Land Use Dynamics in the Khor Abu Habil alluvial fan,Sudan

Introduction African wetlands in arid and semi-arid regions provide a multitude of ecosystem services and have been described as the “heart of Sahelian life systems". The Khor Abu Habil alluvial wetlands (Khor is the name given to ephemeral rivers in Sudan) are situated in the semi-arid zone in the southern part of the Sudan. These ephemeral wetlands are fed by seasonal wadi streams and remain for several months. They provide a habitat for migratory water birds and play a fundamental role in supporting the human population (agriculture, grazing, fishing, hunting and construction).

Goals In this study we analyse the Land Use and Land Cover (LUL) dynamics related to wetlands and the agricultural activities.

Material and Methods Landsat images between 1982 and 2018 were used to run a LULC analysis in the Khor Abu Habil alluvial fan using random forests (RF) and change vector analysis (CVA). Due to the political and the COVID-19 pandemic situations in the study area,  the field work aiming at collecting ground reference points could not be completed. Therefore, we decided to identify training data on different types of LULC classes that were dominant in the study area for the last 30 years using CVA, in addition to the collected ground reference points. High resolution images (Quickbird, Geoeye, WorldView) and expert knowledge were used for the selection of training data. For Landsat images acquired before 2018, the present training data were used where CVA showed no change in LULC. After creating accurate training data, the classification of the different Landsat images was run in R using RF.

Results Different types of LULC classes were detected over the past 30 years: Wetlands, Vegetation, Agriculture, Arenosols, Cambisols, Clays.  Our results show that many of those classes were "transformed" into other classes over the past years. We observe that many of those changes are related to different anthropological activities such as the expansion of agriculture or construction of dams.

Conclusions Wadis or Khors are particular ecosystems that occur in semi-arid regions. In our study area, the economic activities show a relationship between LULC and different human communities. It is crucial to understand those activities and their effects on an ecosystem, especially if the ecosystem is aimed to be protected. Our research is part of the FAO-supported project RESSOURCE with the overall goal to localise and study wetlands of international importance in the sub-saharan Africa and to possibly declare them as Ramsar protected zones.