Adaptation Potential in the Arid and Semi Arid Tropics

Adaptation to climate change in arid and semi-arid tropics of Asian countries depends on the cost of adaptive measures, existence of appropriate institutions, access to technology, and biophysical constraints such as land and water resource availability, soil characteristics, genetic diversity for crop breeding (e.g., development of heat-resistant rice cultivars), and topography. Adaptation measures designed to anticipate the potential effects of climate change could help to offset many of the negative effects. Adaptation measures that ameliorate the impacts of present-day climate variability include sea defences, institutional adaptations, plant breeding and adoption of new technologies in agriculture.

Sustainable development within tropical Asia's agroecosystems is crucial to provide adequate food security for traditional farming communities in developing countries and to ensure in situ conservation of crop biodiversity for sustaining high-input modern agriculture itself. Traditional societies have always manipulated biodiversity to ensure ecosystem resilience and to cope with uncertainties in the environment, rather than to increase production on a short-term basis. There is increasing evidence now to suggest that one could learn from their traditional ecological knowledge base (Gadgil et al., 1993) for coping with uncertainties associated with global change.

The resilience of agricultural practices in the face of climate change depends on the nature and magnitude of region-specific climate change, and the threshold and adaptive capacity of agricultural communities. Adjustment of planting dates to minimize the effect of temperature increase-induced spikelet sterility can be used to reduce yield instability, by avoiding having the flowering period to coincide with the hottest period. Adaptation measures to reduce the negative effects of increased climatic variability as normally experienced in arid and semi-arid tropics may include changing the cropping calendar to take advantage of the wet period and to avoid extreme weather events (e.g., typhoons and storms) during the growing season. Crop varieties that are resistant to lodging (e.g., short rice cultivars) may withstand strong winds during the sensitive stage of crop growth. A combination of farm-level adaptations and economic adjustments such as increased investment in agriculture infrastructure and reallocation of land and water would be desired in the agricultural sector (IPCC, 2001b). Other adaptive options included developing cultivars resistant to climate change; adopting new farm techniques that will respond to the management of crops under stressful conditions, plant pests and disease;

design and development of efficient farm implements; and improvement of post-harvest technologies, which include among other things, the use and processing of farm products, by-products and agricultural waste.

A commonly prescribed adaptation to climate change in the water sector is to enhance characteristics that offer flexibility hence enhancing resilience. Flexibility issues are particularly important with regard to the development of water resources for industry or agriculture. If hydrological patterns change markedly and irrigated agriculture is required to relocate in response, prior investment may be lost as existing infrastructures become obsolete, and additional investments will be needed. This necessitates critical scrutiny of a range of available choices that incorporate economic and environmental concerns. The potential for adaptation should not lead to complacency (Rosenzweig and Hillel, 1995).

Studies have shown that ecologically important keystone species often are socially selected by many rural societies. The possibility for species selection for rehabilitating a degraded ecosystem should be based on a value system that the local people understand and appreciate; therefore, their participation in the process of developmental activity is important. Community perceptions of soil and water management can be a powerful agent for sustainable management of natural resources. In other words, natural resource management in tropical Asia must be sensitive to social and even cultural perceptions (Ramakrishnan, 1998), as well as traditional resource management practices.

The major impact of climate change in arid and semi-arid Asia is likely to be an acute shortage of water resources associated with significant increases in surface air temperature. Conservation of water used for irrigated agriculture, therefore, should be given priority attention. With increased evapotranspiration, any adaptation strategy in agriculture should be oriented toward a shift from conventional crops to types of agriculture that are less vulnerable to evapotranspiration loss (Safriel, 1995). Expansion of commercial and artesian fisheries also could help reduce dependence on food productivity. Protection of soils from degradation should be given serious consideration. Trying out salt water resistant varieties of crops in the areas where drainage is poor; diversifying agriculture and food habits of the people primarily limited to some specific cereals, improving to management of irrigation systems; implementing crop livestock integration; changing crop varieties in cropping patterns to suit changing climatic conditions; implementing agro-forestry systems etc. are the other adaptive options to be considered (Luo and Lin, 1999). Optimum use of fertilizers and ecologically clean agrotechnologies would be beneficial for agriculture.

Cropping systems may have to change to include growing suitable cultivars (to counteract compression of crop development), increasing crop intensities (i.e., the number of successive crop produced per unit area per year) or planting different types of crops (Sinha et al., 1998). Farmers will have to adapt to changing hy-drological regimes by changing crops. For example, farmers in Pakistan may grow more sugarcane if additional water becomes available and they may grow less rice if water supplies dwindle. The yield ceiling must be raised and the yield gap narrowed while maintaining sustainable production and a friendly environment. Development of new varieties with higher yield potential and stability is complementary to bridging the yield gap.

Improvements in run-off management and irrigation technology (i.e., river runoff control by reservoirs, water transfers and land conservation practices) will be crucial. Increasing efforts should be directed toward rainwater harvesting and other water-conserving practices to slow the decline in water levels in aquifers. Recycling of wastewater should be encouraged in drought-prone countries in tropical Asia.

Although the core population of the species may become extinct because of global warming, resistant types in peripheral populations will survive and can be used to rehabilitate and restore affected ecosystems (Kark et al., 1999). The geographic locations of such species usually coincide with climatic transition zones, such as at the edges of drylands or along the transition between different types of drylands. Identifying regions with concentrations of peripheral populations of species of interest and protecting their habitats from being lost to development therefore can play a role in enhancing planned adaptation for semi-arid and arid regions of Asia.

