Trampling of vegetation and soils by recreational activities is a recurrent concern in many lands where trail use is common. The degree of impact can vary with the myriad types of trail users. The Weaver and Dale article, "Trampling effects of hikers, motorcycles and horses in meadows and forests", was the first to provide some insights about how different trampling agents might produce varied impacts. Weaver and Dale showed that horses and motorcycles produced greater impacts to soils and vegetation than hikers. This article appeared early in a relatively young field of study. The direct results of their research are still valuable today, but the greater impact of their paper was that it ushered in a phase of experimental trampling research that is ongoing. Because of their research and continual influence, land managers can now make better decisions about what type of recreation activity to discourage or encourage.
Although the concept of entropy in landscape evolution was proposed over 40 years ago, previous studies of geomorphic entropy paid little attention to the applications of geomorphic entropy in the erosional watershed geomorphic system on the Loess Plateau in China. Therefore, we propose a new concept of entropy called watershed geomorphic entropy (WGE) and its method of calculation based on a digital elevation model and the principles of system theory. To study the geomorphic significances of WGE, we applied the WGE to an artificial rainfall experiment that was originally designed to study erosional processes in a small open watershed geomorphic system on the Loess Plateau. Our study shows that the decrease of WGE in an open watershed geomorphic system means a gradual erosional or erosion-dominated landscape evolutional process and the change of WGE shows a perfectly positive linear correlation with the measured sediment yields of the outlet of the watershed system under our experimental conditions. In addition, to some extent, the decrease of the change of WGE also reflects the reduction of total potential energy of a specific erosional, or erosion-dominated, open watershed geomorphic system.
We propose the use of archetypes as a way of moving between conceptual framings, empirical observations and the dichotomous classification rules upon which maps are based. An archetype is a conceptualisation of an entire category or class of objects. Archetypes can be framed as abstract exemplars of classes, conceptual models linking form and process and/or tacit mental models similar to those used by field scientists to identify and describe landforms, soils and/or units of vegetation. Archetypes can be existing taxonomic or landscape units or may involve new combinations of landscape attributes developed for a specific purpose. As landscapes themselves defy precise categorisation, archetypes, as considered here, are deliberately vague, and are described in general terms rather than in terms of the details that characterise a particular instance of a class. An example outlining the use of archetypes for landscape classification and mapping is demonstrated for granitic catenas in Kruger National Park, South Africa. Some 81% of the study area can be described in terms of archetypal catenal elements. However, spatial clustering of two classes that did not correspond to the archetypes prompted development of new archetypes. We show how the archetypes encoded in the map can be used to frame further knowledge in an ongoing, iterative and adaptive process. Building on this, we reflect on the value of vagueness in conservation science and management, highlighting how archetypes that are used to interpret and map landscapes may be better employed in the future.
A fundamental principal of savanna fire ecology is that the fire regime determines vegetation cover, especially as it pertains to trees. A corollary is that late fires are more damaging to trees than early fires. Much evidence in support of this principle has been derived from a series of long-term burning experiments based on the pioneering work of André Aubréville. Eighty years ago, Aubréville devised an experiment to study the impacts of fire on savanna trees in Africa. The design conventions of this study remain highly influential. It is now clear, however, that the dates chosen by Aubréville and his followers do not reflect the burning practices of West African people. Dates that were chosen for "early" and "late" are not representative of actual fire timing; they represent extremes. This study has four goals: (i) to critically review the results of the burning experiments; (ii) to examine them in the context of results from recent savanna fire studies; (iii) to evaluate their limitations based on data for actual burning practices and fires from West Africa; and (iv) to critically evaluate the use of the early/late terminology in contemporary fire research. We find the majority of West African fires occur during the "middle" of the fire season. Our field studies find that fire temperature and burn completeness are highest in the middle-season. We conclude that the early/late fire dichotomy is not sufficient for understanding the impacts of anthropogenic fires in the region and we make suggestions for rethinking its use more broadly.
The changes of near-surface wind speed (SWS) were induced by the combination effects from anthropogenic activities and natural climate changes, thus the research of the long-term changes and cause of SWS is very important to recognize the effects from natural changes and anthropogenic activities to SWS. Some studies have shown that land use and cover change (LUCC) over China was very distinct in the last 30 years. However, the possible effects of LUCC to the slowdown in SWS are still uncertain. The European Centre for Medium-Range Weather Forecasts Reanalysis from January 1989 onward (to be extended back to January 1979) (ERA-Interim hereafter) dataset includes little information about LUCC, so the effects of LUCC on SWS in China during 1979–2010 have been estimated by using the difference between SWS per the ERA-Interim dataset and that from 492 meteorological stations. The results show the following. (1) The effects of LUCC on the SWS are distinct, and could have caused a decrease in the SWS of 0.12 m s–1 per decade, which could account for decreases of 0.57 and 0.30 m s–1 wind speed for large and small cities, respectively. In addition, a decrease of 0.1 m s–1 in the SWS could be induced by a 10% rise in the urbanization rate. (2) The impacts of LUCC on the SWS in the Beijing-Tianjin-Tangshan region, the Yangtze River Delta region and the Pearl River Delta region are more significant than those for the entire region. (3) The bias in the ERA-Interim dataset could cause a 51% error in the estimation for the entire region during the study period, but had a non-significant effect on the decreasing trend in the SWS. The decrease rate of SWS induced by LUCC based on the traditional observation minus reanalysis method had an error of 0.01 m s–1 decade–1. (4) The results of different methods to quantify the impacts of LUCC on the SWS are also compared in this study.
