Geography is the study of spatial variation on the Earth's surface and of humankind's relation to its environment. Of essential concern to the geographer are spatial patterns and the interrelations of climate, landforms, vegetation, soils, population, economic activities, and political units, either on a global scale or in a more limited area. Geography is thus an exceedingly complex discipline that can be subdivided into numerous specialized areas. The geographer seeks to explain the location of various elements in the environment and to describe and establish the spatial patterns of these elements. The processes that form and change these patterns are also analyzed. One principal means to this end is the map, which for the geographer is an indispensable research tool as well as a visual representation (see \Tmaps and mapmaking\t). HISTORY AND EVOLUTION OF GEOGRAPHY Early Geographers Many consider geography one of the oldest academic disciplines. Its antecedents may be traced to ancient Greece, where they were called by such names as natural history or natural philosophy. In fact, most of the ancient Greek geographers, such as \TThales of Miletus\t (6th century BC) and \THerodotus\t (5th century BC), were actually philosophers or historians. Much of their geographic writings described their physical environment. Indeed, the word geography is derived from the Greek, meaning "Earth description." The physical environment and the location of natural phenomena were of utmost importance to the Greeks. The Greeks dominated most of the known Western world, especially the eastern part of the Mediterranean Sea. They traveled this area in search of trade and new lands to colonize. The clear skies of the Mediterranean were essential in the first attempts of Greek sailors to navigate the seas; wind patterns merited equal consideration in terms of speed and safety. Perhaps most important to the evolution of the discipline, the Greeks wrote down their observations and thoughts for succeeding generations. Notable are the Greek studies of the Nile River in Egypt, which described its annual flooding and the development of its delta. As early as the mid-5th century BC, Herodotus ascended the river to the first cataract and wrote a description of it, stating his hypothesis about the Nile's source. The Greeks also observed the planet as a whole. \TAristotle\t (4th century BC) is most often credited with conceiving the Earth as a sphere, a conclusion he arrived at by using philosophical reasoning and astronomical observations. His speculation about the Earth's shape was seconded by \TEratosthenes\t, librarian of Alexandria. The latter's On the Measurement of the Earth gives his calculation of the circumference of the Earth; he based his computation on a limited, measured arc of longitude. The astronomer \THipparchus\t of Rhodes (2d century BC) developed a location system of lines on the surface of the Earth, the forerunners of latitude and longitude. \TStrabo\t (c.63 BC-AD 21) wrote Geography, a 17-volume work that describes through firsthand observation the world known to him from Gaul and Britain to India and from the Black Sea to Ethiopia. Although his descriptions of lands and peoples are often marred by omissions and errors, he advanced the study of geography by substituting divisions based on natural boundaries (such as mountain ranges and drainage systems) for the less permanent and artificially drawn political units and thus became the father of regional geography. \TPtolemy\t of Alexandria (fl. AD 121-51), perhaps the most famous ancient geographer, further systematized the geographical study of areas by classing regions in terms of size and detail from the general study of large tracts (chorography) to the detailed physical description of small areas (topography). He drew a map of the then-known world that, considering the knowledge available in his day, is remarkably accurate. His eight-volume Guide to Geography consisted of a list of all known places tabulated according to longitude and latitude, a system he devised himself. After the collapse of the Roman Empire, the heritage of Greek geography was preserved in the Arab world. All the geographic works of Ptolemy were translated into Arabic. There were, however, regressions. After about AD 900 indications of longitude and latitude were no longer given on maps. Nevertheless, the Arabs made important contributions to a more profound knowledge of the world. In the 12th century al-\TIdrisi\t devised a refined system of climate classification. The great 14th-century explorer \TIbn Battuta\t found, on his travels through Africa and Asia, concrete evidence that refuted Aristotle's thesis that hot regions of the world would be too warm for human habitation. In the same century \TIbn Khaldun\t wrote an important historical-geographic treatise. Age of Discovery Although the Crusades had stimulated European interest in the outside world, it was not until the Renaissance, when the voyages of Bartolomeu \TDias\t, Vasco da \TGama\t, and