L'impact du réchauffement climatique sur ces évènements extrêmes . et aux conséquences du changement climatique ; il est essentiel de les. Impact du changement climatique sur la santé de la population. Causes. Impacts. Ensablement du cours inférieur du fleuve. - Déforestation incontrôlée ;. Les fictions doivent [aussi] nous rendre plus lucides à une période où, trop souvent, les discours qui sont censés ou qui prétendent dire la vérité ne sont qu' un.
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2 Ce rapport présente une nouvelle évaluation quantitative détaillée des conséquences du changement climatique sur la croissance. La montagne, laboratoire du changement climatique (Boîte 1) des conséquences des changements globaux sur la structure et les Les premiers modèles peuvent être très performants pour décrire le présent, mais ne permettent souvent pas d'analyser les causes des changements en Format PDF · Format ePUB. Le changement climatique est aujourd'hui une réalité au niveau . 7The risks to be feared as a consequence of the accelerated melting of glaciers are of several types. These floods act like a mountain torrent, carrying heavy loads of.
These mutations are indeed complex and diverse, such as innovations or changes alongside the oldest traditions, and permanencies also coexisted with the previous period Luneau , The settlement pattern shifted towards a reduction in the size of sites. The abandonment of sites is also noticeable, but this occurred parallel with the appearance of new sites and a possible territorial expansion. Changes are also obvious in the material culture, in the quantity of items discovered at the sites as well in their morphology. The ceramic production was affected by a higher variability. Technological processes seem globally similar with a trend to less investment of time and skills in the production. A less cultural homogeneity over the whole territory of the Oxus civilization is also noticeable.
The analysis of the soils of the Van Lake, Turkey Lemcke and Sturm illustrates a climatic change towards a more continental climate decrease of the water level and of the humidity between and BP. To sum up, even though Central Asian records are still patchy Fig.
Considering the period of duration of the Oxus civilization ca.
They have been mostly carried out in the ecological niches of low or high river plains Fig. In the Murghab alluvial fan presently in the Karakum desert central Turkmenistan , the work done by M. Cremaschi on different palaeochannels assumes very different climatic conditions than the present day, with a more important water supply until the 4th millennium BP. Accordingly, the Murghab would have been a fertile alluvial plain and the hydrological system near Bronze Age sites Gonur Depe and Takhirbaj were active until the end of the Bronze Age, i.
Thus, these data suggest that there were no major changes in water sources during the period discussed here. Other fluvial geomorphological studies have been made in Afghanistan and Uzbekistan Fouache et al. The examination of the palaeochannels of the Balkh River and the river Zerafshan reveals the strong dynamic of the hydrographical system with an extreme mobility of channels, a large range of movements and a great number of changes.
This constant dynamic is created by classic avulsion processes, due to neotectonic deformations and the intensity of the flow. In northern Afghanistan, the persistency of occupation northwest of the plain Dashly area has been observed from the Bronze Age to Achaemenid times, suggesting a constant water availability.
By contrast, in Iran Fouache et al. Initially located along a river course or at the end of a natural channel during the Chalcolithic and early Bronze Age periods, sites progressively moved according to water availability, which suggests that water was less abundant.
This evolution seems to occur during the chronological range between and BP. Lastly, around the Aral Sea, significant changes in moisture conditions have been reconstructed through the study of the water level from the archaeological data Boroffka ; Boroffka et al. The authors reveal a shift in the course of the Amu-Darya River and the rise of water in the Sea around BP without substantial change in the next centuries.
In short, these environmental analyses carried out in Central Asia and northern Iran mostly record a permanency in occupation patterns and water availability, or coincide with those climatic data which identify a climate variation at the end of the 5th millennium BP.
Open image in new window Fig. The study of climate history still requires special attention and clarification. Consequences from more local changes must be evidenced as well Wilkinson Climate phenomena may be limited to specific, sometimes small, areas.
Environmental effects of climatic changes can vary according to the degree of sensitivity of the geographical area and to the different hydrogeological contexts.
