The work of the grass being done is positive, for one main reason. Decomposition, over time the bodies decompose, feeding the soil and making it richer, making the grass be able to flourish,
"Two years, ten years, and passengers ask the conductor: What place is this Where are we now?"
This from the text showing that the decomposed bodies have given enough "food" for the soil to grow more grass making it look more like it was before the grass died.
Whether readers view the work of the grass as positive or negative is a matter of opinion. A reader might view the grass’s work positively because it allows people to move past tragic events rather than see reminders of them. However, the negative side to moving past tragedy and losing the reminder of brutality in wartime is that people may forget. That people in the poem do not recognize the battlefield suggests that they have indeed forgotten. The fact that the poem ends with the grass repeating its demand to be allowed to work may mean that there are still more battlefields to cover up, that people have not learned from their mistakes, and that the violent and tragic events of war will continue to occur and then be forgotten.