Debris flows represent major hazards in most mountainous regions of the world where they repeatedly result in disasters. In order to protect people and infrastructure against future debris flows, many debris flow catchments have been artificially intervened by employing various mitigation measures, including civil engineering works. However, the commonly adapted engineering measures, such as check dams, are not effective for every debris flow catchment, and the failure of such measures even causes more damage, e.g. the Sanyanyu debris flow catchment in Zhouqu, China, killed 1756 people. In order to research the effectiveness of engineering strategies and explore much more effective mitigation works for debris flows in the mountainous regions, we took the Bailong River catchment of Southern Gansu of China as study area, with special emphasis on Sanyanyu debris flow catchment (with civil engineering works) and Goulinping debris flow catchment (without civil engineering works), and comparatively analysed the two catchments. The comparative results show that both catchments have similar material source, geomorphological/environmental and climatic conditions, however, vegetation cover and rock hardness are poorer in Goulinping than in Sanyanyu, the catchment that underwent larger-scale debris flows, suggesting that the mitigation measures had been applied in Sanyanyu catchment were inappropriate. Subsequently, we simulated the effectiveness of controlling debris flow peak discharge with check dams at the lower part of Sanyanyu and Goulinping catchment using the Kanako simulator, and summarised argument based on the hypothesis and facts from positive and negative aspects. We draw the conclusion that it is not reasonable to build check dams in the two catchments and instead, drainage channels should be primarily considered for reducing debris flow hazards in such densely populated areas. Finally, we undertook detailed field investigations and experiments on the native plants in the region, and found that the ecological mitigation measure with planting Robinia Pseudoacacia on the debris flow deposits is an effective method to alleviate debris flow hazards. It is concluded that channel works combined with ecological measures are the preferable approaches to minimize the debris flow damage in debris flow catchments characterised with high mountains, concentrated rainfalls and active neotectonic movement.
Among the more complex and devastating interactions between climate and hydromorphological processes in mountain environments are landslide lake outburst floods (LLOFs), resulting from mass movements temporarily blocking a drainage system. This work reviews these processes in the Himalayas and highlights the high frequency of this type of phenomenon in the region. In addition, we analyse two recent catastrophic trans-national LLOFs occurring in the Sutlej river basin during 2000 and 2005. Based on high resolution satellite images, Tropical Rainfall Measuring Mission (TRMM), Moderate-Resolution Imaging Spectroradiometer (MODIS) derived evolution of snowline elevation and discharge data we reconstruct the timing and hydrometeorological conditions related to the formation and failure of landslide dams. Results showed that the 2005 flood, originating from the outburst of the Parchu Lake, was not related to heavy precipitation, but was likely enhanced by the rapid and late snowmelt of an unusually deep and widespread snowpack. The flood in 2000 was triggered by the outburst of an unnamed lake located on the Tibetan plateau, identified here for the first time. In this case, the outburst followed intense precipitation in the lake watershed, which raised the level of the lake and thus caused the breaching of the dam. As stream gauges were damaged during the events detailed discharge data is not available, but we estimated the peak discharges ranging between 1100 m3 s–1 and 2000 m3 s–1 in 2005, and 1024 m3 s–1 and 1800 m3 s–1 in 2000. These events caused significant geomorphic changes along the river valleys, with observed changes in channel width exceeding 200 m. Results also demonstrate that remotely-sensed data enables valuable large-scale monitoring of lake development and related hydrometeorological conditions, and may thereby inform early warning strategies, and provide a basis for flood risk reduction measures that focus on disaster preparedness and response strategies.
Mammal burrowing plays an important role in soil translocation and habitat creation in many environments. As a consequence, many burrowing mammals have at some point been studied in an ecosystem engineering context. From a geomorphological point of view, one of the focus areas of burrowing mammal research is on the amount of soil that is excavated and the rate at which this happens. As such, reviews exist on the volumes and rates of sediment removal by burrowing mammals in specific environments or for specific groups of species. Here, a standardised comparison of mammal burrowing across a broad range of burrowing mammal species and environments is provided, focussing on both burrow volume and excavation rate. Through an ISI Web of Science-based literature search, articles presenting estimates of burrow volumes and/or excavation rate were identified. Relationships between species body size and burrow volume/excavation rate were explored and the influence of sociality and method of burrow volume estimation were assessed. The results show that, although larger species construct larger burrows, it is the smaller species that remove more sediment per unit time at larger, site-level spatial scales. Burrow volume estimates are, however, independent of species sociality (solitary versus group-living) and method of burrow volume estimation (excavation-based versus mound-based). These results not only confirm previously established relationships between species body size and burrow volume, but, more importantly, they also add to this, by exploring larger scale impacts of burrowing mammals along a body size gradient.
The frigid swampy meadows of the Qinghai–Tibet Plateau in western China have suffered widespread degradation. The severe degradation of such meadows can lead to the formation of a landscape commonly known as heitutan. Much research has been undertaken to study its triggers, formation mechanism, grading of severity, and rehabilitation. These studies are comprehensively reviewed in this paper. In particular, it attempts to reconcile two divergent theories on heitutan formation by proposing a new model to elucidate the role of a given factor at each stage of degradation. In this model, climate desiccation is the most important in transforming healthy meadow to dry grassland, while rodent attack is the most important in worsening dry grassland to degraded meadow. Overgrazing is the most important factor during the early stages of degradation. Wind and water erosion is important during the final stage, when a large quantity of loose materials has been accumulated by rodent burrowing. Also covered in this paper is how to rehabilitate heitutan to productive use, including the effectiveness of various measures. Finally, this paper identifies the gap in our understanding of swampy meadow degradation and spells out a future research agenda. It is concluded that future research on heitutan will undergo a transformation from descriptive to quantitative. The expected research outcome will inform herders of the appropriate strategies that can be adopted to prevent heitutan formation. This proactive approach will minimize economic loss from swampy meadow degradation and reduce its adverse impact on the environment.
