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Within geography, physical geography is concerned with the characteristics of the natural environment, the atmosphere, the lithosphere and the biosphere; how they influence human activities and how they are affected by them across the face of the globe. It comprises geomorphology, climatology and biogeography, and proceeds by monitoring, modelling and managing environmental change. Geographical research at first concentrated on the direct impacts of glaciation on the geomorphology of Britain, such as the glacial erosion of northern Britain and its indirect impacts, especially the effects of changing sea levels. Physical geographers in the last 100 years have taken some comfort from the knowledge that their skills are applied in matters of public interest and importance. Now the pace of global environmental change is such that these skills will be essential in the next 100 years, in solving some of the great contemporary environmental problems such as global warming, the global disappearance of forests, desertification and water pollution.

New Guinea is a crucial region for the study of prehistory as a key witness for a precontact situation before colonial disruption and/or state formation. The New Guinea region is the most linguistically diverse on earth, but even within it, the Sepik-Ramu basin region takes diversity to an extreme without parallel. This chapter investigates the likely causes of its stupendous linguistic diversity. It looks at geomorphological changes in the region in the last 8,000 years due to rising sea levels and inundation of the low lying land and the gradual filling in of this again by sediment, with a consequent remigration of new peoples into reclaimed land. Further, indigenous beliefs with regard to language and a wide range of language codes to select from, even in a single village, have led to widespread mixing and shifting of languages, as economic advantages and political alignments altered.

Traditional narrative explanations of prehistory have become increasingly difficult to operationalize as models and to test against archaeological data. As such models become more sophisticated and complex, they also become less amenable to objective evaluation with anthropological data. Nor is it possible to experiment with living or prehistoric human beings or societies. Agentbased modeling offers intriguing possibilities for overcoming the experimental limitations of archaeology by representing the behavior of culturally relevant agents on landscapes. Manipulating the behavior of artificial agents on such landscapes allows us to, as it were, "rewind the tape" of sociocultural history and to experimentally examine the relative contributions of internal and external factors to sociocultural evolution (Gumerman and Kohler in press). Agent-based modeling allows the creation of variable resource (or other) landscapes that can be wholly imaginary or that can capture important aspects of real-world situations. These landscapes are populated with heterogeneous agents. Each agent is endowed with various attributes (e.g., life span, vision, movement capabilities, nutritional requirements, consumption and storage capacities) in order to replicate important features of individuals or relevant social units such as households, lineages, clans, and villages. A set of anthropologically plausible rules defines the ways in which agents interact with the environment and with one another. Altering the agents' attributes, their interaction rules, and features of the landscape allow experimental examination of behavioral responses to different initial conditions, relationships, and spatial and temporal parameters. The agents' repeated interactions with their social and physical landscapes reveal ways in which they respond to changing environmental and social conditions. As we will see, even relatively simple models may illuminate complex sociocultural realities. While potentially powerful, agent-based models in archaeology remain unverified until they are evaluated against actual cases. The degree of fit between a model and real-world situations allows the model's validity to be assessed. A close fit between all or part of a model and the test data indicates that the model, albeit highly simplified, has explanatory power. Lack of fit implies that the model is in some way inadequate.

Wetland ecology incorporates the interactions of biota (plants, animals, microbes) with the unique physical and chemical environment present in wetlands. Wetlands are foremost geologic features, and geomorphology coupled with climate forms the template on which wetland ecology occurs. Hydrology is the factor most influenced by geomorphology and climate, and hydrology is also the primary conduit for the control of the physico-chemical environment and the biotic interactions in wetlands. This book examines the ecology of freshwater and estuarine wetlands. The initial chapters address the physical aspects of wetland environments. In particular, they examine the basics of geomorphology, biogeochemistry, soils, and hydrology in wetlands. The book also explores how abiotic factors, specifically hydrology and chemistry, constrain wetland plants and animals, and elaborates on the physiological and ecological strategies employed by biota to cope with those stresses.

