scispace - formally typeset
Search or ask a question
Journal ArticleDOI

World atlas of thematic maps of desertification

01 Jan 1993-Mapping Sciences & Remote Sensing (Taylor & Francis Group)-Vol. 30, Iss: 1, pp 83-84
TL;DR: The author describes the contents and participation of former Soviet republics in the compilation of a global atlas of desertification, published under the auspices of the United Nations.
Abstract: The author describes the contents and participation of former Soviet republics in the compilation of a global atlas of desertification, published under the auspices of the United Nations. Translated by H. L. Haslett, Leamington Spa, UK, from: Izvestiya Akademii Nauk SSSR, seriya geograficheskaya, 1991, No. 6, p. 130.
Citations
More filters
Journal ArticleDOI
TL;DR: In this article, issues of present and future climate variability and change on agriculture and forestry in the arid and semi-arid tropics of the world were examined and discussion under each of these issues had been presented separately for Asia, Africa and Latin America.
Abstract: The arid and semi-arid regions account for approximately 30% of the world total area and are inhabited by approximately 20% of the total world population. Issues of present and future climate variability and change on agriculture and forestry in the arid and semi-arid tropics of the world were examined and discussion under each of these issues had been presented separately for Asia, Africa and Latin America.

353 citations


Cites background from "World atlas of thematic maps of des..."

  • ...The World Atlas of Desertification (UNEP, 1992) defines arid regions as the areas where the ratio of mean annual rainfall (R) to mean annual potential evapotranspiration (PET) varies between 0....

    [...]

  • ...Desertification in this area is highly relevant, since 41% of the area in Bolivia was subject to this phenomena (MDSMA, 1996, cited by Andressen et al., 2000)....

    [...]

  • ...The World Atlas of Desertification (UNEP, 1992) defines arid regions as the areas where the ratio of mean annual rainfall (R) to mean annual potential evapotranspiration (PET) varies between 0.05 and 0.20 and the semi-arid regions as those where the ratio ranges between 0.2 to 0.5....

    [...]

  • ...In an assessment of population levels in the world's drylands, the Office to Combat Desertification and Drought (UNSO) of the United Nations Development Programme (UNDP) showed that the arid and semi-arid regions account for approximately 30% of the world total area and are inhabited by 1.10 billion people or approximately 20% of the total world population....

    [...]

Book
01 Jan 2009
TL;DR: In this paper, a new dryland paradigm is built on the resources and capacities of dryland peoples, on new and emergent economic opportunities, on inward investment, and on the best support that dryland science can offer.
Abstract: Drylands cover 41 percent of the earth’s terrestrial surface. The urgency of and international response to climate change have given a new place to drylands in terms both of their vulnerability to predicted climate change impacts and their potential contribution to climate change mitigation. This book aims to apply the new scientific insights on complex dryland systems to practical options for development. A new dryland paradigm is built on the resources and capacities of dryland peoples, on new and emergent economic opportunities, on inward investment, and on the best support that dryland science can offer.

156 citations


Cites background from "World atlas of thematic maps of des..."

  • ...39 (UNEP, 1992) A new paradigm of dryland development...

    [...]

Book
01 Jan 1994
Abstract: The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations, of the United Nations Development Programme or of the United Nations Environment Programme concerning the legal statue of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

155 citations


Cites methods from "World atlas of thematic maps of des..."

  • ...Only where there apprs to be clear evidence of a data bias in the GLASOD survey have its results been modified from other sources to obtain best estimates as used in the present study....

    [...]

  • ...For reason of cartographic necessity, the GLASOD World Map shows only the dominant form of degradation (as severity times extent) as coloured mapped areas, with the secondary form shown in the map symbol....

    [...]

  • ...The GLASOD assessment (as it will be called) includes all the types of land degradation covered in the present study, somewhat differently subdivided but in ways that are compatible with the classification adopted here....

    [...]

  • ...Next file Global assessment of soil degradation (GLASOD) Other sources of data Variations in data and the need for definition of degrees of severity Global assessment of soil degradation (GLASOD) Under an international project, Global assessment of soil degradation (GLASOD), an attempt has been made for the first time to map the severity of degradation on a world scale, as the World map of the satue of human-induced soil degradation (Oldeman et al., 1990)....

    [...]

  • ...Extensive use was made of a recent comprehensive and primary study, t he Global assessment of land degradation (GLASOD) ( ldeman et al., 1990; UNEP, 1992a)....

    [...]

