RFF’s mission has expanded to include hazardous waste mitigation, climate change, biodiversity, and ecosystem management. RFF researchers have been influential members of the Intergovernmental Panel on Climate Change (IPCC) and have helped in the formulation of U.S. climate policy. Thomas A. Wikle Web Sites Resources for the Future http://www.rff.org/Pages/default.aspx Weathervane: A Climate Blog from Resources for the Future http://www.weathervane.rff.org/ See also: Biodiversity; Climate and resources; Ecosys- tem services; Ecosystems; Greenhouse gases andglobal climate change; Hazardous waste disposal; Resources as a medium of economic exchange; Sustainable de- velopment. Rhenium Category: Mineral and other nonliving resources Where Found Rhenium is widely distributed in the Earth’s crust in small amounts. In the United States, the richest con- centrations of rhenium are found in molybdenum ores in Arizona, Utah, and New Mexico. The major world producer is Chile, followed by Kazakhstan, the United States, and Peru. Primary Uses Rhenium is mostly used for applications in which a high melting pointandstrength at high temperatures are important, as in high-temperature thermocou- ples. It has also found use as a catalyst and in elec- tronic components. Technical Definition Rhenium (abbreviated Re), atomic number 75, be- longs to Group VIIB of the periodic table of the ele- ments and resembles manganese in its chemical and physical properties. It has two naturally occurring iso - topes and an average atomic weight of 186.2. Pure rhenium is a hard, dense, silvery-white metal. Its den - sity is 21.04 grams per cubic centimeter; it has a melt - ing point of 3,170° Celsius and a boiling point of 5,630° Celsius. Description, Distribution, and Forms Rhenium is a rare but widely distributed element resembling manganese. It usually occurs in a con- centration ofabout 1 part per billion,but in molybde- num ores it may be found in a concentration as high as 20 parts per million. It is used with tungsten, irid- ium, molybdenum,or platinum to manufacture high- temperature thermocouples that can measure and control temperatures up to about 2,500° Celsius. History Rhenium was discovered in 1925 by the German chemists Ida Tacke, Walter Noddack, and Otto Berg. It was not produced in a free form until 1929, when Tacke and Noddack produced a gram of it from 600 kilograms of molybdenum ore. Obtaining Rhenium Rhenium is produced as a by-product of molybdenum production. When molybdenum ore is heated it re- leases dust and gas containing rhenium. These sub- stances are treated with water to dissolve the rhenium oxide present. This solution is treated with potassium chloride to form potassium perrhenate or with am- monia to form ammonium perrhenate. These com- pounds are purified by repeated crystallization. The perrhenate is treated with hydrogen to pro- duce free rhenium. Ammonium perrhenate is usually used because it produces a purer rhenium. The rhe- nium is produced in the form of a black powder. It may then be compressed and heated with hydrogento produce bars of metallic rhenium. This metal may be cold-worked and annealed into wire or foil. Uses of Rhenium About 70 percent of rhenium is used in superalloys built to withstand high temperatures, such as those for turbine engines and their components. About 20 percent is used in petroleum-reforming catalysts. Rhenium is also used as a catalyst in various other chemical reactions; in petroleum refining, to pro- duce lead-free gasoline; in electronic components, because of its resistance to electrical erosion; in boat engines, because of its resistance to seawater; and in fountain pen points. An important use of rhenium is in producing ther - 1028 • Rhenium Global Resources mocouples that operate at high temperatures. A ther - mocouple is a device consisting of two wires of differ- ent metals connected at both ends. One end of the thermocouple is placed in a sample, and the other is kept at a constant, cooler temperature. An electric current produced in the thermocouple is used to measure the temperature of the sample. A thermo- couple can also be used to control temperatures likea thermostat. Rose Secrest Web Sites Natural Resources Canada Canadian Minerals Yearbook, 2005: Rhenium http://www.nrcan.gc.ca/smm-mms/busi-indu/cmy- amc/content/2005/rhenium.pdf U.S. Geological Survey Mineral Information: Rhenium Statistics and Information http://minerals.usgs.gov/minerals/pubs/ commodity/rhenium/ See also: Manganese; Molybdenum; Platinum and