NORTH CAROLINA STATE UNIVERSITY LIBRARIES RESERVE ROOM Filename: Item ID: Hitót.0f **BEST COPY AVAILABLE** WARNING CONCERNING COPYRIGHT RESTRICTIONS The copyright law of the United States (Title 17, United States Code) governs the making of photocopies or other reproduction of copyrighted material. Under certain conditions specified in the law, libraries and archives are authorized to furnish a photocopy or other reproduction. One of these specified conditions is that the photocopy or reproduction is not to be used for any purpose other than private study, scholarship or research. If an electronic transmission of reserve material is used for purposes in excess of what constitutes "fair use", that user may be liable for copyright infringement. Course: MR.696F Instructor: O.ßianlc □ Changing Times The Holocene Legacy William R. Dickinson Environmentalism has become a powerful force in global scientific and political affairs. Part of its influence steins from the truism that a viable environment is not just a lofty ideal but a practical necessity for the future of humanitv. Another part comes from a reawakening of prehumanistic thoughts that humanity is not necessarily the sole measure of all things. These two threads of modern environmental thinking underscore the age-old question of the place of humankind in nature. Alternate concepts about the relationship of human beings to nature depend largely on philosophical attitudes independent of anv external realitv. but accurate perception of environmental history is a prerequisite for valid environmental concepts. Understanding how the global environment we observe today has evolved from antecedent conditions is indispensable as part of the basis for guiding future environmental management. An adequate appraisal of environmental history must include a geological perspective. Holocene Time In geological parlance, the time since the last great Pleistocene ice sheets melted away is termec! the Holocene, which has not been a long chapter in the history of the Earth. Together, the Pleistocene and Holocene make up the Quaternary period, marked by waxing and waning of polar glaciers. The round number of 10,000 years ago is commonly taken to mark the beginning of Holocene time, although improved calibration of radiocarbon dating indicates that 11,500-11,600 years is a better estimate (see Figure 1). The time span of the postglacial world has been surprisingly brief, and in geological terms, most modern environments have a short time depth. The glacial world of the Pleistocene was dramatically different from our own. At times of glacial maxima, the most recent of which was only 20,000-22,000 years ago, great ice sheets covered most of North America as far south as Seattle, Chicago, and New York City. In Europe (see Figure 2), a curved line connecting the capital cities of Ion, Berlin, Warsaw, and Moscow delineates the approximate ice limit, with a variety of those locales overrun by ice during periods of intense glacial advances and lying just beyond the ice limit during lesser advances. At such times, the Baltic Sea and the shallower part of the North Sea between Great Britain and Norway disappeared beneath ice cover that crowned Scandinavia, and northern Europe closely resembled modern Greenland in its climate and overall aspect.1 When Pleistocene ice was in place, the geographic tracts of North America and Europe that are now temperate grasslands and mixed forests were verv different places. Tundra and open steppe occupied most of Europe south to the Mediterranean littoral, and a belt of tundra fringing the ice fields in North America met a broad band of coniferous forest, much like the modern Siberian taiga to the south, extending across the midsection of the United States and reaching down perhaps as far as the southern borders of Tennessee and Oklahoma (see Figure 3). None of the familiar landscapes of Euroameriean tradition, nor of Amerindian tradition, existed at the beginning of Holocene time. Continental and island shorelines were also impacted in dramatic fashion bv Pleistocene glaciation, and the direct effects extended worldwide because the continental ice sheets drew water from all the oceans. During peak glaciation, global sea level stood an estimated 410 feet lower than today (see Figure 4). Modern shorelines, together with their associated estuaries, tidal flats and coral reefs, cannot have occupied their present positions for more than a few thousand years. Coastal ecosystems have been forced to migrate staggering distances since the waning of Pleistocene glaciers began to drive the postglacial rise in global sea level, termed eushisyby geologists. Sea level was still perhaps 300 feet below its modern position as recently as 15,000 years ago. Typically, the postglacial biotic migrations were much greater than just the distances landward from svnglacial positions of the strandline directly offshore. Climatic zones and water masses shifted latitude as glaciation waned, meaning that many littoral species also had to move hundreds of miles laterally along coastlines to arrive at congenial Holocene environments. Coastlines near regions of Pleistocene glaciation paradoxically experienced an opposite change in relative sea level when the ice sheets melted. Removal of the weight of thick glacial ice caused the landscape to be uplifted at rates that outpaced the enstatic rise in sea level. Geologists term such postglacial uplift isoshitic rebound because it stems from changes in isostasy, which refers to the processes that balance rock masses at different elevations above the fluid interior of the Earth. Because of isostatic rebound, Pleistocene paleoshorelines in formerly glaciated areas are now exposed far inland or well up the flanks of coastal mountain ranges. Along the Pacific coast of Canada, for example, paleoshorelines of Pleistocene age stand 150-500 feet above modern sea level. The isostatic rebound was time-delayed, because it could only be accomplished through slow worldwide flowage of viscous mantle lying below the stiff crust of the Earth. Simultaneously, continental margins distant from regions of Pleistocene glaciation were tilted downward toward adjacent ocean basins when the weight of glacial mellwalcr was added to seawater volumes. Even al siles far removed from circmu-polar ice masses, isostatic changes in local relative sea level resulting from the additional weight of ocean water left a subtle imprint on coastal landscapes. Re- Eigure 1. Conventional vs. calibrated