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Erle C Ellis - One of the best experts on this subject based on the ideXlab platform.
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the anthropocene Biosphere
The Anthropocene Review, 2015Co-Authors: Mark Williams, Jan Zalasiewicz, Anthony D Barnosky, P K Haff, Christian Schwagerl, Erle C EllisAbstract:The geological record preserves evidence for two fundamental stages in the evolution of Earth’s Biosphere, a microbial stage from ~3.5 to 0.65 Ga, and a metazoan stage evident by c. 650 Ma. We suggest that the modern Biosphere differs significantly from these previous stages and shows early signs of a new, third stage of Biosphere evolution characterised by: (1) global homogenisation of flora and fauna; (2) a single species (Homo sapiens) commandeering 25–40% of net primary production and also mining fossil net primary production (fossil fuels) to break through the photosynthetic energy barrier; (3) human-directed evolution of other species; and (4) increasing interaction of the Biosphere with the technosphere (the global emergent system that includes humans, technological artefacts, and associated social and technological networks). These unique features of today’s Biosphere may herald a new era in the planet’s history that could persist over geological timescales.
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anthropogenic transformation of the terrestrial Biosphere
Philosophical Transactions of the Royal Society B, 2011Co-Authors: Erle C EllisAbstract:Human populations and their use of land have transformed most of the terrestrial Biosphere into anthropogenic biomes (anthromes), causing a variety of novel ecological patterns and processes to emerge. To assess whether human populations and their use of land have directly altered the terrestrial Biosphere sufficiently to indicate that the Earth system has entered a new geological epoch, spatially explicit global estimates of human populations and their use of land were analysed across the Holocene for their potential to induce irreversible novel transformation of the terrestrial Biosphere. Human alteration of the terrestrial Biosphere has been significant for more than 8000 years. However, only in the past century has the majority of the terrestrial Biosphere been transformed into intensively used anthromes with predominantly novel anthropogenic ecological processes. At present, even were human populations to decline substantially or use of land become far more efficient, the current global extent, duration, type and intensity of human transformation of ecosystems have already irreversibly altered the terrestrial Biosphere at levels sufficient to leave an unambiguous geological record differing substantially from that of the Holocene or any prior epoch. It remains to be seen whether the anthropogenic Biosphere will be sustained and continue to evolve.
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anthropogenic transformation of the biomes 1700 to 2000
Global Ecology and Biogeography, 2010Co-Authors: Erle C Ellis, Kees Klein Goldewijk, Stefan Siebert, Deborah Lightman, Navin RamankuttyAbstract: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.
Christopher T Reinhard - One of the best experts on this subject based on the ideXlab platform.
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effects of primitive photosynthesis on earth s early climate system
arXiv: Earth and Planetary Astrophysics, 2019Co-Authors: Kazumi Ozaki, Christopher T Reinhard, Eiichi Tajika, Peng K Hong, Yusuke NakagawaAbstract:The evolution of different forms of photosynthetic life has profoundly altered the activity level of the Biosphere, radically reshaping the composition of Earth's oceans and atmosphere over time. However, the mechanistic impacts of a primitive photosynthetic Biosphere on Earth's early atmospheric chemistry and climate are poorly understood. Here, we use a global redox balance model to explore the biogeochemical and climatological effects of different forms of primitive photosynthesis. We find that a hybrid ecosystem of H2-based and Fe-based anoxygenic photoautotrophs - organisms that perform photosynthesis without producing oxygen - gives rise to a strong nonlinear amplification of Earth's methane (CH4) cycle, and would thus have represented a critical component of Earth's early climate system before the advent of oxygenic photosynthesis. Using a Monte Carlo approach, we find that a hybrid photosynthetic Biosphere widens the range of geochemical conditions that allow for warm climate states well beyond either of these metabolic processes acting in isolation. Our results imply that Earth's early climate was governed by a novel and poorly explored set of regulatory feedbacks linking the anoxic Biosphere and the coupled H, C and Fe cycles. We suggest that similar processes should be considered when assessing the potential for sustained habitability on Earth-like planets with reducing atmospheres.