the platinum group metals; Tungsten. Rhodes, Cecil Category: People Born: July 5, 1853; Bishop’s Stortford, Hertfordshire, England Died: March 26, 1902; Muizenberg, Cape Colony (now in South Africa) An ambitious British imperialist in southern Africa, Rhodes became the owner of tremendous deposits of dia- monds at Kimberley and gold at Witwatersrand, cap- turing a near monopoly of these commodities through ruthless actions against European colonists and na- tive peoples. As prime minister of Cape Colony, he in- troduced legislation that opened additional areas for white settlers and regulated land usage. Biographical Background Born and educated in England, Cecil John Rhodes went, in 1870, to live at his brother’s cotton farm in the KwaZulu-Natal Province of southern Africa for health reasons. Diamond finds in Kimberley lured him into the interior. Between intermittent returns to England, Rhodes began amassing a considerable private fortune in diamonds and gold. He used his wealth to enter politics and serve in the Cape Colony Parliament, from which he expanded his own per- sonal and British national influence throughout southern Africa, hoping to create telegraph and rail links from Cape Town to Cairo. Rhodes hadlittle regard for the nativepeoples and applied pressure and subterfuge to obtain mineral rights and territorial concessions. Rhodes’s British South Africa Company, created by consolidating his claims, functioned as a quasi government over large portions of southern Africa.In 1890, he became prime minister of Cape Colony (now in South Africa), and he held sway over what would later become Rhodesia (now Zimbabwe) with his economic and political power. His overreaching ambition caused him a ma- jor setback when the Jameson Raid (1895-1896), his attempt tooverthrow theDutch Boer territory, failed, Global Resources Rhodes, Cecil • 1029 Cecil Rhodes owned South African mines that produced massive amounts of gold and diamond. (Library of Congress) and he resigned as prime minister. He participated in the BoerWar (1899-1902) and waspresent during the Siege of Kimberley,buthediedbeforethewarended. Impact on Resource Use In southern Africa, Rhodes had an impact on three major global resources: cotton, diamonds, and gold. His impact on cotton was brief, as he left his brother’s cotton farm to head into the interior for the diamond fields at Kimberley. Rhodes and the miners had little concern for the environment; Rhodes’s focus was to acquire claims, which he did with remarkable suc- cess. Once the most accessible diamonds had been worked, economicdepression set in, and Rhodespur- chased claims from disappointed miners.He also pro- cured the contracts for pumping water out of the mines in the rainy season and providing water during the dry season for washing diamonds. This consolida- tion of mining into a large-scale operation eventually led to the creation of the De Beers mining company, which at one time controlled nearly 90 percent of the world’s diamond supply. With the discovery of gold in the Witwatersrand in 1886, a gold rush ensued, and the easily accessi- ble gold was quickly mined. As he had done at the Kimberley diamond fields, Rhodes, on behalf of his Gold Field Company of South Africa,purchased claims from disappointed prospectors who thought that the supply of gold hadbeenexhausted.Using his political leverage, Rhodes extended his control of potential mineral rights by duplicitous negotiations with native tribal leaders. As prime minister of Cape Colony, Rhodes intro- duced the Glen Grey Act (1894), passed by the Cape Colony Parliament. This act impacted land resources by opening up development for white farmers and limiting the size of black African landholdings. It also regulated land usage by dividing land into farm, resi- dential, and common areas and by introducing scien- tific methods of land management and erosion pre- vention. The overarching purpose was to control the black African population and their land usage prac- tices, which were regarded as obstacles to white pros- perity. Mark C. Herman See also: Cotton; Diamond;Environmental degrada- tion, resource exploitation and; Gold; Resources as a source of international conflict; South Africa; Zim - babwe. Rice Category: Plant and animal resources Rice is the most commonly consumed food grain for a majority of the world’s population. Leading producers are Japan, China, India, Indonesia, Thailand, Viet- nam, and Bangladesh. In the United States, rice is grown in California, Texas, Missouri, Mississippi, Louisiana, and