Earth System Functioning Research Articles

Biocrust ecology: unifying micro- and macro-scales to confront global change.

Biocrust ecology: unifying micro- and macro-scales to confront global change.

Methods and approaches to modelling the Anthropocene

The ‘Anthropocene’ concept provides a conceptual framework that encapsulates the current global situation in which society has an ever-greater dominating influence on Earth System functioning. Simulation models used to understand earth system dynamics provide early warning, scenario analysis and evaluation of environmental management and policies. This paper aims to assess the extent to which current models represent the Anthropocene and suggest ways forward. Current models do not fully reflect the typical characteristics of the Anthropocene, such as societal influences and interactions with natural processes, feedbacks and system dynamics, tele-connections, tipping points, thresholds and regime shifts. Based on an analysis of current model representations of Anthropocene dynamics, we identify ways to enhance the role of modeling tools to better help us understand Anthropocene dynamics and address sustainability issues arising from them. To explore sustainable futures (‘safe and operating spaces’), social processes and anthropogenic drivers of biophysical processes must be incorporated, to allow for a spectrum of potential impacts and responses at different societal levels. In this context, model development can play a major role in reconciling the different epistemologies of the disciplines that need to collaborate to capture changes in the functioning of socio-ecological systems. Feedbacks between system functioning and underlying endogenous drivers should be represented, rather than assuming the drivers to be exogenous to the modelled system or stationary in time and space. While global scale assessments are important, the global scale dynamics need to be connected to local realities and vice versa. The diversity of stakeholders and potential questions requires a diversification of models, avoiding the convergence towards single models that are able to answer a wide range of questions, but without sufficient specificity. The novel concept of the Anthropocene can help to develop innovative model representations and model architectures that are better suited to assist in designing sustainable solutions targeted at the users of the models and model results.

Geographies of the Anthropocene

Introduction If humans have become a rival to Nature, then the epic nomenclature of the great forces – the eras, periods, and epochs of geological time – have finally been reconciled with the social, something geographers might cheer or lament. For over a century, there have been calls to recognise human impact with its own geological epoch. The most recent of these calls – and the most significant given the unprecedented shift in Earth system functioning (Steffen et al., 2011) – proposes the name the Anthropocene (Crutzen and Stoermer, 2000). To date, the Anthropocene has been also the most successful in terms of its academic and popular reception. The proposal has led to an explosion of popular and academic debate among both scientific and social thinkers, and for both groups the proposal has refreshed long-standing exploration of the purported division between science and society (Rittel and Webber, 1973; Funtowicz and Ravetz, 1993). This paper introduces concepts and debates within a special issue of Geographical Research that deals with the Anthropocene. Our aim is to contribute to and help consolidate the rapidly expanding discourse that explores humanity as akin to a geological force, but with the added emphasis on geography and geographers. Geographers have a history of both being wary of ‘buzzwords’, only with hindsight to lament missed opportunities when those buzzwords are adopted by other disciplines and become the convention (see environmental studies). Is the ‘Anthropocene’ a fad, an important idea that should be embraced by geographers, or something altogether different? The notion of the Anthropocene is not so far settled that it cannot be influenced by the discipline of Geography, and there is reason to think that Geography has much to offer regardless of whether the concept becomes widely or popularly adopted or discarded. More important than the issue of its definition are the moral, cultural, and political challenges that the Anthropocene is amplifying. Geographers, then, have an opportunity to consider the concept during its ‘adolescence’ (cf Castree, 2014c) and to, simultaneously, consider whether and how the discipline might capitalise on what appears to be a rapid ascension. This ‘opportunity-challenge’ has been recognised and explored by geographers elsewhere (e.g. Dalby, 2007; Gibson-Graham, 2011; Yusoff, 2013b; Castree, 2014a; 2014b; 2014c; Johnson et al., 2014; Whitehead, 2014; Young, 2014), leading us to take up a promising and daunting issue to emerge from those Anthropocene-Geography discussions: whether and how this concept might present a ‘meeting place’ for the heterogeneous groups, framings, and sub-disciplinary specialisms that make up the discipline. The Anthropocene is a concept that is being adopted in wide and divergent ways. Our goal here is not in any way to establish consensus or impose direction, but to explore emergent themes in the context of Geography. The Anthropocene requires a sophisticated approach to space, time, knowledge, politics, social action, and, perhaps most of all, interactions between human and environmental systems, including the empirical and ontological blurring of these categories. As bs_bs_banner

