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Geomorphology in the Anthropocene: Perspectives from the Past, Pointers for the Future?

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Abstract

The term Anthropocene has been introduced to highlight the fact humans have, directly or indirectly – accidentally or intentionally – profoundly transformed the earth system. There is much debate as to whether the magnitude and extent of such change is geologically distinctive and, accordingly, warrants formal designation as a new epoch although, irrespective of this, the magnitude of change is undoubtedly significant. In order to put the Anthropocene into perspective, the chapter briefly reviews various systemic and cumulative drivers of geomorphic change before going on to explore the time-transgressive impacts of humans on virtually all environments of the earth. This is followed by a consideration of three instructive case studies of how the deleterious effects of growing numbers of people using increasingly sophisticated technologies are expressed geomorphologically across a range of environments. The problems of accelerated soil erosion, the impact of large dams and the nature and extent of artificial ground are used to highlight the important role that geomorphology plays in understanding the burgeoning footprint of humanity on earth systems. The Quaternary record offers a foundational understanding of baseline conditions of earth system processes and responses and facilitates increased confidence in evaluating the magnitude of past and future global climate change and its diverse effects. A quarter of a century on from the first IPCC report, the degree to which the strength of its statements, and the confidence with which they are made, is rooted in a better understanding of longer-term past changes should not be underestimated. The fact that geomorphology may still be a ‘Cinderella’ in relation to studies of environmental change is ongoing cause for concern and, if we are to illuminate the range of options available to mitigate and adapt to future change, we need systematically to incorporate a stronger geomorphological perspective into global change science; the Anthropocene represents an appropriate platform from which to inject that perspective.

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... Geomorphologists, therefore, must utilize the opportunities provided by artificial intelligence, GPU computing, and automated mapping processes (Stepinski and Vilalta, 2010;Spina, 2019). If geomorphology is to aid in mitigating and adapting to future environmental change, we need to systematically incorporate a stronger geomorphological perspective into the science of global change; the Anthropocene represents an appropriate platform from which to inject that perspective (Meadows, 2016). ...
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The five largest rivers in East and Southeast Asia (Yellow, Yangtze, Pearl, Red and Mekong) are important contributors of terrigenous sediment to the western Pacific Ocean. Although they have annually delivered ~ 2000 × 10 9 kg of sediment to the ocean since 1000 yr BP, they presently contribute only ~600 × 10 9 kg/yr, which is reverting to a level typical of the relatively undisturbed watersheds before the rise in human activities in East and Southeast Asia at 2000 yr BP. During the most recent decades flow regulation by dams and sediment entrapment by reservoirs, as well as human-influenced soil erosion in the river basins, have sharply reduced the sediment delivered from the large river basins to the ocean. We constructed a time series of data on annual water discharges and sediment fluxes from these large rivers to the western Pacific Ocean covering the period 1950–2008. These data indicate that the short-term (interannual scale) variation of sediment flux is dominated by natural climatic oscillations such as the El Niño/La Niña cycle and that anthropogenic causes involving dams and land use control the long-term (decadal scale) decrease in sediment flux to the ocean. In contrast to the relatively slow historical increase in sediment flux during the period 2000–1000 yr BP, the recent sediment flux has been decreased at an accelerating rate over centennial scales. The alterations of these large river systems by both natural and anthropogenic forcing present severe environmental challenges in the coastal ocean, including the sinking of deltas and declines in coastal wetland areas due to the decreasing sediment supply. Our work thus provides a regional perspective on the large river-derived sediment flux to the ocean over millennial and decadal scales, which will be important for understanding and managing the present and future trends of delivery of terrigenous sediment to the ocean in the context of global change.
