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Item Open Access A formal Anthropocene is compatible with but distinct from its diachronous anthropogenic counterparts: a response to W.F. Ruddiman’s ‘three flaws in defining a formal Anthropocene’(Progress in Physical Geography, 2019-06-01) Zalasiewicz, J; Waters, CN; Head, MJ; Poirier, C; Summerhayes, CP; Leinfelder, R; Grinevald, J; Steffen, W; Syvitski, J; Haff, P; McNeill, JR; Wagreich, M; Fairchild, IJ; Richter, DD; Vidas, D; Williams, M; Barnosky, AD; Cearreta, A© The Author(s) 2019. We analyse the ‘three flaws’ to potentially defining a formal Anthropocene geological time unit as advanced by Ruddiman (2018). (1) We recognize a long record of pre-industrial human impacts, but note that these increased in relative magnitude slowly and were strongly time-transgressive by comparison with the extraordinarily rapid, novel and near-globally synchronous changes of post-industrial time. (2) The rules of stratigraphic nomenclature do not ‘reject’ pre-industrial anthropogenic signals – these have long been a key characteristic and distinguishing feature of the Holocene. (3) In contrast to the contention that classical chronostratigraphy is now widely ignored by scientists, it remains vital and widely used in unambiguously defining geological time units and is an indispensable part of the Earth sciences. A mounting body of evidence indicates that the Anthropocene, considered as a precisely defined geological time unit that begins in the mid-20th century, is sharply distinct from the Holocene.Item Open Access Changes in evapotranspiration and phenology as consequences of shrub removal in dry forests of central Argentina(Ecohydrology, 2015-10-01) Marchesini, VA; Fernández, RJ; Reynolds, JF; Sobrino, JA; Di Bella, CMMore than half of the dry woodlands (forests and shrublands) of the world are in South America, mainly in Brazil and Argentina, where in the last years intense land use changes have occurred. This study evaluated how the transition from woody-dominated to grass-dominated system affected key ecohydrological variables and biophysical processes over 20000ha of dry forest in central Argentina. We used a simplified surface energy balance model together with moderate-resolution imaging spectroradiometer-normalized difference vegetation index data to analyse changes in above primary productivity, phenology, actual evapotranspiration, albedo and land surface temperature for four complete growing seasons (2004-2009). The removal of woody vegetation decreased aboveground primary productivity by 15-21%, with an effect that lasted at least 4years, shortened the growing season between 1 and 3months and reduced evapotranspiration by as much as 30%. Albedo and land surface temperature increased significantly after the woody to grassland conversion. Our findings highlight the role of woody vegetation in regulating water dynamics and ecosystem phenology and show how changes in vegetative cover can influence regional climatic change. © 2015 John WileyItem Open Access Convergent evolution in lemur environmental niches(Journal of Biogeography, 2020-04-01) Herrera, JPAim: To test the hypothesis that adaptive convergent evolution of climate niches occurred in multiple independent lemur lineages. Location: Madagascar. Taxon: Lemurs. Methods: I collected climate and altitude data from WorldClim and summarized the niches of almost all living lemurs (83 species) into phylogenetically controlled principal components. To test for convergent evolution, I searched for multiple, similar climate optima using multi-peak Ornstein–Uhlenbeck models (surface, l1-ou, bayou). I compared the observed level of climate convergence to that simulated under neutral and single-optimum models. To test if behavioural or morphological traits were related to climate niches, I used phylogenetic regressions with activity pattern, diet, and body size. Results: From an ancestral niche with high rainfall and low seasonality, four lemur lineages independently converged on climate niche optima characterized by high temperatures and low rainfall, supporting adaptive evolution in southwest deciduous and arid habitats. The observed level of convergence was more frequent than expected under Brownian motion and single-optimum simulations, which illustrates that the results are likely not a result of stochastic evolution over long time periods. Nocturnal and cathemeral activity patterns were common among lineages in the arid climate niche. Conclusion: Lemur climate niche evolution demonstrated that convergence explains the distribution of four independent clades in hot, arid environments of southwest Madagascar. The timing of these convergent shifts coincided with the origination of modern arid-adapted plant genera, some of which are important lemur food sources. These communities have high endemicity and are especially threatened by habitat loss. Arid environments are arenas in which convergent evolution is predicted to occur frequently.Item Open Access Large trees drive forest aboveground biomass variation in moist lowland forests across the tropics(Global Ecology and Biogeography, 2013-12) Slik, JWF; Paoli, G; Mcguire, K; Amaral, I; Barroso, J; Bastian, M; Blanc, L; Bongers, F; Boundja, P; Clark, C; Collins, M; Dauby, G; Ding, Y; Doucet, J-L; Eler, E; Ferreira, L; Forshed, O; Fredriksson, G; Gillet, J-F; Harris, D; Leal, M; Laumonier, Y; Malhi, Y; Mansor, A; Martin, E; Miyamoto, K; Araujo-Murakami, A; Nagamasu, H; Nilus, R; Nurtjahya, E; Oliveira, A; Onrizal, O; Parada-Gutierrez, A; Permana, A; Poorter, L; Poulsen, J; Ramirez-Angulo, H; Reitsma, J; Rovero, F; Rozak, A; Sheil, D; Silva-Espejo, J; Silveira, M; Spironelo, W; ter Steege, H; Stevart, T; Navarro-Aguilar, GE; Sunderland, T; Suzuki, E; Tang, J; Theilade, I; van der Heijden, G; van Valkenburg, J; Van Do, T; Vilanova, E; Vos, V; Wich, S; Wöll, H; Yoneda, T; Zang, R; Zhang, M-G; Zweifel, NAim: Large trees (d.b.h.