The Magdalena river, which forms the centrepiece of writer and anthropologist Wade Davis’s rich and rewarding new book, is like an inverted Mississippi. Running from south to north, it rises in the Andes and crosses the length of Colombia, flowing through cloud forests, tropical jungle, mangrove swamps and wetlands before disgorging into the Caribbean Sea. Its enormous drainage basin covers a quarter of the nation, including Colombia’s largest cities, Bogotá, Medellín and Cali.

Loosely divided into three parts, one for each of the river’s three sections – the Alto, Medio and Bajo – Magdalena follows no straightforward course. It rather strings together conversations with characters Davis encountered during his exploration of the river, each of whom has a particular take on the spirit of contemporary Colombia, personal observations and episodes drawn from the rich and often tragic history of a country that has been long ‘overlooked and misunderstood’.

At one end of the river, in the Alto Magdalena, Davis travels through a páramo, a neo-tropical alpine biome that resembles ‘an English moor grafted onto the spine of the Andes’. Shrouded in swirling fog, this ancient treeless landscape of espeletias – hardy relatives of the daisy – is a rare and otherworldly ecological niche. So much so that on the brink of death people are said to be ‘getting ready to cross a páramo’. At the other end, on the flood plains of the Bajo Magdalena, the river slows and fans out, becoming an ‘amphibious realm’, host to elevated fishing villages with names like Nueva Venecia and the magical wetlands city of Mompox, ‘a place to dream about, a place that might not exist at all’.

But the Magdalena has also been a place of unimaginable violence, death and environmental destruction. Colombia’s modern history, recounted here in episodic vignettes, appears to be one drawn-out conflict, from the bloodletting of the conquistadors, to the War of Independence and the multiple civil wars that followed, to a post-Second World War era known as La Violencia, which pitted liberals against conservatives in a brutal struggle for power.

All this before the more familiar story of the emergence in the 1960s of the left-wing guerrilla group FARC and its right-wing paramilitary counterparts, and, of course, the rise and fall of Pablo Escobar and the US-sponsored ‘war on drugs’. By the 1980s, thousands were being slain annually. Davis describes horrific scenes of victims being tied to trees and dismembered with chainsaws while still alive, the resulting mess disposed of in the river. At the height of the drug wars, fishermen grew tired of extricating body parts from their nets and the sight of bloated corpses floating down the Magdalena became commonplace.

The violence, much of which was visited on innocent bystanders, was matched by wanton ecological destruction, which has ravaged Latin America since colonisation and accelerated over the past half-century. When the Spanish arrived in the 16th century, they described the river banks teeming with caimans. On the lower Magdalena, turtles were so plentiful that they were seen as obstacles to navigation, and turtle eggs were collected in their tens of thousands. By the time vapores (paddleboat steamships) began plying the river in the late 19th century, vast tracts of forest along the river bank were being cut down to power them. By the early 20th century, the vapores had burned thirty million cubic metres of invaluable tropical hardwoods and the Magdalena’s most accessible forests were gone.

But the situation is far worse today: more than 80 per cent of the forest cover of the Magdalena’s drainage basin has been destroyed; the resulting erosion is silting the river and sewage flows freely into its darkened waters. ‘Every day,’ writes Davis, ‘more than thirty-two million Colombians go to the bathroom and flush their waste directly’ into the river. In one sense, he argues, the river’s desecration mirrors Colombia’s long history of violence: ‘for years we treated it like a sewer,’ says Ahmed, a survivor of a particularly brutal paramilitary massacre, ‘just like we treated each other’.

Among the characters Davis encounters are William Vargas, who from humble beginnings built a successful career as a renowned naturalist; Pacho, who risked his life to pull anonymous corpses out of the river and give them a dignified end; and Xandra Uribe, whom he meets by chance in the Medio Magdalena but who ends up becoming an important travel companion and close collaborator in the project.

The book is studded with Gabriel García Márquez-like imagery. At one point Davis observes ‘a small girl at the door of the shuttered church, playing with a butterfly she had somehow tethered to a yellow thread’. Indeed, towards the end, Márquez himself appears in a brief chapter, as yet another Colombian institution bound to the river. Márquez made eleven round trips up and down the Magdalena, starting in 1943, and used the river as a setting for Love in the Time of Cholera and The General in His Labyrinth.

This is a complex, multi-dimensional and at times overburdened book of ideas, anecdotes and vivid historical reconstructions. Some parts, like those on the extraordinary San Agustín complex of megalithic statues and those on the Spanish conquest of Colombia, describe lesser-known aspects of Latin America’s pre- and early colonial history, so long dominated in the popular imagination by Machu Picchu, Mayan ruins and the exploits of Pizarro and Cortés. Others, such as the short chapter on the influence of the naturalist Alexander von Humboldt on Simón Bolívar, fuse revolutionary politics and ecological renewal in interesting and novel ways.

The facts seem to militate against it, but what emerges from this rich and original portrait of a country in transition is a sense of optimism. As Colombia stands at the crossroads, with a fragile peace process and an opening up of lands long dominated by violence, there is a real desire to heal emotional and environmental wounds: ‘to clean up the river would be to wash the soul of the nation,’ remarks Germán Ferro, the curator of a museum dedicated to the river. If Colombia can achieve this, it will finally unlock the full natural and cultural potential that is so abundantly on display in these pages.