Arkansas. Definition The rice plant, Oryza sativa, is a member of the grass family. World production of rice exceeds 500 million metric tons. Mostcountriescultivate rice for domestic consumption, soless than 5 percent enters the export market. The United States is an exception; it gener- ates only about 2 percent of world rice production, but almost half of U.S. production is exported. Rice cultivation almost certainly began in India, where it dates back to about 3000b.c.e. Duringmedieval times it spread westward to southern Europe. Overview Oryza sativa has been classified into indica and japon- ica varieties. Monsoon tropics are ideal for indica rice, which is commonly cultivated in China and Southeast Asia. The plants can adapt to uncertain conditions. The japonica type of rice requires precise water con- trol as well as weed and insect control. It is cultivated in temperate zones such as the United States, Austra- lia, Japan, North and South Korea, and certain parts of China. Rice is self-pollinated, and the grain is enclosed in the palea, or hull. Harvested but unmilled rice is called paddy or rough rice. Milling of rough rice by any of several processes yields the polished grain that is ready for consumption. Rough rice contains ap- proximately 10 percent protein, 65 percent starch, 2 percent lipids, 5 percent minerals, and 18 percent hull/bran. The unhulled whole rice kernel also con- tains thiamine, niacin, and riboflavin. Parboiled rice can be stored for long periods. The International Rice Research Institute in the Philippines has contributed significantly to the devel- opment of high-yielding types of rice, beginning in the mid-1960’s. The development of these plants is considered a significant part of the 1960’s Green Rev - olution in agriculture. Some of these varieties de - 1030 • Rice Global Resources mand complete irrigation systems all year round that help keep the soil submerged under about 15 centi- meters of water. Next to corn, rice provides the farmer with the greatest yield when plants are cultivated with the nec- essary care. The crop grows well in irrigated and flooded areas. Cooked rice is mostly consumed in its whole grain form. Puffed rice and flakedriceare com- mon breakfast cereals, and rice flour is used in bakery products. Laundry starch is made from rice starch. Rice hull is used in cattle feed as wellas fertilizers, and the rice plant also produces oil for food and industry and thatching material for roofs and mats. The Japa- nese alcoholic beverage sake is made from a process that involves the fermentation of rice. The plant commonly known as “wild rice,” Zizania aquatica, is actually a separate genus found in North America. Wild riceisalsoanannual grass, and it grows mostly in lakes and streams. Lakes in Minnesota, Wis - consin, and southern Canada provide a good harvest of wild rice. Wild rice, once a staple of the diet of American Indians in those regions, has become a pop- ular side dish. Mysore Narayanan See also: Agricultural products; China; Corn; Green Revolution; India; Monoculture agriculture; Wheat. Risk assessment Categories: Scientific disciplines; social, economic, and political issues Many harmful events, especially anthropogenic haz - ards, result from the process of resource exploitation. Risk assessment is an essential tool to analyze existing Global Resources Risk assessment • 1031 Source: U.S. Department of Agriculture, Economic Research Service. 9,000,000 5,000,000 3,500,000 3,500,000 2,900,000 1,300,000 950,000 800,000 500,000 450,000 Metric Tons 1,000,000 2,000,000 3,000,000 4,000,000 5,000,000 6,000,000 7,000,000 8,000,000 9,000,000 10,000,000 Thailand Vietnam Pakistan China Egypt Uruguay Argentina Cambodia India United States Rice: Leading Exporters, 2007 and potential hazards during the extraction of re - sources, the use of resources, and the disposal of re- source products or wastes. Background Risk assessment has been practiced throughout hu- man history. Prehistoric civilizations developedmeth- ods to assess risks associated with some hazards, espe- cially natural disasters. In the 1970’s, risk assessment emerged as a new scientific field to help scientists and public-policy makers understand and quantify risks posed by both natural and anthropogenic hazards. Resources havebeen increasingly impacted by society and environment. Some local impacts, such asmining accidents, can be devastating. Global impacts caused by resource exploitation, such as acid rain and climate change, can