The same event may not have the same impact according to the microscales. Besides, the natural factors, in particular tectonic movements and cataclysms such as earthquakes, sea quakes, storms, etc. Although this area records a high level of seismicity, until now very limited studies are involved in highlighting such disruptions Berberian and Yeats ; Hollingsworth et al. However, if seismic activity may potentially explained some abandonment of settlements, local destructions are likely not sufficient to trigger a long-lasting sociocultural evolution, such as the transformation of the Oxus civilization which mirrors a plurality of changes.
Indeed, climatic change does not always imply a crisis situation. Cases of the independence of prehistoric societies when confronted with climatic conditions are known Magny et al. The difficulty of the study is to correlate the climate scale with the human scale too. Climate changes are not brutal phenomena, but rather an evolution, which suggests possibilities of adaptation to the events Gregoricka ; McAnany and Yoffee ; Miller et al.
Populations often possess the capacity to adapt to changes, which depends upon the production system, the social organization and the interests of the different social groups Rosen : —; Sala Broadly speaking, resilience to climatic modifications can take several forms Binford et al. Climatic change can also be a factor of technological innovations in order to compensate difficulties and to maintain a certain threshold of vital yields for the whole population, such as the adaptation of irrigation techniques or actions on cultivated plants transformations of the plants known, new distribution of the different cultivated plants, etc.
The movements of Bronze Age populations from North to South in the Murghab area according to the retraction of the alluvial fan have been suggested Hiebert ; Sarianidi , First, climatic and archaeological data must correspond in order to confirm such displacement was due to climatic reasons. Second, it should be acknowledged that, according to the proposed periodization, the populations would have already moved since the beginning of the Bronze Age occupation in this area, attested in the north-western area around Kelleli Masimov , dated at least to the Namazga IV period ca.
Especially considering the possible consequences of the 4. In any case, the one-time occupation of the sites in the Murghab has been definitely rejected Luneau ; Salvatori , The settlement pattern in the Murghab alluvial fan appears more complex than previously supposed, with a wider distribution of multi-period sites during the whole Bronze Age and a better geographical stability of sites.
The effect of water availability for the duration of Bronze Age sites in the Murghab alluvial fan, and the systematic displacement of sites according to the water availability during the Bronze Age must still be demonstrated too, according to a detailed chronology in many areas. It is unlikely that a site persisted without a water supply in the vicinity, unless a larger more sophisticated irrigation network was expanded, and this does not seem to be the case according to the current data.
Another example of the dispersion of Final Bronze Age populations is the increase in sites dated to this period only in the foothills in Tajikistan Vinogradova , where the environmental conditions do not necessarily require supplementary water intake.
In Iran as well, Bronze Age populations adapted to the decrease in water resources by changing location Fouache et al. This adaptation to new ecological conditions also demonstrates the capacity of socioeconomic transformation of society.
The intensification of pastoralism would represent a real economic alternative required by the installation of populations in the foothills areas and the exploitation of diverse ecological areas which can be viewed as a flexible strategy.
Along the Kopet Dagh range as well, P. Dolukhanov interpreted the deposits of silts between different layers at several sites as the result of repeated mud flows implied by the deforestation of the mountain slopes or by the increase of herding in the foothills.
Considering the improvement of farming practices, the current state of research on irrigation evokes the high dependency of Bronze Age populations upon the proximity of an active channel. Actual irrigated systems are still not proven in the different areas of the Oxus civilization.
But in some regions, like in northern Afghanistan, ever since the Bronze Age populations succeeded in developing sophisticated techniques of control and regulation of water, demonstrating direct actions on the environment. For instance, even though this is yet to be proven for the Bronze Age, in the Balkh area the former riverbeds abandoned during the successive defluviations were used as irrigation canals, indicating high technological skills of the ancient population to control the hydraulic flow Fouache et al.
Further, the possible intensification 7 of the cultivation of millet in the area during the 4th millennium BP has been discussed, in particular regarding the connection with mobile populations and the exchanges over large distances in Eurasia Miller et al.
This plant is viewed as better adapted to dryness, and it may have been cultivated more with respect to an aridification.
However, millet cultivation could also be linked to other reasons: the wish to increase the yields, an adaptation to the ecological environment of some specific sites, especially in the foothills, an adaptation of the agricultural practices to a possible decrease in irrigation, or a cultural choice influenced by other population groups, such as mobile populations coming from the North.
