Lightning fatalities in Estonia, 1880–1940     

Sepp  Mait  Pae  Taavi  Uuemaa  Evelyn 《Natural Hazards》2021,106(1):255-275

Natural Hazards - Natural disasters are increasing in frequency in China. Enhancing residents' livelihood resilience and adjusting their livelihood strategies have gradually become effective...  相似文献   

Patterns of accessing variable resources across time and space: Desert plants,animals and people     

R.R.J. McAllister  D.M.S. Smith  C.J. Stokes  F.J. Walsh 《Journal of Arid Environments》2009,73(3):338-346

Key resources in arid and semi-arid systems are highly variable in time and space. Biophysical variability is mainly driven directly or indirectly by rainfall. Arid-dwelling people are also exposed to variability – indirectly from their biophysical environments, and directly as a result of sparse, mobile populations and variable, distant signals from policy and markets. The tradeoffs between the benefits and costs of increasing the scale of resource use are comparatively more critical in shaping system dynamics in arid systems than mesic environments. Understanding the strategies employed to scale resource use is vital for arid-system management. We contribute to this discussion using a conceptual model, based on modern portfolio theory, to explore how variability is managed by diversifying access to resources across space and time. The model is developed using ecological ideas and our Australian case knowledge, but demonstrates general learning on how optimal investment in strategies changes with resource distribution, and with the physical characteristics of the entity (e.g. plant, animal) and resource (e.g. water, nutrients) in question. Using pastoral enterprise, arid-system administration and policy cases, we argue that people and organisations need variability-coping strategies that are comparable with biophysical responses, and that strategy behaviour needs greater acknowledgement in managing arid systems.  相似文献   

Stand structure and productivity of the introducedRhizophora mangle in Hawaii     

Evelyn F. Cox  James A. Allen 《Estuaries and Coasts》1999,22(2):276-284

Since its introduction in the early part of this century,Rhizophora mangle L. has spread extensively through most of the main islands of the Hawaiian Archipelago. We investigated the structural properties and estimated productivity of aR. mangle population at Nuupia Ponds Wildlife Management Area (NPWMA), on windward Oahu, where the mangroves were being controlled due to their propensity to overgrow archaeological sites and the habitat of endangered Hawaiian waterbirds. Mangroves within NPWMA were very dense (>24,000 trees ha⁻¹) and most were relatively small (only 3.3% of the trees were ≥10 cm DBH). Mean basal area, aboveground biomass, and number of seedlings were all high, at 37.2 m² ha⁻¹, 279 t (dry wt) ha⁻¹, and 121 m⁻², respectively. The seedling, density may be particularly unusual and appears to be due to extremely high rates of propagule, production coupled with low rates of propagule predation. Stand productivity was estimated by stem growth (allometry), litterfall, and a light attenuation approach to determining net canopy photosynthetic production. All three methods yielded estimates that are higher than previously, reported forR. mangle and comparable with estimates of highly productiveRhizophora spp.-dominated stands in Australia and Asia. The high density, biomass, and productivity of this stand relative to stands within the species' native range may be due to a combination of favorable site conditions, lack of competition from other woody plants, and very low rates of herbivory and propagule predation.  相似文献   

Polar Winter: A Biological Model for Impact Events and Related Dark/Cold Climatic Changes     

Charles S. Cockell  M. Dale Stokes 《Climatic change》1999,41(2):151-173

Models of the climatic perturbation caused by a large scale extraterrestrial impact predict an injection of dust into the stratosphere. This would cause the onset of environmental conditions whose two principal characteristics are a prolonged period of darkness and reduced global temperatures. Similar scenarios follow large scale volcanic eruptions, wildfires and they are predicted for a nuclear winter following a protracted nuclear exchange. A significant drop in temperature and solar insolation are also characteristics of the polar winter. In this paper the onset and emergence from the polar winter is examined as a potential biological framework for studying immediate biological effects following transition into and out of a dark/cold catastrophe. Limitations of the conceptual model, particularly with respect to the fact that polar organisms are well adapted to a regular and severe dark/cold climatic change (which the rest of the Earth's biota is not) are discussed. The model has implications for the poles as an extinction refuge during such climatic changes.  相似文献   

A methodology for community-level hypothesis testing applied to detect trends in phytoplankton and fish communities in Irish waters     

Christopher P. Lynam  Caroline Cusack  David Stokes 《Estuarine, Coastal and Shelf Science》2010

Many simple (univariate, bivariate) and complex (multivariate) statistical techniques are used to investigate trends in biological communities and to test hypotheses about potential relationships between ecosystem components. However, the simple methods that are commonly used (regression and correlation) are prone to Type I error (rejecting a true null hypothesis) when applied repeatedly. Although multivariate methods are preferable for community analysis, their computations are mathematically demanding and the interpretation of their outputs can be challenging. We present simple community analysis (SCA), an intuitive methodology with which to test for trend and correlation at the community-level. We demonstrate SCA using fish survey and phytoplankton count data: the non-parametric test statistic, Kendall's tau, is used to determine the strength of trends in abundance in 65 species of fish sampled during the Irish groundfish survey (maximal length of sampling periods were 1999–2007 in ICES division VIIg and 2002–2007 in divisions VIa, VIIb and VIIj, however catches of numerous species were not recorded prior to 2003) and in 77 genera of phytoplankton sampled at Irish aquaculture sites (1991–2002). The sample distribution of the test statistic (tau is used here, but other measures may be used) is compared to the expected distribution using distributional tests (Kolmogorov–Smirnov) to evaluate the significance of community-level trends. The phytoplankton community has been increasing in abundance on Irish western and southwestern coasts (Kolmogorov–Smirnov test D > 0.5, p < 0.001). Similarly, and in agreement with previously published long-term studies, Lusitanian fish have been increasing on the shelf to the north and west of Ireland (D ≥ 0.35, p < 0.001), while the boreal community has been declining to the south (southeast, D = 0.47, p < 0.001; southwest, D = 0.32, p = 0.03). Although SCA cannot identify causality, the trends in fish communities are as expected given the combined impacts of climate change and fishing: thus, we suggest that these are currently the main drivers of change and the precise mechanisms at play merit further study with long-term data. Biological processes at aquaculture sites should be investigated further as possible mechanisms explaining both the observed positive trends in the phytoplankton community and the restriction of negative trends to Heterosigma and eight dinoflagellate genera. Applied in conjunction with other statistical tools, SCA should aid researchers who aim to describe change in communities and community-level relationships with covariates. SCA is a powerful tool for hypothesis testing at the community-level, which simultaneously produces information at the community member level for more detailed insight, while providing simple summary statistics for managers and policy makers.  相似文献   

