The book itself, however, seems in some ways an odd hybrid. It is a fine popular biography, offered at a remarkably cheap price for something so large, but it also aspires to being a work of intellectual history, and here it sometimes falls short. The publisher's hype tries to present Humboldt as a tragically neglected figure – a 'lost hero of science', as the book's subtitle puts it – but there have been at least three other books on Humboldt over the past ten years, including Laura Dassow Walls's magisterial The Passage to Cosmos: Alexander von Humboldt and the Shaping of America (2009), which won a major scholarly prize in the United States. Wulf's work is more accessible and is clearly designed for a broader audience, but this means she is considerably more perceptive on some aspects of Humboldt's career than others. She is, for example, very good on his celebrity status, his interactions with politicians and other public figures, observing shrewdly of his brother, who served for a while as Prussian Minister to Britain, how 'Wilhelm's diplomatic status in London helped to open some important doors'. As someone who herself grew up in Germany, Wulf is also particularly attuned to Humboldt's time at the Prussian court, and she has assiduously explored the Berlin archives of his German correspondence in a way that has too often been neglected by Anglo-American scholars. But Wulf is relatively weak on the intellectual context of Humboldt's scientific writings, finding herself on more secure ground when describing the marketplace for Humboldt's key work, Cosmos, than when addressing the substance of his scientific contributions. Wulf tells us that 'the first two volumes of Cosmos proved so popular that within four years three competing English editions had been published', whereas the next volume was 'a dense scientific book' whose 'sales were nothing like those of the first two volumes which had appealed to a more general readership'.

Portrait of Alexander von Humboldt, 1806, by Friedrich Georg Weitsch (Alte Nationalgalerie via Wikimedia Commons)

The danger here is of Wulf reinventing Humboldt in her own image, as a public figure intent upon popularising scientific ideas for a 'general readership', when actually his contribution was more subtle than this. Wulf's central thesis is of Humboldt as a forerunner of 'our understanding of ecosystems today', someone who was 'a visionary, a thinker far ahead of his time' through the way he 'saw earth as one great living organism'. It is true that Humboldt's emphasis on situating vegetation in relation to location and his recognition of 'climate as a system of complex correlations between the atmosphere, oceans and landmasses' anticipate much current scientific thinking, and in that sense Humboldt should rightfully be considered a pioneer. But it is also the case that his particular form of global 'interconnectedness' arose from a tradition of Enlightenment universalism that was coming, for good reasons, to seem outdated by the second half of the nineteenth century. Wulf at times implies that there was a conspiracy to suppress Humboldt's thought, describing Cosmos as 'a work that brought together all that professional science was trying to keep apart'; but this is radically to underestimate the change of emphasis that also made Kant and Goethe (a friend and patron of Humboldt) fall into disfavour in late Victorian times, when the more materialist temper of specialised sciences was making older spectres of German Romanticism appear jejune. Equally implausible is Wulf's suggestion that Humboldt's reputation fell in line with 'anti-German sentiment that came with the First World War'. Such sentiment did no lasting damage to Wagner or Nietzsche, two of the key influences on modernism, and it is more likely that Humboldt was by then generally considered a worthy but superannuated figure, someone belonging, like Newton or Bacon, to the history of science.

Wulf's revisionist enthusiasm is welcome enough, but the problem is that her determination 'to reclaim Alexander von Humboldt as our hero' leads to a skewed portrait of this remarkable figure. Her insistence on how 'Humboldt wrote that nature had to be experienced through feeling' presents him as a precursor of contemporary purveyors of sentimental affect: 'Every-thing, from the most unassuming moss or insect to elephants or towering oak trees, had its role, and together they made the whole.' This is to turn Humboldt into a caricature of himself, making him sound less like a rational scientist than a fifth member of the New Seekers, teaching the world to sing in perfect harmony. Wulf is also notably better on Humboldt's public persona than on his private person: he declined to attend his own mother's funeral in 1796, and the German poet Theodore Fontane complained in 1884 of how an early Humboldt biography did not mention the scientist's 'sexual irregularities'; but while such psychological heterodoxy is briefly acknowledged here, it is largely engulfed by Wulf's wave of hagiography. This is all the more unfortunate since several American Transcendentalists with explicit debts to Humboldt – Whitman, Thoreau, Poe – endeavoured provocatively to explore fractious relationships between subjective consciousness and the planetary cosmos. By largely glossing over such quizzical contradictions, Wulf presents Humboldt in a more conventional light, as an epitome of the global media ecology, in a way that makes him appear ultimately less interesting.

This is a finely researched and executed biography, one that includes a wealth of illuminating details about an important figure in the world of nineteenth-century science. But through its unashamed fetishisation of a personal hero – 'In Quito, I held Humboldt's original Spanish passport in my hands' – it forfeits the sense of historical perspective that would have enabled us more fully to appreciate the constraints within which Humboldt was working. To represent Humboldt as a visionary trammelled by the short-sightedness of those around him is a gesture of retrospective romanticism, whereas in fact the enduring nature of his contribution arose in large part because of his own diplomatic skills, a capacity to juggle the approbation of his political paymasters with a deep-rooted sense of intellectual integrity. Humboldt may have been 'far ahead of his time', but he was also very much of it, and it is the adroitness of this balancing act that Wulf's book, welcome as it is, does not wholly capture.