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Northward Shift (northward + shift)
Selected AbstractsPossible effects of habitat fragmentation and climate change on the range of forest plant speciesECOLOGY LETTERS, Issue 4 2002Olivier Honnay Global circulation models predict an increase in mean annual temperature between 2.1 and 4.6 °C by 2080 in the northern temperate zone. The associated changes in the ratio of extinctions and colonizations at the boundaries of species ranges are expected to result in northward range shifts for a lot of species. However, net species colonization at northern boundary ranges, necessary for a northward shift and for range conservation, may be hampered because of habitat fragmentation. We report the results of two forest plant colonization studies in two fragmented landscapes in central Belgium. Almost all forest plant species (85%) had an extremely low success of colonizing spatially segregated new suitable forest habitats after c. 40 years. In a landscape with higher forest connectivity, colonization success was higher but still insufficient to ensure large-scale colonization. Under the hypothesis of net extinction at southern range boundaries, forest plant species dispersal limitation will prevent net colonization at northern range boundaries required for range conservation. [source] Poleward shifts in breeding bird distributions in New York StateGLOBAL CHANGE BIOLOGY, Issue 8 2009BENJAMIN ZUCKERBERG Abstract Like other regions of the northern hemisphere, the northeastern United States has experienced a general increase in regional temperatures over the past 20 years. Quantifying the ecological implications of these changing temperatures has been severely constrained by a lack of multispecies distributional data by which to compare long-term changes. We used the New York State Breeding Bird Atlas, a statewide survey of 5332 25 km2 blocks surveyed in 1980,1985 and 2000,2005, to test several predictions that the birds of New York State are responding to climate change. Our objective was to use an information-theoretic approach to analyze changes in three geographic range characteristics, the center of occurrence, range boundaries, and states of occurrence to address several predictions that the birds of New York State are moving polewards and up in elevation. As expected, we found all bird species (n=129) included in this analysis showed an average northward range shift in their mean latitude of 3.58 km [Prob(Ha|data)=0.87)]. Past studies have found that northern range boundaries are more likely to be influenced by climatic factors than southern range boundaries. Consequently, we predicted that northward shifts would be more evident in northern as opposed to southern range boundaries. We found, however, that the southern range boundaries of northerly birds moved northward by 11.4 km [n=43, Prob(Ha|data)=0.92], but this pattern was less evident in northern range boundaries of southerly birds. In addition, we found that bird species demonstrated a general shift downhill in their mean elevation, but demonstrated little change in their elevational boundaries. The repeated pattern of a predicted northward shift in bird ranges in various geographic regions of the world provides compelling evidence that climate change is driving range shifts. [source] Interactions between land use, habitat use, and population increase in greater snow geese: what are the consequences for natural wetlands?GLOBAL CHANGE BIOLOGY, Issue 6 2005Gilles Gauthier Abstract The North American greater snow goose population has increased dramatically during the last 40 years. We evaluated whether refuge creation, changes in land use on the wintering and staging grounds, and climate warming have contributed to this expansion by affecting the distribution, habitat use, body condition, and migration phenology of birds. We also reviewed the effects of the increasing population on marshes on the wintering grounds, along the migratory routes and on the tundra in summer. Refuges established before 1970 may have contributed to the initial demographic increase. The most important change, however, was the switch from a diet entirely based on marsh plants in spring and winter (rhizomes of Scirpus/Spartina) to one dominated by crops (corn/young grass shoots) during the 1970s and 1980s. Geese now winter further north along the US Atlantic coast, leading to reduced hunting mortality. Their migratory routes now include portions of southwestern Québec where corn production has increased exponentially. Since the mid-1960s, average temperatures have increased by 1,2.4°C throughout the geographic range of geese, which may have contributed to the northward shift in wintering range and an earlier migration in spring. Access to spilled corn in spring improved fat reserves upon departure for the Arctic and may have contributed to a high fecundity. The population increase has led to intense grazing of natural wetlands used by geese although these habitats are still largely undamaged. The foraging in fields allowed the population to exceed limits imposed by natural marshes in winter and spring, but also prevented permanent damage because of their overgrazing. [source] Simulation of the intraseasonal and the interannual variability of rainfall over West Africa with RegCM3 during the monsoon periodINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 12 2010M. B. Sylla Abstract Intraseasonal and interannual variability of rainfall is simulated using the International Centre for Theoretical Physics (ICTP) Regional Climate Model (RegCM3) over West Africa. The intraseasonal variability of rainfall showing three distinct phases and the monsoon jump is well reproduced in the simulation. In addition, the regional model shows that while the monsoon rainbelt moves to the Sahel, the African Easterly Jet (AEJ) undergoes a northward migration and a weakening from June to August, when the core is at its northernmost location. This coexists with the appearance and the strengthening of the Tropical Easterly Jet (TEJ), the development and increased activity of the African