≥70cm) store large amounts of biomass. Several studies suggest that large trees may be vulnerable to changing climate, potentially leading to declining forest biomass storage. Here we determine the importance of large trees for tropical forest biomass storage and explore which intrinsic (species trait) and extrinsic (environment) variables are associated with the density of large trees and forest biomass at continental and pan-tropical scales. Location: Pan-tropical. Methods: Aboveground biomass (AGB) was calculated for 120 intact lowland moist forest locations. Linear regression was used to calculate variation in AGB explained by the density of large trees. Akaike information criterion weights (AICc-wi) were used to calculate averaged correlation coefficients for all possible multiple regression models between AGB/density of large trees and environmental and species trait variables correcting for spatial autocorrelation. Results: Density of large trees explained c. 70% of the variation in pan-tropical AGB and was also responsible for significantly lower AGB in Neotropical [287.8 (mean)±105.0 (SD) Mg ha-1] versus Palaeotropical forests (Africa 418.3±91.8 Mg ha-1; Asia 393.3±109.3 Mg ha-1). Pan-tropical variation in density of large trees and AGB was associated with soil coarseness (negative), soil fertility (positive), community wood density (positive) and dominance of wind dispersed species (positive), temperature in the coldest month (negative), temperature in the warmest month (negative) and rainfall in the wettest month (positive), but results were not always consistent among continents. Main conclusions: Density of large trees and AGB were significantly associated with climatic variables, indicating that climate change will affect tropical forest biomass storage. Species trait composition will interact with these future biomass changes as they are also affected by a warmer climate. Given the importance of large trees for variation in AGB across the tropics, and their sensitivity to climate change, we emphasize the need for in-depth analyses of the community dynamics of large trees. © 2013 John Wiley & Sons Ltd.Item Open Access Soil production and the soil geomorphology legacy of Grove Karl Gilbert(Soil Science Society of America Journal, 2020-01-01) Richter, DD; Eppes, MC; Austin, JC; Bacon, AR; Billings, SA; Brecheisen, Z; Ferguson, TA; Markewitz, D; Pachon, J; Schroeder, PA; Wade, AM© 2019 The Authors. Soil Science Society of America published by Wiley Periodicals, Inc. on behalf of Soil Science Society of America Geomorphologists are quantifying the rates of an important component of bedrock's weathering in research that needs wide discussion among soil scientists. By using cosmogenic nuclides, geomorphologists estimate landscapes’ physical lowering, which, in a steady landscape, equates to upward transfers of weathered rock into slowly moving hillslope-soil creep. Since the 1990s, these processes have been called “soil production” or “mobile regolith production”. In this paper, we assert the importance of a fully integrated pedological and geomorphological approach not only to soil creep but to soil, regolith, and landscape evolution; we clarify terms to facilitate soil geomorphology collaboration; and we seek a greater understanding of our sciences’ history. We show how the legacy of Grove Karl Gilbert extend across soil geomorphology. We interpret three contrasting soils and regoliths in the USA's Southern Piedmont in the context of a Gilbert-inspired model of weathering and transport, a model of regolith evolution and of nonsteady systems that liberate particles and solutes from bedrock and transport them across the landscape. This exercise leads us to conclude that the Southern Piedmont is a region with soils and regoliths derived directly from weathering bedrock below (a regional paradigm for more than a century) but that the Piedmont also has significant areas in which regoliths are at least partly formed from paleo-colluvia that may be massive in volume and overlie organic-enriched layers, peat, and paleo-saprolite. An explicitly integrated study of soil geomorphology can accelerate our understanding of soil, regoliths, and landscape evolution in all physiographic regions.Item Open Access Stratigraphic and Earth System approaches to defining the Anthropocene(Earth's Future, 2016-08-01) Steffen, W; Leinfelder, R; Zalasiewicz, J; Waters, CN; Williams, M; Summerhayes, C; Barnosky, AD; Cearreta, A; Crutzen, P; Edgeworth, M; Ellis, EC; Fairchild, IJ; Galuszka, A; Grinevald, J; Haywood, A; Ivar do Sul, J; Jeandel, C; McNeill, JR; Odada, E; Oreskes, N; Revkin, A; Richter, DDB; Syvitski, J; Vidas, D; Wagreich, M; Wing, SL; Wolfe, AP; Schellnhuber, HJ© 2016 