The Global Precipitation Measurement Mission

Precipitation affects many aspects of our everyday life. It is the primary source of freshwater and has significant socioeconomic impacts resulting from natural hazards such as hurricanes, floods, droughts, and landslides. Fundamentally, precipitation is a critical component of the global water and energy cycle that governs the weather, climate, and ecological systems. Accurate and timely knowledge of when, where, and how much it rains or snows is essential for understanding how the Earth system functions and for improving the prediction of weather, climate, freshwater resources, and natural hazard events. The Global Precipitation Measurement (GPM) mission is an international satellite mission specifically designed to set a new standard for the measurement of precipitation from space and to provide a new generation of global rainfall and snowfall observations in all parts of the world every 3 h. The National Aeronautics and Space Administration (NASA) and the Japan Aerospace and Exploration Agency (JAXA) ...

Improving representation of leaf respiration in large‐scale predictive climate–vegetation models

Improving representation of leaf respiration in large‐scale predictive climate–vegetation models

中国土地利用空间格局动态变化模拟——以规划情景为例

土地利用变化研究在环境可持续发展研究领域中具有重要的地位,其空间分布格局的变化影响到生物地球化学循环、气候变化、生物多样性等。采用土地利用动态变化模型Dyna-CLUE模拟了在规划情景下中国土地利用变化未来空间分布格局。将土地利用类型分为六大类,即耕地、草地、林地、建设用地、水域和其它用地。驱动因子包括地形地貌、气候、社会交通等方面,对动态驱动因子如气温、降水、人口交通等,考虑了其在未来情景下的发展趋势。基于土地利用类型与驱动因子之间的定量关系和土地利用类型之间的转换规则等,模拟出至2020年中国土地利用分布格局。结果表明,至2020年,中国东南部、黄淮海平原、四川盆地等地区耕地面积将增加,东北、西北等农牧交错区、农林交错区和沙漠边缘耕地面积将会呈轻度减少趋势;林地面积将增加1417.91万hm²,主要发生在中国东北部以及西南部水热条件好的地区;中国草地在面积上保持稳定,空间上中东部、东南地区草地面积减少,内蒙古中部,青海东部,四川盆地北缘区和青藏高原等地面积增加;建设用地增加531.76万hm²,主要发生在中国的东部地区。;Land use change is a key subject in the research of sustainable development in environment. The spatial pattern of land use change closely related to earth system functioning, such as climate warming, biogeochemical circle and landscape biodiversity. In order to improve ecological environment and promote social development, a series of land use policies such as afforestation, restoration of degraded grassland and protection of cultivated land had been formulated. These policies will exert a great influence on the spatial pattern of land use in China. However, the land use policies only provide an overview of the land use changes at the national scale but can't give insight into the changes at the regional and landscape scales. In this paper, the Dyna-CLUE model, which is a dynamic, spatially explicit land use change model had been used to simulate the spatial pattern of land use change in China in the coming decades. The planned development scenario was developed, in which the total area for each land use types in the future were defined as required by the land use policies. The Chinese level land use demands were downscaled to land use pattern at 2 km² resolution. Six land use types were distinguished which are built-up land, arable land, grassland, forest land, water area and other land. The spatial allocation of land uses were simulated based on the location suitability and user-specified decision rules. The driving factors include climatic and economic condition, traffic situation, soil texture, topography and demography. Logistic regression was used to quantify the relation between land use patterns and these drving factors. Climatic factors, traffic and population were defined as dynamic driving factors. In the future, the HadCM3 B2 climatic scenario was adopted to provide climatic data; the spatial pattern of population was simulated by SMPD (surface modeling of population distribution), and the railway and road development plan was made by the government. Other stable driving factors such as topography, soil texture were assumed to remain unchanged in the future 15 years. The performance of the land use change model was validated, showing that this method can simulate the spatial pattern of land use change accurately. The results indicate that the area of cultivated land would keep no less than 120.33 million hectares, however, it would decrease in western region where the land is not suitable for cultivation and would increase in central south China. The forest area would increase by 14.28 million hectares, mainly in northeastern and southwestern China, where the climate is sufficiently hospitable for forest growth. The area of built-up land would increase by 5.3176 million hectares, mainly in eastern and southeastern regions of China which are characterized by high population density and advanced economy. The simulation has the potential to help decision makers and scientists identify the critical regions that need specific consideration. The high spatial resolution of the results enable the assessment of impact of land use change on a large number of environmental indicators, including climate change, carbon sequestration and landscape diversity.