last for many years. Risk assessment has become an essential tool in resource management to protect human health and the environment and to ensure sustainable development for future genera- tions. Hazard and Risk There are many definitions for hazard and risk. In general, a hazard is any source of potential harm and damage. In the fields of geosciences and resources, a hazard can be defined as a phenomenon or process that could cause disasters oradverse effects. Most haz- ards are divided into two categories: natural and an- thropogenic. Natural hazards result from events such as earthquakes, volcanic eruptions, floods, droughts, mass wasting, tornadoes, and tropical cyclones. An- thropogenic hazards are caused by human activities such as deforestation and habitat destruction, food and water contamination, and air pollution. In many cases, potential natural hazards can be triggered or worsened by anthropogenic activities. For example, mass wasting and land subsidence can occur, and become severe, if vegetation is destroyed by urban development and human activities. Many experts debate the meaning of risk and risk assessment. Risk is often expressed as a probability or the utility of harmful events. Most of the debates cen- ter on whether risk should be expressed as a probabil- ity or utility of the harmful event. A utility of an event is defined by theprobability of the event multipliedby the value of the event. However, not every undesirable event has a price, especially in terms of global events. For example, a monetary value for the consequences of global warming or tropical deforestation cannot be determined. Therefore, probability and values are used to express a hazard if the valueof harmful events can be assessed. Probability of undesirable outcomes is used to describe a hazard if its consequence cannot be assessed with a value. Hazards and Risks of Resource Exploitation Societal and environmental impacts of resource ex- ploitation exist in three categories: the extraction of resources, the use of resources, and the disposal of re- source products or wastes. Solid mineral and rock resources are normally ex- tracted by quarrying, surface mining, and under- ground mining. Liquid and gas resources such as oil, natural gas, and water are extracted by wells. All these activities have potential risks that may cause harmful events. Underground mining, especially coal mining, is an extremely high-risk profession. In 2006, in the United States, sevety-two miners, including forty-seven coal miners, lost their lives. The majority of thesefatal- ities occurred in Kentucky and West Virginia and in- clude the Sago Mine Disaster. China accounts for the largest number of coal-mining fatalities, with about 80 percent of the world’s total. In 2006, according to the State Work Safety Supervision Administration, 4,746 Chinese coal miners were killed by gas explosions, water inrushes, and other accidents. Other potential risks related to mining, quarrying, and excessive log- ging include landscape destruction and habitat loss, which may impact biodiversity and ecosystems and trigger harmful events, such as mass wasting. In addi- tion, smelting metallic ores and refining oil may re- lease toxic gases and cause substantial air pollution. Overpumping of wells to extract water, petroleum, and geothermal resources can deplete these resources and cause sinkhole collapse and land subsidence. Sometimes oil and gas wells may erupt, causing fire hazards and severe pollution. The use of resources, especially the burning of fossil fuels, has released toxic and greenhouse gases, particles, and excessheatintothe environment. Emis- sion of sulfur oxides and nitrogen oxides by the com- bustion of fossil fuel resulted in global acid-rain prob- lems inthe past. Carbon dioxide concentration in the atmosphere has increased dramatically because of in- creased demand for fossil fuels since the Industrial Revolution. Many scientists believe that anthropo- genic activities, specifically the burning of fossil fuels, lead to global warming. The disposal of resource products or wastes poses 1032 • Risk assessment Global Resources many potential risks to the environment and society. Large piles of waste rocks from mining may cause slope failure and mass wasting. Surface water drain- age and water quality may be affected by wasterocks as well. For example, acid mine drainage can occur if iron sulfide minerals, such as pyrite and pyrrhotite, are exposed and oxidized by moist air or water. Acid mine drainage