Christopher \TColumbus\t in the late 15th century ushered in the so-called age of discovery, that there was a concomitant renewal of interest in world exploration, geographic description, and mapping. As early as 1507 the German cartographer Martin Waldseemuller (c.1470-c.1521) produced a map of the world that clearly indicated both North and South America. It was on this map that the term America was first applied to any part of the New World. Fifteen years later Ferdinand \TMagellan\t's party circumnavigated the Earth, thereby confirming its global shape. This information allowed for greatly increased accuracy of measurements and observations, which again aided the new breed of mapmakers, such as Gerardus \TMercator\t, a Dutchman. Mercator published a series of maps that in terms of accuracy surpassed anything previously produced. This included his famous navigation chart (1569), which introduced the map projection bearing his name, with its parallels and meridians at right angles. Geography as an academic discipline was rejuvenated by Bernhardus Varenius (1622-50), who, in his Geographia Generalis (1650), established the concepts of topical geography and regional geography. He considered the distribution of topics (especially physical topics such as winds and seas) over the surface of the Earth and tried to interrelate their causes and effects. This work may be said to have dominated the field for the following 150 years. Although some 18th-century philosophers and writer-scholars, such as Kant, Goethe, and Montesquieu, took an interest in the human topics of geography (the interaction of humanity and the environment), the general development of the discipline had, by the 19th century, reached a stage of stagnation and was closely identified with \Tgeology\t. Founders of Modern Geography During the 19th century there was a renewed effort to develop geography as a descriptive science. Contributions toward that end were made by the German geographers Alexander von \THumboldt\t, Karl \TRitter\t, and Friedrich \TRatzel\t. The first two have sometimes been called the founders of modern scientific geography, although neither was trained as a geographer. Humboldt laid the foundations of plant geography, performing field work in Europe, South America, Central America, and Asiatic Russia before he wrote his five-volume masterwork, Kosmos (1845-62). This work is a summary and exposition of the laws and conditions of the physical universe, yet it is imbued with the humanism that was Humboldt's hallmark. Ritter, whose interest in geography was stimulated by Humboldt, is credited with introducing humankind into geographical studies, particularly humanity in relationship to its environment. Ratzel took Ritter's human geography still further, subdividing it into anthropogeography and political geography, both of which he dealt with in separate works. He also made investigations into cultural geography, especially in North America, but he is best known for his organic theory of the state, in which he compares the evolution of the state to that of a living organism. In the United States, geography was not pursued by university scholars until the end of the 19th century and the first part of the 20th century--about the same time that the United States emerged as a world power. Many of the early American geographers, such as Ellen Churchill SEMPLE, were former students of Ratzel in Germany. German and French Schools This period in the history of geography was marked by the development in the 19th century of the geographic philosophy referred to as either determinism, environmentalism, or the German school of thought. Determinism held that the environment was the deciding factor in a person's way of living and his or her economic development. One American geographer, Ellsworth \THuntington\t, whose work reflects Ritter's influence, expressed the idea that the climate determined the extent and character of a people's capacity for physical work and intellectual development. Thus, he concluded, a stimulating climate, such as that of the temperate zones, spurs the development of higher civilization, but people who inhabit the constantly hot and humid lands of the tropics face a major barrier to their development. Determinism began to decline during the 1930s and was eventually discredited. Earlier in the century, however, another geographical philosophy had emerged. This French school of thought, called possibilism, held that people had a choice in determining their development within the physical environment. In other words, the choices that people made determined the extent of their cultural advancement. Thus, although neither humans nor their environment existed in isolation, neither was able to control the other, and humans, therefore, were the ultimate master of their destiny. Paul \TVidal\t \TDe La\t BLACHE was a notable proponent of this theory. Quantitative Revolution During the 1960s a major change took place in the methodology of geographic research. The desire to make geography more