Scenarios of changes in the spatial pattern of land use in China

Land use changes affect many aspects of Earth System functioning, for example in impacting global carbon cycle, contributing to climate change, or increasing soil erosion. The simulation of land use change is important in environmental impact assessment and land use planning. We assessed the land use scenarios of China in the next 100 years based on the SMLC (surface modelling of land cover change) model and Dyna-CLUE (dynamic conversion of land use and its effects) model. Three SRES scenarios were evaluated: Global Economy (A1FI): lean government, strong globalization; Continental Markets (A2a): lean government, regional culture and economic development; Regional communities (B2a): much government intervention, regional cultural and economic development. Ten land cover types were simulated, which are cultivated land, woodland, grassland, built-up land, water area, wetland, nival area, desert, bare rock and desertification land. The SMLC model was used to calculate changes in area for each land use types in the future at country level while the spatially explicit land use model Dyna-CLUE was used to simulate land use pattern at 2 km2 resolution based on the country level areas demands for each land cover type. The results show that the cultivated land would decrease in all of the three scenarios, while in the A2a scenario, the cultivated land would decrease with the lowest rate because of the high population growth, high level of market protection and low agricultural efficiency; in the B2a scenario, it would decrease with the highest rate caused by the decreased population numbers and increased crop productivity. The nival area would decrease with the highest rate in the A1FI scenario since the rapid introduce of new technology and the energy system is fossil intensive, which would discharge more greenhouse gas than other two scenarios. The area of natural ecosystems such as wood land, grassland, water area and wet land would increase significantly in the B2a scenario because this scenario puts more weight on environmental sustainability. The land use spatial pattern in China under the B2a scenario is simulated. The results are important to identify hotspots of land use change that need specific attention by the governments and the researchers.

Erratum to: Non-equilibrium thermodynamics and maximum entropy production in the earth system: Applications and implications

The Earth system is maintained in a unique state far from thermodynamic equilibrium, as, for instance, reflected in the high concentration of reactive oxygen in the atmosphere. The myriad of processes that transform energy, that result in the motion of mass in the atmosphere, in oceans, and on land, processes that drive the global water, carbon, and other biogeochemical cycles, all have in common that they are irreversible in their nature. Entropy production is a general consequence of these processes and measures their degree of irreversibility. The proposed principle of maximum entropy production (MEP) states that systems are driven to steady states in which they produce entropy at the maximum possible rate given the prevailing constraints. In this review, the basics of nonequilibrium thermodynamics are described, as well as how these apply to Earth system processes. Applications of the MEP principle are discussed, ranging from the strength of the atmospheric circulation, the hydrological cycle, and biogeochemical cycles to the role that life plays in these processes. Nonequilibrium thermodynamics and the MEP principle have potentially wide-ranging implications for our understanding of Earth system functioning, how it has evolved in the past, and why it is habitable. Entropy production allows us to quantify an objective direction of Earth system change (closer to vs further away from thermodynamic equilibrium, or, equivalently, towards a state of MEP). When a maximum in entropy production is reached, MEP implies that the Earth system reacts to perturbations primarily with negative feedbacks. In conclusion, this nonequilibrium thermodynamic view of the Earth system shows great promise to establish a holistic description of the Earth as one system. This perspective is likely to allow us to better understand and predict its function as one entity, how it has evolved in the past, and how it is modified by human activities in the future.