Journal ArticleDOI
TL;DR: In this article, the authors identify pathways for knowledge management and action at the relevant scales for decision-making in response to a changing climate using the rich experience of information systems across the globe.
Abstract: Drought is among the most damaging, and least understood, of all “natural” hazards. Although some droughts last a single season and affect only small areas, the instrumental and paleoclimate records show that droughts have sometimes continued for decades and have impacted millions of square kilometers in North America, West Africa, and East Asia. To cross the spectrum of potential drivers and impacts, drought information systems have multiple sub-systems which include an integrated risk assessment, communication and decision support system of which early warning is a central component and output. An early warning system is much more than a forecast – it is a linked risk information (including people׳s perception of risk) and communication system that actively engages communities involved in preparedness. There are numerous drought systems warning systems being implemented at different scales of governance. We draw on the lessons of over 21 drought early warning systems around the world, in both developing and developed countries and at regional, national and community levels. The successes illustrate that effective early warning depends upon a multi-sectoral and interdisciplinary collaboration among all concerned actors at each stage in the warning process from monitoring to response and evaluation. However, the links between the community-based approach and the national and global EWSs are relatively weak. Using the rich experience of information systems across the globe, this paper identifies pathways for knowledge management and action at the relevant scales for decision-making in response to a changing climate.

155 citations

Journal ArticleDOI
TL;DR: Using wood sampled from a phylogenetically constrained set of 28 Eucalyptus species, collected from a wide gradient of aridity across Australia, it is shown that hydraulic architecture reflects adaptive radiation of this genus in response to variation in climate.
Abstract: Current theory presumes that natural selection on vascular traits is controlled by a trade-off between efficiency and safety of hydraulic architecture. Hence, traits linked to efficiency, such as vessel diameter, should show biogeographic patterns; but critical tests of these predictions are rare, largely owing to confounding effects of environment, tree size and phylogeny. Using wood sampled from a phylogenetically constrained set of 28 Eucalyptus species, collected from a wide gradient of aridity across Australia, we show that hydraulic architecture reflects adaptive radiation of this genus in response to variation in climate. With increasing aridity, vessel diameters narrow, their frequency increases with a distribution that becomes gradually positively skewed and sapwood density increases while the theoretical hydraulic conductivity declines. Differences in these hydraulic traits appear largely genotypic in origin rather than environmentally plastic. Data reported here reflect long-term adaptation of hydraulic architecture to water availability. Rapidly changing climates, on the other hand, present significant challenges to the ability of eucalypts to adapt their vasculature.

145 citations


Cites background from "World atlas of thematic maps of des..."

  • ...This index denotes the degree of aridity, ranging from hyper-arid to wet with increasing index scores (UNEP 1997)....

    [...]

References
More filters
Journal ArticleDOI
TL;DR: In this article, issues of present and future climate variability and change on agriculture and forestry in the arid and semi-arid tropics of the world were examined and discussion under each of these issues had been presented separately for Asia, Africa and Latin America.
Abstract: The arid and semi-arid regions account for approximately 30% of the world total area and are inhabited by approximately 20% of the total world population. Issues of present and future climate variability and change on agriculture and forestry in the arid and semi-arid tropics of the world were examined and discussion under each of these issues had been presented separately for Asia, Africa and Latin America.

