When I was a young teen, passionately interested in saving the world, my twelfth-grade graduating class wanted to leave behind something meaningful as a gift for the younger students. Because some of us had been involved in setting up and running the school's first Nature Club, we thought of planting trees as a farewell present. We chose four saplings from a local nursery and were allowed to plant them just outside the school walls. But there was a problem. The residential area surrounding the school had a population of bratty little boys, sons of the domestic help that worked in the big bungalows. These urchins roved the neighborhood like sharks, raiding fruit trees, defacing and destroying everything they could get away with. I don't think they were bad kids—very likely they were simultaneously bored and intelligent, and there was nobody to really take care of them. But we knew that they wouldn't let our trees live.

Somebody then came up with a brilliant idea. Why not recruit the enemy? Perhaps we could persuade the kids to own the project in some way. After a few negotiations, this was done. Teams were drawn up and duties assigned, and suitable rewards offered. We left the schoolyards of childhood and moved away to university, to marriage and family, to other shores.

When I returned to the school decades later, I saw that two of the four trees were still there. Where there had originally been barren unpaved land where the fat green and yellow school buses waited for school-weary students, there were now deep pools of shade, and a leafy canopy from which birds sang. A 50% survival rate, I thought, wasn't too bad.

There's something about planting a tree. I'm no gardener, having only recently graduated to the point where I am not killing off my house plants, but on every occasion that I've planted a tree I have remembered for long afterward the feeling of bringing something into being that was greater than myself. But I never imagined that any human being could plant an entire rainforest.

There's some small print worth noting with regard to that statement, and I'll come to it in a moment. Before that, I want to take up where I left off in my last column. There, I stated that even without global climate change we are in deep trouble due to biodiversity loss—destruction of forests and other ecosystems, extinction of species at rates hundreds of times greater than normal. What we've learned in the course of this smash-fest is that we are not masters of the earth, and we are not outside the realm of nature. We are connected to and depend upon other species—or as John Muir so poetically put it, "everything is hitched to everything else." By tearing great holes in the web of life we imperil our own existence. This is as true and inevitable as the law of gravity.

Historically, scientists have called upon people and governments to preserve what is left, to slow, and ultimately stop the rate of destruction of our natural resources. This has been only partially successful because we are up against powerful vested interests primarily looking for short-term gain for a tiny percentage of people. However a question has also arisen in recent years: can we do more? Can we restore what we've lost, partially if not wholly? Is it enough to preserve what little is left? If we need forests, and wetlands, and orangutans and beetles to survive, can we bring them back somehow?

The idea is a sort of dream of Eden, but all potential realities begin with dreams. Imagine, then, herds of elephants thundering across the African savannah, their traditional migration routes restored. Cities and towns and villages still exist but they are designed to be away from the migration routes. Tourists flock to see the herds on the move, bringing economic prosperity to the region.

Imagine a strip of no-man's land between two hostile countries that have agreed to let their disputes go and have given up the land not to each other but to nature. Here in the restored high mountain valleys and passes, herds of mountain goats munch on spring grass, and migrating ducks land like multicolored raindrops on the mirror-like surface of a lake. In the winters, above the glacier, a snow leopard moves like a pale ghost, hunting blue sheep. Villages host climbers and ecotourists in the summertime, when the streams run thick with trout.

Imagine . . .

Imagine rewilding the world.

One of the earliest uses of the word "rewilding" is in a 1998 paper by conservation biologist Michael Soule and his colleague Reed Noss, who set out to formulate a new discipline, a kind of restoration ecology on a vast scale. I first came across the word (and the ideas of Michael Soule) in a book called Rewilding the World: Dispatches from the Conservation Revolution, by environmentalist Caroline Fraser. It is a remarkable and inspiring book. On her website she explains how she came to be radicalized by what she discovered during her travels around the world, studying large scale conservation movements. She speaks of biologists emerging from the ivory tower of science to become "biological knight-errants," joining forces with activists and becoming politicized. In the book itself she speaks in fascinating detail about what rewilding means and what the challenges are.

Let us begin with the ideas of Soule and Noss. The essence of rewilding can be summed up in three words: Cores, Corridors, and Carnivores. The first term refers to the need to preserve what is left: forests and wetlands and other habitats that have not yet fallen to the developer's axe. Such places are not only natural wonders but also storehouses for foods and medicines of the future, pools of genetic diversity, and safe havens that preserve the biodiversity we need to survive. Unfortunately sanctuaries and national parks are not enough, because they are increasingly fragmented and isolated from each other by farmland, cities, and other developed areas. A healthy ecosystem requires the freedom for migratory or long-ranging species to move over hundreds or thousands of miles. Fraser gives the example of Pluie, a wolf who was equipped with a radio collar fitted with a satellite transmitter. Over a period of two years she roamed over five hundred miles through the Rocky mountains. She did so via corridors, areas of wilderness that connect core protected regions. In Africa, elephant herds have lost their traditional corridors, their migratory routes, which means that they are cramped in tiny (from an elephant's perspective) national parks where rangers keep their numbers in check through culling. Apart from cores and corridors, carnivores turn out to be incredibly important to the health of an ecosystem. Predators like wolves keep deer and elk in check and thus keep the forest from being overgrazed and streams from becoming depleted of trout. (One of the most fascinating things about ecology is the discovery of such connections.) Corridors also allow species to expand outside the confines of the core area—places for young bears to go, for instance, once they leave their mothers. The simplest implementation of a wildlife corridor is highway-crossing structures for animals, such as those across the trans-Canada highway. Monitoring shows that use of these by wolves and grizzlies is on the rise. Similar wildlife crossings are planned or being built in the United States.