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atmospheric seasonality as an exoplanet biosignature
arXiv: Earth and Planetary Astrophysics, 2018Co-Authors: Edward W Schwieterman, Christopher T Reinhard, Stephanie L Olson, Andy Ridgwell, Stephen R Kane, Victoria S MeadowsAbstract:Current investigations of exoplanet biosignatures have focused on static evidence of life, such as the presence of biogenic gases like O2 or CH4. However, the expected diversity of terrestrial planet atmospheres and the likelihood of both false positives and false negatives for conventional biosignatures motivate exploration of additional life detection strategies, including time-varying signals. Seasonal variation in atmospheric composition is a biologically modulated phenomenon on Earth that may occur elsewhere because it arises naturally from the interplay between the Biosphere and time-variable insolation. The search for seasonality as a biosignature would avoid many assumptions about specific metabolisms and provide an opportunity to directly quantify biological fluxes--allowing us to characterize, rather than simply recognize, Biospheres on exoplanets. Despite this potential, there have been no comprehensive studies of seasonality as an exoplanet biosignature. Here, we provide a foundation for further studies by reviewing both biological and abiological controls on the magnitude and detectability of seasonality of atmospheric CO2, CH4, O2, and O3 on Earth. We also consider an example of an inhabited world for which atmospheric seasonality may be the most notable expression of its Biosphere. We show that life on a low O2 planet like the weakly oxygenated mid-Proterozoic Earth could be fingerprinted by seasonal variation in O3 as revealed in its UV Hartley-Huggins bands. This example highlights the need for UV capabilities in future direct-imaging telescope missions (e.g., LUVOIR/HabEx) and illustrates the diagnostic importance of studying temporal biosignatures for exoplanet life detection/characterization.
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atmospheric seasonality as an exoplanet biosignature
The Astrophysical Journal, 2018Co-Authors: Edward W Schwieterman, Christopher T Reinhard, Stephanie L Olson, Andy Ridgwell, Stephen R Kane, Victoria S MeadowsAbstract:Author(s): Olson, SL; Schwieterman, EW; Reinhard, CT; Ridgwell, A; Kane, SR; Meadows, VS; Lyons, TW | Abstract: © 2018. The American Astronomical Society. All rights reserved. Current investigations of exoplanet biosignatures have focused on static evidence of life, such as the presence of biogenic gases like O2 or CH4. However, the expected diversity of terrestrial planet atmospheres and the likelihood of both "false positives" and "false negatives" for conventional biosignatures motivate exploration of additional life detection strategies, including time-varying signals. Seasonal variation in atmospheric composition is a biologically modulated phenomenon on Earth that may occur elsewhere because it arises naturally from the interplay between the Biosphere and time-variable insolation. The search for seasonality as a biosignature would avoid many assumptions about specific metabolisms and provide an opportunity to directly quantify biological fluxes - allowing us to characterize, rather than simply recognize, Biospheres on exoplanets. Despite this potential, there have been no comprehensive studies of seasonality as an exoplanet biosignature. Here, we provide a foundation for further studies by reviewing both biological and abiological controls on the magnitude and detectability of seasonality of atmospheric CO2, CH4, O2, and O3 on Earth. We also consider an example of an inhabited world for which atmospheric seasonality may be the most notable expression of its Biosphere. We show that life on a low O2 planet like the weakly oxygenated mid-Proterozoic Earth could be fingerprinted by seasonal variation in O3 as revealed in its UV Hartley-Huggins bands. This example highlights the need for UV capabilities in future direct-imaging telescope missions (e.g., LUVOIR/HabEx) and illustrates the diagnostic importance of studying temporal biosignatures for exoplanet life detection/characterization.