Almost a century ago, observed geographic patterns of plant phenology (such as leaf-out and flowering) were summarized in Hopkins’ Bioclimatic Law. This law describes phenology as varying along climatic gradients by latitude, longitude, and altitude. Yet phenological patterns are not only affected by contemporary climatic differences across space, but also by underlying geographic variations in plant genetics that arise from long-term climatic adaptation. The latter influence on geographic patterns in phenology has been undervalued to this day, mainly due to the difficulty of quantifying it. This study outlines a methodology for bridging this knowledge gap through delineating geographic adaption patterns using common garden and cloned plant phenology. Through synthesizing existing literature, typical geographic adaptation patterns in both spring and autumn phenology of many temperate tree species are identified. Under uniform environment, spring leaf-out of colder climate-adapted populations of a certain species is either earlier than warmer climate-adapted ones due to lower thermal requirements, or later because of higher chilling (for dormancy release) demands. The former leads to a countergradient pattern as it is opposite to an in situ observation, while the latter leads to a cogradient pattern. Autumn leaf senescence, on the other hand, expresses a consistent cogradient pattern that is related to latitude and constrained by the populations’ varied photoperiod requirements. These geographic adaptation patterns allow a clearer understanding of geographical variations in phenological responses to climate change, and provide a theoretical basis for spatially explicit phenological models. In addition, given that these adaptive patterns reveal genotype-based variabilities, they are potentially useful for more accurately tracking phenology-dependent ecosystem processes (e.g. species distribution) and non-weather-related vegetation changes. As a unique subfield of physical geography with broad environmental implications, this line of research needs to be further developed by furnishing a stronger and more explicit spatial structure into current phenological studies.
A warming climate is melting the namesake glaciers of Glacier National Park, Montana, USA. James Dyson’s 1948 paper was one of the earliest publications to emphasize climate change impacts to the cryosphere through an examination of Sperry and Grinnell Glaciers. This paper, combined with his subsequent works, acts as a pillar for current glacier monitoring efforts.
Understanding the rainfall-runoff behaviour of urban land surfaces is an important scientific and practical issue as storm water management policies increasingly aim to manage flood risk at local scales within urban areas, whilst controlling the quality and quantity of runoff that reaches receiving water bodies. By reviewing field measurements reported within the literature on runoff, infiltration, evaporation and storage on common urban surfaces, this study describes a complex hydrological behaviour with greater rates of infiltration than often assumed, contradicting a commonly adopted, but simplified classification of the hydrological properties of urban surfaces. This shows that the term impervious surface, or impermeable surface, referring to all constructed surfaces (e.g. roads, roofs, footpaths, etc.) is inaccurate and potentially misleading. The hydrological character of urban surfaces is not stable through time, with both short (seasonal) and long term (decadal) changes in hydrological behaviour, as surfaces respond to variations in seasonal characteristics and degradation in surface condition. At present these changing factors are not widely incorporated into hydrological modelling or urban surface water management planning, with static values describing runoff and assumptions of imperviousness often used. Developing a greater understanding of the linkages between urban surfaces and hydrological behaviour will improve the representation of diverse urban landscapes within hydrological models.
There are numerous anecdotal examples of drought terminations documented throughout the historical record on most continents. The end of a drought is the critical time during which water resource managers urgently require information on the replenishment of supplies. Yet this phase has been relatively neglected by the academic community, with much of the existing body of research on drought termination assessing the likelihood of droughts ending rather than its temporal profile. In particular, there has been little effort to characterise drought termination events themselves. This is partly explained by existing definitions of drought termination as a specific point in time when drought is considered to have finished, rather than a more holistic consideration based on approaches developed within biological sciences. There is also a lack of understanding about how drought termination propagates through the hydrological cycle. This paper specifically examines and reviews available research on drought termination, highlighting limitations associated with current definitions and offering suggestions for characterising the temporal stages of drought. An alternative definition of drought termination is proposed: a period between the maximum negative anomaly and a return to above-average conditions. Once this phase has been delineated, the duration, rate and seasonality of drought termination can be derived. The utility of these metrics is illustrated through a case study of the 2010–2012 drought in the UK, and the propagation of drought termination between river flows and groundwater levels.
Climate change is likely to have a significant effect on snow globally, with most effect where current winter temperatures are close to 0°C, including parts of upland Britain. There is evidence of decreasing trends in observations of snowfall and lying snow in Britain, and climate projections suggest a continuation of this trend. Although river flows in Britain are generally dominated by rainfall rather than snowmelt, some upland catchments have a significant snowmelt contribution. There is evidence of changes in observed and projected river flows in some catchments in Britain, linked to changes in snow, but it can be difficult to distinguish the effects of snow changes from those of other concurrent changes (climatic and non-climatic). Flow regime changes in catchments with widespread and prolonged winter snow cover usually involve increases in winter flow and decreases in spring flow, but the effect on catchments with more transient snow cover is less clear, as is the effect on high flows and water quality. Snow can also affect a number of other factors of socio-economic or environmental importance (e.g. transport and farming). There is some evidence that disruption due to snow may be less frequent in the future, but disruption from other types of weather events may increase. The impacts of snow tend to be worse in areas where events occur less frequently, due to unpreparedness, so there is a need to guard against complacency when it comes to future snow events in Britain, which can still be expected despite a likely reduction in frequency. Further modelling of the potential impacts of climate change, including modelling the influence of snow changes as well as other climatic and non-climatic changes, would aid adaptation and encourage mitigation.
