In 1995, when Jonathan Slaght was nineteen years old, he travelled with his father, a U.S. diplomat based in Moscow, to the Russian Far East. As their plane approached the port city of Vladivostok, Slaght looked out the window and saw what appeared to be an endless sea of trees. “It seemed like there was no human hand anywhere, just rolling hills of green,” he told me recently. “I was mesmerized.” It was Slaght’s first glimpse of Primorsky Kray, a thinly populated province that lies on Russia’s border with China and North Korea, just across the sea from Japan. Because the region escaped glaciation during the last Ice Age, it was and is a place of wonders, preserving a unique assemblage of high-latitude and subtropical species. It is the only place on Earth where brown bears, leopards, and tigers coexist.

Like many visitors, Slaght would come to learn about the region, known informally as Primorye, through the writing of the explorer, soldier, and naturalist Vladimir Arsenyev, who made more than a dozen expeditions there between 1902 and 1930. As an officer in the Imperial Russian Army, Arsenyev was charged with inventorying the natural resources and strategic advantages of the territory, which China ceded to Russia in the mid-nineteenth century. But he is best remembered for his popular accounts of his adventures, which transported his compatriots to forests and steppes where Chinese and Korean were spoken as often as Russian. “He was the region’s first eloquent champion, the first person to describe why the place was unique,” Slaght said. “Anytime you talk to people in Primorye about nature or wildlife, they start talking about Arsenyev. He’s that ingrained in the region’s cultural identity.”

Slaght returned to Vladivostok for a semester during college, and after graduation he lived in Primorye for three years as a Peace Corps volunteer. Now, as the Wildlife Conservation Society’s coördinator for Russia and Northeast Asia, Slaght spends several months each year in the Russian Far East, working to protect tigers, owls, and other species from illegal logging and the haphazard expansion of the region’s many industrial roads. Though his career was shaped by Arsenyev’s work, he was able to read only a fraction of the explorer’s writings in English, since most existing translations are based on versions heavily censored by Soviet authorities. So, after the birth of his first son, whose middle name is Arsenyev, Slaght began to translate the explorer’s first book, “Across the Ussuri Kray.” (The Ussuri is a river in Primorye.) Slaght is not as comfortable in written Russian as he is in spoken Russian, but the clarity of Arsenyev’s prose and Slaght’s familiarity with the landscape of Primorye eased the way. Eventually he realized that, between his son’s late-night feedings, he had produced a respectable translation. Last month, Indiana University Press published it.

The new translation is based on the first edition of the book, from 1921, which was severely shortened by government censors and not republished in full in Russia until 2007. Like the most recent Russian edition, Slaght’s translation restores hundreds of pages of excised material, including religious references and many detailed descriptions of the places and people of Primorye. The translation makes it easy to see why Arsenyev maintains a fan base among Russian readers: his travelogue is both romantic and closely observed, and he is an appealing narrator, courageous but more than willing to admit faults and share credit. In one of the book’s most memorable scenes, Arsenyev and the tracker Dersu Uzala, a member of the indigenous Nanai people, are caught in a blizzard after Arsenyev disregards his companion’s warnings. Dersu Uzala takes charge of the situation, building a shelter out of a stand of reeds and, as Arsenyev freely admits, saving both of their lives. (In 1972, the Japanese director Akira Kurosawa made an Academy Award-winning film about the pair’s exploits.)

The full translation of “Across the Ussuri Kray” is also an ecological and cultural snapshot. Arsenyev did not always name the plants and animals he saw, but he took such thorough notes that Slaght and his colleagues were in most cases able to identify the species he encountered—from sea lions and raccoon dogs to kestrels and nuthatches—and name them in the text or in footnotes. And while both imperial Russia and, later, the Soviet Union tried to present the Far East as a wilderness awaiting civilization, Arsenyev’s complete account makes it clear that Primorye was already a richly inhabited place, home to the Nanai and Udege peoples and to scattered settlements of Chinese, Koreans, and Russian Old Believers.

Fifteen years after the expedition described in “Across the Ussuri Kray,” Arsenyev reported that much had changed. “The primeval, virgin forests across many of these lands have been burned and replaced by woods of larch, birch, and aspen,” he wrote in a preface to the 1921 edition. “Where before a tiger roared now a locomotive whistles, and where there was once a sparse scattering of Chinese trappers there are now large Russian settlements. The indigenous peoples have retreated north, and wildlife populations in the forest have been greatly diminished.” Primorye, he concluded, had begun “to lose its uniqueness and undergo the transformation inevitable with the advent of civilization.”

A hundred and ten years after Arsenyev travelled up the Ussuri River, it’s easy to extend the trajectory of decline. Primorye is far more crowded than it was in 1906, or 1921, and a web of roads dissects once-continuous forest. But while some species are less common than they once were, the region’s tiger population, which shrank almost to extinction in the nineteen-forties, is now stable at about five hundred and forty animals, thanks to habitat protection and anti-poaching efforts. Slaght and others are negotiating with logging companies to close some roads in key wildlife habitat. In many ways, Primorye remains as Arsenyev knew it—still under threat, and still full of wonders.