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Km Squares (km + square)
Selected AbstractsA method for estimating the extent of standing fresh waters of different trophic states in Great BritainAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2001M.A. Palmer Abstract 1.,The total area of standing fresh water in Great Britain has been estimated at approximately 2400 km2. The aim of the work described in this paper was to estimate the extent of the dystrophic, oligotrophic, mesotrophic and eutrophic habitat types making up this total. 2.,Botanical survey data collected by the statutory nature conservation agencies provided habitat type and surface area for 3500 water bodies, mostly in Scotland. Because survey in England and Wales had been less thorough than in Scotland, it was not possible to estimate the areas of habitat types simply by direct extrapolation from the survey sample to the total resource of standing water in Great Britain. 3.,A system of Trophic Ranking Scores (TRS) has been developed for aquatic plant species. Using plant records from the Biological Records Centre, a mean TRS for each 10×10 km square was produced, and Great Britain was divided into TRS bands. For each of these bands, the percentage by surveyed area of each freshwater habitat type was calculated. These percentages were applied to the total area of standing water in each TRS band, obtained from Ordnance Survey summary statistics, in order to predict the proportions of the different habitat types likely to occur in each band. The extent of these habitats in Great Britain as a whole could then be calculated. 4.,Estimates produced by this method of the extent of the four standing freshwater habitat types in Great Britain are: dystrophic , 11 km2 (0.5%); oligotrophic , 1445 km2 (60%); mesotrophic , 267 km2 (11%); eutrophic , 679 km2 (28%). 5.,The application of this work to nature conservation is discussed. Copyright © 2001 John Wiley & Sons, Ltd. [source] Where do Swainson's hawks winter?DIVERSITY AND DISTRIBUTIONS, Issue 5 2008Satellite images used to identify potential habitat ABSTRACT During recent years, predictive modelling techniques have been increasingly used to identify regional patterns of species spatial occurrence, to explore species,habitat relationships and to aid in biodiversity conservation. In the case of birds, predictive modelling has been mainly applied to the study of species with little variable interannual patterns of spatial occurrence (e.g. year-round resident species or migratory species in their breeding grounds showing territorial behaviour). We used predictive models to analyse the factors that determine broad-scale patterns of occurrence and abundance of wintering Swainson's hawks (Buteo swainsoni). This species has been the focus of field monitoring in its wintering ground in Argentina due to massive pesticide poisoning of thousands of individuals during the 1990s, but its unpredictable pattern of spatial distribution and the uncertainty about the current wintering area occupied by hawks led to discontinuing such field monitoring. Data on the presence and abundance of hawks were recorded in 30 × 30 km squares (n = 115) surveyed during three austral summers (2001,03). Sixteen land-use/land-cover, topography, and Normalized Difference Vegetation Index (NDVI) variables were used as predictors to build generalized additive models (GAMs). Both occurrence and abundance models showed a good predictive ability. Land use, altitude, and NDVI during spring previous to the arrival of hawks to wintering areas were good predictors of the distribution of Swainson's hawks in the Argentine pampas, but only land use and NDVI were entered into the model of abundance of the species in the region. The predictive cartography developed from the models allowed us to identify the current wintering area of Swainson's hawks in the Argentine pampas. The highest occurrence probability and relative abundances for the species were predicted for a broad area of south-eastern pampas that has been overlooked so far and where neither field research nor conservation efforts aiming to prevent massive mortalities has been established. [source] GIS-based niche models identify environmental correlates sustaining a contact zone between three species of European vipersDIVERSITY AND DISTRIBUTIONS, Issue 3 2008F. Martínez-Freiría ABSTRACT The current range of European vipers is mostly parapatric but local-scale allopatric distribution is common and few cases of sympatry are known. In the High Course of Ebro River, northern Spain, there is a contact zone between Vipera aspis, V. latastei, and V. seoanei. Sympatry was detected between aspis and latastei and also specimens with intermediate morphological traits. Presence-data at a local scale (1 × 1 km) and ecological niche-based models manipulated in a GIS were used to (1) identify how environmental factors correlate with the distribution of the three vipers and with the location of the sympatry area, and (2) identify potential areas for viper occurrence and sympatry. Ensemble for casting with 10 Maximum Entropy models identified a mixture of topographical (altitude, slope), climatic (precipitation, evapotranspiration, and minimum and maximum temperature), and habitat factors (land cover) as predictors for viper occurrence. Similar predicted probabilities according to the variation of some environmental factors (indicating probable sympatry) were observed only for aspis-latastei and aspis-seoanei. In fact, areas of probable occurrence of vipers were generally allopatric but probable sympatry between vipers was identified for aspis-latastei in 76 UTM 1 × 1 km squares, for aspis-seoanei in 23 squares, and latastei-seoanei in two squares. Environmental factors correlate with the location of this contact zone by shaping the species range: some enhance spatial exclusion and constrain distribution to spatially non-overlapping ranges, while others allow contact between species. The distribution in the contact zone apparently results from the balance between the pressures exerted by the different environmental factors and in the sympatry area probably by interspecific competition. Further ecological and genetical data are needed to evaluate