Vegetation cover mediates a number of important geomorphological processes. However, the effect of different vegetation types on the retention of fine aeolian sediment is poorly understood. We investigated this phenomenon, using the retention of fine, pyroclastic material (tephra) from the 2011 eruption of the Grímsvötn volcano, Iceland, as a case study. We set out to quantify structural variation in different vegetation types and to relate structural metrics to the thickness of recently deposited volcanic ash layers in the sedimentary section. We utilised a combination of vegetation and soil surveys, along with photogrammetric analysis of vegetation structure. We found that indices of plant community composition were a poor proxy for vegetation structure and were largely unrelated to tephra thickness. However, structural metrics, derived from photogrammetric analysis, were clearly related to variations in tephra layer thickness at a landscape scale and tephra layers under shrub patches were significantly thicker than those outside the shrub canopy. We therefore concluded that: a) vegetation cover was a critical factor in the retention of fine aeolian sediment for deposit depths up to few centimetres; b) structural variation in vegetation cover played a major role in determining the configuration of tephra deposits in the sedimentary section. These findings have implications for the analysis of ancient volcanic eruptions and archaeological/palaeoenvironmental reconstructions based on the interpretation of tephra deposits. Furthermore, they present the possibility that the detailed form of tephra layers may be used as a proxy for palaeo vegetation structure.
The Karakoram Range is one of the most glacierized mountain regions in the world, and glaciers there are an important water resource for Pakistan. The attention paid to this area is increasing because its glaciers remained rather stable in the early twenty-first century, in contrast to the general glacier retreat observed worldwide on average. This condition is also known as "Karakoram Anomaly". Here we focus on the recent evolution of glaciers within the Central Karakoram National Park (CKNP, area: *13,000 km2) to assess their status in this region with respect to the described anomaly. A glacier inventory was produced for the years 2001 and 2010, using Landsat images. In total, 711 ice-bodies were detected and digitized, covering an area of 4605.9 ± 86.1 km2 in 2001 and 4606.3 ± 183.7 km2 in 2010, with abundant supraglacial debris cover. The difference between the area values of 2001 and 2010 is not significant (+0.4 ± 202.9 km2), confirming the anomalous behavior of glaciers in this region. The causes of such an anomaly may be various. The increase of snow cover areas from 2001 to 2011 detected using MODIS snow data; the reduction of mean summer temperatures; and the augmented snowfall events during 1980–2009 observed at meteorological stations and confirmed by the available literature, are climatic factors associated with positive mass balances. Because the response of glacier area change to climate variation is very slow for large glaciers, the presence of some of the largest glaciers of the Karakoram Range in this region might have delayed observed effects of such climate change so far, or alternatively, the change may not be sufficient to drive an actual area increase. In this context, improved understanding the role of debris cover, meltwater ponds, and exposed ice cliffs on debris-covered glaciers, and surging glaciers (which are also found abundant here), are required is still an issue to clarify the mechanisms behind the Karakoram Anomaly.
Dolines or sinkholes are earth depressions that develop in soluble rocks complexes such as limestone, dolomite, gypsum, anhydrite, and halite; dolines appear in a variety of shapes from nearly circular to complex structures with highly curved perimeters. The occurrence of dolines in the studied karst area is not random; they are the results of geomorphic, hydrologic, and chemical processes that have caused partial subsidence, even the total collapse of the land surface when voids and caves are present in the bedrock and the regolith arch overbridging these voids is unstable. In the study area, the majority of collapses occur in the regolith (bedrock cover) that bridges voids in the bedrock. Because these collapsing dolines may result in property damage and even cause the loss of lives, there is a need to develop methods for evaluating karst hazards. These methods can then be used by planners and practitioners for urban and economic development, especially in regions with a growing population. The purpose of the project reported in this paper is threefold: (1) to develop a karst feature database, (2) to investigate critical indicators associated with doline collapse, and (3) to develop a doline susceptibility model for potential doline collapse based on external morphometric data. The study has revealed the presence of short range spatial dependence in the distribution of the dolines’ morphometric parameters such as circularity, the geographic orientation of the main doline axes, and the length-to-width doline ratios; therefore, geostatistics can be used to spatially evaluate the susceptibility of the karst area for doline collapse. The partial susceptibility estimates were combined into a final probability map enabling the identification of areas where, until now, undetected dolines may cause significant hazards.
Various methods have been developed over the past five decades for dependence modeling of multivariate variables in hydrology and water resources, but there has been no overall review of techniques commonly used in the field. This paper, therefore, introduces several methods focusing on dependence structure modeling, including parametric distribution, entropy, copula, and nonparametric. Recent advances in modeling dependences mainly reside in nonlinear dependence modeling (including extreme dependence) with flexible marginal distributions, and in high-dimension dependence modeling via the vine copula construction with flexible dependence structures. Strengths and limitations of different methods and avenues for future research, such as dependence modeling in a changing climate, are discussed to aid water resource planners and managers in the selection and application of suitable techniques.
While karst is not biogenic in the same sense as, say, coral reefs or peat bogs, and carbonate dissolution can occur abiotically, formation of karst landscapes would not occur in the absence of the biosphere. Seven levels of biogeomorphic biotic-abiotic interactions are identified, from indirect impacts to landforms as extended phenotypes. Karst is generally near the biogenic end of that spectrum, featuring reciprocal interactions and mutual adjustments between biota and landforms and interrelated geomorphological and ecological processes. Karst biogeomorphology may also involve niche construction. In many cases biogeomorphic ecosystem engineering in karst is contingent, in the sense that the engineer organisms may have no, or different, biogeomorphic impacts in non-karst environments. Several examples of contingent ecosystem engineering in karst are given, including biogeomorphic effects of chinkapin oak. Abiotic geomorphic features exist on Earth, but consideration of landform types lying between the biotic-abiotic extremes would likely yield broadly similar conclusions to those about karst. However, it is also clear that we know very little about niche construction and coevolution in karst biogeomorphology, and whether karst or any specific karst features can be considered an extended (composite) phenotype is still an open question. Thus far, most work on biogeomorphology and ecosystem engineering has focused on what might be called obligate engineers—organisms whose engineering effects are at least inevitable, if not necessary to their survival. However, in some cases contingent ecosystem engineers have substantial geomorphic impacts.