around waste rocks and abandoned mines can eventually cause water pollution and bar- ren soils if the watershed is affected by acidic drain- age. All wastes produced by extracting or using re- sources need to be recycled and properly disposed of to prevent environmental and health risks. For exam- ple, some radioactive wastes generated by nuclear power plants need to be safely stored in designated sites for at least ten thousand years. Risk Assessment and Cost-Benefit Analysis Risk assessment is the process of characterizing a risk and involves the estimation of the probability of a harmful event. For example, the risk of sinkhole col- lapse in karst areas can be assessed by studying sink- hole distribution, geologic and topographic settings, and human activities. Results of this risk assessment can be expressed as the probability of a potential sink- hole collapse within a certain time period per unit of area. Once a potential hazard is identified and the risk assessment is conducted, the acceptability of the risk also needs to be assessed. Cost-benefit analysis is com- monly used to decidethe acceptability of a risk. Using this approach, risk assessors or policy makers need to determine whether the benefits outweigh the costs. For example, coal mining has benefits such as eco- nomic development and job creation and risks such as mining accidents, pollution, and landscape destruc- tion. If policy makers and the public think the bene- fits outweigh the costs of these risks, these risks will be considered acceptable. Benefits of resources are relatively easier to analyze. The values of economic development, job creation, and markets can be as- sessed. However, values of many costs, such as pan- demic disease or death caused by water pollution, environmental degradation, loss of biodiversity, and climate change, are difficult or impossible to assess. Uncertainties and Limitations of Risk Assessment Risk assessment has inherent uncertainties and limita - tions. Many U.S. Environmental Protection Agency (EPA) programs are designed to develop guidelines on how to regulate metals and how to assess potential risks of metals to human health and the environment. EPA has outlined key principles in metal assessments based on issues such as environmental chemistry, exposure, human health effects, ecological effects, bioavailability, and bioaccumulation. Limitations on data and knowledge exist in almost all these issues. If a risk assessment is based on empirical experi- ence or historical data, it will be difficult to estimate a probability of a rare event. For instance, earthquake frequency is usually low and irregular in many ar- eas. Prediction of earthquakes remains a challenging problem with many uncertainties. Subjectivity is another limitation associated with risk assessment. Scientists may disagree among them- selves on many risks. Policy makers may have their own subjectivity to manage risks. The general public may disagree with policy makers based on their sub- jectivity. For instance, many scientists believe that one cause of global warming is the burning of fossil fuels. However, climate change and thelong-term impact of increased greenhouse gases in the atmosphere are not fully understood. The acceptability of this poten- tial risk varies among public-policy makers in differ- ent countries. Yongli Gao Further Reading Byrd, DanielM., and C. Richard Cothern. Introduction to Risk Analysis: A Systematic Approach to Science-Based Decision Making. Rockville, Md.: Government Insti- tutes, 2000. Chiras, Daniel D., and John P. Reganold. Natural Re- source Conservation: Management for a Sustainable Fu- ture. 10th ed. Upper Saddle River, N.J.: Prentice Hall, 2010. Craig, James R., David J. Vaughan, and Brian J. Skin- ner. Resources of the Earth: Origin, Use, and Environ- mental Impact. 3d ed. Upper Saddle River, N.J.: Prentice Hall, 2001. Framework for Metals Risk Assessment.Washington, D.C.: Office of the Science Advisor, Risk Assessment Fo- rum, U.S. EnvironmentalProtectionAgency,2007. See also: Capitalism and resource exploitation; Envi- ronmental Protection Agency; Greenhouse gases and global climate change; Intergovernmental Panel on Climate Change; International Association for Im - pact Assessment; Natural capital. Global Resources Risk assessment • 1033 Rivers. See Streams and rivers Rock. See Aggregates; Igneous processes, rocks, and mineral deposits; Metamorphic processes, rocks, and mineral deposits; Sedimentary processes, rocks, and mineral deposits