These agricultural changes could have contributed to the decline of the urban Harappan civilization, according to some scholars Madella and Fuller In the case of the Oxus civilization, it is possible, too, that changes of the agricultural strategies on a local scale towards a more diversified and extensive agriculture may have contributed to social changes, implying a possible restructuration of the urban social system.
The hypothesis of a single cause, especially climatic, is likely not the most appropriate. The synchronism between long and one-time events, climatic and sociocultural, always seems difficult to state and hazardous Roberts et al.
Sociocultural evolutions are expected to be more complex than simplistic hypotheses; they can result from multiple causes by the combination of different events, which are not necessarily solely environmental Butzer ; Butzer and Endfield ; Knapp and Manning It should be reminded that changes at the end of the Bronze Age in southern central Asia did not only affect the settlement pattern and the subsistence economy, but also the ideology, the funeral strategy and the relations with neighbouring societies.
The understanding of the convergence of these events is a wider topic of research. In particular, the well-attested 4. On the contrary, the palaeoclimatic data raise questions about the consequences of an aridification at the beginning of the Oxus civilization. In this paper, we discuss the prospects for climate-smart agriculture technologies and enabling policies in dealing with climate change and variability at different sub-regional levels of sub-Saharan Africa to sustain farm productivity and livelihoods of agrarian communities.
The review provides substantial information suggesting that without appropriate interventions, climate change and variability will affect agricultural yields, food security and add to the presently unaceptable levels of poverty in sub-Saharan Africa. Although some of them were already existing, the past decades have seen the development and promotion of climate-smart agriculture innovations such as the use of high yielding drought tolerant crop varieties, climate information services, agricultural insurance, agroforestry, water harvesting techniques, integrated soil fertility management practices, etc.
In the context of climate change, this appears as a stepping up approach to sustainably improving farm productivity, rural livelihoods and adaptive capacity of farmers and production systems while contributing to mitigation. The development of regional, sub-regional and national climate change policies and plans targeted at mitigating climate change and improving adaptive capacity of the African people have also been developed to enable mainstreaming of climate-smart agriculture into agricultural development plans.
Financial commitments from governments and development agencies will be crucial for improving large scale adoption of climate-smart agriculture. These are likely to become more severe as global warming continues IPCC, These scenarios present a major challenge to agriculture in sub-Saharan Africa, severely compromising food security and livelihoods for millions of people. Efforts to reduce food insecurity must not only target increases in production but also include building the resilience of rural communities to shocks and strengthening their adaptive capacity to cope with increased climate variability and change.
The agricultural sectors crops, livestock, forestry, fisheries must therefore be transformed in order to feed a growing global population and provide the basis for economic growth and poverty reduction. This transformation must be accomplished without hindering the natural resource base FAO, In the literature, a lot of information is available about climate change perceptions and impacts in sub-Saharan Africa e.
Serdeczny et al. Globally, the development and promotion of climate-smart agriculture CSA is viewed as an opportunity for building synergies among climate change mitigation, adaptation and food security and minimizing their potential negative trade-offs Lipper et al. In sub-Saharan Africa, CSA is promoted as a development agenda due to its potential positive effect on food security and poverty reduction. Several CSA technologies, tools, approaches and policies tailored to reducing climate-related risks have been developed in sub-Saharan Africa for the various sectors crops, livestock and fisheries.
In this paper, we discuss the prospects for CSA technologies and enabling policies in dealing with climate change and variability at different sub-regional levels of sub-Saharan Africa to sustain the resilience and livelihoods of farming communities. Although local variability is important, trends in Figure 1 generally show declining precipitation and increasing temperatures for the region. In East Africa for instance, Hulme et al. This warmer climate will affect fishing in coastal and aquaculture systems, and will cause a decline in crop production, particularly in maize Adhikari et al.
Increased drought is also eminent, particularly for the lowlands of Ethiopia. Drought-induced famines in East Africa are also expected to be further exacerbated due to the presently limited coping mechanisms and inadequate contingency planning for drought mitigation and the threat of climate change Branca et al. In Ghana, annual mean temperatures are projected to increase by 0. Antwi-Agyei et al. The repercussions of these trends are an expected reduction in the production of major food crops such as sorghum, maize and millet.