While dendrogeomorphology has been recognized as a useful tool to identify past avalanche activity, there is only a handful of papers that focus on the assessment of weather or climatic triggers of tree-ring reconstructed avalanche events. This paper compares the potential of logistic regression and classification tree algorithms to highlight weather scenarios responsible for the occurrence of high-magnitude avalanche activity in the Presidential Range of the White Mountains, New Hampshire (USA). Our tree-ring procedure improves the modern GD-It threshold with the implementation of a second criteria based on the Moran index. 450 trees sampled in seven different avalanche paths allowed us to reconstruct 45 avalanches that occurred during 19 different years for the period 1936–2012. The results show that while statistically significant, the logistic regression models are less accurate than classification trees to assess avalanche activity based on annual and monthly weather variables. Moreover, even if snow related covariates are located at the root node of every classification tree model, the addition of temperature and wind predictors increases their robustness. This suggests that high-magnitude avalanches in the Presidential Range not only respond to snow, but also to atmospheric conditions responsible for the creation of weak layers within the snowpack.
There is now widespread recognition of the degrading influence of urban stormwater runoff on stream ecosystems and of the need to mitigate these impacts using stormwater control measures. Unfortunately, however, understanding of the flow regime requirements to protect urban stream ecosystems remains poor, with a focus typically on only limited aspects of the flow regime. We review recent literature discussing ecohydrological approaches to managing urban stormwater and, building on the natural flow paradigm, identify ecologically relevant flow metrics that can be used to design stormwater control measures to restore more natural magnitude, duration, timing, frequency and variability of both high and low flows. Such an approach requires a consideration of the appropriate flow and water quality required by the receiving water, and the application of techniques at or near source to meet appropriate flow regime and water quality targets. The ecohydrological approach provides multiple benefits beyond the health of urban streams, including flood mitigation, water supply augmentation, human thermal comfort, and social amenity. There are, however, uncertainties that need to be addressed. Foremost is the need to define ecologically and geomorphically appropriate flow regimes for channels which have already been modified by existing land use. Given the excess of water generated by impervious surfaces, there is also an urgent need to test the feasibility of the natural flow paradigm in urban streams, for example using catchment-scale trials.
Most studies focusing on landslide spatial analysis have considered the relationships between predictors and landslide occurrence as fixed effects. Yet spatially varying relationships, i.e. non-stationarity, often occur in any spatial data set and should be theoretically considered in statistical models for a better fit. In Skagafjörður, a landslide-rich north–south oriented area located in northern Iceland, we investigated whether spatial non-stationarity in the relationships between paraglacial variables (glacio-isostatic rebound and post-glacial debuttressing, both captured in this area by latitude) and landslide locations is detectable. To explore the non-stationarity of factors that predispose landslide occurrence, we performed two logistic regression models, one global (GLR) and the other enabling the regression parameters to vary locally (geographically weighted logistic regression, GWLR). Each model was computed with two types of outcome, one based on the entire masses of landslides and the other only on the scarps of landslides. GLR results reveal that increasing latitude is associated with increasing probability of landslide occurrence, confirming that post-glacial rebound is of prime importance at the regional scale. Nevertheless, GWLR indicates that this relationship is absent or reversed at some locations, meaning that the influence of paraglacial and other predisposing factors of landsliding (slope, valley depth and curvature) vary at the local scale. This result sheds light on the spatial clustering of three subzones where landsliding drivers are homogeneous. We conclude that a GWR-based approach provides some significant inputs for spatial analysis of mass movement processes, by identifying multi-scale process control zones and by highlighting local drivers, indecipherable in global models.
Products of CORINE Land Cover (CLC), the National Land Cover Dataset (NLCD), the FAO/UNEP Land Cover Classification System (LCCS), etc. currently provide an important source of information used for the assessment of issues such as landscape change, landscape fragmentation and the planning of urbanization. Assuming that the data from these various databases are often used in searching for solutions to environmental problems, it is necessary to know which classes of different databases exist and to what extent they are similar, i.e. their possible compatibility and interchangeability. An expert assessment of the similarity between the CLC and NLCD 1992 nomenclatures is presented. Such a similarity assessment in comparison with the ‘geometric model’, the ‘feature model’ and the ‘network model’ is not frequently used. The results obtained show the similarity of assessments completed by four experts who marked the degree of similarity between the compared land cover classes by 1 (almost similar classes), 0.5 (partially similar classes) and 0 (not similar classes). Four experts agreed on assigning 1 in only three cases; 0.5 was given 33 times. A single expert assigned 0.5 a total of 17 times. Results confirmed that the CLC and NLCD nomenclatures are not very similar.
The Last Glacial Maximum (LGM) (21±2 ka) is an important period for which to understand past climatic and environmental conditions. In particular it is a key time-slice for evaluating the performance of numerical climate model simulations of glacial palaeoclimates using palaeoenvironmental data sets. However, our palaeoenvironmental data sets and reconstructions of climatic conditions at the LGM are still debated in certain regions. This is the case for southern Africa, despite more than half a century of research since early conceptual models of palaeoclimate were proposed. The greatest debates are about the spatial patterning of relatively wetter and drier conditions than present and the position of the mid-latitude westerlies at the LGM. Different patterns emerge from: separate syntheses of palaeoenvironmental proxies, from different numerical model simulations and from comparisons of the two. In this review of the progress over half a century of research in southern Africa: (1) a brief historical review of key conceptual models is given, (2) key points of conflict that emerge in synthesis of palaeoenvironmental proxy records are outlined and (3) numerical model simulations are considered. From these, some points for future progress are suggested.
