The Book of Eels, Patrik Svensson [bill gates best books .TXT] 📗

observe it and explain what is happening: How is the eel dying? Only once that has been done can we begin to approach the question of why.

And when it comes to the question of the eel’s extinction, this approach has turned out to be a little bit complicated.

The name of the organization coordinating much of the work on environmental protection and biological diversity around the globe, and which has over a thousand member organizations, is the International Union for Conservation of Nature, or IUCN. Among other things, the IUCN compiles the so-called Red List, an inventory of animals and plants that is regularly updated to identify which species are considered threatened around the world. The explicit aim of the Red List is to create a “universally accepted system of classification of species at high risk of extinction globally.” In other words, the IUCN’s criteria serve as a kind of international standard, a scientifically tested assessment of how life in its different forms is doing.

On the Red List, each species is assessed according to established criteria and rated on a scale ranging from the most heartening (“least concern”) through “near threatened,” “vulnerable,” “endangered,” “critically endangered,” and “extinct in the wild,” to the final and irrevocable declaration of “extinct.” And since it is an objectively and methodically compiled inventory of all known life on earth, it provides information on how everything from algae to ringworms and humans are faring.

Humans are doing well. The most recent IUCN assessment of Homo sapiens, from 2008, says the following: “Listed as Least Concern as the species is very widely distributed, adaptable, currently increasing.” It is also noted that “humans have the widest distribution of any terrestrial mammal species, inhabiting every continent on earth (although there are no permanent settlements on Antarctica). A small group of humans has been introduced to space, where they inhabit the International Space Station.” At present, according to the IUCN assessment, “no conservation measures are required.” Homo sapiens is thriving.

The eel, Anguilla anguilla, on the other hand, is in trouble. Or, at least there’s good reason to think it is. It’s what we are led to believe. It goes without saying that since it’s the eel we’re dealing with, we can’t claim to know for certain. As is so often the case, our knowledge comes with caveats. Because it turns out the eel doesn’t quite fit the criteria normally used by the IUCN for its assessments. Firstly, our inability to determine the exact size of the total population is a problem. Population size is, naturally, the first criterion for determining the level of threat to a species. But according to IUCN’s reports, population size should be determined by the number of “reproductive individuals,” which is to say the number of fully grown, sexually mature specimens. That means, the IUCN writes, that ideally, the criterion would be applied to “mature eels at their spawning grounds.” In other words, a headcount of silver eels in the Sargasso Sea would be necessary. However, since no one has managed to find so much as one silver eel in the Sargasso Sea after more than a hundred years of trying, it is obviously impossible. The eel won’t let itself be mapped that way. It avoids even those who would help it.

What could potentially be done is a count of how many mature silver eels set off from the coasts of Europe toward the spawning grounds. But here, too, data is scarce; eels have a habit of disappearing into the dark depths of the ocean very quickly. The observations that have been made, however, suggest that the number of migrating silver eels has plummeted by at least 50 percent in the past forty-five years.

The third-best alternative, which is what the IUCN primarily bases its assessment on, is quite simply to start at the other end and assess what emerges as the result of the eels’ secretive rendezvous in the Sargasso Sea—what Rachel Carson called “the only testament that remained of the parent eels.” In other words, the number of glass eels that turn up in Europe in the spring. A lot more is known about this, and it’s these data that suggest the situation is absolutely catastrophic. All reliable counts indicate the number of newly arrived glass eels in Europe today is only about 5 percent of what it was at the end of the 1970s. For every hundred transparent little glass rods swimming upstream every year when I was a boy, at most a handful make that same journey today.

This is the basis for IUCN’s decision to categorize the European eel, Anguilla anguilla, as critically endangered. Which, according to the official definition, means it’s “facing an extremely high risk of extinction in the wild.” The situation is not only catastrophic but also acute. The eel could really disappear, in the foreseeable future, and not just from our sight and our realm of knowledge, but from our world.

SO THIS IS THE FINAL QUESTION: WHY IS THE EEL DYING? AND THE final answer is not surprising, given that this is the eel we’re talking about: It’s hard to say. It’s the same problem that everyone attempting to understand the eel has been confronted with: The answer eludes us. We don’t know for certain. We know parts, but not the whole. We are, to some extent, forced to rely on faith.

There are several explanations as to why eels are in trouble, and science can confirm them all, but no one knows for sure if they’re the only causes, or even the most pivotal ones. As long as there are unanswered questions about the life cycle of the eel, we can’t say for certain why the eel is dying. As long as we’re uncertain exactly how the eel procreates or how it navigates, we can’t say what’s preventing it from doing those things. In order to save it, we have to understand it. This is what most research on the state of the eel emphasizes nowadays: In order to help the