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and went on to change the world. The
Narrative
also lured Alfred Russel Wallace to the Amazon, to which he set sail in 1848 with Henry Walter Bates, an inspired amateur collector of beetles. Wallace stayed for four years before malaria and gut trouble forced him to return to England—although he set off to the Malay archipelago a couple of years later, in 1854, and stayed for eight years. Bates remained in the Amazon for eleven years and among other things described a form of mimicry in which innocuous and tasty butterflies are protected by their wondrous resemblance to other butterflies that are noxious and toxic. He also collected an estimated 14,712
species
from Amazonia, including 14,000 insects; 8,000 of his creatures were new to science.
    The British explorer Richard Spruce (with whom Wallace corresponded from Malaysia) stayed in South America even longer than Bates—for fifteen years—and gathered more than 30,000 specimens from 7,000 species. Spruce, Wallace, Bates, von Humboldt, Bonpland, and many more were iron men, obsessively collecting, bottling, pickling, pinning, pressing, and drying for year after year, always recruiting the help of the local people, who were and are naturalists par excellence because their lives depend on knowing the creatures around them. Yet I believe that Spruce spoke for all of them, one day on the Amazon, aboard the steamer
Monarca,
when he wrote, “There goes a new
Dipteryx,
there goes a new
Qualea—
there goes a new ‘Lord knows what.’” All that effort over many years provided but a glimpse of what was out there.
    Now, of course, the solo naturalists, the upper-middle-class (though far from rich) von Humboldt, the upper-middle-class (and significantly rich) Darwin, and the self-made artisan collector-naturalists like Wallace, Bates, and Spruce have been replaced by teams of scientists from the world’s great universities and government institutions, relentlessly quartering the Amazon and everywhere else and systematically recording all there is. Now, we might suppose, all is more or less sewn up. In truth, a century and a half after Spruce, his lamentation seems almost as cogent as ever. We have very little idea indeed what’s out there. Estimates even of the total number of species in the world as a whole differ by an order of magnitude, from a possible four or five million to thirty million or more (though neither figure includes bacteria). Most biologists opt for a compromise of around five to eight million. After several hundred years of conscientious natural history and a century of formal science, the task even of listing all there is seems hardly to have begun. Nature is very big, and very various indeed.
    Thus it is impossible to count all the different species of trees—or to be sure that they have all been counted. But biologists can at least guess. 1 Extrapolating from what is known, they estimate that there are around 350,000 species of land plants in general. At least 300,000 of them are flowering plants. Around one-fifth of these are trees. There are also some nonflowering trees, among which the conifers are by far the most important; but there are only about 600 different species of conifers, so they don’t much affect the overall statistics. Thus there are probably around 60,000 species of trees in the world, plus quite a few thousand hybrids. Although any of the species or hybrids might be further subdivided into an indefinite number of wild races or cultivars, 60,000 seems a good working number.
    Most of those species are in the tropics. Britain may seem to have hundreds of different species of trees, but most of them have been imported by human beings. Only thirty-nine are believed to be true natives (and one of them, the common juniper, may in fact have been brought in by ancient people). The vast boreal forests of northern Canada are dominated by only nine tree species—the quaking aspen and a handful of conifers. The total of trees that are native to