Ecological and conservation research has provided a strong scientific underpinning to the modeling of ecosystem services (ESs) over space and time, by identifying the ecological processes and components of biodiversity (ecosystem service providers, functional traits) that drive ES supply. Despite this knowledge, efforts to map the distribution of ESs often rely on simple spatial surrogates that provide incomplete and non-mechanistic representations of the biophysical variables they are intended to proxy. However, alternative data sets are available that allow for more direct, spatially nuanced inputs to ES mapping efforts. Many spatially explicit, quantitative estimates of biophysical parameters are currently supported by remote sensing, with great relevance to ES mapping. Additional parameters that are not amenable to direct detection by remote sensing may be indirectly modeled with spatial environmental data layers. We review the capabilities of modern remote sensing for describing biodiversity, plant traits, vegetation condition, ecological processes, soil properties, and hydrological variables and highlight how these products may contribute to ES assessments. Because these products often provide more direct estimates of the ecological properties controlling ESs than the spatial proxies currently in use, they can support greater mechanistic realism in models of ESs. By drawing on the increasing range of remote sensing instruments and measurements, data sets appropriate to the estimation of a given ES can be selected or developed. In so doing, we anticipate rapid progress to the spatial characterization of ecosystem services, in turn supporting ecological conservation, management, and integrated land use planning.
Recent military base closures and realignments in the United States have opened dozens of former training and testing sites to new uses and priorities. One common transition is to designate these lands as national wildlife refuges. This presents conservation opportunities on hundreds of thousands of hectares previously under military control, but the ecological restoration and subsequent reuse of these lands is complex and fraught with challenges. Unexploded ordnance, soil and water contamination, reinforced structures, and other military remainders exist on many of these sites, and wildlife refuge managers typically receive little funding or training to contend with such relicts. This paper acknowledges some of the real conservation opportunities provided by military-to-wildlife (M2W) refuges, but emphasizes that restoration and conservation measures at these sites remain bounded by physical and sociopolitical constraints. One outcome of these constraints is ‘opportunistic conservation’, where habitat and wildlife goals are shaped or constrained by the lingering presence of prior military uses. Working from case studies and interviews conducted at M2W sites in the United States, this research suggests that opportunistic conservation represents a limited vision for restoration and conservation at these places that also potentially obscures these limitations. At many of these same sites, however, more affirmative opportunistic conservation efforts exhibit creative responses given the conditions that exist.
Applied climatology has long been a niche domain, straddling the intersection between the social and natural sciences and populated largely by geographers explicitly interested in reframing human activities around climate. As human-atmospheric relations become increasingly embedded within institutions of governance, new narratives of and for applied climatology are emerging to champion particular atmospheric objects, orientations, practices and institutions into positions of policy relevance and investment priority. This paper attempts to understand these intersecting politics of ‘climate and society’ research by situating their emergence through three lenses of inquiry. First, we explore the historical disciplinary work of ‘application’ in geographical climatology, paying particular attention to how ‘relevance’ has been understood and practised. Second, we reassemble a missed disciplinary conversation about ideology in applied geography, and link this to definitions and rationales for applied climatology. Third, we explore five recent thematic engagements in applied climatology, to generate thinking about the institutions and practices of assembling climate in new circles of ‘application’, policy and elsewhere. The ‘applications’ that climatologists choose to pursue – and the ways in which they pursue them – are deeply political questions that reproduce decision-making logics, funding rationalities, notions of expertise and problem framings. In conclusion, we argue that, rather than understanding ‘climate’ and ‘society’ as stable entities with standard (e.g. quantitative) practices or modes of association, we might instead concern ourselves with the practices of assembling human-atmospheric relations.
Rocky Flats (RF) is a former nuclear weapons manufacturing complex in Colorado, 26 km northwest of downwind Denver, at the eastern base of the Rocky Mountains’ Front Range. At RF, between 1952 and 1989, the Atomic Energy Commission (AEC) and its successors manufactured plutonium triggers. After remediation (1996–2005), 4000 acres of buffer zone were transferred to the US Fish and Wildlife Service (USFWS), to manage as Rocky Flats National Wildlife Refuge (2007). Drawing on research materials from local libraries and archives, this essay explores the ‘weapons to wildlife’ (W2W) conversion of a militarized environment in Denver’s ‘Gunbelt’. The various phases in RF’s demilitarization (closure, cleanup, transition to wildlife refuge and refuge management planning) are examined with reference to recognition of biodiversity value, debate over the ex-plant’s future, and options for running a refuge still in an arrested state of development – closed to the public for want of funding. A further aim is to bring to the attention of physical geographers a growing body of scholarship by human geographers on environmental contamination at former nuclear sites and debates over remediation and post-industrial uses – and to contribute the additional perspective of an environmental historian.