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effects of primitive photosynthesis on earth s early climate system
Nature Geoscience, 2018Co-Authors: Christopher T Reinhard, Kazumi Ozaki, Eiichi Tajika, Peng K Hong, Yusuke NakagawaAbstract:The evolution of different forms of photosynthetic life has profoundly altered the activity level of the Biosphere, radically reshaping the composition of Earth’s oceans and atmosphere over time. However, the mechanistic impacts of a primitive photosynthetic Biosphere on Earth’s early atmospheric chemistry and climate are poorly understood. Here, we use a global redox balance model to explore the biogeochemical and climatological effects of different forms of primitive photosynthesis. We find that a hybrid ecosystem of H2-based and Fe2+-based anoxygenic photoautotrophs—organisms that perform photosynthesis without producing oxygen—gives rise to a strong nonlinear amplification of Earth’s methane (CH4) cycle, and would thus have represented a critical component of Earth’s early climate system before the advent of oxygenic photosynthesis. Using a Monte Carlo approach, we find that a hybrid photosynthetic Biosphere widens the range of geochemical conditions that allow for warm climate states well beyond either of these metabolic processes acting in isolation. Our results imply that the Earth’s early climate was governed by a novel and poorly explored set of regulatory feedbacks linking the anoxic Biosphere and the coupled H, C and Fe cycles. We suggest that similar processes should be considered when assessing the potential for sustained habitability on Earth-like planets with reducing atmospheres.
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false negatives for remote life detection on ocean bearing planets lessons from the early earth
Astrobiology, 2017Co-Authors: Christopher T Reinhard, Edward W Schwieterman, Stephanie L Olson, Timothy W LyonsAbstract:Ocean-atmosphere chemistry on Earth has undergone dramatic evolutionary changes throughout its long history, with potentially significant ramifications for the emergence and long-term stability of atmospheric biosignatures. Though a great deal of work has centered on refining our understanding of false positives for remote life detection, much less attention has been paid to the possibility of false negatives, that is, cryptic Biospheres that are widespread and active on a planet's surface but are ultimately undetectable or difficult to detect in the composition of a planet's atmosphere. Here, we summarize recent developments from geochemical proxy records and Earth system models that provide insight into the long-term evolution of the most readily detectable potential biosignature gases on Earth-oxygen (O2), ozone (O3), and methane (CH4). We suggest that the canonical O2-CH4 disequilibrium biosignature would perhaps have been challenging to detect remotely during Earth's ∼4.5-billion-year history and that in general atmospheric O2/O3 levels have been a poor proxy for the presence of Earth's Biosphere for all but the last ∼500 million years. We further suggest that detecting atmospheric CH4 would have been problematic for most of the last ∼2.5 billion years of Earth's history. More broadly, we stress that internal oceanic recycling of biosignature gases will often render surface Biospheres on ocean-bearing silicate worlds cryptic, with the implication that the planets most conducive to the development and maintenance of a pervasive Biosphere will often be challenging to characterize via conventional atmospheric biosignatures. Key Words: Biosignatures-Oxygen-Methane-Ozone-Exoplanets-Planetary habitability. Astrobiology 17, 287-297.
Abraham Loeb - One of the best experts on this subject based on the ideXlab platform.
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potential for liquid water biochemistry deep under the surfaces of the moon mars and beyond
The Astrophysical Journal, 2020Co-Authors: Manasvi Lingam, Abraham LoebAbstract:We investigate the prospects for the past or current existence of habitable conditions deep underneath the surfaces of the Moon and Mars as well as generic bound and free-floating extrasolar rocky objects. We construct a simple model that takes into account the thermal limits of life as well as the size, surface temperature, and relative radionuclide abundance of a given object and yields the spatial extent of the subsurface habitable region. We also investigate the constraint imposed by pressure on habitability, and show that it is unlikely to rule out the prospects for life altogether. We estimate the maximum biomass that might be sustainable in deep subsurface environments as a function of the aforementioned parameters from an energetic perspective. We find that it might be a few percent that of Earth's subsurface Biosphere, and three orders of magnitude smaller than Earth's global biomass, under ideal circumstances. We conclude with a brief exposition of the prevalence of rocky objects with deep Biospheres and methods for detecting signatures of biological activity through forthcoming missions to visit the Moon and Mars.
