Be interesting to see how are cities and their larger regions are doing when it comes to their ecosystems and the biodiversity within them. Whether it be new or pre-existing, the importance of both cannot be understated. Climate change and habitat loss a big concern these days. Things like urban forests and naturalized park land can go a long way in reducing our impact and increasing biodiversity and quality of life. Even something as simple as your backyard or balcony can help.
I will start with a Toronto example. It could be anything but this is a man made wildlife habitat.
The Leslie Street Spit, or Tommy Thompson Park, was originally intended as a breakwater for Toronto's outer harbour but for various reason it was never really needed for that purpose. Nature started claiming the land and now the emphasis is on expanding that usage. It is now an important birding area and nature refuge. Fill from construction around projects the GTA are dumped into the lake and it continues to grow to this day. It goes out 5 km into Lake Ontario.

Double-crested Cormorant (Phalacrocorax auritus) by
Edward Kroc, on Flickr

191 by
ontario photo connection, on Flickr

Leslie St. Spit - Toronto by
Garnett Plum, on Flickr