Climate-driven changes in coastal marine systems of western Europe

Coastal marine systems, the interface between the ocean and terrestrial realms, are among the most important systems on the planet both ecologically and economically because of their crucial role in earth system functioning. Although direct impacts of human activities on physical, chemical and biological components of these systems have been widely documented, the potential influence of climate variability is less well known. Here, we used data from Service d'Observation en Milieu Littoral (SOMLIT), a marine monitoring programme that has since 1997 collected samples at 12 sites located along the French coasts from 42° to 51° N. Applying standardised principal compo- nent analysis (PCA), we documented the year-to-year fluctuations in these coastal systems and eval- uated the potential influence of climate variability using data on atmospheric circulation (wind inten- sity and direction), precipitation and temperature. Our study revealed a pronounced sensitivity of these systems to climate variability. As the impact of climate change may become more prominent in the next decades, this study suggests that climate might strongly influence the marine coastal envi- ronment and act in synergism with other anthropogenic pressures to alter the state and functioning of biological and ecological systems and the services they provide.

Non-equilibrium thermodynamics, maximum entropy production and Earth-system evolution

The present-day atmosphere is in a unique state far from thermodynamic equilibrium. This uniqueness is for instance reflected in the high concentration of molecular oxygen and the low relative humidity in the atmosphere. Given that the concentration of atmospheric oxygen has likely increased throughout Earth-system history, we can ask whether this trend can be generalized to a trend of Earth-system evolution that is directed away from thermodynamic equilibrium, why we would expect such a trend to take place and what it would imply for Earth-system evolution as a whole. The justification for such a trend could be found in the proposed general principle of maximum entropy production (MEP), which states that non-equilibrium thermodynamic systems maintain steady states at which entropy production is maximized. Here, I justify and demonstrate this application of MEP to the Earth at the planetary scale. I first describe the non-equilibrium thermodynamic nature of Earth-system processes and distinguish processes that drive the system's state away from equilibrium from those that are directed towards equilibrium. I formulate the interactions among these processes from a thermodynamic perspective and then connect them to a holistic view of the planetary thermodynamic state of the Earth system. In conclusion, non-equilibrium thermodynamics and MEP have the potential to provide a simple and holistic theory of Earth-system functioning. This theory can be used to derive overall evolutionary trends of the Earth's past, identify the role that life plays in driving thermodynamic states far from equilibrium, identify habitability in other planetary environments and evaluate human impacts on Earth-system functioning.

Web-enabled Landsat Data (WELD): Landsat ETM+ composited mosaics of the conterminous United States

Since January 2008, the U.S. Department of Interior / U.S. Geological Survey have been providing free terrain-corrected (Level 1T) Landsat Enhanced Thematic Mapper Plus (ETM+) data via the Internet, currently for acquisitions with less than 40% cloud cover. With this rich dataset, temporally composited, mosaics of the conterminous United States (CONUS) were generated on a monthly, seasonal, and annual basis using 6521 ETM+ acquisitions from December 2007 to November 2008. The composited mosaics are designed to provide consistent Landsat data that can be used to derive land cover and geo-physical and bio-physical products for detailed regional assessments of land-cover dynamics and to study Earth system functioning. The data layers in the composited mosaics are defined at 30 m and include top of atmosphere (TOA) reflectance, TOA brightness temperature, TOA normalized difference vegetation index (NDVI), the date each composited pixel was acquired on, per-band radiometric saturation status, cloud mask values, and the number of acquisitions considered in the compositing period. Reduced spatial resolution browse imagery, and top of atmosphere 30 m reflectance time series extracted from the monthly composites, capture the expected land surface phenological change, and illustrate the potential of the composited mosaic data for terrestrial monitoring at high spatial resolution. The composited mosaics are available in 501 tiles of 5000 × 5000 30 m pixels in the Albers equal area projection and are downloadable at http://landsat.usgs.gov/WELD.php. The research described in this paper demonstrates the potential of Landsat data processing to provide a consistent, long-term, large-area, data record.

