51 research outputs found
Climate variability, climate change and land degradation
No full textEffective response by government and individuals to the risk of land degradation requires an understanding of regional climate variations and the impacts of climate and management on condition and productivity of land and vegetation resources. Analysis of past land degradation and climate variability provides some understanding of vulnerability to current and future climate changes and the information needs for more sustainable management. We describe experience in providing climate risk assessment information for managing for the risk of land degradation in north-eastern Australian arid and semi-arid regions used for extensive grazing. However, we note that information based on historical climate variability, which has been relied on in the past, will now also have to factor in the influence of human-induced climate change. Examples illustrate trends in climate for Australia over the past decade and the impacts on indicators of resource condition. The analysis highlights the benefits of insights into past trends and variability in rainfall and other climate variables based on extended historic databases. This understanding in turn supports more reliable regional climate projections and decision support information for governments and land managers to better manage the risk of land degradation now and in the future
Climatic classification: a consultants' meeting at ICRISAT Patancheru, Andhra Pradesh, India, 14-16 Apr 1980
No full textThis proceedings consists of the following papers: welcome address ( Swindale, L.D.); need, relevance, and objectives of the consultants' meeting on climatic classification (Virmani, S.M.); first session: current concepts and approaches; climatic classification: concepts for dry tropical environments (Grove, A.T.); classification of semi-arid tropics: climatic and phytogeographic approaches (Meher-Homji, V.M.); use of principal component analysis in rational classification of climates (Gadgil, S; J oshi, N.V.); second session: a practical classification system for agriculture in the SAT: climatic classification of semi -arid tropics in relation to farming systems research (Vi rmani, S.M. ; Sivakumar, M.V.K.; Reddy, S.J.); climatic classification, agroclimatic resource assessment, and possibilities for application in the semi -arid tropics ( Williams, G.D.V.; Masterton, J.); agroclimatic classification methods and their application to India (Krishnan, A.); agroclimatic classification for assessment of crop potential and its application to and dry farming tract s of India ( Sarker, R.P.; Biswas, B.C.
Managing Climatic Risks to Combat Land Degradation and Enhance Food security: Key Information Needs
No full textThis paper discusses the key information needs to reduce the negative impacts of weather variability and climate change on land degradation and food security, and identifies the opportunities and barriers between the information and services needed. It suggests that vulnerability assessments based on a livelihood concept that includes climate information and key socio-economic variables can overcome the narrow focus of common one-dimensional vulnerability studies. Both current and future climatic risks can be managed better if there is appropriate policy and institutional support together with technological interventions to address the complexities of multiple risks that agriculture has to face. This would require effective partnerships among agencies dealing with meteorological and hydrological services, agricultural research, land degradation and food security issues. In addition a state-of-the-art infrastructure to measure, record, store and disseminate data on weather variables, and access to weather and seasonal climate forecasts at desired spatial and temporal scales would be needed
The impact of climatic variability over the period 1961- 1990 on the soil water balance of upland soils in the North East Arid Zone of Nigeria
No full textOver the period 1961 – 90 the North East Arid Zone of Nigeria experienced a decline
in annual rainfall totals and increased aridity which placed increasing pressure on
rain fed, millet-based farming systems. The changes in seasonal rainfall total and
distribution have been examined and it has been shown that the rate of decline has
been consistent across the region. The decline has been dominated by reduction in
the number of rain days during the middle of the rainy season and there is no
evidence of a significant change in the length of the growing season. Over the same
time period, there has been a small, but significant, increase in mean air temperature
which has resulted in a small increase in potential evapotranspiration. Other climatic
parameters (vapour pressure, solar radiation and wind speed) appear to have
remained stable, although the paucity and dubious quality of much of the historical
meteorological data make rigorous statistical analysis difficult.
A water balance model (BALANCE) developed by the author, was calibrated for a
millet crop grown on a typical sandy loam soil in Maiduguri (Nigeria). The model
was necessarily parsimonious, but was shown to perform well when calibrated
against observed soil water content. However, the empirical nature and high
sensitivity of key parameters relating to bare soil evaporation and drainage mean that
it is difficult to parameterise the model by laboratory, or independent field
measurements.