radiocarbon ages. Dasl...., line is locus of equal ages. Solid line is actual approximate correlation of conventional and calibrated ages, with the latter derived from tree-ring chronologies for Holocene time and from independent uranium/thorium isotopic dating for Pleistocene time.: 1000's of years ago calibrated gional isostatic adjustments to deglaciation affected sea level much less than the enstatic change in average global sea level resulting from the addition of glacial melhvater, but were quite important locally. Eor most Pacific islands, postglacial isostatic effects led to a relative highstand of five to eight feet in regional sea level during mid-Holocene time, peaking perhaps 4,000 years ago.5 Holocene Humankind Tlie remarkable changes in the physical environments of the Earth during the Holocene have been more than matched by the cultural evolution of humankind. At the end of the Pleistocene, none of our ancestors had access to any tools more sophisticated than could be fashioned by hand from pieces of stone, bone, or wood. Virtually all the technology upon which we now rely has been developed during 1 lolocene time in less than five hundred human generations. I luman civilization as it exists was produced by opportunistic adaptations of the human species to emerging postglacial environments.4 Given the fad lhal glacialions have waxed and waned al least ado/en limes, and probably a score or more times, for well over a million years, the Holocene can be Figure 2.' 'hern limits of Pleistocene glaciations in northern Europe. Successive ice fronts n.cirk southward extent, at various times during the Pleistocene epoch, of the vast continental glacier that blanketed the entire landscape farther north, including marine shelves exposed to the air by eustatic drawdown of sea level.5 viewed as just the latest of a long series of interglacial time intervals, and destined like the others to be succeeded in due course by yet another glaciation. In one crucial respect, Holocene time has been unique among interglacial intervals. It is the first interglaciation during which anatomically modern humans existed (see Figure 5). Whether modern human beings emerged only 50,000 years ago, as many have thought, or have existed for nearly 100,000 years, as some now argue, none were present during the last interglaciation approximately 125,000 years ago. Interglacial climatic conditions analogous to historical experience lasted onlv 12,000 to 20,000 years, nol markedly longer than the duration ot the 1 lolocene to date.'' The impact of the emerging human species on global environments during the last glaciation is moot because the conditions that prevailed then were so extensively modified by the climatic transition to I lolocene time. As modern I lolocene environments evolved from Pleistocene precursors, people of essentially modern aspect, driven by familiar impulses, were active on most parts of the continental landmasses from the very initiation of postglacial conditions. The same cannot be said of oceanic islands or polar regions that people were unable to occupv before acquiring adequate maritime technology and the skills to survive under extreme climatic conditions. Exploration and settlement of the Pacific islands of Oceania, remote from the Australian and Asian landmasses, did not begin until approxi- Figure 3. Environmental belts of eastern North America at peak gkiuation — 20,000 years ago; taiga is spruce-pine evergreen forest analogous to the forests of modern Siberia; varied broadleaf tree species accompanied the oak-pine woodlands farther south.7 mately 3,500 years ago. The peopling of Oceania by the Polynesians and their ancestors is one of the great sagas of prehistory but was delayed until after the middle of I lolocene time.8 In most global environments, the Holocene landscape never established itself without human influence. Landscapes and cultures coevolved over the same intervals. Knowing the propensity of human beings to alter their surroundings indicates that the nature of I lolocene environments was in part determined by human activities, even as people learned to adapt to them and exploit them for their own purposes. The environmental impact of human dispersal through Oceania over several millenia before European contact with island cultures is instructive. In island group after island group, human arrival was followed closely by environmental alteration involving forest clearance, with consequent upland erosion and downstream sedimentation, or replacement of virgin forest by agroforest developed through human silviculture.9 The si tive notion that the world was a pristine place before people gradually hewed their way into it, culminating their impact with the environmental insults of the industrial age, is out of focus. The landscapes of yesteryear, so beloved in our cultural memories, did not spring up wholly untouched by human hands. Nor should we view overt human manipulation, or inadvertent alteration, of the environment during prehistory as necessarily or uniformly deleterious to ambient conditions. The postglacial Holocene world was inherently in flux, and successful aboriginal cultures must have adjusted their environmental practices to modes that improved, rather than reduced, resources for subsistence. Shoreline Evolution The glacial drawdown in global sea level has had lingering effects through much of I lolocenc time. In the protohistoric period of 7000-9000 »c, when many civilizations of the ancient world had their first tentative beginnings, global sea level was still more than seventy-five feet below its modern level, not rising lo within fifteen feet of its present stand until about 5,000 years ago (see Figure 4). Massive encroachment of the sea on almost all landmasses was the rule during the first half of Ho-locene time. During the Pleistocene lowstand, the entire Persian (or Arabian) Gulf, down to the Strait of Hormuz, was dry land, though perhaps dotted with lakes, and the ground where ancient Mesopotamia later thrived stood roughly 600 miles from the open marine waters of the Indian Ocean. Following the postglacial eustatic rise in sea level, some 250 miles of riverine lowlands along the Tigris-Euphrates valley of the Fertile Crescent were flooded by saltwater as recently as 6,000 years ago, to be reclaimed later as dry land by fluvial aggradation. Fven the seaport of Charax, founded by Alexander the Great, now lies ninety miles from open water.10 As the rate of rising sea level gradually