5.2. AFRICA

While there is universal agreement that the direction of climate change, especially at the regional scale, is somewhat uncertain, it should not lead us to a degree of complacency that adaptation to climate change will be easy. The importance of the rate of climate change must be assessed by comparing the rate at which the systems that might be affected change and adapt (Ausubel, 1991). Adaptations are expensive and the level of technological and economic development of a country determines the extent to which countries can cope with climatic changes.

The sensitivity of a crop to climate change depends not only on its physiological response to temperature or moisture stress, but also on other components of the system. The poor soils in the arid and semi-arid regions of Africa with low native soil fertility are a major component affecting this sensitivity. With the reduced ratio of the length of fallows to cropping years, soil fertility has been declining. According to Mudahar (1986), average use of fertilizers in the sorghum (Soghum bicolor (L.) Moench) and pearl millet (Pennisetum glaucum (L.) R.Br.) growing countries of West Africa was only 5 kg/ha. In the absence of added manure or fertilizers on these poor soils, the nutrient reservoir of the soil under continuous cropping is dropping to levels that can no longer sustain the desired yield levels.

Whether or not there will be a significant climatic change, the inherent climatic variability in the arid and semi-arid regions of Africa makes adaptation unavoidable. Environmental problems facing this zone are serious and certain. The need for development and implementation of sustainable agricultural strategies on a regional scale is crucial in this marginal region that is already threatened by environmental degradation. Pre-meditated adaptation that begins with anticipation and information (NAS, 1991b) is a good strategy for this region. The approaches we need should be prescriptive and dynamic rather than descriptive and static.

5.2.1. Improve Monitoring

In order to assess carefully the impact of future climate change on the managed and unmanaged ecosystems in the SSZ, it is crucial to monitor local climate, and natural changes in species adaptation, if any. It will be necessary to install improved methods of climate monitoring by taking advantage of recent developments in automatic weather stations, which enable easy recording of the occurrence of extreme events on a routine basis. For species adaptation, it will be useful to set up phenological gardens at benchmark sites to carefully assess the changes in their adaptation and in the duration of the developmental stages.

5.2.2. Use Strategies for Efficient Natural Resource Use

Increasing the promotion and strengthening of resource conservation is the first step in coping with the climate change. These strategies will include, for example: soil and moisture conservation, better moisture use efficiency, collection and recycling of run-off, reducing deforestation, increasing reforestation, and reduction of biomass burning. Strategies that can increase the water use efficiency, such as relay cropping during years with early onset of rains, are now available and should be transferred to the farm level.

5.2.3. Implement Sustainable Agricultural Practices

It is important to increase the emphasis on the development and adoption of technologies that may increase the productivity or efficiency of crops consistent with the principles of sustainable development. Sivakumar et al. (1991) discussed possible strategies for management of sustainable systems in the SSZ. These include techniques such as minimum/no till systems, traditional agro-silvi-pastoral systems, choice of appropriate crop varieties, intercropping/relay cropping of cereals with legumes, Faidherbia albida systems, mixed tree/grass/crop systems, rotations, use of manures with a limited quantity of fertilizer, and use of crop residues.

5.2.4. Enforce Effective Intervention Policies

One of the adaptation strategies recommended by NAS (1991) is the intervention by governments to manipulate the circumstances of choices. The criteria laid down for government action (NAS, 1991) apply to the Sudano-Sahelian zone even now:

a) Amount of time needed to carry out the adaption is so long that we must act now.

b) Action is profitable even when climate does not change.

c) Penalty for waiting a decade or two is great.

The need for good, timely climate information in the drought-prone regions is too well known to be stressed. Recent developments in the information technology now make it possible to quickly acquire and sort the enormous amount of information into items relevant to the end user. Implementation of policies to provide timely information, improved weather and climate forecasts and good markets should help the farmer adapt quickly.

5.3. LATIN AMERICA

The process of potential adaptation of crops and human beings to environmental impacts in the arid and semi-arid tropics is challenging and is highly dependent on existing technologies.

In the humid tropics, where drought is not a constant phenomenon but rather a periodic abnormality, from year to year, or even in the rainy season, several agricultural practices can be used such as: direct planting, irrigation, choice of drought tolerant varieties. This has been a technological adaptation widely used in countries, such as Brazil, Argentina, Uruguay, and Paraguay among others. On the other hand, in the arid and semi-arid regions where the low rainfall is a limiting factor, the most feasible solution or technological adaptation is to use supplemental irrigation.

For this purpose, large reservoirs have been built in conjunction with power generation. In many cases perennial rivers are exploited for irrigation. These techniques are quite challenging in many cases, especially when improper irrigation methods bring about more damage to the environment by salinization of agricultural soils or depletion of scarce natural resources.

It is possible that intercropping and techniques for sustainable agriculture are more appropriate for these regions. Many options must involve a combination of efforts to reduce land degradation and foster sustainable management of natural resources.

A number of adaptive processes designed to prevent further deterioration of forest cover are already being implemented to some degree. Some of these measures involve natural responses when particular tree species develop the ability to make more efficient use of reduced water and nutrients under elevated CO2 levels. Other adaptive measures involve human-assisted action programs (such as tree planting) designed to minimize undesirable impacts. These strategies will include careful monitoring and microassessment of discrete impacts of climate change on particular species.

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