Applying the calibrated model to daily rainfall and average evapotranspiration data
from Nguru (Nigeria) for the period 1961 – 93 showed that, with the exception of
extreme drought years, the increased aridity would have had little impact on the
viability of traditional millet and millet-cowpea intercropping systems prior to the
early 1980s. However, after that date, predicted seasonal millet transpiration, and
hence predicted yields, have declined, and long duration cowpea intercrops, which
were traditionally matured on residual soil moisture after the millet harvest have had
insufficient water.
Whilst the BALANCE model has been useful in examining the impact of climatic
variability on agro-hydrology, it is not a crop physiological model and the interaction
between soil water and crop development is poorly represented. The model cannot, therefore be applied with confidence to investigate the potential yield benefits of
physical or agronomic interventions to alleviate the impacts of aridity. Although
more complex models exist to do this, they require detailed parameterisation of the
crop physiology, which was not possible within the scope of this study
Agrometeorology of sorghum and millet in the semi-arid Tropics : proceedings of the international symposium
No full textAgrometeorology of sorghum and millet in the semi-arid Tropics : proceedings of the international symposium
No full textWind Erosion in Africa and West Asia: Problems and Control Strategies: Proceedings of the Expert Group Meeting 22-25 April 1997, Cairo, Egypt
No full textDrylands are important sources of aeolian particles (dust and other particulates) associated with a variety of human activities, including vegetation removal and biomass burning. A wide range of empirical and numerical modeling studies, which relate climatic variation in drylands to a variety of forcing mechanisms, has established the strength of the link between the global climate system and specific climate patterns in the dryland areas. Wind erosion, the removal of soil by wind, is one of the most damaging effects of wind in many parts of the world. As a rule, it only assumes the status of a major problem in regions with a strongly-marked annual dry season, and hence
is a potential hazard in all dry environments. Much of the early work on wind erosion was carried out in the great plains of the United ·states, the wheat fields of the Canadian prairies, and the south of the former USSR. The problem has also been studied in Europe, Asia, and Australia. The occurrence of wind erosion is a function of weather events interacting with soil (intrinsic properties) and land management (past and present practices) through its effect on soil structure, tilth, and vegetation cover. As with water erosion, most wind erosion damage comes from relatively rare, severe events. Increased availability of simple and inexpensive "sand catchers" and automatic weather stations over the past 5- 10 years makes the task of monitoring sand flux and weather data easier. Wind erosion presents multiple challenges: identifying where wind erosion is most threatening to sustainable agricultural productivity; what practicable farmer-friendly measures can be devised to contain it; and how these measures can be transferred (for instance, through extension services) and implemented within agricultural land-use systems. According to previous studies, wind erosion in the semi-arid regions of America, North and South Africa, Australia, the Near East, and many parts of Central Asia only reached threatening proportions when man disturbed the ecosystem balance. This is true for West and Central Africa (WCA), and West Asia and North Africa (W ANA), where growing population pressures have led to the replacement of the traditional practice of fallowing with slash and burn practices and continuous cultivation. In regions (WCA and some parts of (WANA) where little or no nutrient amendments are made to replace the rapidly declining soil nutrient pool, the soil cover is declining rapidly, leading to wind erosion and land degradation. In WCA, where wind erosion is usually severe during the beginning of the growing season, young crops are damaged by wind-blown sand, leading to problems of poor crop stand and yield decline. Wind erosion in arable fields and rangeland causes various losses of soil depth, organic matter, clay content, nutrients, and indigenous seed. Downstream effects, e.g., effects, e.g., increased atmospheric dust, reduced visibility, blockage of roads,
railway lines, problems of health, etc., are also causing considerable concern. In Morocco, seasonal hot winds not only carry away soil but also affect crop performance through excessive evapotranspiration and direct wind effects. In the oases, sand encroachment affects wells, palm tree plantations, and traditional irrigation systems. In the southern and southwestern parts of Tunisia, the movement of sand dunes poses a major threat to farmlands. In
much of West Asia and North Africa, large areas of the traditional semi-nomadic rangeland, the steppe, are being opened for barley cultivation. The consequent removal of the natural vegetation cover has exposed the soil
surface, leading to the loss of the fertile fine fraction of the shallow soils through wind erosion. This has led to a tremendous decline in soil productivity and quality of life. Hence, the Government of Syria, for example, has forbidden the conversion of the steppe for barley cultivation
Soil-plant-water relations, growth and nutrient uptake patterns of field-grown soybeans under moisture stress
No full textPredicting rainy season potential from the onset of rains in Southern Sahelian and Sudanian climatic zones of West Africa
No full text
- …