Landscape geomorphology influences how water moves over or through the soil, and thus hillslope hydrology and local hydrologic budgets affect soil properties and determine the formation of wetland soils. A complete understanding of wetland formation, wetland ecology, and wetland management requires a basic understanding of soils, including soil properties, soil processes, and soil variability. This chapter explores how soils and landscapes influence the local hydrologic cycle to lead to the development of wetland hydrology. It then looks at some fundamental soil properties, and how they lead to and respond to the development of wetland hydrology. Finally, the chapter considers specific types of wetland ecosystems and discusses their general distribution, origin, hydrology, soil, and vegetation.

This chapter investigates the role of substrate geology and river basin geomorphology in the formation of the fauna in South America. It suggests that the major biogeographic patterns was influenced by the granitic Guiana and Brazilian shields, the foreland sedimentary basins of the western Amazon and the intracratonic sedimentary basins along the Amazon fault system. It argues against the use of areas of endemism in biogeographic analyses and highlights the composite nature of regional fish species assemblages.

Abstract: Streams play a critical role in the movement of water, sediment and nutrients across our landscape. Streams provide habitat to both aquatic and terrestrial life, and in many instances, streams support societal needs such as transportation and recreation. As such, streams are a vital part of our environment. Unfortunately, anthropogenic activities such as urbanization, agriculture, and resource extraction have degraded many of our streams to the point where they can no longer provide many of these services. Through stream restoration, we are able to restore many of these ecosystem functions while also reconnecting people and communities to streams.

April 18, 1906. “At 5:15 this morning . . . I thought I heard the alarm go off. I reached over to stop it and to my great surprise it was rolling from one side of the stand to the other, & then to the floor. I looked out the window . . . in time to see a few chemnies [sic] sway around and fall. The picture & bed & dresser & chairs were dancing around the room. . . . A house caught fire about 5 blocks off. . . .Then to make matters worse, there was no water when the fire dept. arrived.” April 18. “Within moments, during this period of the city’s greatest emergency, the unusual silence of the [fire] alarm bell told its own story. The system was destroyed as was the function of the city’s 30,000 telephones.” April 18, 7:00 A.M. “The Federal Troops, the members of the Regular Police Force and all Special Police Officers have been authorized [by San Francisco Mayor E. E. Schmitz] to KILL any and all persons found engaged in Looting or in the Commission of Any Other Crime.” April 19. “I have seen the most awful sights to day that I ever saw in my life! . . . It is impossible for you to conceive or in any small degree realize the terrible disaster that has befallen San Francisco. I can’t & I’ve seen it. . . .When I left this afternoon fully 2/3 of San Francisco was in ruins. The streets have great cracks in them & the Car tracks are twisted by the earthquake & heat. The flames are spreading in all directions even against a fresh north wind.” May 5, 1906.“Day and night the dead calm continued, and yet, near to the flames, the wind was often a gale, so mighty was the suck.” May 13. “We have not got our thoughts collected since the big quake—not quite—it has been 24 days since the big awful earthquake and we have had more then 24 earthquakes in them 24 days, small ones.

Water resources geography expanded its spatial, regional, and intellectual horizons during the 1990s. Tobin et al. (1989) reviewed earlier US geographers’ contributions to the hydrologic sciences, water management, water quality, law, and hazards; and they identified three emerging topics: (1) theory development and model formulation; (2) applied problem-solving and policy recommendations; and (3) international water problems. This chapter assesses progress along those and other fronts, beginning with historical and disciplinary perspectives. Charting the progress of a field requires a sense of its history, and Platt’s (1993) review of geographic contributions to water resource administration in the US offers a useful perspective on policy-related research, beginning with George Perkins Marsh and John Wesley Powell. Doolittle (2000) reaches back to Native American antecedents in water resource management in North America (cf. chapters in this volume on cultural ecology, historical geography, and Native American geography). Carney (1998) sheds light on African influences on rice cultivation in the southeastern US. Research on European antecedents ranges from seventeenth-century “hydrologic” theories in England (Tuan 1968) to hydraulic engineering at the École des Ponts et Chausées in France, water courts in Spain, and more distant Muslim and Asian contacts (e.g. Beach and Luzzader-Beach 2000; Bonine 1996; Butzer 1994; Lightfoot 1997; Swyngedouw 1999; Wescoat 2000). In the field of water law and institutions, Templer (1997) has linked recent geographic work on Western water laws with earlier research in political geography. A historical geographic study of water rights transfers from irrigated ranches in the South Platte River headwaters to Denver, Colorado, has shed new light on how urban economic and political power employ and reshape water law (Kindquist 1996). The battle between Owen’s Valley and Los Angeles continues to stimulate historical geographic research on relations among facts, laws, and their social meanings (Sauder 1994). Although a geographic perspective of international water laws has yet to be written, databases on transboundary conflicts and agreements shed light on the evolution of international water law (Wolf 1997, 1999a, b; and <http://www.transboundarywaters.orst.edu>, last accessed 10 February 2003). Historical or contemporary, the pragmatic spirit of water resources geography remains strong (Wescoat 1992).

