I came across some interesting facts regarding megacities and urban forests.
Did you know that a megacities contains at least 10 million people whose well-being largely depends on ecosystem services provided by remote natural areas?
The megacity metropolitan areas ranged from 1173 to 18,720 sq km (median value 2530 sq km), with median tree cover 21%, and potential tree cover another 19% of the city.
The present median benefit value from urban trees in all 10 megacities studied can be estimated as $482 million/yr due to reductions in CO, NO2, SO2, PM10, and PM2.5, $11 million/yr due to avoided stormwater processing by wastewater facilities, $0.5 million/yr due to building energy heating and cooling savings, and $8 million/yr due to CO2 sequestration.
Which megacities? The cities were Beijing, China; Buenos Aires, Argentina; Cairo, Egypt; Istanbul, Turkey; London, Great Britain; Los Angeles, United States; Mexico City, Mexico; Moscow, Russia; Mumbai, India; and Tokyo, Japan
Planting more trees in potential tree cover areas could nearly double the benefits provided by the urban forest. In 2016 there were 40 megacities, totaling 722 million residents, nearly 10% of the human population, who would benefit from nature conservation plans where they work and live. Nature conservation strategies in megacities should work to sustain and grow the benefits of the urban forest, and improve accounting methods to include additional ecosystem services provided by the urban forest.
If you want to read more about this study,the info is below
Source: Endreny, T., Santagata, R., Perna, A., De Stefano, C., Rallo, R.F. and Ulgiati, S., 2017. Implementing and managing urban forests: A much needed conservation strategy to increase ecosystem services and urban wellbeing. Ecological Modelling, 360, pp.328-335.