Impact of climate change and variability on income diversification and food security is also reported Brown, In Senegal, Brown reported that changes in diversity of income sources from the past to the present were related to reductions in rainfall. Only in East Africa is rainfall anticipated to increase Hoerling et al. In addition to drought, flood is thought to be problematic for farmers. Figure 2 shows the frequency of floods recorded in West Africa from to The frequency of flooding has risen 6 to 12 times during the last decades Collins et al.
According to IPCC , climate change may account for this with future floods expected to be more frequent and more intense. It was projected that with a 0. In Benin, increased frequency of floods in affected 25 ha of staple crops and ha of fields planted with cotton with an estimated 53, farmers badly impacted. Changes in precipitations A and temperature B in Africa recorded from to Number of floods recorded in West Africa from to adapted from Collins et al.
In this section, we discuss the prospects for CSA in dealing with climate change and variability at different sub-regional levels of sub-Saharan Africa. FAO defined CSA as agricultural innovations that achieve: increased productivity for improved food security; improved adaptation and resilience to climate change and variability; and reduced greenhouse gas emissions mitigation where possible. There is therefore limited scope for increasing agricultural production through extensification.
Instead, the available literature e.
Buah et al. Sustainable natural resource management is thought to be the most critical factor in agricultural production in the region Rhodes et al. In recent years, the region has witnessed an expansion of the maize mixed farming system in the semi-arid and sub-humid zones Mason et al. There is also growing emphasis on agroforestry and rangeland management, where dominant pastoral systems and livestock feed resources would otherwise decline.
On the other hand, the increasing prospects for both smallholder and large scale irrigated systems are likely to modify crop-livestock interactions and open new opportunities for CSA Rhodes et al.
Meanwhile, opportunities for CSA in Central Africa arise from a growing but food-insecure population, and for which increasing agricultural productivity does not only enhance food security but also save forest resources. Depletion of forests in the forest-based farming systems will most likely lead to large greenhouse gas emissions and loss of ecosystems services. CSA options that limit expansion of cultivated areas into forests or alternatively seek to establish new agricultural production systems that can at least restore ecosystem services and values are required.
Landscape-level approaches will make sure that heterogeneity in land-use and cropping systems is favored, in order to contribute to synergy between climate change adaptation and mitigation Torquebiau, In the highlands of East Africa, improved fallow agroforestry technologies are options to increase soil fertility and crop yields.
Adopters have witnessed a massive economic boost. These options could be applicable although with different species for other parts of Africa. Similar to East Africa, increasing crop productivity through intensification options is a priority for the region. Overall, integrated soil, water, nutrient and organic matter management techniques hold potentials for CSA in Southern Africa Mapfumo et al.
CSA, especially if it targets soil carbon and organic matter, offers a credible entry point for managing these changes in the context of climate change, particularly if interventions can be integrated to address problems at the interface of agricultural productivity, natural resources management and social safety nets.
This can be achieved through systematic and intensive legume cereal rotational systems coupled to inorganic fertilizer use and integrated conservation agriculture and integrated soil fertility management systems that respond to farmer circumstances. The use of tree legumes via agroforestry is popular in Southern Africa and considered an agroecologically sound CSA practice for improving and sustaining soil fertility Mbow et al. It is estimated that about 20, farmers are now using Sesbania sesban, Tephrosia vogelii and Cajanus cajan in two-year fallows followed by maize rotations for two to three years.
Impressive root growth explains the success of these short term agroforestry fallows Torquebiau and Kwesiga, This initiative supported by all African governments is expected to enable farmers and the agri-food system to simultaneously increase productivity, improve resilience and manage natural resources more sustainably, thereby contributing to national, regional and global food security and nutrition CCAFS, As climate change and variability continue to threaten agriculture and livelihoods in sub-Saharan Africa, it is important that actions are taken to reduce risks and capitalize on opportunities.
The past years have seen the promotion of CSA technologies and enabling agricultural policies and investment plans as a stepping up approach to improving farm productivity, rural livelihoods and adaptive capacity of farmers and production systems. In this section, we discuss how developments in agricultural technologies that achieve one or more of the three pillars productivity, mitigation and adaptation of CSA are helping farmers deal with climate-related risks.
