A practical solution: the Anthropocene is a geological event, not a formal epoch

The Anthropocene has yet to be defined in a way that is functional both to the international geological community and to the broader fields of environmental and social sciences. Formally defining the Anthropocene as a chronostratigraphical series and geochronological epoch with a precise global start date would drastically reduce the Anthropocene’s utility across disciplines. Instead, we propose the Anthropocene be defined as a geological event, thereby facilitating a robust geological definition linked with a scholarly framework more useful to and congruent with the many disciplines engaging with human-environment interactions. Unlike formal epochal definitions, geological events can recognize the spatial and temporal heterogeneity and diverse social and environmental processes that interact to produce anthropogenic global environmental changes. Consequently, an Anthropocene Event would incorporate a far broader range of transformative human cultural practices and would be more readily applicable across academic fields than an Anthropocene Epoch, while still enabling a robust stratigraphic characterization

Forecasting the response of Earth's surface to future climatic and land use changes: a review of methods and research needs

In the future, Earth will be warmer, precipitation events will be more extreme, global mean sea level will rise, and many arid and semiarid regions will be drier. Human modifications of landscapes will also occur at an accelerated rate as developed areas increase in size and population density. We now have gridded global forecasts, being continually improved, of the climatic and land use changes (C&LUC) that are likely to occur in the coming decades. However, besides a few exceptions, consensus forecasts do not exist for how these C&LUC will likely impact Earth-surface processes and hazards. In some cases, we have the tools to forecast the geomorphic responses to likely future C&LUC. Fully exploiting these models and utilizing these tools will require close collaboration among Earth-surface scientists and Earth-system modelers. This paper assesses the state-of-the-art tools and data that are being used or could be used to forecast changes in the state of Earth's surface as a result of likely future C&LUC. We also propose strategies for filling key knowledge gaps, emphasizing where additional basic research and/or collaboration across disciplines are necessary. The main body of the paper addresses cross-cutting issues, including the importance of nonlinear/threshold-dominated interactions among topography, vegetation, and sediment transport, as well as the importance of alternate stable states and extreme, rare events for understanding and forecasting Earth-surface response to C&LUC. Five supplements delve into different scales or process zones (global-scale assessments and fluvial, aeolian, glacial/periglacial, and coastal process zones) in detail

Forecasting the Response of Earth\u27s Surface to Future Climatic and Land Use Changes: A Review of Methods and Research Needs

In the future, Earth will be warmer, precipitation events will be more extreme, global mean sea level will rise, and many arid and semiarid regions will be drier. Human modifications of landscapes will also occur at an accelerated rate as developed areas increase in size and population density. We now have gridded global forecasts, being continually improved, of the climatic and land use changes (C&LUC) that are likely to occur in the coming decades. However, besides a few exceptions, consensus forecasts do not exist for how these C&LUC will likely impact Earth-surface processes and hazards. In some cases, we have the tools to forecast the geomorphic responses to likely future C&LUC. Fully exploiting these models and utilizing these tools will require close collaboration among Earth-surface scientists and Earth-system modelers. This paper assesses the state-of-the-art tools and data that are being used or could be used to forecast changes in the state of Earth\u27s surface as a result of likely future C&LUC. We also propose strategies for filling key knowledge gaps, emphasizing where additional basic research and/or collaboration across disciplines are necessary. The main body of the paper addresses cross-cutting issues, including the importance of nonlinear/threshold-dominated interactions among topography, vegetation, and sediment transport, as well as the importance of alternate stable states and extreme, rare events for understanding and forecasting Earth-surface response to C&LUC. Five supplements delve into different scales or process zones (global-scale assessments and fluvial, aeolian, glacial/periglacial, and coastal process zones) in detail

Subfossil leaves reveal a new upland hardwood component of the pre-European Piedmont landscape,Lancaster County, Pennsylvania.

