The Irish Times published an interesting interview last week with Deutsche Bank economist Pavan Sukhdev, who led the U.N.-backed study The Economics of Ecosystems and Biodiversity (TEEB). TEEB, as I’ve mentioned before, is an incredibly ambitious and important effort to place something like empirical dollar values on biodiversity, to create a space in classical economics and conventional GDP accounting for the real worth of the natural world.

Our failure to account for all this stuff has led, among other things, to a worldwide failure to place a cost on greenhouse gas emissions, which in turn has led to what former World Bank chief economist Nicholas Stern has called “the greatest market failure the world has seen,” by which he meant climate change.

In the Irish Times, Sukhdev explained why bringing “natural capital” into the equation is so important:

Natural capital is simply the economic reflection of biodiversity and ecosystems, which are the living fabric of this planet. They provide a huge range of benefits to humans, whether it is fertile-soil formation or fresh-water provision; whether it is food, fuel and fibre; whether it is a clement climate that enables us to survive; whether it is the ability to go into forests and parks and enjoy ourselves; or whether it is the medicines that are so often derived from plants and animals. When we destroy biodiversity, we simply do not know the value of what we are tearing up.

As unequivocal as this statement is, it can sound abstract, ephemeral, a topic far away from dollars-and-cents economic reality. Tighten your focus on a single piece of natural capital, though – one of the earth’s fixed assets, if you will – and the bedrock economic truth of it is vividly clear.

My current case in point: manta rays. Specifically, the 187 manta rays who reside permanently in the waters off the Kona Coast of the Big Island of Hawaii.

So here’s the question: What are those 187 manta rays worth? Well, if you’ve ever had a chance to meet a few of them in person, I bet you’d likely come away with one of the many terms we’ve coined to try and get at something like infinity. Priceless, invaluable, transcendent, beyond measure.

This, in any case, was my initial, visceral reaction last week, as I sat on the seafloor of a small cove on the Kona Coast after dark in 35 feet of water, watching a half dozen mantas swoop and circle and weave through a great plume of plankton above my head. The plankton had been drawn there by the high-powered underwater flashlights of forty-odd scuba divers, myself included. We were participating in a nightly Kona ritual known as the “Manta Ray Night Dive,” and it was one of the single most exhilirating experiences of my life.

The ritual was born somewhat by accident. A waterfront resort in Kona had trained its searchlights on the bay, which had inadvertently attracted plankton, and the mantas followed. Guests started to gather each evening to watch them dance through the lights, and eventually a few local dive shops realized they could do the same thing from below.

More than a decade later, the divemasters have come to know the mantas intimately. They know where to find them, how to entice them into the circle of night lights, how to identify each individual manta by the dark splotches on its white underbelly. Every evening, several dive boats gather at one of the preferred feeding spots, and the divers take their electric candles and gather in what the divemasters call “the campfire,” and the mantas come to feed.

Some of the mantas seem to relish the social aspect of the campfire, others – younger ones, especially – tend to lurk at the edge of the circle of light and dart in and out more furtively. They come within inches of the divers’ heads but almost always avoid contact. When you look up as they pass overhead, they watch you back with their great dark eyes. I don’t think I’ve ever had an encounter with an animal so large that felt so intimate, so communal.

And what was it worth? Well, if you’d told me, at the end of the dive, that I had to pay double what I’d paid back at the dive shop, I’d have done so willingly and called it a bargain. What price, after all, could you place on transcendence? On a completely singular experience? On a point of view permanently altered, forever expanded? On a memory that will surely last a lifetime?

We tend, in such moments, to think economics too small, too crass, to provide an adequate measure of worth. MasterCard has famously built its brand on handling only the quotidian details. Scuba rental: $20. Dive fee: $99. Looking a female manta by the name of Koie straight in the eye and nodding hello: Priceless.

But there are ways, nevertheless, to assign value. And more importantly, there are horrific costs to assigning no value at all. Think of it this way: the mantas come for the plankton. The plankton are there because the little cove is ringed by a healthy coral reef. The coral reef owes its staggering abundance of biodiversity to the delicate interplay between corals and the algae that live on them. The corals expel their calcium exoskeletons, the algae fix those skeletons as calcium carbonate, the limestone thus formed builds the reef. Without this byproduct of biodiversity – what Sukhdev and his TEEB colleagues call an “ecosystem service” – there are no Manta Ray Night Dives, no scuba and snorkeling tours of the Kona Coast, no dolphin lagoon at the big Hilton Resort where your daughter can plant a gleeful kiss on a bottlenose’s snout. No fresh mahi-mahi and ahi tuna at the historic Kona Inn. No trophy sportfishing. No Hawaiian tourism industry as we know it.

And because the oceans absorb a quarter of the carbon dioxide created by human activity, the water off the Kona coast and everywhere else is slowly becoming more acidic. Its pH has dropped from 8.2 circa 1800 to less than 8.1 today. At 8.05 or so, the algae and the coral can no longer make reefs. The whole order collapses.

This phenomenon is called "ocean acidification." The darker phrase is “mass extinction event.” It has befallen the world’s coral reefs five times in the earth’s history. The world’s leading coral reef researchers announced, in 2008’s Honolulu Declaration, that humanity was on a carbon-dioxide-spewing trajectory to trigger the sixth mass extinction event within twenty years. Which would mean that by midcentury or so, the divers’ lights would no longer attract plankton plumes, and the mantas, if they survived the cataclysm, would feed elsewhere.

So then: What is a manta worth? A reef? Something like 40 percent of Hawaii’s GDP, for starters. (That’s the rough estimate of the size of its tourism industry.) Then add in most of the transcendent moments that make life worth living – the mantas dancing in the searchlight beams, the explosive delight on a young girl’s face as she spies a five-day-old dolphin in the lagoon, the singular reinvigoration provided by a meal eaten overlooking the waters that birthed it. I would be comfortable adding another zero or three to the dollar figure for every one of these I can recall.

The true value of biodiversity is, if we are being honest, beyond human calculation. It is infinite. It has no replacement cost because we can’t replace it, no manufacturing cost because we can’t make it, no price tag because we can’t own it. And so we owe it to the mantas and ourselves to place a dollar value on biodiversity large enough that we will cherish it – not just on holiday, 35 feet underwater, but in everything we do.

To trade stories of trascendent nature 140 characters at a time, follow me on Twitter: @theturner.

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Can we calculate the true cost of a manta ray?
By externalizing the costs of human industry, we've pushed the world's coral reefs to the brink of extinction. It's past time to put a price tag on the infinite