slowed, rivers began to build deltas from retreating shorelines into the encroaching seas. This process became important after about 6000 rsc, and led to dramatic impacts on coastal landscapes. The Ho-locene Mississippi River has extended its delta about 150 miles into the Gulf of Mexico, adding more than 12,000 mi2 of land surface south of Baton Rouge to the coastal lowlands (see Figure 6). All the resulting diversity of levee and marshland, with its resident aquatic wildlife, occupies an area that was drowned under shelf sea at the dawn of Old World civilizations. In Kgypt, the arcuate front of the Nile delta, with its classic deltoid shape, has prograded steadily into the Mediterranean at a mean rate of approximately one kilometer per century over the last 5,000 years." Recent human modifications lo river regimens have now begun to reverse delta growth in key instances. Essentially all deltas subside slowly from their isostatie loads on the Earth's crust and from the time-delayed compaction of delta sediment accumulations. Without continuing deltaic sedimentation, seawater encroachment is inevitable along delta margins, t Ipslreain dams and dense networks of irrigation or drainage canals that trap sediment inhibit delta growth, as does the dredging of ship channels to funnel riverine sediment directly into deep water offshore. As a result, the Mississippi delta is currently losing subaerial delta plain at a rate nearly Řs^ikř s) ijdk Figure 4. Approximate latest Pleistocene and I lolocenc rise 1.. mean global sea level from eustatic change in seawater volume as deglaciation transferred mass from circumpolar ice fields to the world ocean.12 modern mean sea level 25- 50- > ra > CD 5 JO The effects of deglaciation on tropical regions are not fully understood, but ambient temperatures at equatorial latitudes were cooler by approximately ^"C during the last glacial maximum. Available evidence from the Amazon basin indicates that the rain forests so prevalent in the tropics today were more restricted in extent during Pleistocene glaciation, probably broken into less continuous tracts, and composed in part of species adapted to cooler conditions than those that now prevail. Forests were nevertheless widespread in the Amazon basin even at peak glaciation.10 Human Influences Few of the dramatic postglacial changes in global environment escaped the attention of aboriginal humans. Even in the Americas, the last continents to be invaded bv the human species, Clovis migrants from Eurasia had spread from Canada to Patagonia, and from Arizona io Boston, by thirteen thousand years ago. Several aspects of the growth of human culture suggest that the impact of human activities became an integral facet of Holocene environmental evolution. Many deltas felt the influence of human occupation almost as soon as they began to grow seaward after 6000 hc. Irrigation in lowland Mesopotamia, which lengthened steadily as the Tigris-Euphrates delta built itself into the Persian Gulf, was practiced at least locally by that time. Rice culture, with its elaborate systems of paddies and terraces, was also born about that time on the delta surfaces of southeast Asia.2' Across the wider terrestrial landscape, perhaps no aboriginal impact was greater than the results of broadcast fire. Aboriginal peoples burned the land deliberately, yC (Ji to flush small game and drive big game, to deny cover to dangerous animal preda- V tors, to clear the growth that might provide cover for enemy ambushes around their settlements and camps, to foster fresh shoots of vegetation that attract favored / * game ;eep woodlands clear of underbrush and easv to traverse, and to keep relatively unproductive woodlands from encroaching upon grasslands richer in usable resources. In precontact Australia, firing of native vegetation was so intensive, to nurture plant communities favored as food bv either humans or their game, that native fire practices have been called "firestick farming." When people turned to growing domesticated crops, they resorted even more assiduously to wild fire to clear garden plots and fields, developing a pattern of behavior that survives today as so-called "slash-and-burn" agriculture. Although "slash and burn" has distinctlv pejorative connotations for lovers of forested lands, the distributions of different tree species in nuinv present forests owe much to the recurrence of past anthropogenic tires." Human Impact Despite decades of general knowledge about the near ubiquity of anthropogenic fire in prehistorv, we are still far from comprehending its full import. On the one hand, we acknowledge that fire was the greatest invention of humankind, Inning in mind its critical application for cooking food, but tending to overlook the fact that it was also the most effective tool of land management available to aboriginal peoples. The grasslands and savannahs of the temperate and tropical regions might owe their very existence to anthropogenic burning, either to remove woodlands or to prevent their initial advance into tundra or steppe inherited from Pleistocene glaciation. Studies throughout the tropics have shown repeatedly that savannah grasslands are dependent for their maintenance, if not their initial creation, on the persistence of anthropogenic fires to combat forest encroachment."' ý* The alternate origin suggested for the development of grasslands is the effect of 'climate. In some semiarid grasslands, tree growth is precluded by lack of sufficient soil moisture. A fortuitous "experiment" shows, however, that aboriginal peoples were capable of converting forest to open land bv deliberate use of wildfire. The arrival of Polynesian migrants roughly a thousand years ago was followed within just a few hundred years by removal of approximately half the previously dense New Zealand forest by repetitive firing to produce grassland, food-rich fernland, and open woodland (see Figure 7).