The 1990s witnessed a significant increase in popular interest in the US regarding the geography of the world’s coastal and marine spaces. Factors motivating this renewed interest included growing public environmental awareness, a decade of unusually severe coastal storms, more frequent reporting of marine pollution hazards, greater knowledge about (and technology for) depleting fishstocks, domestic legislation on coastal zone management and offshore fisheries policies, new opportunities for marine mineral extraction, heightened understanding of the role of marine life in maintaining the global ecosystem, new techniques for undertaking marine exploration, the 1994 activation of the United Nations Convention on the Law of the Sea, reauthorization of the US Coastal Zone Management Act in 1996, and designation of 1998 as the International Year of the Ocean. Responding to this situation, the breadth of perspectives from which coastal and marine issues are being encountered by geographers, the range of subjects investigated, and the number of geographers engaging in coastal-marine research have all increased during the 1990s. As West (1989a) reported in the original Geography in America, North American coastal-marine geography during the 1980s was focused toward fields such as coastal geomorphology, ports and shipping, coastal zone management, and tourism and recreation. Research in these areas has continued, but in the 1990s, with increased awareness of the importance of coastal and marine areas to physical and human systems, geographers from a range of subdisciplines beyond those usually associated with coastal-marine geography have begun turning to coastal and marine areas as fruitful sites for conducting their research. Climatologists are investigating the sea in order to understand processes such as El Niño, remote-sensing experts are studying how sonic imagery can be used for understanding species distribution in three-dimensional environments, political ecologists are investigating the ocean as a common property resource in which multiple users’ agendas portend conflict and cooperation, and cultural geographers are examining how the ocean is constructed as a distinct space with its own social meanings and “seascapes.” Despite (or perhaps because of ) this expansion in coastal-marine geography, the subdiscipline remains fragmented into what we here call “Coastal Physical Geography,” “Marine Physical Geography,” and “Coastal-Marine Human Geography.”

Although the use of mathematical models and quantitative methods in geography accelerated in earnest with the development of quantitative geography and regional science in the late 1950s, such techniques had already made their way into the mainstream of physical geography much earlier. Today, mathematical models and quantitative methods are used in a number of subfields in geography with their proliferation being aided, in part, by the widespread use of remote sensing, geographic information systems (GIS), and computer-based technology. As a consequence, geography as a whole has witnessed a new growth in the development of models and quantitative methods over the last decade, and it is this growth that we seek to elucidate here. Highlighting the advances in the use of models and methods in geography is a difficult undertaking. Such techniques are so widely used in GIS and remote sensing that many developments in these areas also could be considered in this chapter. Moreover, modeling and quantitative techniques are so strongly integrated within some geographic subfields (e.g. climatology and geomorphology, economic and urban geography, regional science) that it is often difficult to separate technique development from application. This is illustrated by the fact that many members of the Association of American Geographers who frequently use and develop quantitative techniques and models are not active participants in the Mathematical Models and Quantitative Methods Specialty Group, choosing instead to favor specialty groups with a more topical, rather than methodological, focus. In a very real sense, the quantitative revolution has been completed in many subfields of geography, with the goals and aims of the revolutionaries having long since passed into the mainstream. Furthermore, geographers who are involved with quantitative methods and mathematical models are extremely diverse in their interests and applications— they contribute to an extremely wide variety of disciplines. While they excel at spreading the geographic word to other disciplines, summarizing their multifarious contributions is nearly impossible. The rather trite statement, “Geography is what geographers do,” seems to apply strongly here. Geographers are largely a collection of individuals who, although united by their interest in spatial models and methods, are unique in the ways that they make contributions to various fields.