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Aim To map and characterize anthropogenic transformation of the terrestrial biosphere before and during the Industrial Revolution, from 1700 to 2000.Location Global.Methods Anthropogenic biomes (anthromes) were mapped for 1700, 1800, 1900 and 2000 using a rule-based anthrome classification model applied to gridded global data for human population density and land use. Anthropogenic transformation of terrestrial biomes was then characterized by map comparisons at century intervals.Results In 1700, nearly half of the terrestrial biosphere was wild, without human settlements or substantial land use. Most of the remainder was in a seminatural state (45%) having only minor use for agriculture and settlements. By 2000, the opposite was true, with the majority of the biosphere in agricultural and settled anthromes, less than 20% seminatural and only a quarter left wild. Anthropogenic transformation of the biosphere during the Industrial Revolution resulted about equally from land-use expansion into wildlands and intensification of land use within seminatural anthromes. Transformation pathways differed strongly between biomes and regions, with some remaining mostly wild but with the majority almost completely transformed into rangelands, croplands and villages. In the process of transforming almost 39% of earth's total ice-free surface into agricultural land and settlements, an additional 37% of global land without such use has become embedded within agricultural and settled anthromes.Main conclusions Between 1700 and 2000, the terrestrial biosphere made the critical transition from mostly wild to mostly anthropogenic, passing the 50% mark early in the 20th century. At present, and ever more in the future, the form and process of terrestrial ecosystems in most biomes will be predominantly anthropogenic, the product of land use and other direct human interactions with ecosystems. Ecological research and conservation efforts in all but a few biomes would benefit from a primary focus on the novel remnant, recovering and managed ecosystems embedded within used lands.
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How will global environmental change affect the landscape and our interaction with it? Apart from climate change, there are other important catalysts of landscape change, including relief, hydroclimate and runoff, sea level variations and human activity. This volume summarizes the state-of-the-art concerning the geomorphic implications of global environmental change, analyzing such effects on lakes, rivers, coasts, reefs, rainforests, savannas, deserts, glacial features, and mountains. Providing a benchmark statement from the world’s leading geomorphologists on the current state of, and potential changes to, the environment, this book is invaluable for advanced courses on geomorphology and environmental science, and as a reference for research scientists. Interdisciplinary in scope, with a primary audience of Earth and environmental scientists, geographers, geomorphologists and ecologists, it also has a wider reach to those concerned with the social, economic and political issues raised by global environmental change, and is useful to policy makers and environmental managers.
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Dust storms, produced by the removal of surface materials from the world's drylands, are a vital component of the environment. This is because of their role in biogeochemical cycling, their potential influence on climate, their role in sediment accumulation and their influence on human affairs. This book, which is exhaustively referenced, explores and summarises recent research on where dust storms originate, why dust storms are generated, where dust is transported and deposited, the nature of dust deposits and the changing frequency of dust storms over a range of time-scales. © Andrew S. Goudie and Nicholas J. Middleton 2006. All rights are reserved.
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Anthropogenic surficial deposits are formed from Holocene and older deposits that have been so modified by human activity that their original form is unrecognizable. Because their characteristics are fundamentally different from those of natural origin, the creation of special stratigraphic categories seems justified. Two new material categories are proposed for the stratigraphic classification of anthropogenic deposits. An anthrostratigraphic unit (ASU) is defined as a stratiform or irregularly shaped body of anthropogenic origin in the sedimentary record distinguished and delineated on the basis of lithologic characteristics and/or bounding disconformities. An anthropogenic origin is indicated if the deposit (1) lies beneath an anthropogenic landform, (2) contains artifacts, (3) shows evidence of artificial mixing or other human disturbance, and/or (4) was imported from offsite and is allochthonous. The basic ASU is the anthrostratum, defined as a mostly stratiform body of artificially mixed earth (rock, sediment, soil, etc.) and artifactual (brick, concrete, etc.) materials. An anthrostratum need only be mappable at a local scale, but anthrostrata of different origins or type may be grouped together as an anthroformation if regionally mappable. A technostratigraphic unit (TSU) is defined as a stratiform body of anthropogenic origin in the sedimentary record defined on the basis of artifacts (objects of anthropogenic origin). TSUs are based on the evolution of technology involved in the creation of artificially altered or manufactured objects. The basic TSU is the technozone defined on the basis of Commercial Ranges (time from beginning to end of commercial availability of certain artifacts). ASUs and TSUs are applicable to anthropogenic deposits assigned to either the Holocene or the Anthropocene.
