illustration (attribution, if any possible, is at the end of the article)
It is often assumed that one has to take care of oneself first, and that all ethics are subordinate to one's survival.
In war zones, some people get it that sometimes sacrificing themselves in order to save many might be the appropriate response to the situation at hand. Others will be happy to distribute posthumous medals while celebrating they were not the ones having to sacrifice, often assuming they had 'better' reasons to live.
When it comes to our environment, most people assume that human survival 'should' come first. Sometimes not just our survival but also our 'economy'!
However, there's a Jakata tale (i.e. a story about a past life of Siddhārtha Gautama, prior to his Awakening) which questions the 'necessity' of preserving one's life, solely on the basis that this life is human:
« One day, three princes rode out to hunt. They came upon a valley lush with trees and fragrant flowers and with a river of sweet water. The brothers sat quite still, admiring the beauty of the valley. Suddenly, not far from them, the princes spotted seven tiger cubs frisking in the grass around their mother.
The tigress was thin and gaunt. She had not eaten for so long that her milk had dried up. The mother tiger stared hungrily at her cubs as they tumbled and rolled around her trying to get at her dry teats.
The eldest brother felt sorry for the tigers but he didn't know what to do about their plight. The middle brother suggested they return to the palace and bring back some fresh meat for the mother tiger.
"If the mother tiger can be saved and her milk can be made to flow again," he argued, "then surely her cubs will also live."
The princely brothers agreed to try and turned their horses back towards the palace. Just as they started out, the youngest prince, whose name was Mahasattva, reconsidered. It would take them half a day to get to the palace, he thought, and another half day of travel for the return trip to the valley. In the meantime, he reasoned, the mother tiger would starve to death. There and then, Mahasattva decided that he would give his own life in order that the tigress and her cubs could live.
"Wait a minute," he called to his two brothers. "I really feel too ill to make the trip back to the palace. I'll just wait here and rest until you return."
When his two elder brothers had galloped out of sight, Mahasattva removed all his clothing and lay down in front of the big tigress. Tentatively, the tigress licked at Mahasattva's naked body but she drew back when she discovered that he was still alive. Mahasattva lay still a while longer but still the tigress made no attempt to eat him since she preferred dead meat.
Finally realising his error, Mahasattva jumped up and climbed the hill above the tigress and her cubs. Once there, he found a length of bamboo that he fashioned into a sharp knife. Holding the splinter of bamboo in his hand he stabbed himself in the throat and, as his life's blood drained away, he fainted and toppled over the edge of the hill, landing right in front of the tigress and her cubs.
The tigress pounced on Mahasattva's dead body, eagerly devouring his flesh, gnawing on his bones and lapping up his spilled blood. In moments, the tigress' breasts began to fill with milk and her cubs suckled greedily. Revived by their meal, the tigress and her seven cubs left the valley.
In the meantime, the two brothers were on their way back to the valley with a load of fresh meat from the palace. When they arrived, they were surprised to find that the tigers were not there. Nothing remained but scattered bones and a heap of clothes. They knew immediately that the clothes belonged to their younger brother and that it was his bones strewn in the grass. It dawned on them now what Mahasattva's real reason for not returning with them to the palace was. He had stayed behind to sacrifice his own life so that the tigers would live.
The king and queen wept when they heard the news of their youngest son's death. Sadly, they rode out to the valley to see where their son had given his life to the tigress and her cubs. When they saw his clothes and bones, they were overwhelmed by grief and cried as though their hearts would break. In memory of their son Mahasattva, the king and queen decreed that a pagoda be built on the very spot where he had made his sacrifice. In a few days the pagoda was completed and Mahasattva's clothes and bones were reverently stored inside.
Since that time, year after year and generation after generation, people from all around have made the pilgrimage to Mahasattva's pagoda to burn incense and pray to Buddha. »
At the end of the day, the human life is precious because it offers a lot of potential… but surviving "merely to survive" is the 'animal' life, not the 'human' life (cf. the psychological interpretation of the "planes of existence" if you interpret rebirth as moment-to-moment).
Survive as humans? Sure! But to do what? This is the key question!
Buddhism ties 'karma' with 'intention': "to do what?"