Ignoring market failure in quota leasing?     

Evelyn Pinkerton  Danielle N. Edwards 《Marine Policy》2010

This short communication is, in part, a response to the Bruce Turris' rejoinder (Marine Policy…2010) to Pinkerton et al., The elephant in the room: The hidden costs of leasing individual transferable fishing quotas (Marine Policy, July 2009). In responding to this article on the unacknowledged problems of unregulated and even unrecorded leasing of individual transferable fishing quotas (ITQs), Turris illustrated the point of the original article well by minimizing the status of leasing as a major influence leading to problems with the fishery: an elephant in the room. Turris focused instead on relatively small and less relevant details, misrepresented the argument, and largely ignored or skirted our discussion of the absent structural conditions important for open competition and efficient outcomes. This response addresses several of his concerns, elaborates on some of the initial points in the original article and contributes some new ones.  相似文献   

The elephant in the room: The hidden costs of leasing individual transferable fishing quotas     

Evelyn Pinkerton  Danielle N. Edwards 《Marine Policy》2009

Despite the increasingly positive reviews of individual transferable quotas (ITQs), few studies have considered how quota leasing activities can reduce the economic benefits to society and to fishermen operating under the ITQ fisheries system. This analysis reveals negative economic impacts of ITQs previously overlooked by examining the extent of quota leasing and the relationship between the catch value, the cost of fishing, and the quota lease price in the BC halibut fishery, long considered a poster child for ITQs. Findings challenge assumptions of economic theory used to promote the benefits of ITQs.  相似文献   

An Acheulian site near Bir Kiseiba in the Darb el Arba'in Desert,Egypt     

C. Vance Haynes  T. A. Maxwell  A. El Hawary  K. A. Nicoll  S. Stokes 《Geoarchaeology》1997,12(8):819-832

A small concentration of Acheulian cleavers and handaxes within the driest region on Earth adds to the increasing evidence that the eastern Sahara was considerably more verdant during the Middle Pleistocene than it is today. The similarities to stone artifact assemblages of Acheulian sites in sub-Saharan Africa and in the Levant support the evidence for the movement of hominids, utilizing the Kombewa lithic technology, between Africa and the Middle East during the Middle Pleistocene. © 1997 John Wiley & Sons, Inc.  相似文献   

Geomorphology under ice streams: Moving from form to process          下载免费PDF全文

Chris R. Stokes 《地球表面变化过程与地形》2018,43(1):85-123

Ice streams are integral components of an ice sheet's mass balance and directly impact on sea level. Their flow is governed by processes at the ice‐bed interface which create landforms that, in turn, modulate ice stream dynamics through their influence on bed topography and basal shear stresses. Thus, ice stream geomorphology is critical to understanding and modelling ice streams and ice sheet dynamics. This paper reviews developments in our understanding of ice stream geomorphology from a historical perspective, with a focus on the extent to which studies of modern and palaeo‐ice streams have converged to take us from a position of near‐complete ignorance to a detailed understanding of their bed morphology. During the 1970s and 1980s, our knowledge was limited and largely gleaned from geophysical investigations of modern ice stream beds in Antarctica. Very few palaeo‐ice streams had been identified with any confidence. During the 1990s, however, glacial geomorphologists began to recognise their distinctive geomorphology, which included distinct patterns of highly elongated mega‐scale glacial lineations, ice stream shear margin moraines, and major sedimentary depocentres. However, studying relict features could say little about the time‐scales over which this geomorphology evolved and under what glaciological conditions. This began to be addressed in the early 2000s, through continued efforts to scrutinise modern ice stream beds at higher resolution, but our current understanding of how landforms relate to processes remains subject to large uncertainties, particularly in relation to the mechanisms and time‐scales of sediment erosion, transport and deposition, and how these lead to the growth and decay of subglacial bedforms. This represents the next key challenge and will require even closer cooperation between glaciology, glacial geomorphology, sedimentology, and numerical modelling, together with more sophisticated methods to quantify and analyse the anticipated growth of geomorphological data from beneath active ice streams. © 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

Assessing groundwater recharge in an Andean closed basin using isotopic characterization and a rainfall-runoff model: Salar del Huasco basin,Chile   总被引：1，自引：0，他引：1  

Javier Uribe  José F. Muñoz  Jorge Gironás  Ricardo Oyarzún  Evelyn Aguirre  Ramón Aravena 《Hydrogeology Journal》2015,23(7):1535-1551

  相似文献