The history of geography is an untidy term that sprawls across an extended chronology and embraces an illdefined body of thought, knowledge, and ideas. Different countries have different histories of geographical thought, and not infrequently North American practitioners study one or more of these national histories. The period of investigation for some may exceed two thousand years while for others it may be decades only. There is no mainstream, but a variety of individual efforts—some oriental, some occidental, some published, others unsung—that do not of themselves come together. The historian of geography studies what other people have thought, said, and studied concerning matters geographical. Islands of knowledge form in seas of ignorance. The canvas is vast and for most of us choices must be made. Over the last thirty years it is probably true to assert that a majority of workers in this enterprise have made special studies of segments of the history of North American geography and its antecedents. The larger purpose of this type of investigation is to understand what has gone before, to comprehend how progress is made in the advancement of thought and how such a body of knowledge in its evolution brought us to recent time. It is a form of historical inquiry cognizant of the context of times past and guarded as to the limitations imposed upon us by lack of sources. In this country, among the academic pioneers of this genre were E. van Cleef, C. T. Conger, J. Paul Goode, C. O. Sauer, E. C. Semple, and E. L. Stevenson of whom four undertook some of their studies in Germany. Arguably, formal recognition of this branch of our field was entered into the literature by Wright (1925, 1926). Development of this body of knowledge has, however, been slow. Occasionally the terms “history of geography” and “historical geography” have been mistaken for one another or used interchangeably. The history of geography seeks to reveal the direction that individuals, institutions, books, beliefs, and concepts have taken in the eventual construction of a discipline and profession. The history of geography relates to and intermingles with histories of other fields (most notably perhaps with geology).

River basins and river characteristics are controlled in part by their tectonic setting, in part by climate, and increasingly by human activity. River basins are defined by the tectonic and topographic features of a continent, which determine the general pattern of water drainage. If a major river drains to the ocean, its mouth is usually fixed by some enduring geologic structure, such as a graben, a downwarp, or a suture between two crustal blocks. The largest river basins constitute drainage areas of extensive low-lying portions of Earth’s crust, often involving tectonic downwarps. The magnitude of river flow is determined by the balance between precipitation and evaporation, summed over the drainage area. Seasonality of flow and water storage within any basin are determined by the seasonality of precipitation in excess of evaporation, modified in some regions by water stored in snow packs and released by melting, and by water stored in wetlands, lakes, and reservoirs. Increasingly the flows of rivers are influenced by human land use and engineering works, including dams, but in South America these anthropogenic influences are generally less intense and widespread than in North America, Europe, and much of Asia. Thus the major rivers of South America can be viewed in the context of global and regional tectonics and climatology. For reference, figure 5.1 outlines South America’s three largest river basins—the Orinoco, Amazon, and Paraguay-Paraná systems—while figure 5.2 shows the locations of rivers referred to in the text against a background of the continent’s density of population per square kilometer. The geologic history of South America has bequeathed to the continent a number of structural elements that are relevant to the form and behavior of its three major river systems. These structural elements are (1) the Andes; (2) a series of foreland basins, approximately 500 km wide immediately east of the Andes and extending southward from the mouth of the Orinoco to the Chaco-Paraná basin, where the crust is depressed by the weight of the Andes and the sediment derived from the mountains; (3) the Guiana and Brazilian shields reflecting Precambrian cratons and orogenic belts of mostly crystalline metamorphic rocks, partly covered with flat-lying sedimentary rocks and deeply weathered regolith; and (4) the Central Amazon Basin, a large cratonic downwarp with some graben structures dating back to early Paleozoic time, which runs generally east-west between the two shields, connecting the foreland basins to the west with a graben that localizes the Amazon estuary at the Atlantic coast.

