Assessment of urban green spaces per capita in a megacity of the Philippines: implications for sustainable cities and urban health management

Megacities house the highest human population due to centralizing economic activities, causing congestion and increased settlements in urban areas. As a result of continuous urbanization in developing countries, access to urban green spaces (UGS) is continuously decreasing, affecting urban settlers' quality of life as UGS provides a wide variety of ecosystem services such as mitigation of climate change effects and as recreational sites for human wellbeing. An example of megacities undergoing the impact of urbanization is Metropolitan Manila, the National Capital Region of the Philippines. To determine the spatiotemporal changes in a megacity, satellite images from USGS Landsat 5 and 8 ranging from 2005, 2010, 2015, 2020, to 2023 were analyzed using ArcMap 10.8. The remotely sensed images were preprocessed using atmospheric corrections, ensuring the quality of the images. Enhanced Vegetation Index (EVI) maps of the cities were used to quantify the vegetation in the urban areas. They were calculated using landscape metrics, which were assessed for accuracy using the Kappa Coefficient. A drastic decrease in UGS was detected in almost two decades (2005–2023) as urban expansion occurred in the area. In addition, the UGS area was used to calculate the UGS per Capita, using the total population census per city. Concerning the recommended UGS per Capita from the World Health Organization in urban areas, all the cities were below the recommended index value, thus having unequal access to UGS quantitatively and qualitatively. As the population increases throughout the years, UGS per capita decreases in all 17 cities. This phenomenon in megacities emphasizes the need for prioritizing further establishment, management, and protection of the remaining UGS in the megacity, giving importance to future urban planning and policy-making for a more sustainable future of urban areas, most especially for the welfare and betterment of the state in developing countries.