Nonequilibrium thermodynamics and maximum entropy production in the Earth system

The Earth system is maintained in a unique state far from thermodynamic equilibrium, as, for instance, reflected in the high concentration of reactive oxygen in the atmosphere. The myriad of processes that transform energy, that result in the motion of mass in the atmosphere, in oceans, and on land, processes that drive the global water, carbon, and other biogeochemical cycles, all have in common that they are irreversible in their nature. Entropy production is a general consequence of these processes and measures their degree of irreversibility. The proposed principle of maximum entropy production (MEP) states that systems are driven to steady states in which they produce entropy at the maximum possible rate given the prevailing constraints. In this review, the basics of nonequilibrium thermodynamics are described, as well as how these apply to Earth system processes. Applications of the MEP principle are discussed, ranging from the strength of the atmospheric circulation, the hydrological cycle, and biogeochemical cycles to the role that life plays in these processes. Nonequilibrium thermodynamics and the MEP principle have potentially wide-ranging implications for our understanding of Earth system functioning, how it has evolved in the past, and why it is habitable. Entropy production allows us to quantify an objective direction of Earth system change (closer to vs further away from thermodynamic equilibrium, or, equivalently, towards a state of MEP). When a maximum in entropy production is reached, MEP implies that the Earth system reacts to perturbations primarily with negative feedbacks. In conclusion, this nonequilibrium thermodynamic view of the Earth system shows great promise to establish a holistic description of the Earth as one system. This perspective is likely to allow us to better understand and predict its function as one entity, how it has evolved in the past, and how it is modified by human activities in the future.

Entropy production by evapotranspiration and its geographic variation

The hydrologic cycle is a system far from thermodynamic equilibrium that is characterized by its rate of entropy production in the climatological mean steady state. Over land, the hydrologic cycle is strongly affected by the presence of terrestrial vegetation. In order to investigate the role of the biota in the hydrologic cycle, it is critical to investigate the consequences of biotic effects from this thermodynamic perspective. Here I quantify entropy production by evapotranspiration with a climate system model of intermediate complexity and estimate its sensitivity to vegetation cover. For present-day conditions, the global mean entropy production of evaporation is 8.4 mW/m<sup>2</sup>/K, which is about 1/3 of the estimated entropy production of the whole hydrologic cycle. On average, ocean surfaces generally produce more than twice as much entropy as land surfaces. On land, high rates of entropy production of up to 16 mW/m<sup>2</sup>/K are found in regions of high evapotranspiration, although relative humidity of the atmospheric boundary layer is also an important factor. With an additional model simulation of a “Desert” simulation, where the effects of vegetation on land surface functioning is removed, I estimate the sensitivity of these entropy production rates to the presence of vegetation. Land averaged evapotranspiration decreases from 2.4 to 1.4 mm/d, while entropy production is reduced comparatively less from 4.2 to 3.1 mW/m<sup>2</sup>/K. This is related to the reduction in relative humidity of the atmospheric boundary layer as a compensatory effect, and points out the importance of a more complete treatment of entropy production calculations to investigate the role of biotic effects on Earth system functioning.