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At some point during the Holocene, human action began to accelerate or redirect landscape and biospheric evolution. Basic questions for this preface are whether we should define this new dynamism as an ‘Anthropocene era’ and how might it be delimited with respect to absolute time or to the Holocene. Traditional geo-stratigraphic nomenclature developed through accretion of field observations, vetted by theoretical discussion, to facilitate four-dimensional reference to lithology, topography, space, and time. Current notions for an Anthropocene carry additional connotations: (1) the focus is on a more dynamic agenda that is far from being synthesized; (2) this revolves around the increasingly salient role of cultural agents that selectively shape a multitude of small and large specific areas, so as to favor divergences and disjunctures; (3) the result is a non-normative dynamic of changing spatial configuration and temporal scales that was superimposed on non-cultural Holocene processes predominantly steered by ‘natural’ forces; and (4) this would argue for a flexible, time-transgressive concept, rather than a firm time-frame, that should stimulate identification and investigation of centers of early or unusual human disturbance. The amplified energy and amplitude of these culturally modified divergences are formidable, but Pleistocene glaciation posed a more severe test for biotic evolutionary success than did past or current global change driven by human actions. This would suggest that instead of proclaiming alarmist schedules, we should concentrate on constructive research and university instruction that better emphasizes environmental and sociocultural resilience, adaptation, and the interplay of buffering feedbacks with systemic micro-evolution.
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The Anthropocene has taken root in popular culture as a new time term, and scientists engaged in research and debate on anthropogenic climate change should benefit from formal stratigraphic adoption. Definition and delineation of a basal Anthropocene boundary would be sufficient to introduce the term, but the boundary could be potentially arbitrary if it lacks temporal precision. Workers commonly use Anthropocene informally, and stratigraphic practice does allow for informal nomenclature where suitable to resolve geological problems. Anthropocene is a tendency to market catch phrases that produce questionable labels. Anthropocene forces people to consider the implications of sending the Earth system into a completely new domain driven by their actions.
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The call to adopt a longer-time perspective in order to better understand contemporary and near-future global environments is not new. Nevertheless, there is a growing recognition that evidence from the geologically recent past, in particular the late Quaternary, is essential if we are to understand the profound changes that have taken place in the human relationship with the living world. This progress report reviews how the understanding of environmental dynamics over extended time periods is now incorporated into science dealing with predictions of future climate change by the IPCC consortium, how possible analogues for a warmer future are still vigorously explored and how information on past environments may better inform an understanding of contemporary ecosystem processes and influence the future management of biodiversity in protected areas.
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Reconstruction of artificial or anthropogenic topographies, sediment thicknesses and volumes provides a mechanism for quantifying anthropogenic changes to sedimentary systems in the context of the proposed Anthropocene epoch. We present a methodology for determining the volumetric contribution of anthropogenic deposits to the geological and geomorphological record and apply it to the Great Yarmouth area of Norfolk, UK. 115 boreholes, drilled to a maximum depth of 6 m below ground level, were used to determine the thickness and distribution of seven geo-archaeological units comprising natural and anthropogenic deposits in the central Great Yarmouth area. This was supplemented by additional depth information derived from 467 existing ground investigation boreholes and published 1:50 000 scale geological maps. The top and base of each geo-archaeological unit were modelled from elevations recorded in the borehole data. Grids were produced using a natural neighbour analysis with a 25 m cell size using MapInfo 8.0 Vertical Mapper 3.1 to produce palaeotopographical surfaces.
