Choosing the best tool for the job requires leaving all options on the table for many city planners.
There are some things nature will always do better than technology, and according to Gizmodo, some cities are experimenting with the integration of more wildlife into their ecosystems.
More animals in an urban area can make the region healthier and more beautiful. Bottom feeders, for instance, help an underwater ecology thrive. Ecologists in San Francisco and New York are now planning to introduce shellfish into the waterways for their cleaning properties.
There are also plans to reconnect some disconnected rivers to the oceans. Some fish, like the blueback herring, have had their populations reduced by pollution, algal bloom and river blockages. So ecologists are planning to make fish passageways in New York's Bronx River and Northern California's Yuba River.
Engineers also are working to integrate plant life into architecture to increase oxygen production within urban areas. Bioreceptive concrete encourages the growth of lichen and moss. Also, urban beekeeping has become a trend in recent years, as some feel an affinity with the insects as they pollinate flowers and encourage plant growth amid slabs of gray city.
More insects and more diverse plant life make the presence of bats in an urban environment more likely, and some groups encourage bats to stay in urban areas by installing bat boxes. In the same vein, bird advocates build "swift towers" and "osprey towers" to give birds a place to nest. Some architects even keep birds in mind when they design; they understand that birds will nest wherever they can, so it's best to plan them into the design.
Ground-nesting birds like turkeys have largely become suburban animals in the U.S., and some suggest that a few turkeys in urban parks could help bring a bit of the wild to the city too. Herds of goats and sheep exist in cities like Chicago, San Francisco and Cleveland to help keep certain regions clear of brambles and trash.
Introducing wild animals should be done with care, however, as illuminated by the explosion of deer populations in Staten Island. Without predators, animals can overrun their regions and damage the local flora.
One study showed that coyotes are pushing into cities because in some suburban areas, they've exhausted the food source. Bobcats can be found on freeway overpasses and golf courses in Dallas; in the suburbs of some Arizona cities and towns; and around the San Francisco Bay Area.
As cities evolve and expand, people likely will find new ways of integrating more plants and animals into their environments, especially since in this day and age, most people have moved out of the wilderness — but few are willing to leave it completely behind.