Arid and semi-arid ecosystems in South America are best illustrated by two desert regions, the Peruvian and Atacama Deserts of the Pacific coast and the Monte Desert of central Argentina. The caatinga of northeast Brazil is often described as semi-arid, but mostly receives 500–750 mm of annual rainfall and is better regarded as dry savanna. Small areas of Venezuela and Colombia near the Caribbean coast, and nearby offshore islands, support desert-like vegetation with arborescent cacti, Prosopis, and Capparis, but generally receive up to 500 mm annual rainfall. Substrate conditions, as much or more than climate, determine the desert-like structure and composition of these communities, and thus they are not discussed further here. Extensive areas of Patagonian steppe also have semi-arid conditions, as discussed in chapter 14. The Peruvian and Atacama Deserts form a continuous belt along the west coast of South America, extending 3,500 km from near the northern border of Perú (5°S) to north-central Chile near La Serena (29°55’S), where the Mediterranean- type climate regime becomes dominant. The eastward extent of the Peruvian and Atacama Deserts is strongly truncated where either the coastal ranges or Andean Cordillera rise steeply from the Pacific coast and, as a biogeographic unit, the desert zone may extend from 20 to 100 km or more inland. A calculation of the area covered by these deserts depends in part on how this eastern margin is defined. Thus the Peruvian Desert covers between 80,000 and 144,000 km2, while the Atacama Desert of Chile extends over about 128,000 km2 if the barren lower slopes of the Andes are included. Actual vegetated landscapes are far smaller and for the lomas of Perú change dramatically between years depending on rainfall. Only about 12,000 km2 of the Atacama contain perennial plant communities, largely in the southern portion known as the Norte Chico but also including a narrow coastal belt of lomas extending northward almost to Antofagasta and the Prosopis woodlands of the Pampa del Tamarugal. The vegetated areas of the coastal lomas of Perú and Chile together probably do not exceed 4,000 km2 as a maximum following El Niño rains.

For several months each year I work in central Africa collecting sediment cores and fossils from a large rift lake, Lake Tanganyika. Periodically my nonscientist friends ask me why I do this. They usually mean both ‘‘why would someone collect mud from the bottom of a lake’’? and perhaps as an even greater challenge to my sanity, ‘‘why would one travel halfway around the world to do this’’? The answer to these questions (and the theme of this book) is deceptively simple. Paleolimnologists study lake deposits because they provide science with archives of earth and ecosystem history that are both highly resolved in time and of long duration. In the particular case of Lake Tanganyika, this combination, in principle, permits us to study events as closely spaced in time as annual events over the lake’s 10-million-year history. Few other records of earth history beyond those found in lake muds provide this combination of duration and resolution. The range of questions that can be examined with these archives is enormous. Paleolimnologists provide constraints on the timing of past climate change, determine rates of evolutionary change in species, and investigate the timing of pollutant introduction into watersheds. One might reasonably ask what good could come from trying to synthesize these disparate questions. I believe that the unifying factor behind all of these fields of study lies in the character of lake sediment archives. Lakes are attractive targets for study by such different fields of investigation because of the special nature of their depositional environment. Considering the contents of lake archives and their characteristics is the best place to start thinking about what makes paleolimnology a distinctive discipline. . . . What Are Lake Archives? . . . An archive is a singularly appropriate term to describe the foundations of paleolimnological research. The term archive can refer both to a historical record, its content, and to the place where such records are housed, its container.