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1. The invasion of fynbos shrublands by woody weed species can reduce the water yield from catchment areas dramatically. We modelled the consequences of uncontrolled invasion on water yield using a geographical information system (Arc/Info). 2. Five important processes were recognized: the occurrence of fire; the spread and establishment of alien plants after fire; rainfall-to-run-off ratios; growth and changes in biomass between fires; and effects of these changes on streamflow. 3. The simulations of water yield were modelled with the Arc/Info GRID module using a 200 x 200-m grid. It was assumed that the interval between fires was 15 years and that proliferation and dispersal of alien plants took place only after fires. 4. Between fires, the model simulated the growth of the vegetation and its effects on streamflow, using relationships between rainfall and run-off, and run-off and above-ground biomass. 5. Results for the Kogelberg area in the Western Cape Province showed that alien plants invaded about 40% of the grid cells within 50 years. Cover of alien plants increased from an initial estimate of 2.4% to 62.4% after 100 years. 6. Invasion of catchment areas would result in an average decrease of 347 m3 of water per hectare per year over 100 years, resulting in average losses of more than 30% of the water supply to the city of Cape Town. In individual years, where large areas would be covered by mature trees, losses would be much greater. 7. In addition, invasion of fynbos by alien plants will cause the extinction of many plant species, increase the intensity of fires, destabilize catchment areas with resultant erosion and diminished water quality, and decrease the aesthetic appeal of mountain areas. 8. Control of alien weed species is necessary to avert the above impacts, and the costs of control operations could be justified by the savings achieved in maintaining adequate water run-off from stable catchments in the long term.
Article
Chile has developed an important economy based on some 2.6 million hectares of planted forests which have been questioned because of their impact on water resources. This report analyses the water response associated with forest plantation expansion and changes in tree species composition in six large river basins (from 94 to 1545 km(2)) of pluvial regime located between 37 degrees 30' and 39 degrees S in central-southern Chile, an area characterized by a Mediterranean climate. Long term discharge and precipitation records were obtained from national data bases and land uses for different time periods were generated using satellite images and digital maps. Annual water reductions were detected in three river basins where net increases in forested area affected more than the 16% of total catchment area. In the same basins and between the same periods reductions of summer runoff were also noticed although these decreases should be carefully considered as summer runoff also decreased in basins where no significant land use changes occurred. The analysis of the daily flow duration curves indicates that the highest effects occur for Q(50%) (daily discharge exceeded 50% of time) while Q(80%), Q(85%) and Q(90%) are much less affected. Although forest plantation expansion and changes in tree species composition have the potential to reduce streamflow, since Q(80%) and Q(90%) are used to define permanent and continuous Water Rights according to the Chilean Water Code, it is possible that already existing permanent and continuous water rights could be only marginally affected by the increase of the planted area. The results presented in this document can be used to support discussions related to the development of water allocation regulations among competing economic water users.
Article
As efforts to recognize the Anthropocene as a new epoch of geological time are mounting, the controversial debate about the time of its beginning continues. Here, we suggest the term Palaeoanthropocene for the period between the first, barely recognizable, anthropogenic environmental changes and the industrial revolution when anthropogenically induced changes of climate, land use and biodiversity began to increase very rapidly. The concept of the Palaeoanthropocene recognizes that humans are an integral part of the Earth system rather than merely an external forcing factor. The delineation of the beginning of the Palaeoanthropocene will require an increase in the understanding and precision of palaeoclimate indicators, the recognition of archaeological sites as environmental archives, and inter-linking palaeoclimate, palaeoenvironmental changes and human development with changes in the distribution of Quaternary plant and animal species and socio-economic models of population subsistence and demise.