^ The impact of wildfire on the nature and density of vegetative cover and the influence of vegetative cover on erosion rates and consequent sedimentation rates suggest that the cumulative effects of anthropogenic fire have exerted a strong control over the evolution of the Ilolocene landscape. Wildfire could not make mountains or govern the general courses of rivers and streams, but fine-tuning the contours of hill slopes, river bottoms, and stream terraces seems well within the scope of possible results from broadcast burning conducted since the end ot Pleistocene time. Human behavior has also influenced evolving I lolocene faunas over much of the world in two salient ways. First, Kurasian domestication of familiar pastoral animals—cattle, goats, horses, sheep, and swine —early in Ilolocene time affected Figure 6. Approximate growth pattern, shown as age ranges of ki_y delta segments, of I lolocene Mississippi River delta below Baton Rouge, I Louisiana (symbols dashed for submerged parts of delta lobes). In detail, time-space relations arc more complex than depicted, for more than fifteen successive delta lobes or subdeltas have been distinguished from landscape feature and coring of the delta plain. "N.O." denotes New Orleans, lying just above the head of the youngest component of the delta plain.15 the viability of wild counterparts over wide areas. Second, the spread of aboriginal peoples to previously unoccupied landmasscs, including previously isolated islands, resulted in the extinction or local extirpation of many animals, both mammals and birds, as a result of intensive hunting. The effect was most notable on large animals, the megafauna, with long gestation periods that make population maintenance or recovery difficult in the face of steady attrition. Megafauna] extinctions were not synchronous globally, but phased sequentially from place to place as aboriginal peoples reached different continents and islands. Only in sub-Saharan Africa, where the native fauna coevolved with humankind and prehistoric domestications were a minor factor did a diverse megafauna survive into modern times. Bv altering fauna, aboriginal peoples might indirectly have affected the flora of main- regions as well. In Australia, the extinction of large herbivores following the late Pleistocene arrival of humans to that continent apparently altered the floral balance, leading to conditions that encouraged the setting of wildfires to control vegetation.26 On .y oceanic islands, destruction of habitat by intensive human occupation and anthropogenic introduction of exotic nonhuman predators probablv contributed, along with hunting pressure, to the population crashes of the prehistoric past. Within the broad Pacific arena, occupying nearly half the globe, the arrival of Polynesian voyagers over the past few millennia led rapidly to the successive decimation of local bird species, and to other pervasive environmental changes in island group after island group.27 Environmental Restoration Although we live in a world of four dimensions, the dimension of time is unique. We may proceed east or west and north or south, retracing our steps at will, and with the aid of aircraft we can move up or down. But we can only move forward in time, with no hope of ever moving backward. We cannot recover past environments, although we might be able to regenerate them as a means of restoration. From a geological perspective, the grand sweep of 1 lolocene environmental changes that are largely irreversible make the likelihood of full success in regenerating or restoring lost environments seem quite slim. Returning to where we began at the outset of 1 lolocene time is certainly impossible, and anv expectation that a beneficent Nature could restore itself .spontaneously to some admired state that existed in the more recent past seems quixotic. Modern industrial civilization and burgeoning population growth have injured the global environment far beyond the perspective or ability of aboriginal peoples to attempt, but the preindustrial environment was already the contingent product of multiple influences, among them the impact of our distant ancestors. Environmental Management The burden of environmental management rests inevitablyon human shoulders, and a clear sense of environmental history over the full course of Holocene time is a prerequisite for wise environmental decisions. Simply trying as human beings to make no mark on our surroundings may not achieve what we desire. Avoiding some practices, such as burning the landscape, which once were pursued with vigor bv aboriginal peoples, introduces wholly new factors into the environmental equation. The popular concept of wilderness as pristine wildland free of any human influence is largely a psychocultural myth, springing more from an uplifting vision of the proverbial Eden than from any historical reality. Eor charting the future, we will have no substitute for understanding the dynamics of varied ecosystems and the rules of landscape evolution well enough to be able to gauge in advance the results of specific actions that we are able to control.211 The challenge to our powers of insight is daunting. In the environmental arena, the temptation is strong to label everything that is "natural" as "good," and anything that seems "bad" as "unnatural," but none of those terms is easy to define in a continuously changing world. Ever since the dawn of Holocene time, when global Figure 7. Changing forest cover (ruled areas forested) in New aland: A) pre-1 lolocene at last glacial maximum; B) Holocene prior to arrival of Polynesian migrants; C) after 750+ years of Polynesian occupation; D) after 120 years of European settlement. Anthropogenic firing of the landscape largely accounted for Polynesian forest clearance, with further reductions in forest cover made by European farmers, stockmen, and city builders. During Pleistocene glaciation, owing to drawdown in sea level, New Zealand was actually one large island half again as large as the two present islands combined (not shown as such here because the nature of synglacial vegetative cover on surrounding marine shelves is unknown from any direct evidence).29 -20,000 yrs. ago c. A.D. 500 c. A.D. 1840 c. A.D. 1960 conditions remotely like those of the present-day first evolved from the ice ages, humans have always impacted the natural environment. Reducing human impact toward a nil level is not only unattainable in practice, but quite literally unprecedented. The task for future human culture is to acquire the knowledge of environmental history and dynamics needed to choose the sorts of human impact that will lead to a posterity of our liking. Faith in a self-regulating and self-restorative nature, independent of humankind, cannot guide us into any environmental harbor where we would wish to moor. Holistic History Existing intellectual traditions have addressed I lolocene history from four largely independent standpoints, none adequate alone for a holistic environmental history. From humanism sprang the discipline of history, basing its insights principally on