Easterly Waves (AEWs), and the intensification and northward shift of the ascent between the AEJ and the TEJ core levels and axis. Similarly, the simulated interannual variability of rainfall over West Africa, the Guinea region, and the Sahel, as well as the variability of atmospheric features during contrasting wet and dry years, is also well captured. In fact, in the simulation during dry years the AEWs activity is decreased while the AEJ is strengthened and migrates southward, the TEJ becomes weaker, and the ascent between the levels of the AEJ and the TEJ decreases. The simulated rainfall variability and the behavior of the related features during the rainy season and during contrasting wet and dry years are in line with previous studies that used observations and reanalysis. We conclude that this model performance is of sufficient quality for application to the study of climate processes and mechanisms over West Africa. Copyright © 2009 Royal Meteorological Society [source] Atmospheric large-scale dynamics during the 2004/2005 winter drought in portugalINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 5 2007J. Santos Abstract The unusually dry conditions during the 2004/2005 winter in Portugal led to the development of an extreme/severe drought episode throughout the country with major socioeconomic impacts. In fact, at some locations, this winter was the driest in at least the last 60 years. A K-means classification of days into a set of five weather regimes (WRs), relevant for winter precipitation in Portugal, reveals a large prevalence of the two driest weather regimes during the 2004/2005 winter. These two regimes are basically linked to either anticyclonic circulation or easterly winds over Portugal and their prevalence explains the significant precipitation deficit. Winter precipitation variability in Portugal is indeed skillfully represented by linear models where the predictors are the frequencies of occurrence (FO) of these weather regimes. The dominance of the ,dry phases' of the main coupled modes between winter precipitation in Portugal and the large-scale atmospheric circulation also supports the prevalence of the dry regimes and the corresponding lack of precipitation. The predominance of the dry regimes can be explained by a remarkably strong enhancement of the climate-mean North Atlantic ridge, manifested by dynamically coherent anomalies in the geopotential heights, vorticity and temperature fields over the North Atlantic. The persistence of a warm-core asymmetrical eddy over the North Atlantic, with a nearly barotropic equivalent structure, is a manifestation of this large-scale anomaly. The blocking of the westerlies and the consequent northward shift in the axis of maximum moisture transports over the North Atlantic was one of the most striking changes in the large-scale atmospheric flow. Consequently, the main track of the developing baroclinic disturbances was sufficiently distant from Portugal to hamper the development of rain-generating conditions. As these dynamical conditions are common to other reportedly dry winters, they effectively constitute a key factor for the occurrence of a precipitation deficit in Portugal. Copyright © 2006 Royal Meteorological Society [source] Mid-Holocene and glacial-maximum vegetation geography of the northern continents and AfricaJOURNAL OF BIOGEOGRAPHY, Issue 3 2000I. Colin Prentice Abstract BIOME 6000 is an international project to map vegetation globally at mid-Holocene (6000 14C yr bp) and last glacial maximum (LGM, 18,000 14C yr bp), with a view to evaluating coupled climate-biosphere model results. Primary palaeoecological data are assigned to biomes using an explicit algorithm based on plant functional types. This paper introduces the second Special Feature on BIOME 6000. Site-based global biome maps are shown with data from North America, Eurasia (except South and Southeast Asia) and Africa at both time periods. A map based on surface samples shows the method's skill in reconstructing present-day biomes. Cold and dry conditions at LGM favoured extensive tundra and steppe. These biomes intergraded in northern Eurasia. Northern hemisphere forest biomes were displaced southward. Boreal evergreen forests (taiga) and temperate deciduous forests were fragmented, while European and East Asian steppes were greatly extended. Tropical moist forests (i.e. tropical rain forest and tropical seasonal forest) in Africa were reduced. In south-western North America, desert and steppe were replaced by open conifer woodland, opposite to the general arid trend but consistent with modelled southward displacement of the jet stream. The Arctic forest limit was shifted slighly north at 6000 14C yr bp in some sectors, but not in all. Northern temperate forest zones were generally shifted greater distances north. Warmer winters as well as summers in several regions are required to explain these shifts. Temperate deciduous forests in Europe were greatly extended, into the Mediterranean region as well as to the north. Steppe encroached on forest biomes in interior North America, but not in central Asia. Enhanced monsoons extended forest biomes in China inland and Sahelian vegetation into the Sahara while the African tropical rain forest was also reduced, consistent with a modelled northward shift of the ITCZ and a more seasonal climate in the equatorial zone. Palaeobiome maps show the outcome of separate, independent migrations of plant taxa in response to climate change. The average composition of biomes at LGM was often markedly different from today. Refugia for the temperate deciduous and tropical rain forest biomes may have existed offshore at LGM, but their characteristic taxa also persisted as components of other biomes. Examples include temperate deciduous trees that survived in cool mixed forest in eastern Europe, and tropical evergreen trees that survived in tropical seasonal forest in Africa. The sequence of biome shifts during a glacial-interglacial cycle may help account for some disjunct distributions of plant taxa. For example, the now-arid Saharan mountains may have linked