Urbanization impact on lst, ndvi, ndbi, and built-up index: A comparative study in the istanbul megacity (2002-2023)

Abstract

In the past twenty years, Istanbul has undergone swift urbanization, with its population now estimated at around 16 million, ranking it among the 25 most populous cities globally. This rapid expansion has caused considerable changes in land cover, as urban materials such as concrete, asphalt, and metal have supplanted natural landscapes like soil and vegetation. The increase in impermeable surfaces, along with the reduction of green spaces, has led to a rise in land surface temperatures (LST), exacerbating Istanbul's susceptibility to heatwaves and climate-related issues. This research utilizes remote sensing technologies, including the Normalized Difference Built-up Index (NDBI), the Normalized Difference Vegetation Index (NDVI), and the Built-up Index (BUI), to evaluate alterations in vegetation and built-up regions in Istanbul from 2002 to 2023. By employing Google Earth Engine (GEE) and MODIS satellite data, significant indices and LST trends were examined, highlighting the notable decrease in vegetation and the increase in built-up areas, which correspond with a rise in surface temperatures. An analysis of median satellite imagery from 2002 and 2023 indicates that the mean geographically averaged LST in Istanbul rose from 22.64°C in 2002 to 24.86°C in 2023. This temperature increase is particularly pronounced in areas that have experienced substantial urbanization. For example, the location of Istanbul's new airport, which was once covered in green vegetation, recorded an LST of 19.81°C in 2002. However, after the airport's construction, the LST escalated to 31.2°C. Comparable patterns have been noted in other areas where green spaces have been replaced by mining and urban developments, such as in Çanta and Esenyurt in Europe, and Samandıra in Asia.