Progress in Physical Geography recent issues

Macroecology: more than the division of food and space among species on continents

Smith, F. A., Lyons, S. K., Morgan Ernest, S.K., Brown, J. H. — 2008-07-31

Macroecology is a big-picture, statistical approach to the study of ecology. By focusing on broadly occurring patterns and processes operating at large spatial and temporal scales and ignoring localized and fine-scaled details, macroecology aims to uncover general mechanisms operating at organism, population and ecosystem levels of organization. Although such an approach is evident in writings dating from the mid- to late 1800s, not until 1989 was the domain of macroecology clearly articulated. Since then there has been an exponential growth in publications employing a macroecological perspective. Here we (1) briefly review the history of macroecology, with emphasis on cultural, scientific and technological innovations that made this approach possible, (2) highlight current developments in the field, including its increasing linkages with biogeography and other disciplines, and (3) point to likely future directions. We also touch upon methodological, statistical and institutional challenges faced by this and other highly interdisciplinary approaches. Our review of macroecology is especially timely, since it has been 20 years since the term was coined and the seminal paper published.

Impacts of climate change on species, populations and communities: palaeobiogeographical insights and frontiers

2008-07-31

Understanding climate change and its potential impact on species, populations and communities is one of the most pressing questions of twenty-first-century conservation planning. Palaeobiogeographers working on Cenozoic fossil records and other lines of evidence are producing important insights into the dynamic nature of climate and the equally dynamic response of species, populations and communities. Climatic variations ranging in length from multimillennia to decades run throughout the palaeo-records of the Quaternary and earlier Cenozoic and have been shown to have had impacts ranging from changes in the genetic structure and morphology of individual species, population sizes and distributions, community composition to large-scale bio-diversity gradients. The biogeographical impacts of climate change may be due directly to the effects of alterations in temperature and moisture on species, or they may arise due to changes in factors such as disturbance regimes. Much of the recent progress in the application of palaeobiogegraphy to issues of climate change and its impacts can be attributed to developments along a number of still advancing methodological frontiers. These include increasingly finely resolved chronological resolution, more refined atmosphere-biosphere modelling, new biological and chemical techniques in reconstructing past species distributions and past climates, the development of large and readily accessible geo-referenced databases of biogeographical and climatic information, and new approaches in fossil morphological analysis and new molecular DNA techniques.

The role of molecular genetics in sculpting the future of integrative biogeography

2008-07-31

We review the expanding role of molecular genetics in the emergence of a vibrant and vital integrative biogeography. The enormous growth over the past several decades in the number and variety of molecular-based phylogenetic and population genetics studies has become the core information used by biogeographers to reconstruct the causal connections between historical evolutionary and ecological attributes of taxa and biotas, and the landscapes and seascapes that contain them. A proliferation of different approaches, sequences, and genomes have provided for the integration of a `biogeography of the Late Neogene' with other Earth and biological sciences under the rubrics of phylogeography, landscape genetics, and phylochronology. Approaches designed explicitly to take advantage of unique properties of molecular genetic information have led to the re-emergence of dispersal as an analytically tractable process that historical biogeographers can now use, along with vicariance, to reconstruct the geographical context of diversification. Concomitant with the expanding amount of information available, molecular data sets often provide for estimates of lineage divergence dates, and analytical tools for doing so continue to improve. The comparability of molecular-based estimates of phylogenetic and population genetic histories across non-related taxa has stimulated deployment of new methods to test for spatial and temporal congruence across co-distributed taxa and ecosystems, and thus increased rigour in hypothesis-testing. We illustrate how a molecular genetics framework has provided robust and novel reconstructions of historical biogeographical pattern and process in three different systems, and finish with some thoughts on the role a molecular genetic-based biogeography will play in predicting alternative futures of biodiversity.

Measuring and modelling biodiversity from space

Gillespie, T. W., Foody, G. M., Rocchini, D., Giorgi, A. P., Saatchi, S. — 2008-07-31

The Earth is undergoing an accelerated rate of native ecosystem conversion and degradation and there is increased interest in measuring and modelling biodiversity from space. Biogeographers have a long-standing interest in measuring patterns of species occurrence and distributional movements and an interest in modelling species distributions and patterns of diversity. Much progress has been made in identifying plant species from space using high-resolution satellites (QuickBird, IKONOS), while the measurement of species movements has become commonplace with the ARGOS satellite tracking system which has been used to track the movements of thousands of individual animals. There have been significant advances in land-cover classifications by combining data from multi-passive and active sensors, and new classification techniques. Species distribution modelling has been growing at a striking rate and the incorporation of spaceborne data on climate, topography, land cover, and vegetation structure has great potential to improve models. There have been significant advances in modelling species richness, alpha diversity, and beta diversity using multisensors to quantify land-cover classifications and landscape metrics, measures of productivity, and measures of heterogeneity. Remote sensing of nature reserves can provide natural resources managers with near real-time data within and around reserves that can be used to support conservation efforts anywhere in the world. Future research should focus on incorporating recent spaceborne sensors, more extensive integration of available spaceborne imagery, and the collection and dissemination of high-quality field data. This will improve our understanding of the distribution of life on earth.

