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

Chapter 11: The potential for agroforestry99coffee and cocoa systems in Southeast Asiaand Central America. However, there arealso contrasting results: Soini (2004) foundlow levels of bird diversity in the multistrataChagga homegardens of Kilimanjaro,Tanzania. Soini postulates that the veryhigh levels of human population in thoseareas have created an inhospitable habitatfor most bird species.Naidoo (2004) presents a novel analysis ofthe relationship between forest types andbird types in and around the Mabira forestin Uganda. He analysed the diversity ofsongbirds along transects across differenttypes of landscapes, from intact primaryforest, to regenerating secondary forests andagricultural fields. Songbirds were classifiedas forest specialists, forest generalists, forestvisitors and open habitat species. He foundroughly similar numbers of total songbirdspecies in each of the three land-use types,but marked differences in the percentagesof different species groups. Forest specialistswere not found in the agricultural area;open habitat species were not found in theintact forest. Statistical models of the habitat–speciesrelationship showed that treedensity and distance to intact forest had thegreatest impacts on number of forest species.Model results indicate that greater treedensity in agricultural fields could result ina sizeable expansion in the habitat of forestspecialists within the forest and forest generalistsin the forest margin.Agroforestry can enhance connectivity andlandscape heterogeneity in multi-functionalconservation landscapes. Zomer etal. (2001) found that an agroforestry systeminvolving Alnus nepalensis and cardamomcontributed to the integrity of riparian corridorsfor wildlife conservation around theMakalu Barun National Park and ConservationArea of eastern Nepal.Griffith (2000) suggests a different ecologicalmechanism by which agroforestry cancontribute to biodiversity – by providinga low risk refuge in the case of fire. Heassessed bird biodiversity in two agroforestryfarms in the buffer zone of the MayaBiosphere Reserve in Guatemala in orderto determine whether those farms hadserved as biodiversity refuges during thefires of 1998 that burned eight percent ofthe reserve. He found high numbers of birdspecies, including forest specialists and forestgeneralists – birds that are not usuallyfound in agroforestry areas.4. Agroforestry and the threats ofinvasive alien speciesProposition: Agroforestry developmentcan be implemented in a way thatreduces the risk of alien invasive speciesto acceptable levels, if adequateprecautions are taken.In the introduction to this chapter wenoted that there are major concerns in theconservation community about the potentialthreat that farmer planting of treesmay pose to biodiversity. For example, theUNCBD Thematic Programme of Workstates: “Tree plantations and agroforestry areimportant sources of biological invasions…Of species used for agroforestry aroundseven percent are said to be weeds undersome conditions, but around one percentare weedy in more than 50 percent of theirrecorded occurrences.”Evidence from across the world indicatesthat agroforestry projects have contributedto the ecological problems associated withalien invasive species. News of impending‘fuelwood crises’ a generation ago ledto the creation of a large number of newagroforestry projects across the developingworld in the late 1970s and early 1980s.While many of these projects undoubtedlycontributed to increased energy supplies,they have also had negative consequencesfor welfare, biodiversity and water availability.Better design of the current generationof agroforestry projects should help tominimize negative impacts in the future. Forexample, ICRAF has adopted a policy thatfocuses on reducing the risk of introducinginvasive alien species as part of newagroforestry research and developmentprogrammes. We are also conducting researchon effective management of selectedinvasive alien species. For example, ongoingresearch on Prosopis juliflora inthe Baringo area of Kenya indicates thepotential benefits and limitations of effectivemanagement through sustained use.Challenges for the futureThe overall conclusion that emerges fromthis review is that agroforestry generallyproduces biodiversity benefits that are intermediatebetween monocrop agricultureand primary forests. The overall contributionof agroforestry to biodiversity conservationdepends, therefore, on the type of land usethat it replaces and on the attributes of thespecific agroforestry system. The effectivenessof agroforestry in biodiversity conservationdepends on the design of the system and thenature of the biodiversity to be conserved.Agroforestry is not a stand-alone approachto conservation. Rather, it needs to be seenas an element of conservation strategies,which also include policy and institutionalchanges, and spatial configurations that emphasizemaintenance of natural habitats.Additional research, including appropriatemeasurement, modelling and