1977,airborne erosionidentical to the 1930’s Dust Bowl occurred, with dramatic eco- nomic consequences. Deep-well irrigation was intro- duced, lessening the apparent risks of large-scale monocrop agriculture in the region. Technology has become essential to maintaining agriculture in the Great Plains. Anita Baker-Blocker Further Reading Hazell, Peter, and Stanley Wood. “Drivers of Change in Global Agriculture.” Philosophical Transactions of the Royal Society of London 363, no. 1491 (February 12, 2008): 495-515. Liebesman, Lawrence R., and Rafe Petersen. Endan- gered Species Deskbook. Washington, D.C.: Environ- mental Law Institute, 2003. Worster, Donald. Dust Bowl: The Southern Plains in the 1930’s. 25thanniversary ed.New York: Oxford Uni- versity Press, 2004. Web Sites Environment Canada: Canadian Wildlife Service Species at Risk http://www.cws-scf.ec.gc.ca/ theme.cfm?lang=e&category=12 NOAA Fisheries Service: Office of Protected Resources Endangered Species Act http://www.nmfs.noaa.gov/pr/laws/esa U.S. Fish and Wildlife Service Endangered Species Program http://www.fws.gov/endangered See also: Climate and resources; Deserts; Drought; Erosion and erosion control; Food shortages; Irriga- tion; Overgrazing; Soil management; United Nations Convention to Combat Desertification; World Bank. 298 • Desertification Global Resources Deserts Category: Ecological resources Deserts are regions defined by the scarcity of a crucial resource, water. They are unique ecosystems with their own types of plant and animal life; a number of desert plants have been used by humans for thousands of years. Mining for minerals and petroleum also occurs in desert regions around the world. Background Although deserts are characterized by general aridity, there is no universal definition of a desert. Webster’s dictionary defines a desert as an “arid land with usu- ally sparse vegetation; especially such land having a very warm climate and receiving less than 25 centime- ters of sporadic rainfall annually.” Deserts are gener- ally thought of as hot and dry, but heat is not necessar- ily a requisite of most definitions of a desert. Low precipitation does not, alone, characterize a desert. Arctic tundra landscapes often receive scant precipi- tation, yet tundra soils are often saturated from low evaporation and restrictive permafrost below a nar - row active thawed layer during the summer. The com- mon perception of a desert is a trackless expanse of sand such as the Sahara or the Arabian Desert. In real- ity, however, deserts are often fairly well vegetated. The characteristic that all deserts have in common is aridity. Aridity refers to a general dryness, not to short drought periods. Characteristics of Deserts Deserts are located on all continents; Antarctica is considered a desert. They occur on a variety of sub- strates but often are characterized by historical ero- sion patterns leaving alluvial fans on the foothills of small mountains or hills and isolated islands of more resistant material. These remnants are called buttes in the western United States. Sandy soils are common, but wind-blown soils and ash deposits from volcanoes are also prevalent in many deserts. Desert soils often lack structural aggregation and are subject to erosion. They often have surface crusts from raindrop impact and depositsfromsediments thatare leftas waterinfil- trates into the soil. Global Resources Deserts • 299 Camels are led through the Sahara Desert, the largest hot desert on the planet. (Fei Xuan/Xinhua/Landov) . 290 • Department of Energy, U.S. Global Resources U.S. Department of Energy Secretary of Energy Deputy Secretary Federal Energy Regulatory Commission ChiefofStaff Office of the Under Secretary For. a wealth of resources, the Department of the Interior has been prone to scandal. In 1929, Depart - ment of the Interior secretary Albert Falls was con - victed of bribery in the Teapot Dome scandal the unofficial title of “Department of Ev- erything Else.” As Congress created additional de- partments to assume these manifold tasks, the chief purpose of the Department of the Interior came