The Overstory by Richard Powers.
An artist inherits a hundred years of photographic portraits, all of the same doomed American chestnut. A hard-partying undergraduate in the late 1980s electrocutes herself, dies, and is sent back into life by creatures of air and light. A hearing- and speech-impaired scientist discovers that trees are communicating with one another. An Air Force crewmember in the Vietnam War is shot out of the sky, then saved by falling into a banyan.
This is the story of these and five other strangers, each summoned in different ways by the natural world, who are brought together in a last stand to save it from catastrophe.