How green the urban development units in Sofia are: Earth observation and population time series analysis

Abstract

Over the last decades, the pressure that people and their activities put on the environment has increased. Green areas in many cities are diminishing in size due to urbanization, which inevitably leads to a decrease in quality of life. This study uses remote sensing (RS) data for Sofia, Bulgaria, for a period of nearly four decades, analyzing the dynamics of NDVI of the urban development units (UDUs). Statistics for NDVI per were calculated for each UDU for eleven dates in the following years: 1987, 1990, 1992, 1993, 1996, 2000, 2001, 2002, 2011, 2015, and 2020.  An estimate was made of the amount of green vegetation per capita, similar to other coefficients used for population analysis. NDVI profiles for major urban parks showed differences for the studied period. Sentinel-2 data for 2020 was used for visualization of the current situation, in combination with detailed population data for all UDUs. The obtained data will help the decision-making process for the development of UDUs, while the methodology can be applied in any other city worldwide.