The value of biodiversity can be argued from various perspectives. Foremost, in practical terms, there’s its ecological service value, as we depend on it to provide us with breathable air, useable water and productive soil, for filtration of global gases and liquids, and as the resource for all of our agriculture and much of our construction — not to mention its critical role in global temperature regulation.

We utilize biodiversity in a myriad ways, not least for food, drinks and medicines, and to provide us with compounds and organisms for research.

Biodiversity can also be argued for as a genetic resource; as a link to genetic material we may one day come to need; as a species bank for future reference.

But all of these reasonings assume that biodiversity is a commodity, and one solely to be used at the discretion of us humans — as if we were somehow independent of it, and not just one (overly impactful one) species among perhaps 100 million species on Earth.

Shouldn’t it be self-evident that all of the other species contributing to global biodiversity have just as much right to life as do we? What makes us so special?

We may view biodiversity “commodities” through filters of greed, indifference or awe, but we shouldn’t underestimate the depth of the human emotional response to it.

Biodiversity in its natural state has so much to offer us from a therapeutic perspective, as valuable a human emotional support system as physical exercise, psychotherapy or medication.

From a personal perspective, I spend half of each year traveling and exploring the natural regions of our Earth, from the Arctic tundra of northeast Russia to the tropical forests of South America, from seabird colonies of the North Atlantic to the sub-Antarctic Islands of New Zealand. The other half of my year is spent contemplating all this and writing about it. A week in the forest is uplifting; a week at my desk is soul-corrupting. O f all the habitats I have explored, none is so threatened, none so endangered, yet none so exciting and overwhelming in its diversity as the Atlantic Forest of Brazil.

Seventy percent of the Brazilian population now live in the southeast, an area once covered with a forest that predates the Amazon. By various accounts, between 95 and 98 percent of that forest has already been lost to waves of settlers opening up land for subsistence farming, then for a globally linked coffee crop among other things. And, of course, there’s urbanization.

Where once this forest spread broadly across several southeastern Brazilian states from Sao Paulo to southern Bahia, today it is found only in tiny, isolated fragments and patches, most of which now comprise a UNESCO-designated World Biosphere Reserve.

From 1986, when I first visited the Atlantic Forest, until my most recent visit this month, every time I had entered a rich forest patch and climbed to a high point to look out, it was across a scene of deforestation, or across some limited form of agricultural monoculture or ranchland of limited productivity at the forest’s edge.

Earlier this month, though, I visited Intervales, a state park in Sao Paolo State, and for the first time I reached a mountaintop and looked out across a pristine scene, across a forested valley to another range of hills complete with native forest — and to further forested hills beyond. It was an astonishing moment.

So this is what this amazing region had looked like before human settlement!

The astonishing diversity of this forest, so ancient as to make ancient forests in other parts of the world seem young, is hard to contemplate. Each day I encountered unfamiliar species, yet for the uninitiated visitor seeing beyond the dense wall of vegetation to the diversity is difficult.

Such forest gives up its secrets slowly. Specialization has occurred to such a degree that one rarely encounters the same species twice, since each one occurs at such low densities.

Such a high-diversity and low-density system can only come about in a region of high energy, in a large area where evolutionary time has been stretched and extended over many millions of years, and where limited climatic variation occurs from season to season. The results are baffling in their complexity.

A single tree becomes a complex ecosystem supporting dozens of species of moss, hundreds of epiphytes and countless thousands of insects and higher-order species. And that tree is but one in a complex ecosystem built like a three-dimensional interlocking jigsaw puzzle with millions of pieces.

There, one high-pitched squeak I heard from the canopy sounded so birdlike, almost insectlike, yet a bouncing movement through the branches showed it to be one of the rarest of all monkeys, a tiny, squirrel-like Golden Lion Tamarin.

Similarly, a whir of wings, so easily mistaken for those of a massive beetle, turned out to be the blurring sound of a Brazilian Ruby, an endemic hummingbird, as it streaked past. Flashes of bright colors moving steadily through the trees come from fruit-eating birds called tanagers, many of which are also endemic here; while the insect-life is so overwhelmingly diverse that it’s easy to be blinded to anything but the myriad butterflies.

In such a rare habitat, a large proportion of its species are themselves rare. Many of them are endemic and are found only in this habitat in this small part of Brazil; many are critically endangered. Amazingly, though, even these forest fragments are so poorly known that new species are still being discovered there each year.

How many were lost in the missing 95 percent of those forests?

The Atlantic Forest is my reminder that on everyone’s doorstep there is extraordinary diversity increasingly dependent on us for its survival. Yet ultimately, we rely on it for our survival.

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