Ecological State Assessment of Urban Green Spaces Based on Remote Sensing Data. The Case of Aktobe City, Kazakhstan

The rapid pace of urban development triggers complex problems mostly related to urban environment pollution, and shortcomings of city’s improvement. The modern city is characterized by the highest man-made pressure on the natural environment, the main problems being overcrowding, lack of open-access green areas, as well as the decrease of vegetation areas, fact that does not create comfortable living conditions for urban residents. At present, remote sensing methods are some of the priority tools used in vegetation state assessment, particularly, the calculation of vegetation index (NDVI). But often, obtaining the necessary information is limited only to the analysis of satellite data, without geobotanical field surveys, which considerably increase the reliability of the detected results. In addition, the definition of dependencies when using an integrated approach of different man-affected surfaces with a different type of overgrowth within the city remains insufficiently studied. The purpose of this study is to assess the ecological condition of the green area (parks and squares) in Aktobe city. A comprehensive processing of satellite images including the calculation of NDVI index, mapping of green areas and data statistical analysis, was carried out. We learned that the average value of NDVI for green spaces in Aktobe ranges from 0,11 µm to 0,47 µm, which allows for the categorization of planted areas by levels of photosynthetic activity, from “unsatisfactory” to “good”, yet, with 59% of them in an unsatisfactory condition. This means that the city is underdeveloped in terms of modern landscape and infrastructure. The obtained results make it possible to assess the current situation, determine the dynamics of urban green spaces and optimize spatial planning measures for green space management.