Article
Numerous studies document the extent and intensity of human appropriation of ecosystem services and the manipulation of Earth's surface and fluxes of water, sediment and nutrients within the critical zone of surface and near-surface environments. These studies make it increasingly clear that wilderness is effectively gone. This paper explores the implications for critical zone studies and management from a geomorphic perspective. Geomorphologists possess knowledge of the long history of human alteration of the critical zone. This knowledge can be applied to characterizing: historical range of variability and reference conditions; fluxes of matter and energy; and integrity and sustainability of critical zone environments. Conceptual frameworks centered on connectivity, inequality, and thresholds or tipping points are particularly useful for such characterizations, as illustrated by a case study of beaver meadows in the Front Range of Colorado, USA. Specifically, for connectivity, inequality, and thresholds, geomorphologists can identify the existence and characteristics of these phenomena, quantify and predict changes resulting from past or future human manipulations, and recommend actions to restore desirable conditions or prevent development of undesirable conditions. I argue that we should by default assume that any particular landscape has had greater rather than lesser human manipulation through time. This history of manipulation continues to influence critical zone process and form, and geomorphologists can use knowledge of historical context in a forward-looking approach that emphasizes prediction and management.
Article
The start of the period of large-scale human effects on this planet (the Anthropocene) is debated. The industrial view holds that most significant impacts have occurred since the early industrial era (˜1850), whereas the early-anthropogenic view recognizes large impacts thousands of years earlier. This review focuses on three indices of global-scale human influence: forest clearance (and related land use), emissions of greenhouse gases (CO2 and CH4), and effects on global temperature. Because reliable, systematic land-use surveys are rare prior to 1950, most reconstructions for early-industrial centuries and prior millennia are hind casts that assume humans have used roughly the same amount of land per person for 7,000 years. But this assumption is incorrect. Historical data and new archeological databases reveal much greater per-capita land use in preindustrial than in recent centuries. This early forest clearance caused much greater preindustrial greenhouse-gas emissions and global temperature changes than those proposed within the industrial paradigm.
Article
The value of a formally defined Anthropocene for geomorphologists is discussed. Human impacts have been diachronistic, multifaceted and episodic, as demonstrated by the record of alluvial deposition in the UK. Rather than boxing time into discrete eras or periods, modern research uses calendar dates and multiple dating techniques to explore co-trajectories for a range of human impacts. Despite the value of ‘The Anthropocene’ as an informal concept and as a prompt to useful debate, arriving at a single, generally acceptable formal definition is impractical, and has some disadvantages. Copyright © 2013 John Wiley & Sons, Ltd.
Article
In the last 400 years floodplains in England and Wales have changed drastically. This has been steered by changes brought about through diverse human activities including river regulation for transport, water abstraction and power generation; mining, industrial and urban pollution; the spread of buildings and transport link construction; land drainage; minimization of flood risk through engineering; floodplain gravel extraction; and environment redesign for recreation and conservation. Adding to the evolving complexity of floodplains, a sequence of post-Enlightenment impacts from the earliest of industrial societies provides an interesting precursor for other transforming global systems. Historical and sedimentological evidence for this history is available, despite limited quantitative monitoring data. A four-phase floodplain transformation model is presented for the period. Novel patterns of erosion and sedimentation (in location and quality) have emerged as geomorphological processes have continued in ‘genetically-modified’ form. Problems building up for the future are likely to rest particularly with more extreme events. Understanding the last four centuries of floodplain history can aid enlightened remedies and adaptations. Copyright
Article
An important feature of the ongoing debate about the acceptance of the Anthropocene as a formal chronostratigraphic unit with the same rank as the Holocene (epoch) has been either the existence or the lack of a Global Stratotype Section and Point (GSSP). In addition, the utility of the Anthropocene as a stratigraphic unit has also been questioned. In this paper, it is proposed that the discovery of the GSSP may not be a major problem and could only be a matter of time. However, the term Anthropocene itself, defined on the basis of the stratigraphic expression of human activities (e.g. large-scale agriculture and land clearance, accelerated release of greenhouse gases to the atmosphere) may significantly impact the current stratigraphic framework guided by the International Commission on Stratigraphy (ICS). Indeed, the formal usage of this term can not only lead to stratigraphic and terminological inconsistencies but can also influence the future development of the established chronostratigraphic scheme. These points should be considered by the ICS Anthropocene Working Group before making a final decision. The stratigraphic status of the Anthropocene, however, is a formal issue that should not affect current and future research on human-induced environmental and sedimentary changes, including their stratigraphic imprint. The message is twofold: leave the formal chronostratigraphic aspects to the ICS, and keep producing and organizing knowledge independently of the formal debate. Doing so would require the development of a parallel and likely transitory chronological system without formal stratigraphic value, from which the term Anthropocene would be, at least temporarily, excluded.
