Because were are not kings with dominion over the earth with all animals as our subjects for protection. That's an odd and antiquated way of looking at it. — schopenhauer1
In a perverse way we do have kingly dominion over the earth. Heard about global warming? Heard about chemical contamination? Heard about soil exhaustion? Heard about 8 billion humans? Heard about Silent Spring?
Because we had the capacity to change global climate and everything that depends on a stable climate AND because we used that capacity, we have become responsible.
Because there is a distinction with the "natural world" and the human world. The natural world is that which does its thing without human (beings who are self-aware and can reason) — schopenhauer1
I wish we could reason better, and act on the results.
I used to think that the human and natural worlds were discreet, separate; it does its thing, we do our thing, and the two do not communicate. Take the trillions of bacteria in your gut: They are not you and they are part o the "natural world". It turns out that the relationship between these many species and us is far more interrelated and intimate than we would like to think.
As a species, we are part of the natural world, sharing DNA with everything from bacteria on up. Why are fungal infections difficult to treat? Because fungi and animals have a bit too much biology in common. Drugs that kill fungi negatively affect animals too.
Without the rest of nature, we'd be dead--starved, suffocated, sickened by all sorts of attackers.
Bears in the northwest help forests grow. How? The catch a lot of salmon, take it into the woods, and eat it/digest it. The bears bring specific nutrients to the forest floor through their kind of messy eating habits. Wolves help forests grow too. They eat animals that chew on trees, like deer and moose (elk). Too few wolves, too many munchers. The forest starts shrinking. Adding wolves results in fewer trees killed; hence, a thicker forest. [This has been extensively demonstrated on Lake Superior's Isle Royale, a 200+ square mile island 18 miles off the shoreline of Minnesota.]
We introduced 'exotic' earthworms into various states around a century ago. They have been working their way northward. These are the big nightcrawlers that people use for fishing bait.). They are now chewing up the leaf-litter under northern hardwood forests. They digest the leaves, of course, and leave worm castings behind. That's fine. But without the leaf litter, the thin soil in northern forests erodes too fast, impoverishing the soils.
Everything we do, and everything that happens in the natural world, including the affairs of gazelles, eventually affects everything else.