Final Report: A Land Degradation and Desertification Appraisal System for South Africa (LanDDApp)

Symeonakis, Ilias (2018) Final Report: A Land Degradation and Desertification Appraisal System for South Africa (LanDDApp). UNSPECIFIED. UNSPECIFIED.

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Abstract

Land degradation and desertification (LDD) is a serious global threat to humans and the environment. Globally, 10-20% of drylands and 24% of the world’s productive lands are potentially degraded, which affects 1.5 billion people and reduces GDP by €3.4 billion. Large parts of southern African arid, semi-arid and sub-humid areas are considered to be undergoing severe degradation processes, such as forest degradation, deforestation and bush encroachment that affect up to a third of the area, leading to a decline in the ecosystem services provided to some of the continent’s poorest and most vulnerable communities. There is, therefore, a pressing need for an objective, repeatable, systematic and spatially explicit measure of land degradation over the region and this is why the main aim of the LanDDApp project was to develop an appraisal system for assessing LDD in the southern African region. According to some assessments, only in South Africa bush encroachment, i.e. the advancement of woody plants into grasslands, and the subsequent conversion of savannahs and open woodlands into shrublands, has rendered 1.1 million ha of savannah unusable, it threatens another 27 million ha (~17% of the country), and has reduced the grazing capacity throughout the region by up to 50%. For this reason, one of the key objectives of LanDDApp was to devise an accurate methodology for mapping and monitoring bush encroachment using open access Earth Observation (EO) data. The use of multi-temporal and multi-sensor data from both the dry and the wet seasons proved to be a highly successful approach. To describe and map changes in ecosystem functioning at the regional scale, LanDDApp also carried out time-series analyses of vegetation index data: a proxy for vegetation vigour. Spatio‐temporal patterns of change in two different vegetation indices covering 33 years from 1981–2014 were identified. Areas of diverging trends in the vegetation indices were linked to well‐known changes in land use and land cover, such as deforestation and bush encroachment. Moreover, the patterns of diverging vegetation index trends were used as a reference in evaluating the impacts of environmental changes related to trends in Net Primary Productivity and Rain Use Efficiency. Field visits to three diverse study sites were carried out to verify the results using a variety of cameras mounted on poles, fixed wing and octocopter Unmanned Aerial Vehicles (UAVs), as well as expert knowledge. The results indicate areas of localized land degradation where ecosystem functioning has been reducing. Degradation impacts were reflected as reductions in productivity that varied along a continuum from slight to severe, depending on the specific land use/cover. The results from LanDDApp are relevant to various local, regional, national and international stakeholders related with savannah LDD, from small communal to larger private farmers, NGOs related with helping local communities maintain sustainable livelihoods while protecting their environment, Provincial and Central Government Organisations, Universities from all affected countries in the southern African region, research organisations as well as SMEs working on mapping tools and UAV/EO technologies.