Article
The Palaeocene-Eocene Thermal Maximum (PETM), an approximately 170,000-year-long period of global warming about 56 million years ago, has been attributed to the release of thousands of petagrams of reduced carbon into the ocean, atmosphere and biosphere. However, the fate of this excess carbon at the end of the event is poorly constrained: drawdown of atmospheric carbon dioxide has been attributed to an increase in the weathering of silicates or to increased rates of organic carbon burial. Here we develop constraints on the rate of carbon drawdown based on rates of carbon isotope change in well-dated marine and terrestrial sediments spanning the event. We find that the rate of recovery is an order of magnitude more rapid than that expected for carbon drawdown by silicate weathering alone. Unless existing estimates of carbon stocks and cycling during this time are widely inaccurate, our results imply that more than 2,000Pg of carbon were sequestered as organic carbon over 30,000-40,000years at the end of the PETM. We suggest that the accelerated sequestration of organic carbon could reflect the regrowth of carbon stocks in the biosphere or shallow lithosphere that were released at the onset of the event.
Tectonic uplift and erosional denudation of orogenic belts have long been the most important geologic processes that serve to shape continental surfaces, but the rate of geomorphic change resulting from these natural phenomena has now been outstripped by human activities associated with agriculture, construction, and mining. Although humans are now the most important geomorphic agent on the planet's surface, natural and anthropogenic processes serve to modify quite different parts of the Earth landscape. In order to better understand the impact of humans on continental erosion, we have examined both long-term and short-term data on rates of sediment transfer in response to glacio-fluvial and anthropogenic processes. Phanerozoic rates of subaerial denudation inferred from preserved volumes of sedimentary rock require a mean continental erosion rate on the order of 16 meters per million years (m/My), resulting in the accumulation of about 5 giga-tons of sediment per year (Gt/y). Erosion irregularly increased over the ~542 million year span of Phanerozoic time to a Pliocene value of 81 m/My (~19 Gt/y). Current estimates of large river sediment loads are similar to this late Neogene value, and require net denudation of ice-free land surfaces at a rate of about 74 m/My (~25 Gt/y). Consideration of variation in large river sediment loads and the geomorphology of respective river basin catchments suggests that natural erosion is primarily confined to drainage headwaters; ~83% of the global river sediment flux is derived from the highest 10% of the Earth's surface. Subaerial erosion as a result of human activity, primarily through agricultural practices, has resulted in a sharp increase in net rates of continental denudation; although less well constrained than estimates based on surviving rock volumes or current river loads, available data suggest that present farmland denudation is proceeding at a rate of about 600 m/My (~74 Gt/y), and is largely confined to lower elevations of the Earth's land surface, primarily along passive continental margins; ~83% of cropland erosion occurs over the lower 65% of the Earth's surface. The conspicuous disparity between natural sediment fluxes suggested by data on rock volumes and river loads (~25 Gt/y) and anthropogenic fluxes inferred from measured and modeled cropland soil losses (74 Gt/y) is readily resolved by data on thicknesses and ages of alluvial sediment that has been deposited immediately down slope from eroding croplands over the history of human agriculture. Accumulation of post-settlement alluvium on higher order tributary channels and floodplains (mean rate ~12,600 m/My) is the most important geomorphic process in terms of the erosion and deposition of sediment that is currently shaping the landscape of the Earth. It far exceeds even the impact of Pleistocene continental glaciers or the current impact of alpine erosion by glacial and/or fluvial processes. Human beings are therefore the dominant agent of topographic change operating on the surface of the planet today.
