DOI: 10.7910/dvn/msgnou
title: Drivers of landuse and landcover change in western Kenya, Lake Victoria Drainage Basin

description: In 1983 The Lake Basin Development Authority (LBDA) commissioned an Integrated Land Use Survey (ILUS) of the ≈38,000 km2 LBDA Region defined by that part of the Lake Victoria drainage basin falling within Kenya. The core data of the LBDA/ILUS consisted of some 12,000 high resolution (1:6000 image scale), sample, aerial colour photographs spaced systematically across the LBDA area. A wide range of landcover and landuse attributes were measured off these sample photographs at sub‐meter resolution, including the cover of crops and intercrops; the cover of both natural and "managed" vegetation in terms of natural forest, plantations, woodlots, hedgerows and other woody vegetation; and the extent of bush and herbaceous cover. Furthermore, these ≈12,000 point data had been integrated with a wide range of environmental and socio‐economic data sets within a formal geographical information system (GIS) environment. ICRAF has, over the last few years, developed a number of programmes in western. Kenya involved specifically with the application of agroforestry to enhance both food security and resilience to climate change among the smallholder farming sector. ICRAF has also established in western Kenya, within the Nyando and Yala River Basins, five Sentinel Sites of 10km * 10km (100km2) each in which they use a variety of remote sensing applications to monitor ecosystem health and soil conditions. ICRAF acquired modern (2010) Quickbird satellite imagery for assessing landcover and landuse, and for general environmental mapping, in each of their five Sentinel Sites in western Kenya. T
his modern Quickbird satellite imagery has comparable resolution to the 1983 sample photography obtained for the LBDA/ILUS. Since LBDA had archived all the reports and photography from the 1983 ILUS along with critical georeferencing data for each of the ≈12,000 sample photographs, a rare opportunity was created to quantify landuse and landcover changes over an approximately 30 year period by comparing landuse and land cover on the 1983 sample photographs with that on the modern Quickbird satellite imagery and to relate these changes to environmental and socio‐economic drivers. The initial work carried out at ICRAF had already indicated that it was possible to reconcile the landcover and landuse classifications used on the 1983 ILUS with modern Quickbird imagery. Although more work needed to be done it was clear that a strictly comparable set of landuse and landcover attributes could be determined for each set of data. ICRAF and LBDA therefore agreed to pool their resources to develop a methodology for comparing these two sources of landcover and landuse data. In Phase 1, these five ICRAF Sentinel Sites were to be used to: develop and refine a strictly comparable set of landuse and landcover attributes between the 1983 photography and the 2010 Quickbird satellite imagery; and develop and refine robust statistical procedures to analyse the extent and rates of change between 1983 and 2010. In addition, the availability and quality of data on potential environmental and socioeconomic drivers of landuse and landcover change would be investigated, over the LBDA area as a whole and specifically for the five ICRAF Sentinel Sites. Once these objectives were achieved, a full Phase 2 programme would be designed (and costed) to extend the analysis of change and the drivers of change over the entire LBDA Region. In one respect these results are very encouraging and demonstrate that data on potential drivers of landuse and landcover change are available at a regional level for the LBDA area, including such esoteric variables as the contemporary and predicted rates of change in rainfall and temperatures. It is also clear that the spatial variation in the force of these drivers throughout the LBDA area is well described which will be of significant importance when designing the Phase 2 studies. However, in general the five ICRAF Sentinel Sites are not representative of the spatial patterns seen throughout the area. Accordingly, these five sites cannot be used on their own to analyse the importance of these drivers on changes in landcover and landuse. It is also clear that more up‐to‐date data will be required for the Phase 2 studies for some of the drivers, for example land tenure – which is rapidly evolving throughout the LBDA area – and the quality of the A
&B roads.