The ecosystem as protagonist
In eco-SF at its most ambitious, the ecosystem is not setting but protagonist: it has a state, a trajectory, and the capacity to be affected by and to affect the human characters in ways the narrative tracks with genuine investment. Writing the ecosystem as protagonist means caring about its health and survival as narrative outcomes with the same weight as caring about a human character's survival. The reader should feel the loss when the ecosystem is degraded and the satisfaction when it recovers, not merely as context for human events but as events in their own right. This requires treating ecological data as emotional data: the decline of a species is a plot event, the collapse of a food web is a character death, the recovery of a forest is a resolution. The ecosystem that has been established as a protagonist gives these events the weight they deserve.