Rockefeller, John D. Category: People Born: July 8, 1839; Richford, New York Died: May 23, 1937; Ormond Beach, Florida Founder of the Standard Oil Company, Rockefeller was one of the world’s most famous industrialists. He started an American dynasty that made an indelible mark not only on the oil business but also on philan- thropy, politics, commerce, corporate management, and industry. Biographical Background John D. Rockefeller had the foresight to realize that oil would be one of the most essential of natural re- sources, and he had the business instinct to attempt to capitalize on this realization. Standard Oil was founded before the production of mass-market auto- mobiles increased the market for oil exponentially. Standard Oil was also influential indirectly in that its near-monopoly of the American oil industry spurred public distrust and governmental regulation of big business. Rockefeller began his career in Cleveland, Ohio. At the age of twenty he had established a commission business dealing in commodities such as grain and meats. He built his first oil refineryin1863nearCleve- land. Recognizing the enormous potential of oil, he soon took control of several other refineries and ex- panded his business into the Pennsylvania oil fields. By 1865, his Cleveland refinery had become the larg- est in the area. He founded the Standard Oil Com - pany of Ohio in 1870 and concentrated on monopo - lizing the oil industry. Impact on Resource Use Rockefeller encouraged aggressive (critics said “ruth- less”) business practices and emphasized economical operations. Consequently, Standard Oil prospered and had almost monopolizedtheoil business by 1882. At its peak, Standard Oil accounted for 80 to 90 per- cent of the oil produced in the United States. A num- ber of states enacted antimonopoly laws, which proved ineffectual, and Standard Oil was at the center of vari- ous investigations and exposés. Standard Oil included more than thirty corporations and helped Rocke- feller to amass a personal fortune of more than one billion dollars. In 1911, the U.S. Supreme Court held that Rockefeller and Standard Oil had “a monopoly of restraint of trade” and had violated the Sherman AntiTrust Act of 1890. Standard Oil was dissolved and broken up into thirty-nine companies. Rockefeller retired at the age of seventy-two and devoted the rest of his life primarily to philanthropy. He and his son John D. Rockefeller, Jr., spent almost half their personal fortune and established world- famous institutions such as the Rockefeller Founda - 1034 • Rockefeller, John D. Global Resources John D. Rockefeller founded the Standard Oil Company in 1870. (Library of Congress) tion and the Rockefeller Institute for Medical Re - search (Rockefeller University). In 1955, estimates indicated that their benefactions had exceeded a half billion dollars. Mysore Narayanan See also: Energy economics; Getty, J. Paul; Oil in- dustry. Roosevelt, Franklin D. Category: People Born: January 30, 1882; Hyde Park, New York Died: April 12, 1945; Warm Springs, Georgia Roosevelt, the thirty-second president of the United States, led the country through the Great Depression and World War II. His New Deal, intended to provide relief from the Depression and get business moving again, had an impact on resource use and conserva- tion. Biographical Background Franklin Delano Roosevelt was born into a political family and furthered that tradition as a legislator, gov- ernor, and four-term U.S. president. First educated at the family’s Hyde Park estate, Roosevelt went on to Groton School, Harvard University, and the Colum- bia Law School. He did not graduate from law school but passed the bar and was admitted to practice in New York in 1907.As state senator, beginningin 1910, he served on the Forest, Fish, and Game Committee and the Canals,Railways,andAgricultureCommittee. Impact on Resource Use Roosevelt was elected to the presidency in 1932 dur- ing the Great Depression, a time of business stagna- tion and tremendously high unemployment. He en- gineered administrative and legislative reforms and crafted the NewDeal,aseriesofprograms intended to provide help for the unemployed, businesses, and farmers. TheNew Deal established theTennesseeVal- ley Authority for flood control, hydroelectric power, and economic development; the Civilian Conserva- tion Corps for jobs and the completion of conserva- tion projects; and the Social Security Act for retire - ment security for blue-collar workers. More than two million men ultimately served in