GIS: biodiversity applications

Foody, G.M. — 2008-07-31

The use of historical data and artifacts in geomorphology

Trimble, S. W. — 2008-03-28

Historical data and artifacts, as commonly used in historical geography, can provide powerful tools for dating geomorphological processes over the past century or more and applications can range from months to millennia. Investigations in geomorphology and environmental management can be greatly enhanced by the use of historical techniques. The approach is useful for tracing human-induced changes as well as for those occurring naturally. Several primary techniques are introduced in this essay.

Airborne LiDAR for DEM generation: some critical issues

Xiaoye Liu, — 2008-03-28

Airborne LiDAR is one of the most effective and reliable means of terrain data collection. Using LiDAR data for digital elevation model (DEM) generation is becoming a standard practice in spatial related areas. However, the effective processing of the raw LiDAR data and the generation of an efficient and high-quality DEM remain big challenges. This paper reviews the recent advances of airborne LiDAR systems and the use of LiDAR data for DEM generation, with special focus on LiDAR data filters, interpolation methods, DEM resolution, and LiDAR data reduction. Separating LiDAR points into ground and non-ground is the most critical and difficult step for DEM generation from LiDAR data. Commonly used and most recently developed LiDAR filtering methods are presented. Interpolation methods and choices of suitable interpolator and DEM resolution for LiDAR DEM generation are discussed in detail. In order to reduce the data redundancy and increase the efficiency in terms of storage and manipulation, LiDAR data reduction is required in the process of DEM generation. Feature specific elements such as breaklines contribute significantly to DEM quality. Therefore, data reduction should be conducted in such a way that critical elements are kept while less important elements are removed. Given the high-density characteristic of LiDAR data, breaklines can be directly extracted from LiDAR data. Extraction of breaklines and integration of the breaklines into DEM generation are presented.

Goal functions in ecosystem and biosphere evolution

Phillips, J. D. — 2008-03-28

Although natural selection operates at the gene or individual level, a number of proposals, hypotheses and theories exist postulating the evolution of entities such as ecosystems, and indeed the entire biosphere. Further, there exist theories of evolution that are based not on the relative advantages (be they competitive or mutualistic) conferred on individuals, populations, or taxa, but on community, ecosystem, or biosphere-level goal functions, typically related to productivity criteria. A key question is why nature would seek to optimize energy flux or efficiency, biogeochemical cycling, or anything else. While development along some optimal pathway does occur, whether this is a rule, a tendency, or merely a possibility is not clear. This paper reviews theories of evolution and ecosystem development based explicitly or implicitly on goal functions. If the environment is conceptualized as a multidimensional resource space allocated among organisms, then only three assumptions are necessary for a developmental pathway toward increasing productivity: (1) higher rates of resource procurement and use are associated with ecological or selective advantages; (2) the environment is biologically saturated (or tending in that direction); and (3) the resource space is not contracting due to external abiotic forcings. This suggests that a tendency for evolution along a pathway toward maximum energy and/more matter fluxes, storages, transformations, or cycling does not require goal functions or natural selection operating at levels beyond the individual. Key research needs involve rigorous testing of these assumptions (particularly the first two), and the relative importance of, and relationships between, various notions of productivity.

Glaciohydraulic supercooling

Knight, P. G., Cook, S. J. — 2008-03-28

Biodiversity and extinction: the importance of being common

Gaston, K. J. — 2008-03-28

Arid geomorphology: recent progress from an Earth System Science perspective

Tooth, S. — 2008-03-28

Grove, J.M. 1988: The Little Ice Age. London: Routledge, xxii + 498 pp

Fagan, B. — 2008-03-28

Book review: Gopalakrishnan, C. and Okada, N., editors 2008: Water and disasters. London: Routledge. 144 pp. {pound}65 cloth, {pound}22.99 paper. ISBN: 978 0 415 45426 1 cloth, 978 0 415 46207 5 paper

