This poem inspired the director to create that scene
Traveling Through The Dark By William E. Stafford Traveling through the dark I found a deer dead on the edge of the Wilson River road. It is usually best to roll them into the canyon: that road is narrow; to swerve might make more dead. By glow of the tail-light I stumbled back of the car and stood by the heap, a doe, a recent killing; she had stiffened already, almost cold. I dragged her off; she was large in the belly. My fingers touching her side brought me the reason— her side was warm; her fawn lay there waiting, alive, still, never to be born. Beside that mountain road I hesitated. The car aimed ahead its lowered parking lights; under the hood purred the steady engine. I stood in the glare of the warm exhaust turning red; around our group I could hear the wilderness listen. I thought hard for us all—my only swerving—, then pushed her over the edge into the river.
The documentary film maker from the beginning of the film said there was no "big solution" to saving the planet, the solution was for people to focus on a lot of small plans which would enable people to work together on an unlimited number of small scale solutions and bring together people with shared concerns, which would pave the path to larger, more far-reaching solutions.
The pregnant doe was a small-scale problem the trio could have tackled, but they did not do so because the doe situation interfered with their plans to tackle the dam. The very pregnant doe, pregnant with the next generation of deer, pregnant with hope and the very future of her species' existence, was soundlessly pushed out of existence, hope destroyed, the seed of the future destroyed, evolution briefly interrupted.
The pregnant doe scene reinforced the documentarian's earlier comments about small scale solutions, and foreshadowed the failure of the trio's plans, whatever those plans were - at that point in the film, their plans were not yet revealed, but we knew they were embarking on a life-changing plan that for them was of greater import than saving an unborn fawn. A heart-stopping moment.
The dam was a massive large-scale problem, a type of large-scale problem obviously requiring a massive a number of people to tackle with a massive number of small solutions. The dam problem could not be "fixed" with a piece of legislation shutting it down nor with a bomb blowing it up.
Dena watched the documentary at the beginning of the film and she was the person who asked the director what the "big plan" was to save the planet, and was told by the director that small plans were the first step to take. Dena ignored that message, and failed to appreciate the meaning and the ethics and morality of the doe situation until she was informed a camper was missing and likely dead as a direct result of the trio bombing the dam.
When she learned the camper was missing as a result of their bombing, she, like the doe, became pregnant, with guilt, very pregnant with guilt, and wandered out of her normal routine, much like the doe wandering on the road, and was eventually struck dead, like the doe. She was soundlessly strangled and slid out of the viewers' sight, just as the doe was soundlessly slid out of the viewers' sight.
The pregnant doe situation was a no-win situation because the situation could not be fixed:, the fawn had a 50/50% chance of survival had they cut the fawn out of the doe because the fawn would be on his/her own (much like Dena and Josh were fawns on their own....) and because the road would still remain. The road would still remain, cutting the chances of survival of the fawn, and the deer species, in half. The wilderness was bounded by roads and highways on the perimeter, and the roads themselves were technically criss-crossing through what had once been wilderness.
The dam situation was a no-win situation because Dena said she wanted to eliminate the dam to restore salmon migration, which meant she wanted fish farmers to resume their own ecological destruction of the waters. So much for "sustainable" agriculture. The water and the forest and fish lose no matter what.
The dam situation was a no-win situation because environmental remediation, restoration and redevelopment projects require the support of entire peoples and communities and cities and regions, and wide-ranging support from local and state and tribal and federal partners, etc, which seemed non-existent in Dena's locality. The river-route they took to reach the dam was through an endless tract of irreversible forest destruction, indicating the destruction had been occurring for years and years unchecked. The organic farming cooperatives Dena and Josh were living in were just barely nominally committed to environmental causes - the farmers seemed like they were trying to live off-the-grid more out of a desire to give the govournment the middle finger to regulations and taxes as opposed to any environmental concern.Peter Sarsgaard's character seemed he was in it to give the govournment the middle finger for what the govournment put him through in the war zone (he was an ex-marine), and to cop a feel from Dena. It seemed that particular area seriously lacked the pro-environmental infrastructural network needed to generate positive and legal change.
And the dam situation was a no-win situation because even with massive support to remediate and restore and redevelop the region, there's always some amount of unintended damage in the aftermath. There's always unintended negative consequences. Legislation shutting down the dam would result in a resumption of the local fishing industry with its own irreversible fish genocide and other ecological blowback. Windmill farms kill hundreds of thousands of birds each year. Certain types of solar panels incinerate thousands of birds mid-flight each year. Blowing up the dam stopped the hydraulics but destroyed land animals and water animals and destroyed tracts of trees and families of birds, and resulted in the death of a camper and probably resulted in shutting down the camping grounds indefinitely. You're dammed if you do and you're dammed if you don't, pun intended.