Just wanted to make a summary of some of the research I've done recently.
I got the book 'Landscape Infrastructure' with case-studies by SWA [Sasaki, Walker, and Associates - see website here] which has turned out to be a fantastic resource for real-world applications of 'urban nature.'
One of the essays in the book is entitled Second Nature by Adriaan Geuze & Matthew Skjonsberg. Here I am going to quote/paraphrase some of the main points, as influential on my thesis. (Emphasis mine)
"In the current urban context often the superficial presence of greenery appears as a stage setting to fill an intuitive void--the absense of nature--but lacking genuine substance of productive performance, such gestures ring hollow and do disservice to the optimism of any progressive society.
The generative potential of second nature can be found in its inclusiveness of the rural and urban as polarities of the same civilizing force.
It is possible... to reintroduce an integrative 'tabula rasa'--a performative second nature--in which ecological relations, water management, and microclimate become part of the engineering of the city.
...this orchestrated nature can even surpass the original nature in accomodating homo sapiens.
After a short period of groundwork, planting, and new cultivation, irrepressible pioneering vegetation will lay the basis for an ecological structure that will then slowly grow into a climax of habitats with an array of distinct biotopes and microclimates.
In principle, the city dweller--a permanent hostage to the 100 percent predetermined use of space--craves [the] sort of undefined spaces that have no speficied function but are nevertheless useful because they are accessible.
Cicero: "...we sow cereals and plant trees; we irrigate our lands to fertilize them. We fortify river banks, and straighten or divert the courses of rivers. In short, by the work of our hands we strive to create a sort of second nature within the world of nature."
For Cicero, "first nature" refers to wilderness, belongs to the realm of the gods, and is the raw material for "second nature"--the realm of human beings.
Second nature specifically describes a designed nature created in adjacency to existing urbanization, capable of absorbing future city growth into itself while maintaining the continuity of ecological systems.
The ambition of second nature is the radically humane reformulation of the relationship between urban and rural, amplifying civilization's cultural legacy..." (24-29)
I think it's pretty clear what the message is in this essay. We have a need to be connected with nature, and try to accomodate that by planting/arranging greenery within our urban contexts through parks and gardens.
However, because this nature isn't enabled to be productive--that is, it doesn't operate the way 'real' nature does--the urban nature can only fulfill our needs superficially, often in an aesthetic way. We plant extensive grass lawns which are essentially monocultures that require constant resources to maintain, all in the name of having 'green space in the city.'
Nature, however, has the potential to do things. It can grow food, sure, but it can be productive in much deeper ways. For instance, nature can act as a filter for our water runoff. It can filter air and water pollution. It can accomodate animal species that are necessary for the protection of our food supply. It provides habitat that would otherwise disappear. This is what is meant by productive potential--the ability for nature to take on our urban 'problems' in a totally efficient way. Nature can actually become a "part of the engineering of the city", just like roads, electricity, sewage pipes, and stormwater drains.
The essay argues that nature has meaning only if we use it with these potentials in mind--not simply as a visual solution to our desire for green space.