Abstract
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 bioinvasion 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 six 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.
Highlights
Urban forests are recognized for both their environmental and socio-economic benefits to cities and urban areas across the globe
Major losses were recorded in Ngong road forest with an approximate tree cover loss of 56.9ha, Dagoreti forest with a loss of 34.8ha, and Muguga forest at 27.7ha
In terms of the spatial distribution of tree cover loss, major losses were recorded in Dagoreti, Kibiku, Muguga, Ngong road and Ngong forests respectively
Summary
Urban forests are recognized for both their environmental and socio-economic benefits to cities and urban areas across the globe. Trees and forests in urban areas contribute to carbon dioxide sequestration, air quality control, noise reduction, urban hydrology, and regulation of both land surface and air temperatures [1]. Urban forests and other green spaces within urban areas have been linked to the general quality of life of urban populations. 2020, 1, Firstpage-Lastpage; doi: FOR PEER REVIEW www.mdpi.com/journal/environsciproc Proc. 2020, 1, Firstpage-Lastpage; doi: FOR PEER REVIEW www.mdpi.com/journal/environsciproc
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.