The challenge of HIV/AIDS: Where does agroforestry fit in? - World ...

118World Agroforestry into the FutureTable 4.TreatmentMean temperature (T), duration when temperature exceeds 40°C (H40),photosynthetically active radiation (PAR) and millet biomass harvested underand away from the tree canopies. (Standard errors in parentheses).T(°C)V. paradoxa (large) –V. paradoxa (small)P. biglobosa (large)P. biglobosa (small)Control 129.10 (0.3)28.30 (0.5)27.00 (0.3)29.98 (0.4)H40(h week –1 )–19527PAR(µE m –2 s –1 )429 (57)541 (64)451 (57)660 (45)2158 (40)Millet biomass(g dry weight plant –1 )46.2 (16.5)43.3 (17.5)56.2 (14.6)36.8 (14.3)39.8 (15.2)Crops Research Institute for the Semi-AridTropics (ICRISAT) in Niger during 2002.The estimated income from a 1-ha farmwas US$600, some 12 times the value of atypical millet crop (Table 5). The estimatedcosts of establishing the SEF are not high;the plant material costs about US$60 perha, and the one-time application of fertilizerabout US$10. The labour requirementsfor land preparation and tree planting aremet by farmers and their families.1Control plots away from tree canopies.Source: Jonsson et al. (1999).play in mitigating the negative effects ofextreme temperatures on crops, especiallyin semi-arid regions.Pests, diseases and weeds already standas major obstacles to crop production inmany tropical agroecosystems and there arestrong reasons to believe that their prevalenceand deleterious effects on crops mayincrease with a warmer climate (Beresfordand Fullerton 1989; Hill and Dymock1989; Rosenzweig et al. 2000). It is stronglybelieved (Altieri and Letourneau 1982;Speight 1983), yet not sufficiently tested,that enhancing plant biodiversity and mixingtree and herbaceous species in agriculturallandscapes can produce positiveinteractions that could contribute towardscontrolling pest and disease outbreaks. Thepotential of agroforestry to control both ordinaryweeds (Gallagher et al. 1999; Impala2001) and parasitic weeds such as Strigahermonthica (Rao and Gacheru 1998) hasalso been demonstrated.Income generation throughtree productsBesides the biophysical resilience, whichallows the various components of the agroforestrysystems to withstand shocks relatedto climate variability, the presence of treesin agricultural croplands can provide farmerswith alternative or additional sourcesof income, so strengthening the socioeconomicresilience of rural populations. Treeproducts (including timber, fodder, resinsand fruits) are normally of higher valuethan maize or hard grains such as milletand sorghum, and can buffer against incomerisks in cases of crop failure.The Sahelian Eco-Farm (SEF) providesan eloquent example of how an agroforestry-basedintegrated natural resourcemanagement regime can help improve thelivelihood of the rural poor in vulnerableregions such as the Sahel (Pasternak et al.2005). The SEF is an integrated land-usesystem that incorporates high-value multipurposetrees/shrubs with soil and waterconservation structures. The value producedis in the form of food, fuelwood and forage(which can all be converted into cash),plant nutrients, biomass for mulch (whichcontributes to increased infiltration of rainfall,and addition of organic matter to thesoil), and protection from wind erosion. Thefirst on-station test of the SEF took placeat the Sahelian Center of the InternationalIn the semi-arid zone of Kenya, the parklandsystem is showing similar success.The fast-growing indigenous species Meliavolkensii is highly compatible with cropsand can provide high-value timber in 5–10years (Stewart and Blomley 1994). A studyby Ong et al. (2002) in the Kitui district ofKenya showed that in an 11-year rotationperiod, the accumulated income from treeproducts exceeds the accumulated valueof crop yield lost through competition. Thisincome difference is worth US$10 or 42percent during average years, and US$22or 180 percent if a 50 percent rate of cropfailure owing to drought (reasonable forKitui) is assumed. In such a hostile environment,where crops normally fail every otheryear, good and secure financial returnsfrom M. volkensii even in drought yearscan provide significant relief for farmers.This will be all the more necessary as extremeclimate events (droughts and floods)are likely to increase in frequency and inmagnitude in the near future.ConclusionsThe impact of climate change will be felton several levels in the agricultural sector.Most of the effects will hit the rural poorin developing countries, who are the mostvulnerable because of their poor ability toadapt. The adaptive capacity of farmers indeveloping countries is severely restricted