Competing discourses of nature in exurbia

This paper explores different ways that the category of nature is used in addressing landscape changes associated with exurbia and exurbanization. Nature is an important category in the practices and representations that residents and planners use to construct and maintain exurban landscapes. However, common ways of mobilizing nature in exurban planning discourses often obstruct better discussion, rather than facilitate it. Invoking nature can make planning processes more difficult by providing a means for naturalizing planning decisions and also by exacerbating struggles over whose nature will be managed in what ways. More explicitly framing what is meant by nature in exurban planning may improve discussion of landscape problems associated with sprawl. The goal of this paper is to contribute to creating a framework for more actively contextualizing how “nature” is used in discourses relating to exurbanization. I suggest that such a framework would need to consider—and make explicit—themes such as the four that I discuss in this paper: (1) the centrality of the production of nature to exurban landscapes; (2) multiple meanings of nature that are often confused; (3) ways that normative statements about nature tend to be unquestioned in exurban planning; and (4) the simultaneous difficulty and usefulness of critiquing and “denaturalizing” both material and discursive nature. Explicit conversations about the role and representation of nature within residents’ and managers’ land-use practices and ideologies could create opportunities for dialogue between residents, planners, and academics about the valuation of and preferences for constructing particular landscapes, especially in addressing problematic aspects of the phenomena of “amenity migration” and “sprawl.”     

Impact of the Atlantic Warm Pool on precipitation and temperature in Florida during North Atlantic cold spells

Recurrent phases of increased pine at Lake Tulane, Florida have previously been related to strong stadials terminated by so-called Heinrich events. The climatic significance of these pine phases has been interpreted in different ways. Using a pollen?Cclimate inference model, we quantified the climate changes and consistently found that mean summer precipitation (P _JJA) increased (0.5?C0.9?mm/day) and mean November temperature increased (2.0?C3.0°C) during pine phases coeval with Heinrich events and the Younger Dryas. Marine sea surface temperature records indicate that potential sources for these moisture and heat anomalies are in the Gulf of Mexico and the western tropical Atlantic. We explain this low latitude warming by an increased Loop Current facilitated by persistence of the Atlantic Warm Pool during summer. This hypothesis is supported by a climate model sensitivity analysis. A positive heat anomaly in the Gulf of Mexico and equatorial Atlantic best approximates the pollen-inferred climate reconstructions from Lake Tulane during the (stadials around) Heinrich events and the Younger Dryas.     

Geomechanical and geochemical effects on sandstones caused by the reaction with supercritical CO2: an experimental approach to in situ conditions in deep geological reservoirs

The geochemical and geomechanical behaviour of reservoir rocks from deep saline aquifers during the injection and geological storage of CO₂ is studied in laboratory experiments. A combination of geochemical and geomechanical studies was carried out on various sandstones from the North German Basin. After the mineralogical, geochemical and petrophysical characterization, a set of sandstone samples was exposed to supercritical (sc)CO₂ and brine for 2–4 weeks in an autoclave system. One sample was mineralogically and geochemically characterised and then loaded in a triaxial cell under in situ pressure and temperature conditions to study the changes of the geomechanical rock properties. After treatment in the autoclaves, geochemical alterations mainly in the carbonate, but also in the sheet silicate cements as well as in single minerals of the sandstones were observed, affecting the rocks granular structure. In addition to partial solution effects during the geochemical experiments, small grains of secondary carbonate and other mineral precipitations were observed within the pore space of the treated sandstones. Results of additional geomechanical experiments with untreated samples show that the rock strength is influenced by the saturation degree, the confining pressure, the pore fluid pressure and temperature. The exposure to pure scCO₂ in the autoclave system induces reduced strength parameters, modified elastic deformation behaviour and changes of the effective porosity in comparison to untreated sandstone samples. Experimental results show that the volume of pore fluid fluxing into the pore space of the sandstones clearly depends on the saturation level of the sample.     

Rare gas diffusion studies in individual lunar soil particles and in artificially implanted glasses

The linear heating technique was applied to study the release of solar wind implanted He and Ne in single glass spherules and minerals of lunar soils. In addition, the diffusion of rare gases artificially implanted into simulated lunar glass was investigated. Activation energies derived for lunar glasses are much higher than for virginal glasses of similar chemical composition. Volume diffusion of the lunar surface cannot explain the high retentivity for the trapped gases. It is expermentally shown that various types of radiation damage are of paramount importance to the understanding of the secondary alterations of elemental abundances after solar wind implantation on the lunar surface.Paper dedicated to Prof. Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.     