The book is a world tour of conservation success stories, failures, and lessons learned, from the incredibly biodiverse demilitarized zone between North and South Korea to the European Green Belt, and the linked national parks in southern Africa. One of the things that stood out to me is that the success stories invariably involve the initiative and cooperation of local communities. This is not a given; often, conservation is imposed from above by governments with no regard for the people who live in the protected areas, who might lose their lands and livelihood as a result of conservation efforts. Done this way, conservation pits itself against people, and the people turn against such efforts with good reason. One of the most fascinating stories in the book details the initial animosity of the Maasai in Kenya to the Kenyan National Park system, which infringed on Maasai land. In some regions the Maasai were evicted from their traditional homes, accused of overgrazing the land. This did not endear the Maasai to conservation efforts, which they bitterly opposed. However when a rhino sanctuary was formed by a far-seeing cattle rancher who had grown up with a Maasai youth from whom he had "never grown apart,"—and when the local Maasai were invited to be part of the effort, things changed. Maasai became involved in ecotourism, and the conservancies in which they worked granted them significant ownership rights along with community control of the land and wildlife.

Other stories in the book include the astonishing things that happen when humans leave a piece of land alone. The demilitarized zone between North and South Korea, which is thick with landmines and empty of humans, has become astonishingly biodiverse, with rich, varied habitats busy with animal life, including 67 endangered species. It is the last stronghold of the Korean peninsula's wildlands. But to me one of the most fascinating chapters is the one on restoration ecology, where we return to the question I asked a few paragraphs ago: can we recover what we've lost?

There are inherent problems in restoration of a once-natural landscape. Restore to what? Some ideal of primeval perfection? asks the book. And how would one prevent restoration efforts from becoming greenwashing, slapdash efforts that do more harm than good?

Restoration ecology is actually a very complex discipline. To do it right, you not only have to clean up pollution but also remove invasive species, plant native vegetation, restore the health of the soil, and so on. The goal is to make the system self-sufficient, like any functioning ecosystem. How do you do that?

How do you regrow a rainforest?

It turns out, according to an article in New Scientist, that it might take about 4000 years to fully regenerate a rainforest. However, certain aspects of the forest are restored in as little as 60 years—or less. Meet environmentalist Willie Smits, who regrew a rainforest in Borneo. He took a region where plant and animal life had dwindled to almost nothing, where the original forest had been replaced by barren land or grassland, where the local people had a 50% jobless rate and crime and poverty were both high. With the essential involvement of the local people, not only did the rainforest start to come back in the next ten years but the economy turned around and the microclimate changed. It is one of the most inspiring stories I have ever heard and you can watch Smits talk about it with passionate eloquence in a short video.

However rewilding is not without controversy. Caroline Fraser refers to Smits as "something of an eccentric" and states that the project has not been supported by international conservation organizations who prefer to expend their efforts on saving pristine forests. Some biologists are concerned that any excitement about rewilding will obscure the fact that secondary forests, such as the one Smits helped create, are not anywhere near as biologically diverse as untouched forests. The latter contain some species found nowhere else—biologists fear that their irreplaceability will be undermined by the notion that one can always restore what has been lost, allowing for more exploitation and plunder of what remains. However others argue that both things—restoration and preservation—must happen simultaneously.

In my last column I spoke about a trip I took to the Himalayas as a teenager, along with other young people, mostly from New Delhi. The trip changed my life and opened my eyes to a number of surprising things, including the idea that illiterate villagers could rise up spontaneously and make a grassroots movement that was both environmental and socio-feminist. There I saw without completely recognizing their significance at the time, that these villagers were not only preserving what was left but restoring forests that had been destroyed. They were doing this because they depended on the forests for their very survival and were refreshingly and unabashedly emotional about them. In a sense they anticipated the work of Michael Soule and Willie Smits. The impressionable young teens from Delhi were suitably impressed and came home and formed a group called Kalpavriksh, after a mythical wish-fulfilling tree. The group still exists and one of the things that distinguishes it from more conventional conservation groups (apart from its complete lack of hierarchical structure) is that it has always stood by the tenet that conservation and community are not oppositional—that one can't successfully save forests and grasslands and other habitats without confronting social justice issues and allowing local communities to take leadership roles. One of their numerous publications, Environment and Human Rights, speaks to this theme directly. For one example from this booklet, consider villages in the western state of Rajasthan, most of which is an arid desert. Water is obviously not plentiful here; traditionally water was trapped during the short rainy season via a series of small reservoirs and dams. The hilly areas above the villages had some vegetation that also helped maintain the water table. With tree felling and the replacing of traditional water collecting measures by state-provided irrigation, water scarcity became the norm in these areas. After a successful NGO-led campaign in the 1980s, however, the community came together, worked hard to restore and construct the reservoirs and dams, and by the 1990s hundreds of these villages became self-sufficient in water. Agricultural production doubled or tripled and forests regenerated.

It is interesting to me to look back at the school tree-planting project with which I began this column, and see in it the elements—albeit on a very small scale—of the ambitious conservation projects of today. Plant trees. Involve local people as stakeholders! Caroline Fraser speaks in her book about a term coined by Michael Soule: the demographic winter. This refers to the scarcity and loss of the numbers of species that share the earth with us. Their loss is our loss in a very real and literal way. If we are to restore the earth to one that can support our continued existence—if not its former glory then as close as we can get to it—we must change the way we live. We must use our imaginations in unaccustomed ways to think beyond conventional "wisdoms," to dream beyond our perceived limitations. Such exercises will yield new literatures and art, new designs—everything from cars to cities—and new ways of being. May this demographic winter also be the winter of our discontent—where we dispense with economic and social systems inimical to both humankind and the rest of nature and reinvent systems based on reality, social justice, and science—and where we work to return ourselves and our fellow travelers to an earth that can sustain us once again.