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

110World Agroforestry into the Futurecourse of profitability and the substantialvariation in soil properties, often at shortspatial range, with substantial differencesbetween soils in susceptibility tocompaction.Negotiations betweenstakeholders of solutions onthe basis of trade-offsThe basics of watershed functions arewell understood in most local ecologicalknowledge systems that have so far beenexplored (Joshi et al. 2004), as well as informal ecohydrological science. Their representationin general public debate andpolicy circles, however, leaves much scopefor improvement.Indonesia is rich in examples of landscapeswhere farmers have combined the use oftrees and other elements of the natural forestthat provide environmental serviceswith areas that are used for intensive foodcrop production. These agroforestry mosaiclandscapes can be seen as ‘kebun lindung’(protective gardens) that offer great opportunityfor combining development andenvironment targets (Pasya et al. 2004; vanNoordwijk et al. 2004a). Yet, there are obstaclesto the recognition of these systems,as they may not meet the legal definitions offorest or be in harmony with existing landuseregulation systems and policies – eventhough they could pass the test when functionalcriteria and indicators would be used.In negotiating solutions to local problems,the following aspects may require specificattention:1. Creation of local infiltration sites is oftenthe first step required to break out froma soil degradation–surface runoff erosioncycle. Such sites will both reduce negativeimpacts on downhill neighbouringzones and allow for a positive feedbackloop of vegetation that stimulates formationof soil structure, increasing infiltrationand acting as a further stimulus toplant growth. Triggers of such a positivefeedback can be remarkably simple:stone lines (as used in the Sahel), plantingholes made for trees (that may be thebest part, initially, of reforestation effortsand is often not considered as such) orsmall strips left to natural vegetationsuccession in between ploughed fields(‘natural vegetative strips’, see Chapter 7this volume) as used in the Philippinesand Indonesia.2. Taking natural forest soil as a baseline,soil compaction will initially have astronger effect on the lateral flows thataffect watershed functions than on theon-site productivity of the soil. Whereprotection of forest soils is feasible byreduction of the drivers of degradation,it is likely to be much more effectivethan efforts to rehabilitate degraded locations.Unfortunately, environmentalgovernance and reward systems tendto be reactive, and have difficulties indealing with avoidance of degradation,while rehabilitation is considered worthyof public investment.3. Enhancing soil organic matter levels haslittle direct influence on plant-availablewater, but a strong indirect effect via soilstructure, depending on the texture ofthe soil and the rainfall regime. Susiloet al. (2004) discuss the relationshipbetween total organic input in the agroecosystemand the various levels of thebelow-ground food-web.4. The most important part of a forest froma perspective of soil and water flows islikely to be in the litter and root turnovereffects, and that in turn supports soil biotato maintain soil structure. Half-open(agroforestry) land-use systems with treescan approach the same functionalitywhile providing better livelihood opportunitiesand income (see van Noordwijket al. 2004b, for discussion of trade-offbetween relative ecological and relativeagronomic functions, or REF and RAF).5. For assessment and monitoring purposes,new methods and models thatprovide internal controls in the form ofreference values for soil carbon and BDcan be used to deal with the inherentvariation in soil properties and the relationshipsbetween lateral flow processacross spatial scales.The discussion so far has highlighted theecological/technical side of soil structureand function. If agroforestry is to achieve itsaims, understanding of and actions targetingthese technical aspects at farm-managementscale will have to be embedded in a structureof rules and incentives that relate boththe downstream users of landscapes and thestakeholders in maintenance of watershedfunction to the decisions made on-farm. Thepast focus of watershed managers on forestcover per se may now give way to a moresubtle view in which land uses such as the‘kebun lindung’ in Indonesia get the recognitionthat they are due (Pasya et al. 2004;van Noordwijk et al. 2004a).AcknowledgementsOur research on these topics in Indonesia inthe context of the Alternatives to Slash andBurn consortium is supported by the AustralianCentre for International AgriculturalResearch (ACIAR) and the UK’s Departmentfor International Development (DFID), butthe views expressed remain the authors’responsibility.