the dynamics of the probable hybrid zone. GIS and niche-modelling tools proved to be powerful tools to identify environmental factors sustaining the location of contact zones. [source] Effects of habitat history and extinction selectivity on species-richness patterns of an island land snail faunaJOURNAL OF BIOGEOGRAPHY, Issue 10 2009Satoshi Chiba Abstract Aim, Local-scale diversity patterns are not necessarily regulated by contemporary processes, but may be the result of historical events such as habitat changes and selective extinctions that occurred in the past. We test this hypothesis by examining species-richness patterns of the land snail fauna on an oceanic island where forest was once destroyed but subsequently recovered. Location, Hahajima Island of the Ogasawara Islands in the western Pacific. Methods, Species richness of land snails was examined in 217 0.25 × 0.25 km squares during 1990,91 and 2005,07. Associations of species richness with elevation, current habitat quality (proportion of habitat composed of indigenous trees and uncultivated areas), number of alien snail species, and proportion of forest loss before 1945 in each area were examined using a randomization test and simultaneous autoregressive (SAR) models. Extinctions in each area and on the entire island were detected by comparing 2005,07 records with 1990,91 records and previously published records from surveys in 1987,91 and 1901,07. The association of species extinction with snail ecotype and the above environmental factors was examined using a spatial generalized linear mixed model (GLMM). Results, The level of habitat loss before 1945 explained the greatest proportion of variation in the geographical patterns of species richness. Current species richness was positively correlated with elevation in the arboreal species, whereas it was negatively correlated with elevation in the ground-dwelling species. However, no or a positive correlation was found between elevation and richness of the ground-dwelling species in 1987,91. The change of the association with elevation in the ground-dwelling species was caused by greater recent extinction at higher elevation, possibly as a result of predation by malacophagous flatworms. In contrast, very minor extinction levels have occurred in arboreal species since 1987,91, and their original patterns have remained unaltered, mainly because flatworms do not climb trees. Main conclusions, The species-richness patterns of the land snails on Hahajima Island are mosaics shaped by extinction resulting from habitat loss more than 60 years ago, recent selective extinction, and original faunal patterns. The effects of habitat destruction have remained long after habitat recovery. Different factors have operated during different periods and at different time-scales. These findings suggest that historical processes should be taken into account when considering local-scale diversity patterns. [source] Predicting the distribution of four species of raptors (Aves: Accipitridae) in southern Spain: statistical models work better than existing mapsJOURNAL OF BIOGEOGRAPHY, Issue 2 2004Javier Bustamante Abstract Aim, To test the effectiveness of statistical models based on explanatory environmental variables vs. existing distribution information (maps and breeding atlas), for predicting the distribution of four species of raptors (family Accipitridae): common buzzard Buteo buteo (Linnaeus, 1758), short-toed eagle Circaetus gallicus (Gmelin, 1788), booted eagle Hieraaetus pennatus (Gmelin, 1788) and black kite Milvus migrans (Boddaert, 1783). Location, Andalusia, southern Spain. Methods, Generalized linear models of 10 × 10 km squares surveyed for the presence/absence of the species by road census. Statistical models use as predictors variables derived from topography, vegetation and land-use, and the geographical coordinates (to take account of possible spatial trends). Predictions from the models are compared with current distribution maps from the national breeding atlas and leading reference works. Results, The maps derived from statistical models for all four species were more predictive than the previously published range maps and the recent national breeding atlas. The best models incorporated both topographic and vegetation and land-use variables. Further, in three of the four species the inclusion of spatial coordinates to account for neighbourhood effects improved these models. Models for the common buzzard and black kite were highly predictive and easy to interpret from an ecological point of view, while models for short-toed eagle and, particularly, booted eagle were not so easy to interpret, but still predicted better than previous distribution information. Main conclusions, It is possible to build accurate predictive models for raptor distribution with a limited field survey using as predictors environmental variables derived from digital maps. These models integrated in a geographical information system produced distribution maps that were more accurate than previously published ones for the study species in the study area. Our study is an example of a methodology that could be used for many taxa and areas to improve unreliable distribution information. [source] Expanding ranges of wild and feral deer in Great BritainMAMMAL REVIEW, Issue 2 2005ALASTAIR I. WARD ABSTRACT 1.,It is often stated that wild deer in Great Britain are increasing in range and number. This study presents the first quantified estimate of national range expansion for all six species. From national surveys of deer presence in 10 km squares between 1972 and 2002, the red deer range is estimated to have expanded at a compound rate of 0.3% per year, fallow deer at 1.8%, Chinese water deer at 2.0%, roe deer at 2.3%, Japanese sika at 5.3% and Reeves' muntjac at 8.2%. 2.,Each species is expected to expand its range further for the foreseeable future. The most widespread species, roe deer, is predicted to be present within 79% of all 10 km squares in mainland Britain within 10 years. 3.,Deer range expansion brings a combination of benefits and costs, and some degree of management is considered necessary to limit both environmental damage and deer suffering. [source] | ||||||||||