the Civilian Con - servation Corps, undertaking projects ranging from planting millions of trees to preserving wildlife. Al- though Roosevelt’s primary goal was to give Ameri- cans hope andputpeople to work, he nonethelessleft a legacy in the use and conservation of soil, water, for- est, and energy resources. The United States’ entry into World War II in 1941 brought further government involvement with soci- etal and business affairs as the president rallied the initially reluctant nation to the defense of democracy. Industry geared up to produce tanks, warplanes, and munitions, diverting resources such as iron and rub- ber (which became a scarce commodity during the war) from the production of consumer goods to the manufacture of crucial military equipment. Roose- velt also approved plans and funding for the top- secret Manhattan Project, which produced the first atomic explosion, leading both to atomic bombs and to nuclear reactors for producing electricity. Kenneth H. Brown See also: Civilian Conservation Corps;Conservation; Dams; Dust Bowl; Hydroenergy; Manhattan Project; Tennessee Valley Authority. Global Resources Roosevelt, Franklin D. • 1035 Franklin D.Roosevelt’sNewDeal had aprofoundimpacton the use and protection of American resources. (Library of Congress) Roosevelt, Theodore Category: People Born: October 27, 1858; New York, New York Died: January 6, 1919; Oyster Bay, New York As U.S. president and as a private citizen, Roosevelt personified the early movement for the conservation of national resources. Biographical Background An outdoorsman from hisyouth, Theodore Roosevelt considered a career as a naturalist while at Harvard University and was later a rancher in the Dakota Bad- lands. After leaving the White House, he took part in an African safari and then explored Brazil’s River of Doubt, later renamed in his honor. Impact on Resource Use Roosevelt’s tenures as governor of New York and, most notably, as president of the United States gave him the power and the responsibility to implement measures pertaining to his environmental concerns. He assumed the presidency in 1901; during the fol- lowing eight years, congressional legislation and exec- utive orders reclaimed through irrigation 12 million hectares of western lands, added 61 million hectares to the forest reserves, set aside thousands of hectares for mineral and water power development, established more than fifty wildlife refuges, and cre- ated five national parks and eighteen na- tional monuments. In 1908, he hosted a conference on the conservation of natural resources for the nation’s governors. Sympathetic to John Muir’s preserva- tionist ethos but also to the utilitarian con- servationism of Gifford Pinchot, Roosevelt was committed to maintaining the coun- try’s natural resources for all generations, claiming, “We must handle the water, the wood, the grasses, so that we will hand them on to our children and children’s children in better and not worse shape than we got them.” Eugene Larson See also: Conservation; Forest Service, U.S.; Muir, John; National Park Service; Pinchot, Gifford; Reclamation Act. Rubber, natural Category: Plant and animal resources Rubber is a macromoleculeorpolymer of repeated chains of carbon and hydrogen atoms. Its unique properties of extensibility, stretchability, toughness, and resilience have made itauseful commodity in applications rang- ing from tires to clothing. The name “rubber” origi- nates from its ability to erase pencil marks; its chemical designation is polyisoprene with several isomers. Background When Christopher Columbus arrived in Haiti in 1492 he found Indiansplaying a game withaball made from the latex of rubber. Indians were also known to have used latex for makingfootwear, bottles,andcloaks. By 1735, latex had been described as caoutchouc by a French geographical expedition in South America. Thus, in the seventeenth and eighteenth centuries rubber and rubber products were already in use. The role that rubber could play in clothing and footwear attracted the attention of chemists and in- ventors throughout the world in the eighteenth and nineteenth centuries. Charles Macintosh and Thomas 1036 • Roosevelt, Theodore Global Resources Theodore Roosevelt (left) with John Muir in Yosemite. (Library of Congress) Hancock, working as colleagues, discovered two sepa - rate means of using rubber in fabrics and footwear. Macintosh found that placing rubber and naphtha between layers of fabric resulted in a fabric with no sticky and brittle surfaces, and