Urban ecology!

"Urban ecology is the discipline of the future, bringing geography, ecology, landscape architecture and urban planning together to create cities where people and biodiversity can thrive together. “Global urbanisation and global climate change are the two biggest threats to humanity in the future,” says Associate Professor McDonnell, who established the Australian Research Centre for Urban Ecology in 1998. A rapidly growing body of knowledge shows people benefit enormously from nature in cities, from the shade and natural air-conditioning of trees, to the psychological boost that natural views give workers, to the role of gardens in managing stormwater."

from: http://3tags.org/article/how-urban-ecology-can-provide-a-greener-alternative-to-the-concrete-jungles-of-the-future

And one way that can happen is urban agriculture:

"The burgeoning urban and near-urban agriculture trend in North America and around the world exemplifies how many small-scale, entrepreneurial businesses are inherently inefficient in how much labour they use. But this is something we should encourage and recognize as important for both economies and societies. When we talk about efficiency, we are usually talking about producing the most product or service for the least input or cost, including labour cost. But this definition of efficiency is counterproductive for job creation and for the environment."

from: http://www.theglobeandmail.com/urban-agriculture-may-be-inefficient-but-its-a-model-for-a-sustainable-future