the written record and deriving much of its basic posture from times when even the most rudimentär}' facts about Pleistocene glaciation and its lingering effects on the Holocene aftermath were unknown. From the social sciences, archaeology came later upon the scene with a primary focus on strictly human prehistory in the sense of cultural events prior to the advent of comprehensive written records. From the pliv d sciences, Quaternary geology developed as a discipline that was initially at., .it entirely divorced from considerations of human behavior. Krom the life sciences, ecologists and biogeographers have evaluated modern and historic-biota with increasing sophistication but with minimal attention to prehistoric antecedents, except for documenting evolutionary taxonomie (rends. Each of these disparate approaches leads to only partial understanding of the full tapestry of the Holocene past. Casting off discipline-oriented blinders might allow us to achieve a more integrated vision of Holocene history hv working from the premise that environmental and human history are parallel tracks along the same road map across an ever-changing I lolocene landscape. Our very ability to forecast the environmental future with any accuracy may depend upon the blending of insights from diverse intellectual wellsprings. William R. Dickinson is Emeritus Professor ofCeosciences at the Uniwrsih of Arizona. He is the author of numerous articles in geological and archaeological journals, is a member (since ígtp) of the National Academy of Sciences, was first Chair (igSi-igSj) of the Board on Earth Sciences of the National Research Council, and sened as President (iagj-ic)i)_f) ofthe Geological Societ}- ofAmerica (CSAj. I lis honors include the Penrose Medal (u)i)i) and the Sloss Award for Sedimentary Geology (iqqc,) from GSA, and the Twenhofcl Medal (2000) from the Society for Sedimentary Geology. Notes 1. For an overview of the Pleistocene world, see A. G. Dawson, Ice Age Earth (London: Routlcclge, 1992), 1-293. ''or 'he southern limit of North American ice sheets, see G. 11. Denton and 'ľ. J. Hughes, The Last Great Ice Sheets (New York: Wiley, 1981), 1-484. For accurate (calibrated radiocarbon) liming of the last glacial maximum, see A. \1. Tnshinglunn and VV. R. Peltier, "Implications of the Radiocarbon Thnescalc for Ice-Sheet Chronology and Sea-I ,evel Change," Quaternary-Research 39 (January 1993): 125-29. 2. For the correlation shown by the curve, see Minze Stuiver and Bernd Becker, "1 ligh-Precision Decadal Calibration of the Radiocarbon Time Scale," Radiocarbon 35 (Calibration 1993): 35-65; Fdouard Bard, Maurice Arnold, R. C. Fairbanks, and Bruno llamelin, "-'T'h-^U and '<" Ages Obtained by Mass Spectrometry on Corals," Radiocarbon 35 (Calibration 1993): 191-99. Cosmic-ray bombardment of nitrogen in the upper atmosphere produces radiocarbon (a radioactive isotope with a half-lite of 5730 years), which is incorporated into the carbon dioxide present in air, and dissolved in waters of oceans and lakes exposed to lbe atmosphere. Living organisms acquire a characteristic minor fraction of radiocarbon by equilibrating with the carbon dioxide of ambient air or surrounding waters. After death, their body pails lose radiocarbon at its known radioactive decay rate, allowing fossil materials such as wood, charcoal, bone, and shell to be daleci (up to a limit of about 40,000 years, after which the amount of remaining radiocarbon is too low to measure with confidence). Conventional and calibrated radiocarbon ages differ because conventional ages are calculated with the assumption of constant atmospheric radiocarbon production, which actually varies through time as fluctuations in the magnetic field of the Farth modulate the intensity of the cosmic-ray flux reaching the atmosphere from outer space, ;... ..iscussed by Carlo Laj, Alain Mazaud, and J. C. Duplessy, "Geomagnetic Intensity and ''C Abundance in the Atmosphere and Ocean During the Past 50 Kyr," Geophysical Research Letters 23 (1 August 1996): 2045-48; 11. Kitagawa and J. van der Plicht, "Atmospheric Radiocarbon Calibration to 45,000 yr B.P.: Laie Glacial Fluctuations and Cosmogcnic Isotope Production," Science 279 (20 February 1998): 1187-90. The round number of 10,000 years ago was proposed for the beginning of Holocene time by D. M. Hopkins, "Time-Slialigrapluc Nomenclature lor the Holocene Epoch," Geolog) 3 (January 1975): 10, and coincides well with the end of the Younger Dryas glacial readvance in conventional (uncalibrated) radiocarbon years. The best current estimate for the beginning of Holocene time is 11,530 calibrated (calendar) years BP (before AD 1950) by Sleinar Culliksen, II. II. Birks, Goran Possnert, and Jan Mangerud, "A Calendar Age Estimate of the Younger Drvas-I lolocene Boundary at Krakcnes, Western Norway," The I lolocene S (May 1998): 249-59. 'he chronological implications of calibrating radiocarbon dates for the prehistory of the Americas is discussed by S. J. Fiedel, "Older Than We Thought: Implications of Corrected Dates for Paleoindians," American Antiquity 64 (January 1999): 95—115;. 3. For Pleistocene paleoshorelines in British Columbia, sec J. J. Clague, "Claeio-lsoslatic Effects of the Cordilleran Ice Sheet, British Columbia," in Shorelines and Isoslasy, edited by D. E. Smilh and A. C. Dawson (London: Academic Press, 1983), 321-43. For the mid-1 lolocene highstand in relative sea level on Pacific islands, see J. X. Milroviea and W. R. Peltier, "On Postglacial Geoid Subsidence over the Equatorial Oceans," Journal of Geophysical Research 96 (10 November 1991): 20,052-71. For the general background theory of worldwide glaeio-hydro-isostasy, see R. I. Walcott, "Past Sea I ,cv-els, Fustasv, and Deformation of the Earth," Quaternary Research 2 (July 1972): 1-14; John Chappell, "Late Quaternary Glacio- and llydro-Isostasy, on a Layered Earth," Quaternary Research 4 (December 1974): 405-428. 4. The impact of the Pleistocene-Holocene transition on the development of human culture has been discussed recently by Andrew Sherratt, "Climatic Cycles and Behaviourial Revolutions: The Emergence of Modern I lumans and the Beginning of Farming," Antiquity ~/i (June 1997): 271-87. 5. Positions of European ice fronts adapted from B. C. Anderson and II. W. Boms, Jr., The Ice Age World (Oslo: Scandinavian Universit)' Press, 1994), 1-208. 