Various research centers within the CGIAR and elsewhere have announced the release of climate resilient crop varieties. In rice, the adaptation of flowering processes to heat is crucial since high temperature can cause flower sterility. Research is on-going for varieties which can escape early anthesis time , avoid panicle cooling through transpiration or tolerate presence of genes of interest heat at flowering Lafarge et al.
This has been reported in the maize-growing regions of Kenya and Mozambique, where farmers are rejecting new hybrid maize varieties in favour of existing traditional varieties due to difficulties of obtaining the necessary inputs for growing hybrid seed. Research is on-going to develop crop varieties with other traits for resilience e.
The use of intermittent irrigation for flooded rice has seen water efficiently utilized and yields increasing significantly. The system of sustainable rice intensification SRI has seen high adoption as a climate-smart option in about 20 African countries Nyasimi et al.
Up to 4—5 million smallholder farmers are expected to have benefitted from the system since Nyasimi et al. Similar adoption levels and success stories of SRI as a climate-smart option have been reported in Rwanda, Mali and Burundi Uphoff, Moreover, there are also increased investments in irrigation in the quest to meet the water requirements of cropping fields in Africa particularly for high value vegetables Wanvoeke et al.
Solar powered drip irrigation facilities are in particular being promoted in the Sudano-Sahel zones of West Africa due to their cost-effectiveness and significant correlation to increased household income and nutritional intake in the region Burney et al.
In addition, the promise of distributed irrigation has led to recent momentum around smallholder irrigation in contrast to large-scale centralized irrigation projects require specific institutional arrangements for successful adoption and support Burney et al. In Cape Verde, traditional irrigation techniques that maximize water use through fog water collection are also recognized as climate-smart options for smallholder agriculture Hiraldo, In Niger and in the Sahel, an African alliance to combat desertification has improved food security through farmer-managed natural regeneration, i.
This approach has not only yielded climate change mitigating benefits but also improved soil fertility and household fodder, food and fuelwood needs Nyasimi et al. However, the existence of many traditional agroforestry practices e. Supporting policies or other incentives are necessary. In the highlands of East Africa and in Southern Africa nevertheless, adopters of improved fallow agroforestry technologies witnessed improved income Mbow et al.
Many options exist to increase the prevalence of trees on farms, ranging form multilayer agriculture, to hedges, contour lines hedgerows, fodder trees in rangelands, trees in homegardens, etc.
The use of seasonal forecast information to predict the expectation of rains has a long tradition in Africa with even pastoralists in Ethiopia and northern Kenya still using indigenous forecasting methods to reduce climate-related risks Luseno et al.
With CIS, farmers are able to plan their planting and make projections about rainfall distribution patterns and temperature variations Giorgi et al. Application of climate information services is new to many farmers in Africa but evidence from Ghana and Senegal demonstrates great potential in improving the adaptive capacity of smallholder farmers to climate variability and extreme events CCAFS, In these countries, an approach was successfully implemented: to design tailored CIS; to communicate the results appropriately to farmers for their farm management decision making CCAFS, A collaboration between scientists, the national meteorological agencies and information and communications technology ICT -based service providers facilitated the development of more accurate and specific seasonal rainfall forecasts, and raised the capacity of partners to do longer-term analysis and provide more targeted information for farmers.
The use of ICT radio, mobile phones and associated agro-advisory services is becoming increasingly important in order to reach more farmers and overcome the high transactions costs incurred by face-to-face interaction associated with conventional extension services Etwire et al.
The forecast information provided includes the total seasonal rainfall, the onset and end of the rainy season, plus a day weaher forecast across the rainy season.
The information is conveyed to farmers as agro-meteorological advisories that are tailored to meet their local needs. In Senegal for instance, a partnership with 82 rural community-based radio stations is promoting economic development through communication and local information exchange, and the seasonal forecast is now reaching about rural households across the 14 administrative regions CCAFS, In Ghana, through a private ICT-based platform, market price alerts, agro-advisories, weather forecast and voice messages on climate-smart agricultural practices are sent out to farmers in the North of the country in the language of their choice.