Article
Rock uplift and erosional denudation of orogenic belts have long been the most important geologic processes that serve to shape continental surfaces, but the rate of geomorphic change resulting from these natural phenomena has now been outstripped by human activities associated with agriculture, construction, and mining. Although humans are now the most important geomorphic agent on the planet's surface, natural and anthropogenic processes serve to modify quite different parts of Earth's landscape. In order to better understand the impact of humans on continental erosion, we have examined both long-term and short-term data on rates of sediment transfer in response to glacio-fluvial and anthropogenic processes. Phanerozoic rates of subaerial denudation inferred from preserved volumes of sedimentary rock require a mean continental erosion rate on the order of 16 m per million years (m/m.y.), resulting in the accumulation of ∼5 gigatons of sediment per year (Gt/yr). Erosion irregularly increased over the ∼542 m.y. span of Phanerozoic time to a Pliocene value of 53 m/m.y. (16 Gt/yr). Current estimates of large river sediment loads are similar to this late Neogene value, and require net denudation of ice-free land surfaces at a rate of ∼62 m/m.y. (∼21 Gt/ yr). Consideration of the variation in large river sediment loads and the geomorphology of respective river basin catchnients suggests that natural erosion is primarily confined to drainage headwaters; ∼83% of the global river sediment flux is derived from the highest 10% of Earth's surface. Subaerial erosion as a result of human activity, primarily through agricultural practices, has resulted in a sharp increase in net rates of continental denudation; although less well constrained than estimates based on surviving rock volumes or current river loads, available data suggest that present farmland denudation is proceeding at a rate of ∼600 m/m.y. (∼75 Gt/yr), and is largely confined to the lower elevations of Earth's land surface, primarily along passive continental margins; ∼83% of cropland erosion occurs over the lower 65% of Earth's surface. The conspicuous disparity between natural sediment fluxes suggested by data on rock volumes and river loads (∼21 Gt/yr) and anthropogenic fluxes inferred from measured and modeled cropland soil losses (75 Gt/ yr) is readily resolved by data on thicknesses and ages of alluvial sediment that has been deposited immediately downslope from eroding croplands over the history of human agriculture. Accumulation of postsettlement alluvium on higher-order tributary channels and floodplains (mean rate ∼12,600 m/m.y.) is the most important geomorphic process in terms of the erosion and deposition of sediment that is currently shaping the landscape of Earth. It far exceeds even the impact of Pleistocene continental glaciers or the current impact of alpine erosion by glacial and/or fluvial processes. Conversely, available data suggest that since 1961, global cropland area has increased by ∼11%, while the global population has approximately doubled. The net effect of both changes is that per capita cropland area has decreased by ∼44% over this same time interval; ∼1% per year. This is ∼25 times the rate of soil area loss anticipated from human denudation of cropland surfaces. In a context of per capita food production, soil loss through cropland erosion is largely insignificant when compared to the impact of population growth.
Article
We propose that the Anthropocene be defined as the last c. 2000 years of the late Holocene and characterized on the basis of anthropogenic soils. This contrasts with the original definition of the Anthropocene as the last c. 250 years (since the Industrial Revolution) and more recent proposals that the Anthropocene began some 5000 to 8000 years ago in the early to mid Holocene (the early-Anthropocene hypothesis). Anthropogenic soil horizons, of which several types are recognized, provide extensive terrestrial stratigraphic markers for defining the start of the Anthropocene. The pedosphere is regarded as the best indicator of the rise to dominance of human impacts on the total environment because it reflects strongly the growing impact of early civilisations over much of the Earth’s surface. Hence, the composition of anthropogenic soils is deemed more appropriate than atmospheric composition in providing ‘golden spikes’ for the Anthropocene.