India, Jan. 7 -- By Maneka Sanjay Gandhi

There is a tale that too many of us have forgotten, a sombre reminder that cities are not machines, but are living, breathing ecosystems where every species, every action, every choice has a ripple effect. That tale is of what happened in Surat in 1994 - the plague scare, a moment when human hubris and ecological ignorance collided with devastating consequences.

When we speak of public health, we instinctively focus on medicine, vaccines, sanitation and hospitals. What we rarely confront with equal urgency is the ecological balance that underpins the health of our cities.

People like to imagine cities as structures of concrete alone. They are not. They are built on relationships between water an...