Hancock developed the rubber masticator, which welded rubber scraps to be used for further manufacturing. The dramatic increase in the use of rubber that oc- curred in the twentieth century is attributable largely to the development of the automobile industry (and the resultant increase in tire production) and ad- vances in industrial technology. Although rubber’s percentage of use compared with other elastomers decreased from the end of World War II to about the late 1970’s, the development of radial automobile tires in Europe in the late 1940’s and early 1950’s and their popularization in the United States in the late 1960’s and 1970’s resulted in increased use of natural rubber. The Origin of Rubber The early use of rubber involved all-natural rubber formed from a number of different plant species be- longing to theEuphobiaceae family, of whichthe rub- ber tree (Hevea brasiliensis), native to Brazil, has be- come the exclusive commercial source of natural rubber. As a coagulated milk substance, rubber is ob- tained from a fluid in latex vessels located in the bark of the tree. A number of other tropical and subtropi- cal plant species also contain such latex vessels, in- cluding Manihot species, Castilla species, the Russian dandelion, guayule (Parthenium argentatum), and Funtumia elastica. In fact, both the Russian dandelion and guayule were widely used during World War II. Research continued on guayule, a plant native to the southwestern United States and northern Mexico. Similarly, Funtumia elastica, native to West and Central Africa, received some research attention. Guayule, used by American Indians, is an alternative rubber source to synthetic rubber (or “para rubber”) in North America, particularly the southwestern UnitedStates. The production of natural rubber is based on Hevea brasiliensis, which is grown mostly in tropical and subtropical environments. While production is concentrated in developing countries, consumption occurs mostly in the industrialized countries. Until about 1913 Brazil was the major producer of natural rubber, which was obtained mostly from wild rubber trees growing in the jungles of the Amazon River basin. However, around the beginning of the twentieth century, plantation rubber for commercial production began, based on the work of Henry Riley in Singapore around 1890. Riley developed the “tap- ping” method for extracting latex from Hevea bra- siliensis. This method has since been improved upon; improvements have included the mechanization (mo- torization) of the tapping knife. During tapping, a slice of bark is systematically re- moved from one side (panel) of the tree, starting from an upperleft corner and shaving to a lowerright corner; care is taken not to damage the cambium. The cut usuallyhas an angleof 25 to 30 degrees. Once the cut is made, latex flows into a collecting cup through an inserted spout on the tree. Generally, tapping is done from just before sunrise to about 10:00 a.m. totake advantage of maximumturgor pres- sure within the tree in the early morning hours. Stop- page of latex flow is attributable to a coagulum that plugs latex vessels. The Growing of Rubber Plants Commercial rubber plantationsare vegetatively prop - agated by means of bud grafting. The bud from a high-yielding tree is cut and inserted under the bark Global Resources Rubber, natural • 1037 Production of Natural Rubber, 1988 and 1998 Metric Tons 1988 1998 Africa 265,000 334,000 China 218,000 450,000 India 231,000 591,000 Indonesia 1,120,000 1,680,000 Latin America 24,000 112,000 Malaysia 1,506,000 866,000 Philippines 77,000 64,000 Sri Lanka 111,000 96,000 Thailand 884,000 2,065,000 Vietnam 60,000 219,000 Other countries 49,000 113,000 Sources: Statistics for 1988 adapted from H. P. Smit and K. Burger, in Natural Rubber: Biology, Cultivation, and Technology, edited by M. R. Sethuraj and N. M. Mathew, 1992. Statistics for 1998 from the World Trade Organization. . impacts of resource ex- ploitation exist in three categories: the extraction of resources, the use of resources, and the disposal of re- source products or wastes. Solid mineral and rock resources. Valley Authority. Global Resources Roosevelt, Franklin D. • 1035 Franklin D.Roosevelt’sNewDeal had aprofoundimpacton the use and protection of American resources. (Library of Congress) Roosevelt,. high-yielding types of rice, beginning in the mid-1960’s. The development of these plants is considered a significant part of the 1960’s Green Rev - olution in agriculture. Some of these varieties