You're right, in the sense that of course the tardigrades, archaea around deep ocean vents, and blue-green algae will continue trucking along more or less whatever happens. We, however, are not tardigrades.
It also supports the balance of all the ecosystems: forests, seas, rivers... Which we also depend on to survive.
It's what makes us live on a beautiful, comfortable planet instead of survive in a terraformed rock we have to fight against while rushing to the next scientific way to palliate yet a new deficiency.
In our planet system, everything is connected.
Let's take a very naive but simple to understand example, the tomatoe.
Planting so much, and always the same kind of tomatoes makes the land nutritionally poor and the plant susceptible to parasites. We compensate this unnatural state by addition artificial nutrition and pesticides to the plant.
The result ?
Most tomatoes are tasteless garbage that looks more like a plastic ball than a fruit. Their nutritional content has been divided by 10 during the last 80 years, so that you need to eat much more to remotely get the same minerals and vitamins. When you eat them, you also absorb a small amount of all the products we put on them, with consequences we still don't know about.
That's just for a simple tomato. Bring together all the food, the water, the air, the temperature, etc. together, and that's how much we are disturbing.
It's not just emotional. We are seated on branch we are sawing.
Due to nutrient pollution of the ocean, large dead zones are spreading, these are zones without enough oxygen to support life caused by nitrogen and phosphorous pollution. 70% of the earths oxygen is produced by marine plants. Forests produce most of the rest and we are cutting them down at an accelerating rate.
So from an objective point of view, not enough oxygen is a pragmatic cause for concern. Looking at it from the perspective of nature, species evolve to survive, it is their prime directive. We are actually doing a pretty good job of working against this directive to our species own detriment.
This mass extinction caused by humans is an order of magnitude faster and affects far more varity of species and plants.
Furthermore, even if the pace and breadth of current extinction were that dramatic, isn't the argument against that a purely emotional one? I sincerely doubt that most humans can even name a hundred species; would they really miss a few million if a few million others remained?
Just to be clear again: I'm not arguing against conservationism, I'm interested in the arguments being made for it. I believe we are conserving for own selfish purposes, and I'm perfectly OK with that. I just think it's wrong to call that "natural".
[1] https://en.wikipedia.org/wiki/Permian%E2%80%93Triassic_extin...
Nothing. But you can say that about asteroids that kill the planet as well.
That's basically nihilism. Many people want to live and enjoy nature, that's why. We just got conflicting interests of short-term thinking that resembles nihilism (Nothing matters - let's live life to the fullest) and long-term thinking / delayed gratification (I want my kids / all the animals / the next generation to have a nice life as well).
edit: for the semantics of "natural" - humans can be seen as a part of nature. It's just intellectual gymnastics if one defines us as natural or not. Some say humans aren't natural and have good reasons for it, some say they are and have good reasons for that. This discussion really isn't that meaningful. Many peole say we have responsibility because we have consciousness, but even that could be argued. It all depends on what you believe.
If you extrapolate the speed of current devastation, extinction and let it play out over the time-span of the last mass-extinction, there really wont be anything living on earth besides micro-organisms.
Non-selfish arguments for why we should not kill off other species? Why should we not kill all life bigger than a pea on earth? Ill let you take that one.
There are medicinal and practical uses for plants, and some are have only recently been discovered. Losing them is losing this these potential discoveries and uses.
Humans inherently enjoy nature. We like to see trees, greenery , wildlife. The loss of these things hurts our enjoyment of the world.
Examples that come to mind immediately include the huge number of medicines that have been derived by isolating compounds derived from plants, an area which we are probably far from done exploring. Another more specific case I can think of, is how one of the most important compounds in molecular biology today (Taq polymerase) came from bacteria found in the Lower Geyser Basin at Yellowstone. (https://en.wikipedia.org/wiki/Thermus_aquaticus)
What is going to have problems is the health of the ever growing Human population. Us Humans may well be heading towards a crisis, the planet won't even notice.
BTW, I think we should be working hard to support a sustainable future for Humanity and the rest of the environment.
It might be how the nature works, but it is definitely not how Nature works. Capitalisation matters.
Sure, we can keep looking at the half-full glass focusing what is not extinct yet, but over few generations, we might be pretty lonely on this planet when it comes to complex life. It's more an indication of how badly we're screwing our own environment, also for ourselves. It's clear that life itself will survive much harsher situations compared to mankind and repopulate once we're long extinct.
Humans may be responsible for the decimation or outright extinction of entire species, but isn't that how Nature works? Nature has encountered countless extinctions before us (where's the Megalodon now?) and at least 5 mass extinctions, so why should this dynamic cease now?
(I get the emotional argument for conservationism, and I even share it, even though I might not sound that way. But I've always considered that something purely subjective, not objective, and arguably just as manipulative of Nature.)