Land-use and Landscape Pattern Changes in Holeta-Berga Watershed, Ethiopia

摘要

A study on the land-use/land-cover pattern changes, spatio-temporal landscape modification, forest degradation risk and landscape disturbance index was made around the Holeta-Berga watershed in Ethiopia. The dynamics and pattern of changes for a period of 33 years (1973-2006) were analysed using GIS and Remote Sensing techniques. The total area of built-up and crop land increased from 4382.7 ha (4.35%) to 12198.02 ha (12.3%) and from 33144.3 ha (32.93%) to 62916. 02 ha (62.51%), respectively, during this period. On the other hand, the extent of forest cover decreased at the rate of 546.32 ha yr-1 from 22549.6 ha (22.4%) to 4521 ha (4.49%) and the extent of grassland decreased from 37416.5 ha (37.17%) to 17437.2 ha (17.33%) during the same period. The landscape of the study area showed transformation on composition. The mean patch size index of forest cover and grassland decreased from 10 ha to 1.11 ha and 17.4 ha to 0.87 ha, respectively. In relation to this, the landscape configuration change indicators such as the interspersion-juxtaposition index increased in crop land from 65.16% to 83.58%, and decreased in grassland from 57.685 to 34.74%. Shape complexity of the study site also increased in each of the types of land-use/land-cover classes in terms of area weighted mean fractal dimension, except grassland. It is revealed that an extent of 981.05 ha of the study area is under high degradation risk and 8378.58 ha is under medium to high disturbance scales. Most of the land-use/land-cover conversions and landscape pattern changes are the results of unscientifically planned resource utilization and management programmes. It is important to understand the spatio-temporal changes of the landscape pattern and land-use/land-cover changes to implement reliable and sustainable land-use and development programmes.