Widespread deforestation, agriculture, and construction of milldams by European settlers greatly influenced valley-bottom stream morphology and riparian vegetation in the northeastern USA. The former broad, tussock-sedge wetlands with small, anastomosing channels were converted into today's incised, meandering streams with unstable banks that support mostly weedy, invasive vegetation. Vast accumulations of fine-grained "legacy" sediments that blanket the regional valley-bottom Piedmont landscape now are being reworked from stream banks, significantly impairing the ecological health of downstream water bodies, most notably the Chesapeake Bay. However, potential restoration is impaired by lack of direct knowledge of the pre-settlement riparian and upslope floral ecosystems. We studied the subfossil leaf flora of Denlingers Mill, an obsolete (breached) milldam site in southeastern Pennsylvania that exhibits a modern secondary forest growing atop thin soils, above bedrock outcrops immediately adjacent to a modified, incised stream channel. Presumably, an overhanging old-growth forest also existed on this substrate until the early 1700s and was responsible for depositing exceptionally preserved, minimally transported subfossil leaves into hydric soil strata, which immediately underlie post-European settlement legacy sediments. We interpret the eleven identified species of the subfossil assemblage to primarily represent a previously unknown, upland Red Oak-American Beech mixed hardwood forest. Some elements also appear to belong to a valley-margin Red Maple-Black Ash swamp forest, consistent with preliminary data from a nearby site. Thus, our results add significantly to a more complete understanding of the pre-European settlement landscape, especially of the hardwood tree flora. Compared with the modern forest, it is apparent that both lowland and upslope forests in the region have been modified significantly by historical activities. Our study underscores that generally overlooked subfossil leaves can provide important, local, temporally constrained paleoecological data, with much potential value in this case for stream and wetland restoration decisions in the mid-Atlantic region

Radiocarbon ages of leaf macrofossils from Denlingers Mill.

<p><i>Footnotes</i>: In uncalibrated years BP & calibrated calendar years AD; analytical uncertainties of calibrated ages ±2 sigma. Calibrated ages obtained using CalPal 2007 online radiocarbon calibration package <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079317#pone.0079317-Danzeglocke1" target="_blank">[69]</a> available: <a href="http://www.calpal-online.de/" target="_blank">http://www.calpal-online.de/</a>. Samples were analyzed for accelerator mass spectrometry (AMS) radiocarbon dating at the Center for Applied Isotope Studies, University of Georgia.</p

Stratigraphic profile of the Denlingers Mill leaf mat site.

<p>Green blocks indicate the presence of dense leaf mat layers within the hydric soil unit. Subfossil leaves in this study were taken from all leaf mat layers. Yellow triangles indicate locations of samples taken for ¹⁴C dating. The X at the top of the section represents the covered interval. See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079317#pone-0079317-g002" target="_blank">Figure 2</a>.</p

Denlingers Mill leaf mat site (arrow).

<p>(A) Limestone and phyllite bedrock and quartz gravel composing channel bed. (B) Darker hydric soil layer containing plant macrofossils. (C) Approximately 4 m of silty legacy sediment. (D) Exposed bedrock supporting a contemporary riparian forest. Arrow points to exposure from which all subfossils for this study were collected. Each scale bar unit = 1 m. See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079317#pone-0079317-g003" target="_blank">Figure 3</a>.</p

<i>Acer spicatum</i> (Mountain Maple).

<p>(A) Whole subfossil EMS 419502. (B) EMS 419502, axillary tufts of acicular, aduncate, and filiform trichomes. Epifluorescence image. (C) Dense acicular, aduncate, and filiform basal trichomes of sample EMS 419502. Epifluorescence image. (D) and (E) <i>Acer spicatum</i> reference image from sample M5-2 of the Allegheny National Forest, Pennsylvania collection <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079317#pone.0079317-Hardin1" target="_blank">[72]</a>. Epifluorescence images. (D) Image shows axillary tufts with the same types and configuration of trichomes as (B), while (E) exhibits the same dense basal trichomes seen in (C).</p