Abstract
Assessments of land degradation vary in methodology and outcome. The objective of this study is to identify the state, extent and patterns of land degradation in Eastern Africa (Ethiopia, Kenya, Malawi and Tanzania). More recently (2000s), satellite-based imagery and remote sensing have been utilized to identify the magnitude and processes of land degradation at global, regional and national levels. This involves the use of Normalized Difference Vegetation Index (NDVI) derived from Advanced Very High Resolution Radiometer data and the use of high-quality satellite data from Moderate Resolution Imaging Spectroradiometer. This study is the first in Eastern Africa to complement remote sensing with ground-level assessments in evaluating the extent of land degradation at national and regional scales. The results based on NDVI measures show that land degradation occurred in about 51%, 41%, 23% and 22% of the terrestrial areas in Tanzania, Malawi, Ethiopia and Kenya, respectively, between the 1982 and 2016 periods. Some of the key hot spot areas include west and southern regions of Ethiopia, western part of Kenya, southern parts of Tanzania and eastern parts of Malawi. To evaluate the accuracy of the NDVI observations, ground-truthing was carried out in Tanzania and Ethiopia through focus group discussions (FGDs). The FGDs indicate an agreement with remotely sensed information on land degradation in seven sites out of eight in Tanzania and five sites out of six in Ethiopia. Given the significant magnitude of land degradation, appropriate action is needed to address it.
Highlights
Land degradation is defined as ‘‘the persistent reduction of the production capacity of a land, which may be manifest through any combination of a number of interrelated processes, such as: soil erosion, deterioration of soil nutrients, loss of biodiversity, deforestation or declining vegetative health’’ [31]
The land degradation hot spots in Eastern Africa are presented in Fig. 2 and Fig. 3
In Ethiopia, land degradation was reported in about 228,160 km2 (23%) and just about 127,424 km2 (22%) in Kenya
Summary
Land degradation is defined as ‘‘the persistent reduction of the production capacity of a land, which may be manifest through any combination of a number of interrelated processes, such as: soil erosion, deterioration of soil nutrients, loss of biodiversity, deforestation or declining vegetative health’’ [31]. There are two broad approaches to evaluate land degradation: ground-based measurements and remote sensing. Ground-based measurements, referred to as survey-based (direct) field observations, include approaches such as experts’ opinions, land users’ opinion, field monitoring and measurements, productivity changes, farmlevel studies and modeling. These approaches are important in evaluating land degradation process at the national and local levels [55]. An extensive review of these methods including their appropriateness, strengths and limitations is provided in [39] and [27]
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