6. The timing of the last inlerglaciation has been established within narrow limits by R. L. Edwards, J. II. Chen, T. L. Ku, and G. J. Wasserburg, "Precise Timing of the Last Interglaeial Period from Mass Speetrometric Determination of'ľhorium-230 in ("orals," Science 236 (19 June 1987): 1547-53; J. H. Chen, II. A. Curran, B. White, and C. J. Wasserburg, "Precise Chronology of the Last Interglaeial Period: -TP'Th Data from Fossil Coral Reefs in the Bahamas," Geological Society of America Bulletin 103 (January 1991): 82-97; ^- "■ Stirling, T. M. Esat, M. T. McCulloch, and Kurt Lambeck, "High-Precision U-Series Dating of Corals from Western Australia and Implications for thcTiniingand Duration oflhe Last Interglaeial," Earth and Planetary Science Leiters 135 (October 1995): 115-30; Carsten Israelson and Barbara Wohlfarlh, "Timing oflhe Lasl-lnlerglacial I ligh Sea Level on the Seychelles Islands, Indian Ocean, Quaternary Research 51 (May 1999): 306-316. Recent discussions of the duration oflhe last inlerglaciation include B. J. Szabo, K. R. Ludwig,, D. R. Mulis, and K. R. Simmons, "Thoriuin-230 Ages of Corals and Duration of the Last Interglaeial Sea-Level High Stand on Oahu, Hawaii," Science 266 (7 October 1994): 93-96; I- J- Winograd, J. M. Landwehr, K. R. Ludwig, T. B. Coplen, and A. C. Riggs, "Duration and Structure of the Past Four Interglaciations," Quaternary Research 48 (September 1997): 141-54; C. 20 I ding, T. M. Estal, Kurt Limbeck, and M. T. iVIeCiilloch, "Timing and Duration ol ...c Last Interglaeial: Kvidence fora Restricted Interval of Widespread Reel Growth," Earth and Planetary Science Letters 160 (August 1998): 745-62. 7. Svnoptie maps depicting the pollen record of svnglacial and postglacial Vegetation in eastern North America have been presented by ľ. I''. McDowell, Thompson Webb III, and ľ. J. Barllcin, "Long-Term Knvironmcnlal Change," in 7Vic l'Áirth as Transformed by Human Action, ed. B. L. Turner II, W. C. Clark, R. W. Kates, J. K. Richards, J. T. Matthews, and W. B. Meyer (Cambridge: Cambridge University Press, 1990), 143-152 (Fig. 9-6); Thompson Webb III, P. J. Bartlein, S. P. Harrison, and K. II. Anderson, "Vegetation, Lake Levels, and Climate in Lastern North America for the Past 18,000 Years," in Global Climates Since the Lust Glacial Maximum, eel. 11. L. Wright, Jr., J. L. Kutzbaeli, Thompson Webb III, W. K Ruddimau, K. A. Sired-Perroll, and P. J. Bartlein (Minneapolis: University of Minnesota Press, 1993), 449-5o(Kig. 17.10). I. C. Prentice, P. J. Hartlein, and Thompson Webb III, "Vegetation and Climate Chnage in Lastern North America Since the [«ist Glacial Maximum," ľ'colog\i2 (June 1993): 2038-56 (Figs. 7-9). 8. The expansion of Oceanian cultures across (he Pacific arena is recounted bv Paul Rainbird, "Prehistory in the Northwest Tropical Pacific: The Caroline, Mariana, and Marshall Islands," Journal of World Prehistory 8 (September 1994): 293-349; Matthew Spriggs, The island Melancsians (Oxford: Blackwell, 1997), 1-326; P. V. Kirch, 77?e Lapita Peoples (Cambridge: Blackwell, 1997), 1-353. 'he varied settings and diverse environments of islands within the ocean basins are outlined bv P. D. Niinn, Oceanic Islands (Oxford: Blackwell Publishers, 1994), 1-413 9. An extensive literature describing preeontact environmental changes on Pacific islands is typified by P. V. Kirch and 1). L. Yen, likopia: The Prehistory and Ideology of a Polynesian Outlier (Honolulu, Hawaii: Bishop Museum Press, 1982): 1-396, esp. 346-49; P. V. Kirch, "Man's Role in Modifying Tropical and Subtropical Polynesian Ecosystems," Archaeology in Oceania 18 (April 1983): 261-31; Atholl Anderson, "Faunal Depletion and Subsistence Change in the Karly Prehistory of Southern New Zealand," Archaeology in Oceania 18 (April 1983): 1-10; B. V. Rolett, "Faunal Kxtinctions and Depletions Linked with Prehistory and Knvironmental Change in the Marquesas Islands (French Polynesia), Journal of the Polynesian Society \oi (March 1992): 86-94; J. S. Athens and J. V. Ward, "Fnvironmental Change and Prehistoric Polynesian Settlement in llawai'i, Asian Perspectives (fall 1993): 205-223; P. V. Kirch, "Late llolocene 1 luman-lnduced Modifications to a Central Polynesian Island Kcosvsteni," Proceedings ol the National Academy of Sciences iß (May 1996): 5296-5300; Dana Lepofskv, P. V. Kirch, and K. P. Lertzman, "Stratigraphic and Paleobotanies Kvidence for Prehistoric Human-Induced Environmental Disturbance on Mo'orea, French Polynesia," Pacific Science 50 (July 1996): 253-73; J. S. Athens, J. V. Ward, and G. M. Murakami, "Development of an Agroforcsl on a Microuesiau High Island: Prehistoric Kosracan Agriculture," Antiquity 70 (December 1996): 834-46; P. V. Kirch and ľ. L. Hunt, eds., Historical Ecology in the Pacific Islands (New I laven, Conn.: Yale University Press, 1997), 1-331. 10. The llolocene geohistory of Mesopotamia is outlined bv Michael Sarntheini, "Sediments and History of the Postglacial Transgression in the Persian Gulf and Northwest Gulf of Oman," Marine Geology12 (April 1972): 245-66; 'P. A. Al-Asfour, Changing Sca-Levcl along the North Coast of Kuwait Bay (I .ondon: Kegan Paul International, 1982), 1-182; G. A. Cooke, "Reconstruction of the llolocene Coastline of Mesopotamia," Geoarchaeology 2 (January 1987): 15-28. 11. The timing of llolocene delta initiation lias been established bv D. J. Stanley and A. C. Warne, "Worldwide Initiation of I lolocene Marine Delias by Deceleration of Sea-Level Rise," Science 265 (8 July 1994): 228-231. Subsequent growth of the Nile Delta is outlined by Vincent Coutillier and D. J. Stanley, "Late QuaL ..,ry Stratigraphy and Paleogeography of the Lastern Nile Delta, Kgypt," Marine Ccologi'jj (August 1987): 257-75. 12. Curve redrawn from combined data of John Chapcll and I lenry Polach, "Post-Glacial Sea-Level Rise from a Coral Record at Iluon Peninsula, Papua New Guinea," Nature 349 (10 January 1991): 147-49; Kdouard Bard, Bruno I lamelin, Maurice Arnold, I .ucien Montaggioni, Guy Cabioch, Gerard Faure, and Francis Rougerie, "Dcglacial Sea-Level Record from Tahiti Corals and the Timing of Global Meltwater Discharge," Nature 382 (18 July 1996): 241-44. 13. See S. M. Gagliano, K. J. Meyer-Arendt, and K. M. Wicker, "Land Loss in the Mississippi River Deltaic Plain," Gulf Coast Association of Geological Societies Transactions 17 (1981): 295-300; D. J. Stanley, "Nile Delta: Extreme Case of Sediment Entrapment on a Delta Plain and Consequent Coastal I .-and I -oss," Marine Geolog\' 129 (April 1996): 189-95. 14. See J. VV. Valentine and David Jablonski, "Biotic Effects of Sea Level Change: The Pleistocene Test," Journal of Geophysical Research 96 (10 April 1991): 6873-78. 