Maybe the term I am looking for is moral convenience. That good feeling of saving the earth or its biodiversity won't be worth it because everything has an end, including our lives. Even if we destroy humanity to restore nature (which I wouldn't be surprised if that was the last resort) to feel good about it, it won't be worth it for what has been built will be destroyed sooner or later be it with a bang or a whimper.
I think you really need to read much more around this subject, develop / mature your ideas and practice critical thinking much more as you make very large leaps to very vapid nihilistic conclusions without having entertained other possibilities / realities.
Does the fact of human mortality and the finitude of human lives bear any relevance at all to the argument of whether we should work to conserve biodiversity in the anthropocene ?
That kind of shallow argument predisposes that ultimately what constitutes something being "good" and "worthwhile" pursuing is predicated upon the hedonistic self-gratification of the individual in the here and now.
Though that kind of nihilistic individualism and postmodernism may be the dominant force that permeates our current economic and cultural paradigm it is one which is both very new in civilizational terms and deeply flawed as to be collectively suicidal.
Previous generations worked towards building things (whether symbols, systems, monuments, scientific or philosophical theories, technology etc ) which they did not rationally expect to see the benefits of within their own lifetime and that has been the way things have been throughout human history until the peculiar idea arose in the 20th century thanks to the self absorbed / entitled baby boomer generation of the importance of instant gratification.
On this subject there was a brilliant anthropologist / philosopher who was called Ernest Becker who wrote a book called "The Denial of Death" (I highly recommend it) which posited that one of the strongest basic motivations within human behavior is our biological need to control our basic anxiety, to deny the terror of death and suggested that a significant function of culture is to provide successful ways to engage in death denial.
"Yet, at the same time, as the Eastern sages also knew, man is a worm and food for worms. This is the paradox: he is out of nature and hopelessly in it; he is dual, up in the stars and yet housed in a heart-pumping, breath-gasping body that once belonged to a fish and still carries the gill-marks to prove it. His body is a material fleshy casing that is alien to him in many ways—the strangest and most repugnant way being that it aches and bleeds and will decay and die."
So Becker argues very convincingly IMO that culture whether of the secular or religious kind is a symbolic system through which individuals, tribes and nations subsconciously are driven seek to obtain a symbolic immortality and denial of their own mortality through what he calls "cultural heroics" which are projects that are greater than the individual and their life (Nietzsche says something quite similar about this too in "The Birth of Tragedy" and the need to affirm the tragic aspect of existence like mortality in culturally constructive ways).
"It doesn’t matter whether the cultural hero-system is frankly magical, religious, and primitive or secular, scientific, and civilized. It is still a mythical herosystem in which people serve in order to earn a feeling of primary value, of cosmic specialness, of ultimate usefulness to creation, of unshakable meaning. They earn this feeling by carving out a place in nature, by building an edifice that reflects human value: a temple, a cathedral, a totem pole, a sky-scraper, a family that spans three generations."
"The hope and belief is that the things that man creates in society are of lasting worth and meaning, that they outlive or outshine death and decay, that man and his products count. When Norman O. Brown said that Western society since Newton, no matter how scientific or secular it claims to be, is still as “religious” as any other, this is what he meant: “civilized” society is a hopeful belief and protest that science, money and goods make man count for more than any other animal. In this sense everything that man does is religious and heroic."
If we are to believe that this drive towards "cultural heroics" in order to symbolically deny mortality as Becker terms it is at work subsconciously within individual human behaviour and human civilization (and that it can't be escaped) might it not be said that the conservation of biodiversity (whether of species or ecosystems) is the best and most constructive means of the expression of this drive and that the drive itself could be pushed away from the self-gratification and consumerism of modernity in that direction?
Becker himself had the belief that the industrial revolution and the environmental crisis was the result of the continuation of the "cultural heroic" system of the 19th century :
“Today we are living the grotesque spectacle of the poisoning of the earth by the nineteenth-century hero system of unrestrained material production. This is perhaps the greatest and most pervasive evil to have emerged in all of history, and it may even eventually defeat all of mankind.”
Finally, here is a quote (not by Becker) that I like on this topic:
"A man who plants a tree where none grew before is a benefactor of his species. We may yet live to see the ground covered with stately oaks and spreading elms, under which may sit the children and grandchildren of the present generation"
