You can't separate concepts like "benefit" or "purpose" from your human perspective.

There are so many different preconceptions to try to cut through here, it's hard to know where to start. One thing I might as well get out of the way is this: I'd love to see the Galapagos preserved. I want polar bears to stop losing habitat, and to regain what they've lost. I'd like for the vast islands of plastic garbage to disappear from the oceans, for the excess carbon dioxide to be cleared from the atmosphere.

As far as we know, however, we humans are the only ones who give a damn about any of that. We're ironically both the perpetrators of great ecological damage and the only ones with a "big picture" perspective to care about the damage we're doing. The other species on this planet aren't worrying about how their grand-descendants will live, they aren't conscientiously performing vital functions and nobly refraining from damaging behavior. They're just doing what they do.

Do you know why it's hard to find examples, apart from humans, of organisms that destroy the environment they depend on, kill themselves off, and take plenty of other species down with them? It's not because that doesn't happen. It's not because there's some "natural law" that other organisms are scrupulously obeying that humans have uniquely decided to break.

It's because nature has "let" it happen, has let all of the bad side-effects befall all of the other species as a destructive species kills itself off, and then natural selection puts and end to that particular species, or the ecosystem adapts to the new species and it's no longer obviously destructive in the newly adjusted environment.

The first cyanobacteria are a perfect example of this. Before photosynthesis came along, the world was nearly devoid of "free" oxygen (that is molecular oxygen, pure O₂). Oxygen was a poison to most life on earth. That didn't trouble the non-conscience of the cyanobacteria, however. Blithely emitting oxygen without hesitation or remorse, they went on to radically alter the chemistry of the atmosphere and the oceans, to plunge the world into an ice age, and to kill off most other life on the planet (and plenty of their own kind too) until a new equilibrium was reached over millions of years where life eventually not only adapted to, but came to depend upon, abundant oxygen. (http://en.wikipedia.org/wiki/Great_Oxygenation_Event)

If you think of "nature" not just as living organisms, but inclusive of the Earth itself, this planet has indiscriminately killed organisms and species in vast numbers many times, as the result of major seismic, volcanic, and tectonic disruptions. Only by unprovable faith can you imagine that the physical planet is somehow guided by concern for some ultimate "benefit" to all life when it goes about causing so much death.

Expand the idea of "nature" to the universe as a whole, or at least our cosmic neighborhood, and then you have asteroids and comets causing death and extinction without a plan, without consideration of purpose or benefit. Only luck has saved us from total extinction of all life. There's no reason at all to imagine that nature somehow chooses the timing and the size of major impacts with a mind toward creating specific planned results, or that nature is even slightly constrained by any rough guiding principle to create some sort of "balance". If large enough an asteroid comes along, the impact will boil the oceans and turn the surface of the Earth into lava. If the melting is deep enough, every last living creature down to the hardiest subterranean bacteria will die.

If you do want to believe that there's some plan, some intelligence, some guiding principle, then humans would be part of that plan. How could you dismiss the purpose or benefit of humans if we're part of such a plan? Either the Planner or the Intelligence isn't that smart, or some mind much better than ours has its reasons for putting us here.

If you don't believe in such things (as I personally don't), then humans aren't apart from nature, we are nature. We're just one of those random things that nature churns out. "Artificial" is not the opposite of natural, it's a subset of natural. Only in the context of our own human thinking can we regret our impact on other life, possibly change course and prevent things from getting worse. Outside of that kind of human self-reflection, the destruction we cause is merely a different form of natural disaster (albeit a particularly elaborate form), among others that nature produces from time to time without any moral "right" or "wrong" about it, without purpose, without consideration of benefit to other living organisms.

Not one thing I'm saying here, or that I've seen anyone else say in this thread, is remotely equivalent to saying "Fuck the Galapagos!", no matter how strong your urge to repeat such an outcry out of exasperation or petulance, simply because others aren't willing to go along with your notions of "purpose" or "benefit".

Purpose is contextual. Without a defined context, defined goals, desired outcomes, "purpose" makes no sense. In the absence of humans, who or what would the context be? What would the goals be? "Benefit" doesn't mean anything without a context is which "the good" has been defined.

Is life itself a goal? If so, is more life better than less life? Should "more" be measured in bulk quantity, in metric tons of biomass? Is diversity what's supposed to be important about life, and if so, is having a billion species intrinsically better than a million? Is complexity of life a value, making alligators more valuable than lichen? Are intelligence and self-awareness important, making whales more valuable to preserve than yet another species of beetle? If you value whales for their intelligence, why not humans then?

You're utterly and completely applying your own human standards if you propose a system of value for life that tempers valuing intelligence and self-awareness with a moral judgment about perceived destructiveness. It's contradictory to wish away humans in order to preserve a world whose value is defined by humans. You might protest that there are "intrinsic" values that exist without us humans, but if you dig deeper than your surface emotional responses you'll find those supposed intrinsic values are elusive, and you'll see that nature shows no signs of itself promoting or maintaining those values.

And by the way, unless you're actively planning, like some action movie supervillian, to plot the destruction of the entire human race, isn't bitching about humans having no purpose, moaning about how the Earth would be better off without us, just a lot of sound and fury signifying nothing?

If you want to define a possible purpose for humans, consider this: Life on this planet is doomed without us anyway. It's just a matter of time. If a giant collision doesn't kill us all first, or a massive gamma burst, then the sun is slowly heating up and in a few hundred million years will boil and burn away all life on this planet. In a few billion years the sun will expand into a red giant, likely expanding far enough to swallow up the entire planet.

For all of our human potential for destruction, we're currently also the best bet for preserving life on this planet and spreading it out among the stars, allowing life to go on without dependence on a single, fragile world.