Materials embodied in international trade – Global material extraction and consumption between 1995 and 2005

Production and consumption activities in industrialized countries are increasingly dependent on material and energy resources from other world regions and imply significant economic and environmental consequences in other regions around the world. The substitution of domestic material extraction and processing through imports is also shifting environmental burden abroad and thus extends the responsibility for environmental impacts as well as social consequences from the national to the global level. Based on the results of the Global Resource Accounting Model, this paper presents the first trade balances and consumption indicators for embodied materials in a time series from 1995 to 2005. The model includes 53 countries and two world regions. It is based on the 2009 edition of the input–output tables and bilateral trade data published by the Organisation for Economic Co-operation and Development (OECD) and is extended by physical data on global material extraction. The results quantify the global shift of embodied material resources from developing and emerging countries to the industrialized world. In addition to the level of industrialization and wealth, population density is identified as an important factor for the formation of physical trade patterns. Exports of embodied materials of less densely populated countries tend to surpass their imports, and vice versa. We also provide a quantitative comparison between conventionally applied indicators on material consumption based on direct material flows and indicators including embodied material flows. We show that the difference between those two indicators can be as much as 200%, calling for an adjustment of conventional national material flow indicators. Multi-regional input–output models prove to be a useful methodological approach to derive globally consistent and comprehensive data on material embodiments of trade and consumption.     

Challenges of analyzing multi-hazard risk: a review

Many areas of the world are prone to several natural hazards, and effective risk reduction is only possible if all relevant threats are considered and analyzed. However, in contrast to single-hazard analyses, the examination of multiple hazards poses a range of additional challenges due to the differing characteristics of processes. This refers to the assessment of the hazard level, as well as to the vulnerability toward distinct processes, and to the arising risk level. As comparability of the single-hazard results is strongly needed, an equivalent approach has to be chosen that allows to estimate the overall hazard and consequent risk level as well as to rank threats. In addition, the visualization of a range of natural hazards or risks is a challenging task since the high quantity of information has to be depicted in a way that allows for easy and clear interpretation. The aim of this contribution is to give an outline of the challenges each step of a multi-hazard (risk) analysis poses and to present current studies and approaches that face these difficulties.     

A time-domain electromagnetic sounder for detection and characterization of groundwater on Mars

A prototype time-domain electromagnetic (TDEM) sounder was developed to technical readiness level (TRL) 5 to detect and characterize deep groundwater on Mars. The TDEM method induces eddy currents in the subsurface by abrupt extinction of a steady current in a large, flat-lying loop antenna, and the subsurface response is measured using the same loop or a separate receiver. TDEM has been widely used in terrestrial groundwater exploration and is ideally suited to sense the high electrical conductivity associated with saline groundwater expected on Mars. The inductive regime of TDEM is distinct from ground-penetrating radar: the latter has higher resolution but smaller depth of investigation. Our Mars-prototype TDEM was tested in the laboratory and at a local field site before the principal test was performed on Maui, Hawaii. This location was chosen because of its analogy to Mars in electrical properties: dry, resistive basalt over saline pore water. Results compared favorably to soundings made with a commercial TDEM, clearly detecting the seawater interface at depths of 250 m. We subsequently developed a ballistic deployment system for the loop antenna suitable for robotic missions. Compressed gas launches two projectiles; each consists of two spools on a guide stick. Payout on one spool is back towards the launcher and on the other toward its twin on the other projectile. In this way a triangular loop antenna is formed. The full system was tested twice, successfully achieving a distance of ∼70 m in both. A system capable of deploying a 200 m loop antenna on Mars would have mass <6 kg (including 0.3 kg electronics) and within one sol could detect groundwater at depths up to 5 km. TDEM can probe to depths not possible for radar and answer the question: does groundwater - and a likely subsurface habitable zone - exist on Mars?     