15. Glacial-interglacial cycles adapted after R. B. Morrison, "Introduction," in Quaternary Nonglacial Geology: Conterminous U.S., edited bv R. B. Morrison (Boulder, Colo.: Geological Society of America, The Geology of North America, Volume K-2, 1991), 1-12. Alternate dates for the advent of modern humans arc discussed by Chris Stringer, "The Dates of Eden," Nature 331 (18 February 1988): 565-66. 16. The individualistic past migration of littoral organisms is discussed bv J. W Valentine and David Jablonski, "Fossil Communities: Compositional Variation at Many Time Scales," in Species Diversity in Ecological Communities: Ilislorieal and Geographical Perspectives, ed. R. C. Ricklefs and Dolph Schlüter (Chicago: University of Chicago Press, 1993), 341-49. The dispersal of marine organisms from available species pools is discussed by M. A. Buzas and S. J. Culver, "Species Pool and Dynamics of Marine Paleocommunities," Science 264 (3 June 1994): 1439-41. 17. See Matsuo Tsukada, "Vegetation in Prehistoric Japan: The Last 20,000 Years," in Windows on the Japanese Past: Studies in Archaeology and Prehistory, ed. R. J. Pearson (Ann Arbor: Universit)' of Michigan Center for Japanese Studies, 1986), 11-56. 18. Postglacial vegetation changes in the Great Basin and the Desert Southwest are summarized by D. K. Grayson, 77ie Insert's Past: A Natural Prehistory of the Great Basin (Washington, D.C.: Smithsonian Institution Press, 1993), 1-356; J. I.. Betancourt, 'ľ. R. Van Devender, and P. S. Martin, eds., Packrat Middens: The l,astj.o,ooo Years of Biotic Change (Tucson: University of Arizona Press, 1990), 1—467. 19. Elevation contrasts in the habitats of modern and similar but somewhat different Pleistocene floral communities in the American Southwest are discussed by J. L. Betancourt, "Late Quaternary Biogeography of the Colorado Plateau," in Packrat Middens: The I.ast jo.ooo Years of Biotic Change, ed. J. L. Betancourt,'ľ. R. Van Devender, and P. S. Martin (Tucson: University of Arizona Press, 1990), 259-92; VV. C. Spaulding, "Environmental Change, Ecosystem Responses, and Late Quaternary Development of the Mo jave Desert," in hitc Quaternary Environments and Deep Ilistory, ed. D. W. Steadman and J. I. Mead (Hot Springs, S.Dak.: The Mammoth Site of 1 lot Springs Scientific Papers, Volume 3, 1995), 139-04. 20. Synglacial temperatures in the tropics have been discussed by T. P. Guilderson, R. C. Fairbanks, and J. L. Rubenstone, "Tropical Temperature Variations Since 20,000 Years Ago: Modulating Interheinispheric Climate Change," Science 263 (4 Februar)' 1994): 663-65; M. Stute et ak, "Cooling of 'I ropical Brazil (5°C) During the 1st Glacial Maximum," Science 269 (21 July 1995): 379-83. The historical ecology of tropical rain forests was discussed on a global scale by J. R. Flenlcy, The E.ijuatorial Rain forest: A Geological /7/sroiy (London: Bufterworths, 1979), 1-162, and the overall distribution of floral provinces 11 i Hitli America at peak glaeialíon bv C. M. Clappcrlon, "Nature ol Environmental i. ..iges in South America at the Last Glacial Maximum," Palaeogeographv, Paiaeoclimatologv, Palaeoecology 101 (April 199-5): 189-208. For the pollen record of svnglacial Amazon forests, sec K. B. Liu and P. A. Colinvaux, "Forest Changes in the Amazon Basin During the Last Glacial Maximum," Nature 518 (12 December 1985I: 556-57; P. A. Colinvaux, P. Ľ. De Oliveira, J. F. Moreno, M. C. Miller, and M. B. Bush, "A Long Pollen Record from Lowland Amazonia: Forest and Cooling in Glacial Times," Science 274 (4 October 1996): 85-88; S. G. I Liberie and M. A. Maslm, "I,ate Quaternary Vegetation and Climate Change in the Amazon Basin Based on a 50,000 Year Pollen Record from the Amazon Fan, ODP Site 952," Quaternary Research 51 (January 1999): 27-58; P. A. Colinvaux, P. F. de Oliveira, and iVl. B. Bush, "Amazonian and Neotropical Plan! Communities on Glacial Time-Scales: The Failure ol I he Ariditv and Refuge Hypotheses," Quaternary Science Reviews 19 (January 2000): 141-69. 21. Dating of Clovis sites in terms of calibrated radiocarbon ages is appraised by R. F. lavlor, C. V. llaynes, Jr., and Minze Stuiver, "Clovis and Folsom Age Estimates: Stratigraphic Context and Radiocarbon Calibration," Antiquih' 70 (September 1996): 515-25. Early human agricultural development on delta surfaces is reviewed by D. J. Stanley and A. C. Warne, "Holocene Sea-Level Change and Farlv I Iiinian Utilization of Deltas," CSA Today 7 (December 1997): 1-6. 22. For extended discussions of aboriginal wildfires, see S. J. Pvne, Fire in America: A Cultural History of Wildland and Rural Fire (Princeton, N.J.: Princeton University Press, 1982), 1-654; fuming Bush: A Fire Ilistorv ot Australia (New.'York: 1 lolt, 1991), 1-520. Specific studies of pre-contac! fire practices bv Native Americans (USA area) include Galen Clark, "Yosenlite —Past and Present," Sunset Magazine (Ay>x\\ 1907): 79-81; G. M. Day, "The Indian as an Ecological factor in the Northeastern Forest," Feolog\ 54 (April 1955): 529-46); Homer Aschniann, "The Evolution of a Wild Landscape and its Persistence in Southern California," Association of American (Geographers Annals (Supplement 1959): 54-56; D. II. Harris, "Recent Plant Invasions in the Arid and Semi-Arid Southwest of the United States," Association of American Geographers Annals 56 (September 1966): 408-422; H.T. Lewis, "Patterns of Indian Burning in California: Ecology and Ethnohistorv," Ballcna Press Anthropological Papers No. 1 (1975): 1-101; Jan Timbrook, J. R. Johnson, and D. D. Earle, "Vegetation Burning bv the Chuniasli," Journal of California and Great Basin Anthropology 4 (winter 1982): 163-86; William Cronon, Changes in the Land: Indians, Colonists, and the F.eologv of New England (New York: Mill and Wang, 1983, 1-241, especially 49-51; Robert Boyd, "Strategies of Indian Burning in the Williamette Valley," Canadian journal of Anthropology 5 (fall 1986): 65-86. The term "firestick farming" was introduced bv Rhvs Jones, "Fire-Stick Farming," Australian Natural History 16 (September 1969): 224-28; although his concept that anthropogenic fire has played a key role in fostering the structure of Australian plant communities has been disputed bv D. R. Horton, "The Burning Question: Aborigines, Eire, and Australian Ecosystems," Mankind r^ (April 1982): 237-51, and R. L. Clark, "Pollen and Charcoal Evidence lor Ihe Elfecls ol Aboriginal Burning on the Vegetation of Australia," Archaeology in Oceania 18 (April 1983): 32-57, detailed accounts of