Asher Kelman said:
With no diversity, we will get down to bacteria and fungi once more!
I am all for diversity, and I love that humans are capable of using their brains for protecting species and environments. We just have to recall that we may be wrong. Other than you I don't think Earth will go back to bacteria and fungi only. Actually - and that has always been my reason for environmental protection - the only species threatened is Homo sapiens.
Estimates show that roughly 99% of all species ever have vanished. Some of them of natural causes others, well, of equally natural causes. A meteor hitting Earth, vast volcano activity, melting of ice caps, building of ice caps - all natural. What about man? It may be as inconvenient a truth as the one the documentary featuring Al Gore propounds but it is, nevertheless, a truth: Homo sapiens is part of nature. As are other members of the genus Homo, Australopithecus, Ramapithecus and several other still to be classified anew.
When neanderthals and early sapiens helped diminishing loads of species, i.e. the wooly mammoth, it was a natural act. When current sapiens killed off the dodo for good, wasn't that equally a natural act?
Setting us apart is that after WW2 we learned a lot and gained insight into ecosystems. Our philosophy changed, we now rely on ourselves and our own minds instead of others to decide what's right and wrong. We also learned that every species, every habitat lost impoverishes ourselves. This realisation is important; at the same time it is - as is so often with truth - deeply unsettling and painful.
A quarter of a century ago I was against nuclear power plants. Now I see them as an important part in our energy politics. The operative here is 'part'; I think they are necessary ATM to overcome the idiotic burning of non-renewable fossils like oil and coal. I am not so much concerned about carbon dioxide set free, I just ask myself, why the heck we are just burning up a precious resource like oil? There's so many things we can do with it, already do with it. Virtually every plastic we use is made from oil - and we just burn it up in gallons and megatons in minutes?
When I grew up children could and would go into forests, parks, to rivers etc. and see for themselves what the world around them is like. Although I have never lived in the countryside, only in big cities, I knew what my steak looked like before it landed on my plate*. I learned that from my parents and in school, in a subject called "Sachkunde" (general knowledge; a hodgepodge of biology, physics, chemistry and geography in primary school).
One of the reasons poeple don't care much anymore is the black and white stance that developed over the past 30 years. Environmentalists shocked us with The-end-is-nigh scenarios, they showed us the killing machines in slaughterhouses, they successively took everything from us as "bad for the environment". their counterparts were equally moronic, trying to persuade us that carbon dioxide is life, that God wanted us to kill off everything (and everyone) in order to make us Master of the World.
Sorry, folks, that's not how life works. For every species lost (in a local environment) we gain another (wandering in). As we now know, the dinosaurs did not vanish, some of them evolved into birds. This will happen over and over again since life and evolution is much more wondrous than many of us want to imagine.
You may now ask, what is my position towards the original question. Photographers have to show the beauty of the world and the ugliness in all their glory [ambiguity intended]. We should follow the simple and intuitive rules you, Asher, wrote up above. We should also alwayd be aware that we have an impact on other people and on the ecosystem we are taking photos off. Our observing and documenting changes the observed. This holds true in a completely different sense that Heisenberg originally intended on the macrosphere.
*Just read over the week-end that the German fast food chain Wienerwald (our homely version of KFC) retired their old logo since it showed a domestic fowl. The reason behind it: "People, particularly children, want to eat meat but not know where it comes from."