I assure you the wheat field will survive without the skyscraper, the other way around not so much. Cities may believe that they are independent of agrarian and rural society but the reality is that modern cities consume an incredible amount of raw resources and by necessity require the resources that an agrarian society produces. While it may sting and be sub optimal an agrarian society doesn't per say need an urban one to survive.
No, no, no: you can't have the skyscraper without the wheat field. Agriculture and city are part and parcel of each other since Ur.
(I often wonder how dense you could get and still be ecologically harmonious using e.g. Permaculture; you might be able to reach the density of a town.)
Which I agree with, history shows that urban folks and rural folks are often at odds, to put it mildly.
However, you also said,
> Two types of completely different civilizations clashing.
Which I disagree with, rural (not wild) areas are just as artificial and man-made (for all that they have more foliage and critters per area) as cities. Agriculture and urbanity have proceeded hand-in-glove. Farms and cities are both parts of the same civilization.
I don't follow, wild areas are not the same as rural areas.
What you're describing is hunter-gatherer (which IS a different civilization, in my opinion, from urban/agriculture) even if it's happening on the fringes of some other civilization.
As far as i know, and I'm not a historian, there haven't been farming (rural or pastoral) civilizations without some town or city involved, farms have always been the umbra of the city.
There were nomadic herders, hunter-gatherers, and farmer/city-states, but there never were cities without farmers nor farmers without cities, ever. So I say they are part of the same civilization even though they are in tension within that system.