current Aborigine fire practices tend !o support Rhvs Jones: Richard Kiniber, "Black Lightning: Aborigines and Fire in Central Australia and the Western Desert," Archaeology in Oceania 18 (April 1985): 38-45; D. B. Rose, ed., Country in Flames [Proceedings of the 1994 Symposium on Biodiversity and Fire in North Australia J (Canberra: North Australia Research Unit, Australian National University, Biodiversity Series Paper No. 3, 1995), 1-127. ''or fnt* influence of anthropogenic fires on the distribution of forest species, see J. G. Saldarriaga and D. C. West, "Holocene Fires in the Northern Amazon Basin," Quaternary Research 26 (Noveml, .986): 358-66; P. A. Delcourt, II. R. Delcourt, C. R. Ison, W. Ľ. Sharp, and K. J. Cennillion, "Prehistoric 1 luman Use of Fire, the Eastern Agricultural Complex, and Appalachian Oak-Chestnut Forests: Paleoecologv of Cliff Palace Pond, Kentucky," American Antiquity 63 (April 1998): 569-85; J. S. Athens and J. V. Ward, "The Late Quaternary of the Western Amazon: Climate, Vegetation, and Humans," Antiquity j^ (June 1999): 287-302. 23. Pionccering studies that demonstrated the dominant role of anthropogenic fire in protecting tropical savannahs from tree invasion include Gerard Budowski, "Tropical Savannahs, a Sequence of Forest Felling and Repeated Burnings," Turrialba 6 (June 1956): 23-33; M. J. Eden, "Palaeoclimatic Influences and the Development of Savanna in Southern Venezuela," Journal ofBiogeograph v 1 (June 1974): 95-109; R. N. Seavoy, "The Origin of Tropical Grasslands in Kalimantan, Indonesia," Journal ot Tropical (Geography ^o (June 1975): 48-52; R. A. Pullan, "Burning Impact on Alrican Savannahs," Geographical Magazine47 (April 1975): 432-58; G. A. J. Scott, "The Role of Fire in the Creation and Maintenance of Savanna in the Montana of Peru," Journal of liiogcogra-p/)\'4 (June 1977): 141-67. Recent studies showing its importance for replacing forest with savannah on newly occupied Pacific islands include Janelle Stephenson and J. R. Dodson, "Paleoenvironmental Evidence for Human Settlement of New Caledonia," Archaeology in Oceania 50 (April 1995): 36-41; J. R. Dodson and Michiko Intoh, "Prehistory and Palaeoecology of Yap, Federated States of Micronesia," Quaternary International 59 (October 1999): 17-26. 24. Fire as the prime tool of aboriginal land management was argued bv O. C. Stewart, "Burning and Natural Vegetation in the United States," Geographical Review 41 (April 1951): 317-20; "I'ire as the First Great Force Employed by Man," in Man's Role in Changing the Face ot the Earth, ed. W. L. Thomas, Jr. (Chicago: University of Chicago Press, 1956), 115-33. An example of semiarid grassland persistent without anthropogenic influence is described by M. E. Meadows, "Late Quaternary Vegetation I listorv of the Nyika Plateau, Malawi," Journal of'Biogcographyn (May 1984): 209-222. 25. Extent and age of delta lobes generalized after D. E. Frazier, "Recent Deltaic Deposits of the Mississippi River: Their Development and Chronology," (Gulf Coast Association of Geological Societies Transactions 17 (1967): 287-311; W. J. Autin, S. F. Burns, B. J. Miller, R. T. Saucier, and J. I. Sncad, "Quaternary Geology of the Lower Mississippi Valley," in Quaternary Nonglacial Geology: Conterminous U.S., ed. R. B. Morrison (Boulder, Colo.: Geological Society of America, The Geology of North America, Volume K-2, 1991), 547-82; J. M. Coleman, II. II. Roberts, and O. W. Stone, "Mississippi River Delta: An Overview," Journal of Coastal Research 14 (summer 1998): 698-716. 26. The process and results of animal domestication are addressed by Jared Diamond, Guns, Germs, and Steel (New York: Norton, 1997), 1-480, especially 157-75. Megafaunal extinctions were treated for the Americas by P. S. Martin, "The Discovery of America," Science 179 (9 March 1975): 969-74; for Australia by Tim Flannery, Ihe Future Eaters (Melbourne: Reed, 1994), 1-425, especially 180-86; and in sequential global overview bv P. S. Martin, "40,000 Years of Extinctions on the Planet of l~)omu," Palaeogeographv, Palaeocliwatology, Palaeoecology ((Global and Planetary Change Section) 82 (May 1990): 187-201; P. S. Marlin and D. W. Steadman, "Prehistoric Extinctions on Islands and Continents," in Extinctions in Near Time, ed. R. D. F. McPhee (New York: Plenum, 1999), 17-55. For the inferred effect of niegaherbivore extinctions on Australian flora, see Tim Flannery, "Pleistocene I'aunal Loss: Implications of the Aftershock for Australia's Past and Future," Archaeology in Oceania 25 (July 1990): 45-67. 27. For depletion of avifauna within Oceania, see S. L. Olson and 11. F. James, "The Role of Polynesians in the Extinction of the Avifauna of the Hawaiian Islands," in Quaternary 502 Environmental History Extinctions, ed. P. S. Martin and R. G. Klein (Tucson: Universit)' of Arizona Press, 1995), 768-80; D. W. Steadman, "Prehistoric Extinctions of Pacific Island Birds: Biodiversity Meets Zooarchaeology," Science 267 (24 February 1995): 1123-31; D. W. Steadman, "Extinctions of Polynesian Birds: Reciprocal Impacts of Birds and People," in Historical Ecolog) in the Pacific Islands, ed. P. V. Kirch and T. L. Hunt (New Haven, Conn.: Yale University Press, 1997), 51-79. 28. For the myth of wilderness, see W. M. Denevan, "The Pristine Myth: The Landscape of the Americas in 1492," Association of American Geographers Annals 82 (September 1992): 369-85; Arturo Gomez-Pompa and Andrea Kaus, "Taming the Wilderness Myth," BioScience 42 (April 1992): 271-79. 29. The areal extent of New Zealand forests at different times is indicated bv M. S. McGlonc, "Polynesian Deforestation of New Zealand," Archaeology in Oceania 18 (April 1983): 11-25; Atholl Anderson and Matt McGlone, "Living on the Edge —Prehistoric Land and People in New Zealand," in The Naive Lands, ed. John Dodson (Melbourne: Longman Cheshire, 1992): 199-241; M. S. McGlone, M. j. Salinger, and N. T. Moar, "Paleovegetation Studies of New Zealand's Climate Since the Last Glacial Maximum," in Global Climates Since the Last Glacial Maximum, ed. H. E. Wright, Jr., J. Ľ. Kutzbach, Thompson Webb III, W. E Rnddiman, F. A. Strect-Pcrrott, and P. J. Bartlein (Minneapolis: University of Minnesota Press, 1993), 294-317. The timing of Polynesian arrival in New Zealand is documented bv Atholl Anderson, "The Chronology of Colonization in New Zealand,".Antiquihb^ (December 1991): 7Ď7-95; M. S. McGlone and J. M. Wilmshurst, "Dating Initial Maori Environmental Impact in New Zealand," Quaternary International 59 (October 1999): 5-16.