Made with open source software, the maps have an accuracy of around 75% but -especially in the absence of field assessments -this does not mean that there has not been a sharp decline of flora.
A look at the original diversity of plant species in the city indicates a composite of two major landscapes -coastal and the associated wetlands, and human-impacted or modified terrestrial system.
The terrestrial areas were characterised by scat tered vegetation, often dense thickets dominated by woody plants such as cactus-like euphorbia. With this type of vegetation, trees are scarce or are stunted. While it is not often acknowledged, grass and shrub vegetation acts as ecological guardians, helping limit the devastation of floods.
"Large spaces covered by a combination of grasses and shrubs earlier prevented flooding by allowing free flow of surface water. It also contributed to groundwater retention," says Jayshree Vencatesan, co-founder of Care Earth Trust.
Post-CycloneVardah, the city looks like barren land. A bare city with very sparse green cover is the Chennai of 2017.
"We may attribute the loss of green cover to the cyclone, which resulted in large-scale tree fall, but the sad truth is that the city has been losing its greenery for years due to unregulated and ill-planned urbanisation," says Vencatesan, adding that in addition to wetlands, farmlands have been converted into built-up spaces, including houses, linear infrastructure like roads and public utilities, pushing the city toward an ecological disaster.