Two things are required in order for a lake to exist on the earth’s surface: a topographically closed hole in the ground and water. The subject of how topographical depressions form on the earth’s continental crust has frequently been cast as one of lake origins, emphasizing the hole’s initial formation. However, it is important to realize that the hole itself has a history, which is partly independent of the lake that fills it, and that this history interacts with that of the water body. This chapter will emphasize this dynamic interplay that occurs throughout a lake’s history between a lake and its underlying substrate. In this sense, lake basin evolution is a more useful concept than the more static one of lake origin. The basin evolution process is manifest in everything from the three-dimensional geometry of the lake deposits that underlie the lake, to the rates of sediment accumulation, and the probable history and life span of the lake. Furthermore, different types of lakes are better or worse suited to answer specific paleolimnological questions. Some evolutionary mechanisms predispose lakes to persist for millions of years. Records in these lakes are ideally suited to answer questions that require long temporal records. Other questions require high-resolution records of short duration, which may be better represented in lakes formed by different mechanisms. And still other mechanisms result in the formation of numerous lakes with similar characteristics within a region, ideally suited for comparative studies. Understanding lake basin evolution is therefore an essential element in the design of a paleolimnological study, because the quality of paleolimnological records is directly linked to the mechanisms of basin evolution. The formation of lakes has intrigued earth scientists for more than 100 years (W.M. Davis, 1882, 1887; Penck, 1882, 1894; Russell, 1895; Supan, 1896). Hutchinson (1957) elaborated on these earlier works, recognizing 11 major categories of lake origins and 76 subcategories. Numerous advances in understanding basin evolution have been made since Hutchinson’s work, especially from improved radiometric dating techniques, seismic stratigraphy, and lake drilling over the past 50 years.

The lacustrine fossil record comprises a mixture of endogenic fossils, such as cladocerans, derived from lakes, and exogenic fossils, such as insects or pollen, which are carried into lakes, by wind and water from surrounding areas. Our primary emphasis here will be on the endogenic fossil record of lakes; we will only briefly consider general aspects of the taphonomy and paleoecological significance of exogenic fossils for terrestrial plant and insect fossils. Information about lake fossils varies greatly between groups. Some taxa, such as diatoms, are virtual workhorses of the field, with numerous investigators, and established methods of sampling, analysis, and interpretation. At the other extreme are organisms such as copepods, which, despite their importance in lacustrine ecosystems, are so poorly fossilized that they are unlikely to ever play a major role in paleolimnology. In between these extremes lie the majority of lacustrine organisms. Many relatively common groups have great potential for paleoecological interpretation, but, for reasons of inadequate study, a lack of researchers, or difficulties in taxonomy, have thus far been little used by paleolimnologists. Major opportunities await new students in the field who are willing to take up the challenges of studying these clades. Despite their importance in lacustrine communities, cyanobacteria remain a relatively unexploited source of information for paleolimnology. Isolated cells have poor preservation potential, and fossil cyanobacterial cells are preserved in Late Quaternary lake muds primarily by their more resistant reproductive spores (akinetes), or occasionally by filaments. Planktonic cyanobacteria are only rarely recorded in older sediments. In contrast, benthic cyanobacterial communities are well represented in ancient lake beds by their constructional deposits, lithified algal mats, stromatolites, and thrombolites. Although their body fossils have been used only rarely to solve paleolimnological problems, planktonic cyanobacteria have great potential for this purpose, given their obvious importance in many lacustrine communities. Relatively resistant akinetes might be very useful for understanding changes in plankton communities, especially in cases where better- studied siliceous microfossils (diatoms and chrysophytes) are not well preserved, for example, in very alkaline lakes. However, almost nothing is known of the taphonomic biases that control the planktonic cyanobacterial fossil record.

The Cenozoic evolution of Africa cannot be comprehended satisfactorily without reference to the early history of the Gondwana supercontinent and the events that occurred during and following its fragmentation. Gondwana first formed during the Neoproterozoic Pan-African-Brazilian orogeny (720–580 million years ago (Ma)). The closing of the Paleotethys gulf during the collision of Laurasia with Gondwana in the late Palaeozoic completed the growth phase. The volcanism that preceded rifting along both coasts of southern Africa had one particularly important consequence: a combination of thermal effects and magmatic underplating created a high “rim bulge” that resulted in the presence of significant coastal escarpments when separation occurred. This chapter discusses the impact of plate tectonics on Africa during the Phanerozoic. It chronicles the closing of the Neotethys to form the Mediterranean Sea when Arabia and Asia collided between 16.5 and 15 Ma. It also discusses the East African Rift System and its importance for paleontology, macroscale geomorphic evolution during the Cenozoic, African geomorphology and the African Surface, and the deserts of Africa.