In the mid-1950s, US Senator John F. Kennedy was bed-ridden for many months, recovering from surgery to repair his war-damaged back. He used some of this time to research and author (with the notable assistance of his speechwriter, Ted Sorensen) the Pulitzer Prize-winning book Profiles in Courage. The book chronicled the lives of eight senators in American history who had risked their careers to act on principle rather than politics. The book inspired a generation of young Americans – including me.

The history of conservation, I reasoned, could serve a similar purpose to inspire a new generation of young – and old – to act on behalf of our common environment. So I set out on a similar exercise to Kennedy’s. The result is a book, Nature’s Allies, in which I profile the lives of eight great conservationists of the past century. A few are familiar names, like John Muir, Rachel Carson and, perhaps, Aldo Leopold. But others are less well known (particularly, I fear, to many Americans) – Chico Mendes, Ding Darling, Wangari Maathai, Billy Frank Jr. and Gro Harlem Brundtland – purposefully demonstrating that any person, from anywhere, can change our world.

What do these eight have in common? Certainly not their education, life circumstances or professions, nor their social status or access to power. What they share is much more basic – a passion to conserve our natural resources, and the persistence to keep at it, no matter the cost.

Consider first their passion. Chico Mendes (1944–88) was a poor rubber-tapper from the far reaches of the Brazilian Amazon. His passion began with a desire to help fellow rubber-tappers by forming a labour union to represent their interests. Realising that Brazilian policy to convert forest to pasture was short-sighted, he began the dangerous work of fighting for the rainforest itself. A man who never condoned violence, he was murdered a few days before his 44th birthday. Today Mendes is a national hero, and rainforest clearing rates have fallen, though the forests remain threatened.

Rachel Carson (1907–64), a best-selling author of natural history books about the sea, was a shy, reticent woman who let her writing speak for her. When she realised that the spraying of pesticides was causing widespread damage to non-target organisms, particularly birds, she put aside her personal interests to research and write the book – Silent Spring – that arguably spawned the modern environmental movement. Not a desire for fame or fortune, but a passion to right a terrible wrong drove her to complete the manuscript as she was dying from breast cancer.

John Muir (1838–1914), the Scottish-born founding father of American conservationism, loved trees. So much so, that in a violent storm he climbed a tall tree and lashed himself to the trunk for hours, just so that he could experience the life of a tree. Seeing the destruction that excess logging, sheep grazing and shabby tourism were causing in his beloved Yosemite Valley, he stopped hiking and took up lobbying, a task he detested. But dauntless in his efforts for conservation, he eventually won, and the glorious Yosemite National Park is a testimony to his passion.

During the first half of the 20th century, American newspapers regularly featured cartoons by Ding Darling (1876–1962), an insightful and humorous commentator on politics and life. Darling was also a dedicated conservationist. Unlike most Americans, he abhorred the policies of President Franklin Roosevelt – and he made no secret about it. But when Roosevelt surprisingly asked Darling to lead the U.S. Biological Survey – the forerunner of the Fish and Wildlife Service – he put aside his pride and followed his passion. In a short 22 months, he put the agency on the map, along with millions of acres of wildlife refuges.

The second characteristic these eight conservationists share is their persistence. Wangari Maathai (1940–2011) grew up in rural Kenya, enjoying a life of relative plenty amid the subsistence agricultural communities of the region. But when she returned as a veterinary professor, she found a landscape robbed of its trees and natural places. She determined to remedy this by organising small groups of women to grow and replant native trees. She kept at it, tree after tree, group after group, until she had done the impossible – planted 50 million trees!

Billy Frank Jr. (1931–2014) was a member of the Nisqually Indian tribe in Washington State. Following traditions guaranteed by an 1854 treaty, he caught salmon for a living. But when salmon became scarce after the second world war, the state blamed Indian fishing and set out to stop it. Frank was always at ground zero, arrested more than fifty times and raising the cause to the highest levels. Eventually the courts gave the Native Americans half the catch and shared responsibility for the fish – and a new era of fisheries science and management began.

The only conservation professional in my list is Aldo Leopold (1887–1948), generally considered the father of American wildlife management. But that isn’t why he appears. Instead, it was his commitment to the land, exemplified in his restoration of a small, exhausted Wisconsin farm. There he laboured, season after season, year after year, to bring back the native flora and fauna. Along the way he recorded his observations in a series of essays that became A Sand County Almanac, the philosophical bible for today’s conservationists.

My final choice was Gro Harlem Brundtland. The only one of the eight still living, she has done it all. Born into a prominent Norwegian family in 1939, Brundtland trained as a doctor. As she learned the connections between public health and a healthy environment, she became a spokeswoman for the concept of sustainability, as Norway’s environment minister and prime minister and then as chair of the World Commission on Environment and Development. She coined the definition of sustainability that the world uses today – to meet today’s needs without compromising the ability of future generations to meet their own needs.

These eight people, different in so many ways, have lighted the path of conservation. But thousands more have shared that leadership, perhaps in smaller, less recognised ways. Thousands more will lead us towards a more sustainable world in the future. I’m optimistic that our progress will continue unbroken as our science and our ethics drive us forward. Wouldn’t it be wonderful if a future edition of Nature’s Allies had not eight, but nine biographies – and the ninth was yours?

Larry A. Nielsen is Alumni Distinguished Undergraduate Professor of Natural Resources at North Carolina State University. Nature’s Allies is published by Island Press.