353 citations

Journal ArticleDOI
TL;DR: In this paper, the authors reviewed the current knowledge of the role that groundwater-surface water (GW-SW) interactions play in the ecology of arid/semi-arid wetlands.
Abstract: In arid/semi-arid environments, where rainfall is seasonal, highly variable and significantly less than the evaporation rate, groundwater discharge can be a major component of the water and salt balance of a wetland, and hence a major determinant of wetland ecology. Under natural conditions, wetlands in arid/semi-arid zones occasionally experience periods of higher salinity as a consequence of the high evaporative conditions and the variability of inflows which provide dilution and flushing of the stored salt. However, due to the impacts of human population pressure and the associated changes in land use, surface water regulation, and water resource depletion, wetlands in arid/semi-arid environments are now often experiencing extended periods of high salinity. This article reviews the current knowledge of the role that groundwater–surface water (GW–SW) interactions play in the ecology of arid/semi-arid wetlands. The key findings of the review are as follows: 1.GW–SW interactions in wetlands are highly dynamic, both temporally and spatially. Groundwater that is low in salinity has a beneficial impact on wetland ecology which can be diminished in dry periods when groundwater levels, and hence, inflows to wetlands are reduced or even cease. Conversely, if groundwater is saline, and inflows increase due to raised groundwater levels caused by factors such as land use change and river regulation, then this may have a detrimental impact on the ecology of a wetland and its surrounding areas. 2.GW–SW interactions in wetlands are mostly controlled by factors such as differences in head between the wetland surface water and groundwater, the local geomorphology of the wetland (in particular, the texture and chemistry of the wetland bed and banks), and the wetland and groundwater flow geometry. The GW–SW regime can be broadly classified into three types of flow regimes: (i) recharge—wetland loses surface water to the underlying aquifer; (ii) discharge—wetland gains water from the underlying aquifer; or (iii) flow-through—wetland gains water from the groundwater in some locations and loses it in others. However, it is important to note that individual wetlands may temporally change from one type to another depending on how the surface water levels in the wetland and the underlying groundwater levels change over time in response to climate, land use, and management. 3.The salinity in wetlands of arid/semi-arid environments will vary naturally due to high evaporative conditions, sporadic rainfall, groundwater inflows, and freshening after rains or floods. However, wetlands are often at particular risk of secondary salinity because their generally lower elevation in the landscape exposes them to increased saline groundwater inflows caused by rising water tables. Terminal wetlands are potentially at higher risk than flow-through systems as there is no salt removal mechanism. 4.Secondary salinity can impact on wetland biota through changes in both salinity and water regime, which result from the hydrological and hydrogeological changes associated with secondary salinity. Whilst there have been some detailed studies of these interactions for some Australian riparian tree species, the combined effects on aquatic biodiversity are only just beginning to be elucidated, and are therefore, a future research need. 5.Rainfall/flow-pulses, which are a well-recognized control on ecological function in arid/semi-arid areas, also play an important, though indirect, role through their impact on wetland salinity. Freshwater pulses can be the primary means by which salt stored in both the water column and the underlying sediments are flushed from wetlands. Conversely, increased runoff is also a commonly observed consequence of secondary salinity, and so, wetlands can experience increased surface water inflows that are higher in salinity than under natural conditions. Moreover, changes in rainfall/flow-pulse regimes can have a significant impact on wetland GW–SW interactions. It is possible that in some instances groundwater inflow to a wetland may become so heavy that it could become a major component of the water balance, and hence, mask the role of natural pulsing regimes. However, if the groundwater is low in salinity, this may provide an ecological benefit in arid/semi-arid areas by assisting in maintaining water in wetlands that become aquatic refugia between flow-pulses. 6.There has been almost no modelling of GW–SW interactions in arid/semi-arid wetlands with respect to water fluxes, let alone salinity or ecology. There is a clear need to develop modelling capabilities for the movement of salt to, from, and within wetlands to provide temporal predictions of wetland salinity which can be used to assess ecosystem outcomes. 7.There has been a concerted effort in Australia to collect and collate data on the salinity tolerance/sensitivity of freshwater aquatic biota and riparian vegetation. There are many shortcomings and knowledge gaps in these data, a fact recognized by many of the authors of this work. Particularly notable is that there is very little time-series data, which is a serious issue because wetland salinities are often highly temporally variable. There is also a concern that many of the data are from very controlled laboratory experiments, which may not represent the highly variable and unpredictable conditions experienced in the field. In light of these, and many other shortcomings identified, our view is that the data currently available are a useful guide but must be used with some caution. Copyright © 2008 John Wiley & Sons, Ltd.

278 citations

Journal ArticleDOI
TL;DR: It is hypothesize that the degree of dependence of functional diversity on species diversity might be mostly related to the amplitude of the species' traits pool and on how species partition the niche space available.
Abstract: Different components of biodiversity may vary independently of each other along environmental gradients giving insights into the mechanisms that regulate species coexistence. In particular, the functional diversity (FD) or the presence of rare or endemic species in natural assemblages do not necessarily increase with species diversity. We studied if different components of plant species diversity (species richness, Simpson diversity, evenness) varied similarly to FD (measured as a generalization of the Simpson index) and rarity along grazing intensity and climatic gradients. Plots under different sheep grazing regimes (high and low intensity, abandonment) were surveyed in five locations along a climatic gradient in north-eastern Spain, from semi-arid lowland to moist upland locations. Variation in species diversity, functional diversity and rarity followed different patterns. Species diversity was lowest in water-stressed environments (arid locations and southern aspects) and increased with grazing more makedly in humid locations. The FD was comparable between the most species-poor and species-rich locations and decreased with grazing in the moistest location, i.e. where species diversity markedly increased. The FD did not show a strong correlation with species richness nor with the Simpson index and less specious communities could show the highest functional diversity. The rarest species in the region were more frequently found in the abandoned areas, which held the lowest species diversity. Consequently, the mechanisms that enhance the diversity of species do not necessarily support a functional differentiation among those species or the maintenance of rare species in a region. We hypothesize that the degree of dependence of functional diversity on species diversity might be mostly related to the amplitude of the species' traits pool and on how species partition the niche space available.

260 citations

Book
01 Jan 2009
TL;DR: In this paper, a new dryland paradigm is built on the resources and capacities of dryland peoples, on new and emergent economic opportunities, on inward investment, and on the best support that dryland science can offer.
Abstract: Drylands cover 41 percent of the earth’s terrestrial surface. The urgency of and international response to climate change have given a new place to drylands in terms both of their vulnerability to predicted climate change impacts and their potential contribution to climate change mitigation. This book aims to apply the new scientific insights on complex dryland systems to practical options for development. A new dryland paradigm is built on the resources and capacities of dryland peoples, on new and emergent economic opportunities, on inward investment, and on the best support that dryland science can offer.

156 citations

Book
01 Jan 1994
Abstract: The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations, of the United Nations Development Programme or of the United Nations Environment Programme concerning the legal statue of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

155 citations