Mumbai Embraces Its Booming Flamingo Population

"The phenomenon illustrates the wealth and complexity of urban coastal ecosystems in India, say experts. Sometimes, “human impact results in conditions that seem terrible for nature at a glance, but are actually a gold mine for some species"

What a cool point. What are other well-documented examples of this?

One question--where's the line between "invasive species" and a new welcomed/prized species in a new ecosystem.