The main objective of this research was to study the streamflow evolution of a representative sample of the Spanish near-natural-regime fluvial system over the last four decades of the 20th century. The focus of this study was on those headwater river basins that, not having been subject to substantial human alteration directly via the flow regime, might still have been affected by changes in land management. A representative sample of 74 rivers was selected and a statistical analysis was performed to detect seasonal and annual trends, and the magnitude of streamflow change. Almost all of the rivers studied experienced reductions in streamflow, and three quarters of them had negative and significant (p<0.05) trends in streamflow change. It was impossible to detect any spatial pattern in terms of the type or trend magnitude. The main decreases in the discharge of these near-natural rivers in Spain was observed in the spring and summer, when 81% and 70% of the rivers, respectively, exhibited significant negative trends. The magnitudes of the changes are also remarkable. The average annual percentage change in streamflow magnitude of the 74 basins was –1.45% per year, which corresponds to an average streamflow reduction equivalent to 153 hm3 every year. The results of this study are relevant in view of future climatic scenarios and the evolution of land management in rural and mountain areas, as has already been observed in many parts of the Mediterranean and other regions. Global warming, resulting in continuous temperature increases and therefore evapotranspiration increases, is clearly one factor potentially affecting streamflow, together with land abandonment and subsequent continuous forest expansion. These results obtained in Spain could be extrapolated to other areas in the Mediterranean and beyond and should be taken into account in any water policy and water management in the near future.
Global sea-level rise (SLR) is projected to accelerate over the next century, with research indicating that global mean sea level may rise 18–48 cm by 2050, and 50–140 cm by 2100. Decision-makers, faced with the problem of adapting to SLR, utilize elevation data to identify assets that are vulnerable to inundation. This paper reviews techniques and challenges stemming from the use of Light Detection and Ranging (LiDAR) digital elevation models (DEMs) in support of SLR decision-making. A significant shortcoming in the methodology is the lack of comprehensive standards for estimating LiDAR error, which causes inconsistent and sometimes misleading calculations of uncertainty. Workers typically aim to reduce uncertainty by analyzing the difference between LiDAR error and the target SLR chosen for decision-making. The practice of mapping vulnerability to SLR is based on the assumption that LiDAR errors follow a normal distribution with zero bias, which is intermittently violated. Approaches to correcting discrepancies between vertical reference systems for land and tidal datums may incorporate tidal benchmarks and a vertical datum transformation tool provided by the National Ocean Service (VDatum). Mapping a minimum statistically significant SLR increment of 32 cm is difficult to achieve based on current LiDAR and VDatum errors. LiDAR DEMs derived from ‘ground’ returns are essential, yet LiDAR providers may not remove returns over vegetated areas successfully. LiDAR DEMs integrated into a GIS can be used to identify areas that are vulnerable to direct marine inundation and groundwater inundation (reduced drainage coupled with higher water tables). Spatial analysis can identify potentially vulnerable ecosystems as well as developed assets. A standardized mapping uncertainty needs to be developed given that SLR vulnerability mapping requires absolute precision for use as a decision-making tool.
Use of multi-model ensembles from global climate models to simulate the current and future climate change has flourished as a research topic during recent decades. This paper assesses the performance of multi-model ensembles in simulating global land temperature from 1960 to 1999, using Nash-Sutcliffe model efficiency and Taylor diagrams. The future trends of temperature for different scales and emission scenarios are projected based on the posterior model probabilities estimated by Bayesian methods. The results show that ensemble prediction can improve the accuracy of simulations of the spatiotemporal distribution of global temperature. The performance of Bayesian model averaging (BMA) at simulating the annual temperature dynamic is significantly better than single climate models and their simple model averaging (SMA). However, BMA simulation can demonstrate the temperature trend on the decadal scale, but its annual assessment of accuracy is relatively weak. The ensemble prediction presents dissimilarly accurate descriptions in different regions, and the best performance appears in Australia. The results also indicate that future temperatures in northern Asia rise with the greatest speed in some scenarios, and Australia is the most sensitive region for the effects of greenhouse gas emissions. In addition to the uncertainty of ensemble prediction, the impacts of climate change on agriculture production and water resources are discussed as an extension of this research.
Soil erosion and land degradation are serious problems in tropical Africa, especially Sub-Saharan Africa, where they are widely recognized as more serious problems than in non-tropical areas. Sub-Saharan Africa experiences deleterious levels of soil erosion, largely due to the interaction between harsh climates of high erosivity, fragile soils of high erodibility, steep slopes, and poor natural resource management. The fundamental challenge is to separate purely background-level soil erosion due to biophysical, geomorphic, topographic, and climatic conditions from what is caused by humans. This review shows that the human-induced causes of soil erosion and land degradation in Sub-Saharan Africa are not fully understood and some of the commonly listed causes may not always stand the test of critical scrutiny. The popular views of human-induced soil erosion and land degradation not only fail to take into consideration the fact that land degradation is primarily a physical process, but also they do injustice to adaptive ecosystem management by the local inhabitants. The review specifically questions the stereotypes of overpopulation, overgrazing, deforestation, overstocking, and general rangeland degradation due to human resource use in Sub-Saharan Africa. Empirical evidence suggests that biophysical factors including soil properties, climatic characteristics, topography, and vegetation can sometimes interact among themselves to yield high soil erosion and degradation rates independent of anthropogenic impacts.
Studying the temporal pattern of savanna gross primary productivity (GPP) is essential for predicting the response of the biome to global environmental changes. In this study, MODIS satellite data coupled with eddy covariance based flux measurements were used to estimate GPP using a remote sensing based light use efficiency model across a significant rainfall gradient in the Northern Territory (NT) region of Australia. Closed forest that occurred in wet and often fireproof environments assimilated (GPP) 4–6 times more carbon than grasslands and Acacia woodlands that grow in arid environments (<600 mm annual rainfall). However, due to their small spatial extent, closed forests contributed <0.5% of the regional budget compared to savanna woodlands (86%) and grasslands (32%). Annual rainfall was found to exert a significant influence on GPP for different vegetation types except for closed forest which was less sensitive to above-average rainfall. Interannual variability in GPP showed that arid ecosystems had a higher variation (>20%) compared to woodlands and forest (~5%). This variation in GPP was correlated with that of rainfall (R2 = 0.88, p<0.05). Analysis of the impact of wettest and driest years on GPP showed a strong positive correlation between the magnitude of the relative maxima in rainfall and maxima in GPP (R2 = 0.89, p<0.05). In contrast, the relative rainfall minima exhibited an insignificant relationship with relative GPP minima (R2 = 0.45, p = 0.07). These findings provide valuable information on the carbon uptake across the savanna biome and show the sensitivity of different vegetation systems to rainfall, a variable that may change in quantity and variability with projected climate change. Such data also show regions of high levels of carbon that could be linked with savanna management to protect the resources in the Australian savannas.