Meriem Bouamrane - One of the best experts on this subject based on the ideXlab platform.
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Stakeholder engagement and biodiversity conservation challenges in social-ecological systems: some insights from Biosphere reserves in western Africa and France
Ecology and Society, 2016Co-Authors: Meriem Bouamrane, Marja Spierenburg, Arun Agrawal, Amadou Boureima, Marie-christine Cormier-salem, Michel Etienne, Christophe Le Page, Harold Levrel, Raphaël MathevetAbstract:Biosphere reserves are an example of social-ecological systems that combine biodiversity conservation and socioeconomic development with knowledge generation and dissemination (both scientific and local). We review lessons learned from case studies Biosphere reserves in western African and France, highlighting the importance of early stakeholder engagement to build knowledge for achieving sustainable development. We discuss the evolution of the concept of Biosphere reserves and its application over time in different socioeconomic and cultural settings. The diversity of stakeholders and their different needs and perceptions about nature conservation complicate implementation processes, sometimes resulting in conflicts about the objectives and zonation of Biosphere reserves. Dialogue among the different stakeholders must start at an early planning phase and be based on the principle of social and ecological solidarity. Dialogue must then be pursued, formalized, ritualized, and translated both in terms of Biosphere reserve management and in terms of political support. Tools and methods exist that can facilitate such dialogue and colearning.
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reporting progress on internationally designated sites the periodic review of Biosphere reserves
Environmental Science & Policy, 2010Co-Authors: Martin F Price, Jung Jin Park, Meriem BouamraneAbstract:For sites designated within international networks, reporting processes have been established to ensure that these sites continue to exhibit their special characteristics and contribute to the goals of their respective network. One such network is the World Network of Biosphere Reserves (WNBR), composed of sites designated under UNESCO’s Man and the Biosphere programme. This paper summarises the evolution of the concept and the realities of Biosphere reserves since 1976; describes the introduction of the Statutory Framework for the WNBR, which formalised the concept and introduced a periodic review process to provide oversight of its implementation; evaluates the extent to which, since 1996, this process has been successful in achieving its aims; discusses changes which have been proposed and implemented; and provides suggestions for future action.
Raphaël Mathevet - One of the best experts on this subject based on the ideXlab platform.
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Stakeholder engagement and biodiversity conservation challenges in social-ecological systems: some insights from Biosphere reserves in western Africa and France
Ecology and Society, 2016Co-Authors: Meriem Bouamrane, Marja Spierenburg, Arun Agrawal, Amadou Boureima, Marie-christine Cormier-salem, Michel Etienne, Christophe Le Page, Harold Levrel, Raphaël MathevetAbstract:Biosphere reserves are an example of social-ecological systems that combine biodiversity conservation and socioeconomic development with knowledge generation and dissemination (both scientific and local). We review lessons learned from case studies Biosphere reserves in western African and France, highlighting the importance of early stakeholder engagement to build knowledge for achieving sustainable development. We discuss the evolution of the concept of Biosphere reserves and its application over time in different socioeconomic and cultural settings. The diversity of stakeholders and their different needs and perceptions about nature conservation complicate implementation processes, sometimes resulting in conflicts about the objectives and zonation of Biosphere reserves. Dialogue among the different stakeholders must start at an early planning phase and be based on the principle of social and ecological solidarity. Dialogue must then be pursued, formalized, ritualized, and translated both in terms of Biosphere reserve management and in terms of political support. Tools and methods exist that can facilitate such dialogue and colearning.