Mapping and managing the spread of Prosopis Juliflora in Garissa County, Kenya

ABSTRACT

More than three decades after the introduction of prosopis species in the drylands of Kenya there is now increasing concern about the negative impacts of the plant on the livelihoods of dryland communities and on the ecological integrity of the fragile arid and semiarid lands. The extent of the species coverage in the arid and semiarid lands has, however, not been fully mapped owing in part to the recent nature of the problem. As such the aim of this study was to map out the extent of the spread of the species and propose community-friendly management options for this invasive plant. Geographic information system methodology and satellite imageries (Landsat images from 2000 and 2006), maps and GPS points were the main tools used for this work. Standard spatial statistical analysis procedures were employed using the software Erdas Imagine 8.4 and ESRI ArcView to generate land cover changes associated with prosopis species. The study found that a total of 440 square kilometres were newly colonised between the years 2000 and 2006, with Bura division having the highest area of land colonised at 143km² (33% of total land area). The study also noted that the riverine land use/land cover system was the most infested, with 631km2 colonised. This automatically puts the livelihoods of thousands of pastoralists who depend on the River Tana ecosystem at risk. The study also employed a socio-economic survey that involved the use questionnaires and interviews to ascertain the perceptions of the local community regarding origin, impact and uses of the species. Eighty four per cent of the respondents indicated that prosopis’ presence has had negative effect on the indigenous biodiversity of Garissa through loss of native vegetation. The three major local uses of prosopis were charcoal, fuelwood and animal fodder. The study shows that prosopis is a major environmental problem in the study area through its swift colonisation of strategic grazing reserves and is rapidly colonising new lands. The findings of this study call for commercialising production of prosopis for charcoal burning as a strategic management strategy for the plant. This should be accompanied with the use of efficient kilning technologies. In addition deliberate and pro-active policy changes should be put in place to delineate land specifically for this environmental business. Spread of the plant outside designated areas should be controlled by use of environment-friendly mechanical approaches. This further calls for community capacity building in partnership with key stakeholders like Kenya Forest Service. In this way, prosopis will cease to be a liability and instead contribute to community development through wealth creation.