Accelerated soil erosion threatens sustainable food production by degrading the physical and biogeochemical functioning of arable field soils and lowering crop yields. Much less recognized is the potential for soil erosion to impinge on wider ecosystem services including the weed seedbank that underpins much of the biodiversity in temperate agro-ecosystems of northern Europe. This paper assesses the likely impact of soil erosion on the composition and abundance of the arable weed seedbank, and presents an overview of erosion mechanisms affecting arable land coupled with an outline of the main factors influencing arable weed seedbank abundance and composition. The information presented on both these sets of processes enables assessment of the likely impact of soil erosion on arable seedbank biodiversity at the field and landscape scales. Combining mean annual net erosion rates of c. 7 t ha-1 yr-1 and seedbank densities c. 2000 seeds m-2, both figures broadly representative of UK conditions, produces an average annual loss of the field seed inventory of c. 0.5% yr-1. Where seedbank abundance is otherwise relatively stable (i.e. losses through death, germination and weed control are largely balanced by gain through seed rain), average soil loss rates could export c. 10% of the arable weed seedbank in 20 years. Net erosion data conceal within-field sediment deposition within swales, foot slopes, buffer strips and hedgerows which provides a further dimension of spatial restructuring of weed assemblages. Seed size and shape also influence hydrodynamic behaviour through selective entrainment and preferential deposition. It is concluded that earth surface processes play an under-recognized role in structuring field-scale weed-based biodiversity in agro-ecosystems over decadal timescales.
Assertions of a ‘naughty world’ (Kennedy, 1979) point to the importance of place-based knowledge in informing landscape interpretations and management applications. Building upon conceptual and theoretical insights into the geomorphic character, behaviour and evolution of rivers, this paper outlines an approach to the practice of fluvial geomorphology: ‘reading the landscape’. This scaffolded framework of field-based interpretations explicitly recognizes the contingent nature of biophysical interactions within any given landscape. A bottom-up, constructivist approach is applied to identify landforms, assess their morphodynamics, and interpret the interaction and evolution of these features at reach and catchment scales. Reading the landscape is framed as an open-ended and generic set of questions that inform process-form interpretations of river landscapes. Rather than relying unduly on conceptual or theoretical representations of landscapes that suggest how the world ‘should’ ideally look and behave, appropriately contextualized, place-based understandings can be used to detect where local differences matter, thereby addressing concerns for the transferability of insights between locations and the representativeness of sample or reference sites. The approach provides a basis for scientifically informed management efforts that respect and work with the inherent diversity and dynamics of any given river system.
Geomorphology offers an effective entry point into wider debates across geography and the sciences, framing understandings of landscapes as manifestations of complex and emergent relationships that can be used as a platform to support conversations among multiple and diverse worldviews. Physical geographers have much to contribute in moving beyond monological (one only) views of landscapes. This paper draws upon concepts of emergence, connectivity and space-time relationality to develop an ‘ethnogeomorphic’ outlook upon biophysical-and-cultural (‘living’) landscapes. This perspective is grounded through ethnographic case studies with Indigenous<xref ref-type="fn" rid="fn1-0309133313483164">1</xref> communities in Australia and Canada that examine knowledge production and concerns for environmental negotiation and decision-making. Extending beyond a traditional approach to ethnosciences, ethnogeomorphology seeks to move beyond cross-disciplinary scientific disciplines (and their associated epistemologies) towards a shared (if contested) platform of knowledge transfer and communication that reflects multiple ways of connecting to landscapes. Convergent perspectives upon landscape understandings are highlighted from Indigenous knowledges and emerging, relational approaches to geomorphic analysis. Ethnogeomorphology presents a situated, non-relativist response to people–landscape connections that reflects and advocates sentient relationships to place. Potential applications of ethnogeomorphology as an integrating theme of geographic inquiry are explored, highlighting important tensions in the knowledge production process.
The authors regret that the paper published by <xref ref-type="bibr" rid="bibr5-0309133312447025">Nadal-Romero et al. (2011</xref>) contains an error related to 19 Spanish Sediment yield (SY) data reported by <xref ref-type="bibr" rid="bibr1-0309133312447025">Cantón et al. (2001b</xref>, <xref ref-type="bibr" rid="bibr2-0309133312447025">2003</xref>) and by <xref ref-type="bibr" rid="bibr4-0309133312447025">Lázaro et al. (2008</xref>). <xref ref-type="table" rid="table1-0309133312447025">Table 1</xref><anchor graphic="tbl1"/> indicates the correct SY data. Re-plotting these data results in some changes in <xref ref-type="fig" rid="fig7-0309133312447025">Figures 7</xref><anchor graphic="fig7"/> to <xref ref-type="fig" rid="fig16-0309133312447025">16</xref> of the paper by <xref ref-type="bibr" rid="bibr5-0309133312447025">Nadal-Romero et al. (2011</xref>). Most changes in the re-drawn figures occur for SY measured on very small areas (i.e. < 0.0001 ha) (<xref ref-type="fig" rid="fig7-0309133312447025">Figures 7</xref> to <xref ref-type="fig" rid="fig11-0309133312447025">11</xref>). Here we briefly discuss each of these figures focusing on the changes due to the use of the correct SY data.