Thermal constraints on the early history of the H-chondrite parent body reconsidered

Reconstructions of the early thermal history of the H-chondrite parent body have focused on two competing hypotheses. The first posits an undisturbed thermal evolution in which the degree of metamorphism increases with depth, yielding an “onion-shell” structure. The second posits an early fragmentation-reassembly event that interrupted this orderly cooling process. Here, we test these hypotheses by collecting a large number of previously published closure age and cooling rate data and comparing them to a suite of numerical models of thermal evolution in an idealized parent body. We find that the onion-shell hypothesis, when applied to a parent body of radius 75-130 km with a thermally insulating regolith, is able to explain 20 of the 21 closure age data and 62 of the 71 cooling rates. Furthermore, six of the eight meteorites for which multiple data (at different temperatures) are available, can be accounted for by onion-shell thermal histories. We therefore conclude that no catastrophic disruption of the H-chondrite parent body occurred during its early thermal history. The relatively small number of data not explained by the onion-shell hypothesis may indicate the formation of impact craters on the parent body which, while large enough to excavate all petrologic types, were small enough to leave the parent body largely intact. Impact events fulfilling these requirements would likely have produced transient crater diameters at least 30% of the parent body diameter.     

Long-term Trends in Vegetation Dynamics and Forest Fires in Brandenburg (Germany) Under a Changing Climate

The human influence on environmental processes has been described for many types of land use. One of the oldest tools to modify people’s environment is fire, which has dominated fire regimes in many regions over long time scales. This paper focuses on a German case study region, where 80–90% of the fires are human-caused. The objectives of this study are the application of the Regional Fire Model (Reg-FIRM), a process-based fire model that is incorporated into the LPJ Dynamic Global Vegetation Model, to temperate forests under historic climate conditions and to explore ranges of potential impacts of future climate change on fire and vegetation dynamics. Simulation experiments are designed to simulate historic fire pattern and to explore influences of vegetation on fire. Simulated fire pattern reproduced the observed average fire conditions reasonably well although with a smaller amplitude. This leads to underestimation of extreme fire years as well as an overestimation of low fire years. Vegetation composition influenced fire spread conditions in the temperate forest and had little impact on fire ignition potentials, except when only broad-leaved deciduous forests were assumed. Fire is likely to change under climate change conditions. Simulated experiments were conducted to explore the effects of climate change and rising CO₂ concentration given the potential natural vegetation as the best-case for Brandenburg. Three GCM scenarios predicting different future climatic changes were applied, and resulted in quantitatively different future fire patterns. Depending on future precipitation pattern and the influence of the CO₂ effect on canopy conductance and thus litter moisture, fire was predicted to either decrease or slightly increase in Brandenburg forests, but the burnt area would not exceed current, extreme fire years. Generally, fire changes had no implication for vegetation composition in Brandenburg, but reduced vegetation carbon gain after 2050. In the HadCM3 application, simulated increase in grass cover due to a large burnt area after 2075 accelerated fire spread conditions, thus still increasing the burnt area, while climatic fire danger and number of fires already began to decline. These interactions underline the importance to consider the full range of fire processes and interactions with vegetation dynamics in a simulation model.     

Twentieth Century Climate in the New York Hudson Highlands and the Potential Impacts on Eco-Hydrological Processes

During the 20th century the northeastern U.S.A. has undergone an annual temperature increase of 1 °C, the combined effect of winter warming and an increase in daily summer minimum temperatures. A significant cooling of spring through autumn in maximum air temperatures is also evident since 1950. Therefore, the primary objective of this study is to document these climate trends and variability over the last century. A secondary objective is to provide a preliminary analysis of how these changes may have impacted hydrologic and ecosystem processes. Specifically, with respect to ecosystem processes, we examine how the cooling of daytime maximum temperatures may have impacted plant respiration and biomass accumulation. The study site is the Black Rock Forest, an experimental forest located in Hudson Highlands of New York that has been maintained as a conservation area over the last 100 years. For the region centered about the forest, there exists a climate/weather record and an extensively maintained biomass record that extends continuously from the early part of the 20th century through present. With such an extensive physical and biological record to draw from, this forest provides a microcosm for studying how changes in 20th century local and regional climate may have impacted ecosystem processes such as species adaptation, biomass growth, and 20th century carbon sequestration. In a subsequent paper we will more extensively explore the relationship between this record of changing climate and eco-hydrological processes.