Usha Alexander in Pangyrus:
Human beings are the type of animal that depend upon the diversity and plenitude of other life to sustain us. It’s no coincidence that our presence arrived concomitant with the richest biota the earth has ever developed. This wealth of life created the complex and flexible niche that we’ve come to fill, not only passively, as our food source, but even actively, as symbionts living on our skin and in our guts, literally as part of us. Beyond this too, our fellow living things each play their part in providing what we call “ecosystem services,” like preparing the soil, adding in nutrients, oxygenating the air and water, pollinating plants, breaking down waste, and sustaining one another in an environmental balance that supports our survival. Without them, we would have no food to eat nor air to breath.
Microbiota, fungi, plants, and other animals, including those of which we remain unaware, constitute an interdependent web of life, complex beyond our ken. This rich diversity of species is essential for maintaining this world as we know it. And to sustain resilient, adaptable populations of each kind of living thing, each must remain in great enough number and genetic variety to represent a diversity within species, as well.