I have looked into bridges which make full use of nature to get from place to another, some of my findings are below.
All of these examples create what are essentially hills over roads. Although they are technically bridges built to go over the roads, it feels more natural to consider them as a part of the landscape, which the roads go through. I like the use of trees and shrubbery more than when only grass is used. However, what I have noticed from my findings is that the bridges often fit with context, using the same trees or ground covering that is found in the surrounding areas. The only exception to this seems to be the bottom left image, which has used a completely different grass, not fitting in at all.