The Kingdom of Rarities

  • Eric Dinerstein
Island: 2013. 312 pp. $29.95 9781610911955 | ISBN: 978-1-6109-1195-5

No writer of fiction would dare to invent the great naturalist Alfred Russel Wallace's adventures. In 1848, he funded his trip to the Amazon by collecting butterflies. Returning years later, his ship burned and sank mid-Atlantic; he lost his specimens, survived, and then set out for Asia. From Sarawak, Wallace nailed evolution's key consequences: “Every species has come into existence coincident both in space and time with a pre-existing closely allied species.” He did it in so few words, he could have published it in Nature. But the scientific world largely ignored him.

When Wallace later worked out what caused these laws — that is, these patterns in both time and space — he wrote to Charles Darwin for support. What islands in tropical Asia did for Wallace, the Galapagos had already done for Darwin. Familiar history follows. Less familiar is that Wallace and Darwin had discovered ecological rarity, the subject of Eric Dinerstein's engaging new book.

Jaguars were scarce even before they came under threat from humans. Credit: MARK CARWARDINE/ARDEA.COM

As Dinerstein explains in The Kingdom of Rarities, “many, many species on Earth are rare, but few people ... are even aware of this”. He gives us a kind of zoological travelogue, observing rare species across the planet and contemplating, as he does so, why rarity is profoundly important for our understanding of nature and our efforts to conserve it. Dinerstein — who is lead scientist of conservation science at wildlife charity WWF — starts by explaining that there are two kinds of rarity. Some species are widespread but sparse. Others are found only in very special places.

Large predators, such as jaguars, are an example of the sparse, widespread species. Dinerstein tracks these animals in South America and it soon becomes obvious why they are rare. Large-bodied species need a lot of food — and that demands large areas to support enough prey. Large fierce predators figure prominently in our imagination (“Lions and tigers and bears, Oh my!” says Dorothy in The Wizard of Oz). Dinerstein explains why Dorothy's fears are increasingly unfounded. We hunt these creatures to extinction — all too easy, given that they are rare to start with. This sets further problems in train: their herbivorous prey often become superabundant and decimate vegetation on which yet other species depend.

Most of the book is, however, about rare species in special places, giving it a flavour of high adventure. We travel to a remote mountain top in the Indonesian province of Papua, accessible only by helicopter, through terrifying descents in thick mist. The species here are so rare that some are new to science. They live in isolation from “closely allied species” — and isolation from humans, too, as is clear from the abundance and tameness of large-bodied species in the area. There are species of marsupial tree-kangaroo, but no monkeys, leopards or tigers. As Wallace proposed, those species could walk to Bali and Borneo, but no farther, when sea levels were lower during glacial advances.

Dinerstein then takes us to mainland Southeast Asia, travelling with the first Western scientists to go there after the Vietnam War. Extensive bombing and the bush-meat trade make this an unlikely place for rare species to survive. Indeed, the rhinoceros (Rhinoceros sondaicus) is now extinct in Vietnam. In Hanoi, Dinerstein unexpectedly finds himself sitting next to General Vo Nguyen Giap, a “superb tactician” in the conflict with the United States. Now a conservationist, Giap says “the forest is our friend”, adding that “it hid us and provided shelter”. Dinerstein thinks that Vietnam has become “the last sanctuary for the region's forest-dwelling rarities”: the forest hid them too.

Credit: STEVE GETTLE/MINDEN PICTURES/FLPA

Unexpectedly, Dinerstein then takes us to the United States, to Michigan, to visit the Kirtland's warbler (pictured), another rare species with a small range. Its existence suggests that the special places that host rare species can be anywhere, but then begs the question of where rare species are found most often. There are salient laws about diversity, beyond those that Wallace described.

First, most species have small ranges. Only a few species have large geographical ranges, but they are by far the most familiar to us. I've watched common kingfishers (Alcedo atthis) on British streams and on lakes in Japanese cities. To see other species in the same genus, however, I had to travel to Madagascar and Bali, and would need to travel to different islands in the Philippines to see two more.

Second, species with small ranges tend to be concentrated in special places — such as coastal Brazil or the eastern Himalayas. Most are tropical. Moreover, these areas are generally not where the greatest numbers of species are found in one place. So Dinerstein doesn't dwell on the Amazon: it has many species in any given location, but most have large ranges.

I sense that the Amazon disappointed Wallace too. It provided species, but not the unique ones his patrons craved. Darwin had no better luck in Patagonia, where the Beagle spent most of its famous voyage. When Wallace finally tripped over species with small, idiosyncratic ranges in the islands of Southeast Asia, and Darwin stopped briefly in the Galapagos on the way home, species rarity changed science forever.

Neither Darwin nor Wallace visited Hawaii, where Dinerstein's most poignant chapter is set. Different Hawaiian islands once had different “closely allied species”. Dinerstein marvels at birds with strange names — the 'akiapola'au, for example — and even stranger beaks, and at lovely lobelias with flowers that fit other strange beaks. He sees a few of these in the wild; but most are extinct, just specimens in museums. Those that remain hang on in low numbers in the face of numerous threats such as habitat loss. When species such as these disappear forever, they take into oblivion all that we might learn about rarity and all that it tells us about the natural world.