Mediterranean and African tropical montane floras during enhanced monsoon regimes. Major changes in physical land-surface conditions, shown by the palaeobiome data, have implications for the global climate. The data can be used directly to evaluate the output of coupled atmosphere-biosphere models. The data could also be objectively generalized to yield realistic gridded land-surface maps, for use in sensitivity experiments with atmospheric models. Recent analyses of vegetation-climate feedbacks have focused on the hypothesized positive feedback effects of climate-induced vegetation changes in the Sahara/Sahel region and the Arctic during the mid-Holocene. However, a far wider spectrum of interactions potentially exists and could be investigated, using these data, both for 6000 14C yr bp and for the LGM. [source] Expressed sequence tag-derived microsatellites for the cool-water marine copepod Calanus finmarchicusMOLECULAR ECOLOGY RESOURCES, Issue 6 2007JIM PROVAN Abstract The copepod Calanus finmarchicus is the major contributor to zooplankton biomass in the North Atlantic and Norwegian Sea, but recent studies have shown a 70% decrease in abundance as well as a northward shift in the species' range. Insights into dispersal capabilities gained from population genetic studies will be crucial in predicting the response of C. finmarchicus communities to climate change and, consequently, we have developed a set of expressed sequence tag-derived microsatellite markers to allow fine-scale elucidation of population structuring and dispersal. Ten polymorphic markers displayed between two and 19 alleles, with levels of expected heterozygosity ranging from 0.044 to 0.924. [source] Poleward shifts in breeding bird distributions in New York StateGLOBAL CHANGE BIOLOGY, Issue 8 2009BENJAMIN ZUCKERBERG Abstract Like other regions of the northern hemisphere, the northeastern United States has experienced a general increase in regional temperatures over the past 20 years. Quantifying the ecological implications of these changing temperatures has been severely constrained by a lack of multispecies distributional data by which to compare long-term changes. We used the New York State Breeding Bird Atlas, a statewide survey of 5332 25 km2 blocks surveyed in 1980,1985 and 2000,2005, to test several predictions that the birds of New York State are responding to climate change. Our objective was to use an information-theoretic approach to analyze changes in three geographic range characteristics, the center of occurrence, range boundaries, and states of occurrence to address several predictions that the birds of New York State are moving polewards and up in elevation. As expected, we found all bird species (n=129) included in this analysis showed an average northward range shift in their mean latitude of 3.58 km [Prob(Ha|data)=0.87)]. Past studies have found that northern range boundaries are more likely to be influenced by climatic factors than southern range boundaries. Consequently, we predicted that northward shifts would be more evident in northern as opposed to southern range boundaries. We found, however, that the southern range boundaries of northerly birds moved northward by 11.4 km [n=43, Prob(Ha|data)=0.92], but this pattern was less evident in northern range boundaries of southerly birds. In addition, we found that bird species demonstrated a general shift downhill in their mean elevation, but demonstrated little change in their elevational boundaries. The repeated pattern of a predicted northward shift in bird ranges in various geographic regions of the world provides compelling evidence that climate change is driving range shifts. [source] Differential effects of past climate warming on mountain and flatland species distributions: a multispecies North American mammal assessmentGLOBAL ECOLOGY, Issue 1 2007Robert Guralnick ABSTRACT Aim, The magnitude of predicted range shifts during climate change is likely to be different for species living in mountainous environments compared with those living in flatland environments. The southern edges of ranges in mountain species may not shift northwards during warming as populations instead migrate up available elevational gradients; overall latitudinal range appears therefore to expand. In contrast, flatland species should shift range centroids northwards but not expand or contract their latitudinal range extent. These hypotheses were tested utilizing Late Pleistocene and modern occurrence data. Location, North America. Methods, The location and elevation of modern and Late Pleistocene species occurrences were collected from data bases for 26 species living in mountain or flatland environments. Regressions of elevation change over latitude, and southern and northern range edges were calculated for each species for modern and fossil data sets. A combination of regressions and anovas were used to test whether flatland species shift range edges and latitudinal extents more than mountain species do. Results, Flatland species had significantly larger northward shifts at southern range edges than did mountain-dwelling species from the Late Pleistocene to the present. There was also a significant negative correlation between the amount of change in the latitude of the southern edge of the range and the amount of elevational shifting from the Late Pleistocene to the present. Although significant, only c. 25% of the variance could be explained by this relationship. In addition, there was a weak indication that overall range expansion was less in flatland-dwelling than in mountain-dwelling species. Main conclusions, The approach used here was to examine past species' range responses to warming that occurred after the last ice ages as a means to better predict potential future responses to continued warming. The results confirm predictions of differential southern edge and overall range shifts for species occupying mountain and flatland regions in North America. The findings may be broadly applicable in other regions, thus allowing better modelling of future range and distribution related responses. [source] | ||||||||||