The Anthropocene: Are Humans Now Overwhelming the Great Forces of Nature

We explore the development of the Anthropocene, the current epoch in which humans and our societies have become a global geophysical force. The Anthropocene began around 1800 with the onset of industrialization, the central feature of which was the enormous expansion in the use of fossil fuels. We use atmospheric carbon dioxide concentration as a single, simple indicator to track the progression of the Anthropocene. From a preindustrial value of 270-275 ppm, atmospheric carbon dioxide had risen to about 310 ppm by 1950. Since then the human enterprise has experienced a remarkable explosion, the Great Acceleration, with significant consequences for Earth System functioning. Atmospheric CO2 concentration has risen from 310 to 380 ppm since 1950, with about half of the total rise since the preindustrial era occurring in just the last 30 years. The Great Acceleration is reaching criticality. Whatever unfolds, the next few decades will surely be a tipping point in the evolution of the Anthropocene.

The Arctic in an Earth System Context: From Brake to Accelerator of Change

Human activities over the past few centuries have profoundly changed the functioning of the earth system as a whole. These changes are particularly evident in the high latitudes of the Northern Hemisphere, where environmental change has been pronounced and rapid. Such changes have implications beyond the region, as they can lead to two important feedback processes: the ice-albedo feedback and the terrestrial carbon cycle-climate feedback. These processes play an exceptionally important role in earth system functioning, particularly because they may switch this century from damping the effects of anthropogenic climate change to accelerating them. Rapid environmental change in the high latitudes also has consequences for issues of direct importance to humans, particularly water resources.

Beyond Gaia: Thermodynamics of Life and Earth System Functioning

Are there any general principles that govern the way in which life affects Earth system functioning? Most prominently, the Gaia hypothesis addresses this question by proposing that near-homeostatic conditions on Earth have been maintained “by and for the biosphere.” Here the role of the biota in the Earth system is described from a viewpoint of nonequilibrium thermodynamics, particularly with respect to the hypothesis of maximum entropy production (MEP). It is argued that the biota introduce additional degrees of freedom to Earth system processes. Therefore, we should expect biotic activity, and Earth system processes affected by the biota, to evolve to states of MEP. The consistent effects of the biota on entropy production are demonstrated with a conceptual model of biogeochemical cycling, by using extreme climate model simulations of a “Desert World” and a “Green Planet”, and by a simple coupled climate-carbon cycle model. It is shown that homeostatic behavior can emerge from a state of MEP associated with the planetary albedo. This thermodynamic perspective is then discussed in the context of the original Gaia hypothesis and in light of a recent discussion in Climatic Change. Potential implications of the MEP hypothesis for global change research are also discussed. It is concluded that the resulting behavior of a biotic Earth at a state of MEP may well lead to near-homeostatic behavior of the Earth system on long time scales, as stated by the Gaia hypothesis. However, here homeostasis is a result of the application of the MEP hypothesis to biotically influenced processes rather than a postulate. Besides providing a fundamental perspective on homeostasis, the MEP hypothesis also provides a framework to understand why photosynthetic life would be a highly probable emergent characteristic of the Earth system and why the diversity of life is an important characteristic of Earth system functioning.

Emergence of the Study of Global Ecology: Is Terrestrial Ecology an Impediment to Progress?

The emergence of the study of how the earth system operates and is responding to global change has seen the development of large-scale cross-disciplinary research efforts in addition to progress in traditional single-discipline, single-investigator approaches. Although terrestrial (I use this word in the broad sense to include continental systems encompassing terrestrial, wetland, lake, and river ecosystems) ecology is a central area of research for understanding earth system functioning, this field has not engaged in, nor has it the mechanisms for, strategic research planning, and thus it has not provided the momentum apparent in the allied earth sciences. The development and execution of the International Geosphere-Biosphere Program provides one forum for more integrated research planning by ecologists, as well as research opportunities along the entire spectrum of concern of this discipline. However, there needs to be a national focal point for continuing strategic planning for research in terrestrial ecology.