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Quantifying Tree Cover Loss in Urban Forests within Nairobi City Metropolitan Area from Earth Observation Data
* 1, 2, 3 , 1 , 1
1  Department of GeoInformation and Earth Observation, Technical University of Kenya
2  Hydrology and Earth Information Lab, Technical University of Kenya
3  GeoPsy Multidisciplinary Research


Urban forests contribute significantly to the ecological integrity of urban areas and the quality of life of urban dwellers through air quality control, energy conservation, improving urban hydrology, and regulation of Land Surface Temperatures (LST). However, urban forests are under threat due to human activities, natural calamities, and bio-invasion continually decimating forest cover. Few studies have used fine-scaled earth observation data to understand the dynamics of tree cover loss in urban forests and the sustainability of such forests in the face of increasing urban population. The aim of this work was to quantify the spatial and temporal changes in urban forest characteristics and to assess the potential drivers of such changes. We used data on tree cover, Normalized Difference Vegetation Index (NDVI), and land cover change to quantify tree cover loss and changes in vegetation health in urban forests within the Nairobi Metropolitan Area in Kenya. We also used land cover data to visualize the potential link between tree cover loss and changes in land use characteristics. From approximately 6600 hectares (ha) of forest land, 720 ha have been lost between 2000 and 2019, representing about 11% loss in 20 years. In 6 of the urban forests, the trend of loss was positive, indicating a continuing disturbance of urban forests around Nairobi. Conversely, there was a negative trend in the annual mean NDVI values for each of the forests, indicating a potential deterioration of the vegetation health in the forests. A preliminary, visual inspection of high-resolution imagery in sample areas of tree cover loss, showed that the main drivers of loss are the conversion of forest lands to residential areas and farmlands, implementation of big infrastructure projects that pass through the forests, and extraction of timber and other resources to support urban developments. The outcome of this study reveals the value of earth observation data in monitoring urban forest resources.

Keywords: Urban forests dynamics; Remote sensing of forests; forest sustainability; tree cover loss; Kenya
Comments on this paper
Rodolfo Picchio
Session Chair comment
Dear Authors,

your topic full fit with the main aims of this section and conference, congratulation. The undeniable key role of urban forests to guarantee life quality and ecological integrity of urban areas is becoming increasingly needy to be monitored and preserved. The approach presented in this work deals with fine-scale earth observation data, in order to describe changes in forest cover, structure and vegetative health, along with identifying potential drivers of such changes. The results obtained within the Nairobi Metropolitan Area in Kenya, assure the quality of remote sensing applied in dynamic contexts of land-use and social development. I hope to read further developments of this research soon.

Session Chair

Rodolfo Picchio