scientific, or at least more intellectually acceptable as a discipline, led to the adoption of statistical methods as a major research technique. Location (or spatial) analysis, as this new aspect of geography is called, seeks to analyze and explain the factors that control humankind's spatial organization, specifically by statistical methods and models. Mathematically constructed models became tools useful to the geographer in coping with rapidly accumulating knowledge, and they could also be used to predict future trends or spatial patterns. This was not the first time statistics had been used for geographical research. As early as the 1920s and '30s, Torsten Hagerstrand in Sweden and Walter \TChristaller\t in Germany had used statistical techniques. Only in the 1960s, however, did significant growth in statistical methodology occur. Since the late 1960s new techniques have aided the analysis of geographic information. Two developments have been most significant: the electronic computer and remotely sensed imagery of the Earth from satellites. APPROACHES TO GEOGRAPHY Two principal approaches to the study of geography have developed: topical, or systematic, and regional. Regional and topical geography are often pursued in combination. Topical geography is the study of the spatial organization or locational distribution of a specific phenomenon and its relation to human presence. Medical geography, an example of topical geography, studies the distribution of disease-causing organisms and their relation to local populations. Regional geography concerns all aspects of a relatively small area and compares that area with other areas. A region can be defined by physical criteria or by sociopolitical criteria. For example, a region may be an area receiving 100 mm (4 in), or less, of rainfall annually, or an area where more than 50% of the population are under the age of 15. BRANCHES OF GEOGRAPHY Physical Geography Physical geography studies the natural conditions and processes on the Earth's surface and the resulting spatial structures and encompasses several important subdisciplines. 1. Geomorphology studies landforms, or the Earth's relief features, and examines their origins and evolution. The field of geomorphology is a bridge between geography and geology. 2. Biogeography, or ecogeography, is the study of plant and animal distribution. Plant geography, or phytogeography, and zoogeography are allied with \Tecology\t, which studies the relationships of plants and animals to their habitat. 3. Climatology examines the distribution of weather patterns, their seasonal changes, and the processes that shape the patterns. Human (or Social) Geography Human geography studies the changing spatial distributions of people and their activities and their interaction with the natural environment. It draws on the knowledge of the related social sciences but is particularly concerned with spatial analysis and description. 1. Cultural geography is the examination of the distribution of cultural groups or of specific cultural traits such as religions, languages, architecture, place names, or burial rites. 2. Population geography studies the numbers and distribution of people and the changing patterns of distribution. 3. Economic geography deals with the location of economic activities and analyzes the reasons for location. Included in economic geography are such subdivisions as agricultural geography, manufacturing geography, and transportation geography. 4. Historical geography is concerned with the local or regional environments of humankind as they existed in the past. This involves assessing both historical events and the role of the natural environment. 5. Political geography is the study of governmental units as observed on the landscape. This can involve the regional study of a specific political unit or the effect of political phenomena on an area. 6. Urban geography analyzes the origin and growth of cities as well as the spatial arrangement within cities. Many of the new statistical methods used in modern geography were introduced by urban geographers. Robert S. Weiner Bibliography: Berry, Brian J., et al., Economic Geography (1987); Boyce, R.R., Geographical Perspectives on World Problems (1982); De Blij, Harm J., and Muller, Peter, Geography: Regions and Concepts (1982; repr. 1990); Douglas, Ian, The Urban Environment (1984); Forbes, Dean K., The Geography of Underdevelopment (1985); Hartshorn, T.A., and Alexander, J.W., Economic Geography (1987); Hartshorne, Richard, Perspectives on the Nature of Geography (1959); James, Preston E., and Martin, Geoffrey J., All Possible Worlds: A History of Geographical Ideas, 2d ed. (1981); Matthews, John A., Quantitative and Statistical Approaches to Geography (1981); Pacione, Michael, ed., Historical Geography (1987); Strahler, Arthur N. and Alan H., Modern Physical Geography, 4th ed. (1989); Whyte, Robert O., Spatial Geography (1982). See also: \Taerial photography\t; \Tcentral place theory\t; \Texploration\t; \Tgeopolitics\t; \Tremote sensing\t.