The Authors. Stratigraphy provides insights into the evolution and dynamics of the Earth System over its long history. With recent developments in Earth System science, changes in Earth System dynamics can now be observed directly and projected into the near future. An integration of the two approaches provides powerful insights into the nature and significance of contemporary changes to Earth. From both perspectives, the Earth has been pushed out of the Holocene Epoch by human activities, with the mid-20th century a strong candidate for the start date of the Anthropocene, the proposed new epoch in Earth history. Here we explore two contrasting scenarios for the future of the Anthropocene, recognizing that the Earth System has already undergone a substantial transition away from the Holocene state. A rapid shift of societies toward the UN Sustainable Development Goals could stabilize the Earth System in a state with more intense interglacial conditions than in the late Quaternary climate regime and with little further biospheric change. In contrast, a continuation of the present Anthropocene trajectory of growing human pressures will likely lead to biotic impoverishment and a much warmer climate with a significant loss of polar ice.Item Open Access Towards a global drylands observing system: Observational requirements and institutional solutions(Land Degradation & Development, 2011) Verstraete; MM; Hutchinson, CF; Grainger, A; Smith, M Stafford; Scholes, RJ; REYNOLDS, JF; Barbosa, P; Léon, A; Mbow, CQuantitative data on dryland changes and their effects on the people living there are required to support policymaking and environmental management at all scales. Data are regularly acquired by international, national or local entities, but presently exhibit specific gaps. Promoting sustainable development in drylands necessitates a much stronger integration, coordination and synthesis of available information. Space-based remote sensing systems continue to play an important role but do not fulfill all needs. Dedicated networks and observing systems, operating over a wide range of scales and resolutions, are needed to address the key issues that concern decision-makers at the scale of local communities, countries and the international community. This requires a mixture of 'bottom-up' and 'top-down' design principles, and multiple ownership of the resultant system. This paper reviews the limitations of current observing systems and suggests establishing a Global Drylands Observing System, which would capitalize on the achievements of systems already established to support the other Rio Conventions. This Global Drylands Observing System would provide an integrated, coherent entry point and user interface to a range of underlying information systems, identify and help generate missing information, propose a set of standards for the acquisition, archiving and distribution of data where these are lacking, evaluate the quality and reliability of these data and promote scientific research in these fields by improving access to data. The paper outlines the principles and main objectives of a Global Drylands Observing System and calls for renewed efforts to invigorate cooperation mechanisms between the many global environmental conventions. Copyright © 2010 John Wiley & Sons, Ltd.Item Open Access Zostera marina meadows from the Gulf of California: conservation status(Biodiversity and Conservation, 2016-02-01) Lopez-Calderon, Jorge M; Riosmena-Rodríguez, Rafael; Torre, Jorge; Meling, Alf; Basurto, Xavier© 2016, Springer Science+Business Media Dordrecht. Eelgrass (Zostera marina) population estimates show a decreasing trend worldwide in the second half of the twentieth century. Mexico lacks long-term time series to determine trends for major eelgrass populations and has made no conservation efforts. Therefore, we present the first report on the historic presence of this annual coastal ecosystem in two wetlands of the Gulf of California (GC), the Infiernillo Channel (CIF, largest Z. marina population inside GC) and Concepcion Bay (BCP, the only eelgrass population along GC’s west coast), combining field surveys (1999–2010), aerial photography (2000–2010), satellite imagery (1972–2005), and published reports (1994–2007). Three parameters were used as indicators of conservation status: shoot density, seed banks, and aerial coverage. Average shoot density in the CIF (741 shoots m−2) was 3.8 times higher than in BCP (194 shoots m−2), and average seed bank density was similar in both wetlands (17,442 seeds m−2 vs. 17,000 seeds m−2). Opportunistic seagrass Ruppia maritima was observed in both wetlands, with higher abundance in summer when Z. marina disappears due to high water temperatures. Eelgrass coverage was three orders of magnitude greater in the CIF (9725 ha) than in BCP (3 ha). The striking difference between these wetlands is the lack of environmental protection for BCP and the protection of the CIF by the Seri indigenous community, which increases human pressure in the former, putting it at high risk of disappearing. Conservation of eelgrass meadows is not only necessary to preserve their ecosystem services but to insure the survival of migratory populations (Pacific brant goose, Branta bernicla), endangered species (Black turtle, Chelonia mydas), and fisheries-related species.