Goudie, A.S. — 2008-03-28

Passive microwave remote sensing of seasonal snow-covered sea ice

Langlois, A., Barber, D. G. — 2008-01-31

The Arctic is thought to be an area where we can expect to see the first and strongest signs of global-scale climate variability and change. We have already begun to see a reduction in: (1) the aerial extent of sea ice at about 3% per decade and (2) ice thickness at about 40%. At the current rate of reduction we can expect a seasonally ice-free Arctic by midway through this century given the current changes in thermodynamic processes controlling sea-ice freeze-up and decay. Many of the factors governing the thermodynamic processes of sea ice are strongly tied to the presence and geophysical state of snow on sea ice, yet snow on sea ice remains poorly studied. In this review, we provide a summary of the current state of knowledge pertaining to the geophysical, thermodynamic and dielectric properties of snow on sea ice. We first give a detailed description of snow thermophysical properties such as thermal conductivity, diffusivity and specific heat and how snow geophysical/electrical properties and the seasonal surface energy balance affect them. We also review the different microwave emission and scattering mechanisms associated with snow-covered first-year sea ice. Finally, we discuss the annual evolution of the Arctic system through snow thermodynamic (heat/mass transfer, metamorphism) and aeolian processes, with linkages to microwave remote sensing that have yet to be defined from an annual perspective in the Arctic.

Tsunami geoscience

Dawson, A., Stewart, I. — 2008-01-31

Research in tsunami geoscience has accelerated markedly ever since the tragedy of the Indian Ocean tsunami of Boxing Day 2004. Yet, for many decades and centuries, scholars have been describing a multiplicity of tsunami events. Thus the Royal Society devoted a whole volume to the effects of the Great Lisbon earthquake and tsunami of November AD 1755 while in the early nineteenth century Charles Darwin was describing the great tsunami at Valdivia, Chile, in his account of the Voyage of the Beagle. Today, research in tsunami geoscience is still finding its feet. Thus, whereas there has been a wealth of publications on the reconstruction of Late Quaternary and Holocene tsunamis, the literature describing evidence for tsunamis in the geological record are rare. In this paper, we describe how our understanding of tsunamis has changed over time and we try also to identify areas of tsunami geoscience worthy of future study.

Towards accurate determination of surface height using modern geoinformatic methods: possibilities and limitations

Gao, J. — 2008-01-31

Over recent decades several modern geoinformatic height-finding methods have emerged, including global positioning system (GPS), interferometric radar, and airborne laser scanner (ALS) or lidar. In conjunction with the conventional survey and photogrammetric method, they have found wide applications that demand varying levels of accuracy. In this paper, the principles of each method are briefly summarized. The discussion then concentrates on the accuracy level achievable with each method. The factors that affect the accuracy, wherever possible, are comprehensively evaluated. This review has revealed that the highest accuracy achievable is still with the levelling method, followed by the photogrammetric method. This situation is likely to change in light of real-time kinematic GPS coupled with ALS. In contrast to the imaging methods that are suited to obtain highly accurate, fine-resolution digital elevation models (DEMs) at a local scale, GPS is the most efficient at obtaining heights at spots or along lines accurately. ALS is the only method applicable to acquisition of subsurface heights in vegetated areas. These airborne methods are complementary to their space-borne counterparts, such as Shuttle Radar Topographic Mapping and Shuttle Laser Altimeter, both being ideal in obtaining DEMs at the regional and global scales. The synergistic use of GPS with lidar offers the best hope in obtaining cm-level accuracies essential for monitoring ground subsidence and tectonic uplift. Height measurements accurate to subcentimetres needed for national levelling surveys are possible only after the tropospheric path delay is externally calibrated using Raman lidar data during GPS data analysis.

Nutrient transport associated with water erosion: progress and prospect

Yihe Lu, , Bojie Fu, , Liding Chen, , Guohua Liu, , Wei Wei, — 2008-01-31

Along with the major water erosion process, large amounts of soil nutrient can be transported to water bodies that may degrade the erosion sites and result in water pollution problems in the nutrient-receiving water bodies. Because of the far-reaching ecological and environmental impacts of the nutrient transport processes during water erosion, much research has been done on this topic. The progress of this research topic is reviewed from the perspective of nutrient sources, covering triggers, carriers and forms of nutrient transport, and the factors regulating nutrient transport. Although much progress has been made, challenges still lie ahead. A multidisciplinary and integrative approach, therefore, needs to be taken to resolve the theoretical, methodological and practical problems in water erosion and nutrient transport research. More specifically, the interactions between landscape pattern and nutrient transport processes and spatiotemporal scale and scaling are the two central themes of consideration in methodological integration. It is also important to respect the dynamic and stochastic nature of nutrient transport which is closely related to rainfall-runoff events. The human dimension, formerly a relative weak point in research, needs to be strengthened to gain understanding and a more informed practical control over soil and nutrient loss and conservation.

Sea levels: resolution and uncertainty

Edwards, R. — 2008-01-31

Dynamic changes in savanna and seasonally dry vegetation through time

Furley, P. A., Metcalfe, S. E. — 2008-01-31

Biogeography and macroecology: now a significant component of physical geography

Kent, M. — 2008-01-31

Elton, C.S. 1958: The ecology of invasions by animals and plants. London: Methuen

Richardson, D. M., Pysek, P. — 2008-01-31

Short review notes

Goudie, A.S. — 2008-01-31

Assessment and prediction of natural hazards from satellite imagery

Gillespie, T. W., Chu, J., Frankenberg, E., Thomas, D. — 2007-10-29

Since 2000, there have been a number of spaceborne satellites that have changed the way we assess and predict natural hazards. These satellites are able to quantify physical geographic phenomena associated with the movements of the earth's surface (earthquakes, mass movements), water (floods, tsunamis, storms), and fire (wildfires). Most of these satellites contain active or passive sensors that can be utilized by the scientific community for the remote sensing of natural hazards over a number of spatial and temporal scales. The most useful satellite imagery for the assessment of earthquake damage comes from high-resolution (0.6 m to 1 m pixel size) passive sensors and moderate resolution active sensors that can quantify the vertical and horizontal movement of the earth's surface. High-resolution passive sensors have been used successfully to assess flood damage while predictive maps of flood vulnerability areas are possible based on physical variables collected from passive and active sensors. Recent moderate resolution sensors are able to provide near real-time data on fires and provide quantitative data used in fire behavior models. Limitations currently exist due to atmospheric interference, pixel resolution, and revisit times. However, a number of new microsatellites and constellations of satellites will be launched in the next five years that contain increased resolution (0.5 m to 1 m pixel resolution for active sensors) and revisit times (daily < 2.5 m resolution images from passive sensors) that will significantly improve our ability to assess and predict natural hazards from space.

The modifiable areal unit problem (MAUP) in physical geography

Dark, S. J., Bram, D. — 2007-10-29

Of particular importance to the study of large-scale phenomena in physical geography is the modifiable areal unit problem (MAUP). While often viewed as only a problem in human geography (particularly demographic studies), the MAUP is an issue for all quantitative studies in geography of spatial phenomena (Openshaw and Taylor, 1979). Increasingly, remote sensing and Geographic Information Systems (GIS) are being used to assess the distribution of phenomena from a large scale. These phenomena are modelled using areal units that can take any shape or size resulting in complications with statistical analysis related to both the scale and method used to create the areal units. In this paper, we define the modifiable areal unit problem, present examples of when it is a problem in physical geography studies, and review some potential solutions to the problem. Our aim is to increase awareness of this complicated issue and to promote further discussion and interest in this topic.

Using the past to constrain the future: how the palaeorecord can improve estimates of global warming

Edwards, T. L., Crucifix, M., Harrison, S. P. — 2007-10-29

Climate sensitivity is defined as the change in global mean equilibrium temperature after a doubling of atmospheric CO₂ concentration and provides a simple measure of global warming. An early estimate of climate sensitivity, 1.5—4.5°C, has changed little subsequently, including the latest assessment by the Intergovernmental Panel on Climate Change. The persistence of such large uncertainties in this simple measure casts doubt on our understanding of the mechanisms of climate change and our ability to predict the response of the climate system to future perturbations. This has motivated continued attempts to constrain the range with climate data, alone or in conjunction with models. The majority of studies use data from the instrumental period (post-1850), but recent work has made use of information about the large climate changes experienced in the geological past. In this review, we first outline approaches that estimate climate sensitivity using instrumental climate observations and then summarize attempts to use the record of climate change on geological timescales. We examine the limitations of these studies and suggest ways in which the power of the palaeoclimate record could be better used to reduce uncertainties in our predictions of climate sensitivity.

Recent developments in estimating land surface biogeophysical variables from optical remote sensing

Liang, S. — 2007-10-29

Earth system models and many other applications require biogeophysical variables, and remote sensing is the only means by which to estimate them at the appropriate spatial and temporal scales. Developing advanced inversion methods to solve ill-posed multidimensional nonlinear inversion problems is critical and very challenging. This article reviews state-of-the-art algorithms for estimating land surface biogeophysical variables in optical remote sensing (from the visible to the thermal infrared spectrum) to stimulate the development of new algorithms and to utilize existing ones.

Tansley, A.G. 1935: The use and abuse of vegetational concepts and terms. Ecology 16, 284 307

Trudgill, S. — 2007-10-29

Fire ecology

Bowman, D.M.J.S. — 2007-10-29

Book review: Hofer, Thomas and Messerli, Bruno 2006: Floods in Bangladesh: history, dynamics and rethinking the role of the Himalayas. Tokyo, New York, Paris: United Nations University Press. ISBN: 9280811215

Chapman, G. P. — 2007-10-29

Short review note: Bell, F.G. 2007: Basic environmental and engineering geology. Dunbeath: Whittles Publishing and Boca Raton, FL: CRC Press. ix + 342 pp. {pound}65. ISBN: 1904445020

Goudie, A.S. — 2007-10-29