FOR ALMOST MY ENTIRE ADULT LIFE, I've spent some portion of the summer backpacking through the Sierra Nevada, and during that time I've witnessed profound changes. Three out of the past five years, the range was filled with smoke from fires burning on the western slope. I've hiked through the aftermath of major forest fires, visited meadows desiccated by drought, and watched the retreat of glaciers. The mountain icefields are a fraction of the size they were when I first visited them. It's very likely they will be gone by the end of this century—gone like the grizzly bears.

There can be no argument: Our world is changing fast. Of course, our planet has always changed, and always will change. But now the changes are happening hundreds of times faster than they used to, spurred by human actions. The changes are occurring so rapidly that they have forced scientists to come up with a new name for this unprecedented epoch: the Anthropocene, the "human age."

Humans' sweeping transformations of Earth—some of them deliberate, many of them accidental—have put civilization in a precarious position that forces on us existential questions about where we go from here. If we continue to burn ancient carbon, stripmine the soil, and raze forests, we could be headed for the sixth great mass extinction event in Earth's history. If we ignore the consequences of the manmade changes, then famine, war, and pandemics could result from wrecking Earth's life-support systems. It can't be emphasized enough just how awful a bad Anthropocene could be.

If, however, we change our technologies and our economic system to better match the physical and biological realities of life on Earth, the resulting history could be quite amazing, what some are calling "a good Anthropocene." That future would, in effect, be the story of humanity devoting itself to nurturing the health of the biosphere and creating a sustainable prosperity for all the living creatures on this planet. While not exactly utopia, that future could be called optopia—the "optimal place," the best possible outcome given the current conditions.

This huge spread of possible futures—from very bad to very good—is one of the things about this moment in time that create such powerful feelings of urgency and disorientation. But the window of opportunity to shape our future for the best is closing fast. Ecological destruction is accelerating, new environmental problems keep cropping up, and the outdated thinking that informs today's status quo is proving all too resistant to thoughtful response.

And still. There is, just barely, time remaining to initiate a good Anthropocene. It is still physically possible to create an optopia on Earth.

Human civilization has become an ecological—it's fair to say evolutionary—force on this planet. It's a daunting, even terrifying, thought. But that's what it means to be in the Anthropocene. Since we aren't, at this point, able to return to the way things were before the Anthropocene, our best option is to adapt and adjust as best we can to this new world we have unwittingly created. How should we respond to such a responsibility? Where, when, and at what scale should we intervene in natural systems?

Some of the adaptations being talked about are globally grandiose—and truly scary. If the situation becomes genuinely apocalyptic, our species may attempt large-scale interventions that today sound dangerous or repugnant. One example is what climatologists call "solar radiation management"—that is, the planetary equivalent of pulling down the shades to cool off the globe. Were millions of people to perish owing to heat-related crop failure or heatstroke fatalities, national governments would be sorely tempted to take emergency action, such as injecting small particles into the upper atmosphere in an attempt to imitate a volcanic eruption and cool global temperatures. This is the most discussed method of what's called geo-engineering, and it would represent an unprecedented deliberate manipulation of Earth—the whole world embarking on an experiment in planetary management.

But, as environmental scientist Erle C. Ellis has cautioned, there is no cockpit on Planet Earth. We don't have the knowledge or the power to engineer the planet's biophysical flows; we only have the power to nudge our gigantic planetary system a little bit this way or that. "Geo-engineering" is a misnomer. It would be more appropriate to call these attempts at planetary remodeling by another name: geo-tweaking or geo-finessing or geo-begging. These terms better indicate how puny civilization's powers are relative to giant forces such as the chemistry of the oceans, the balance of the atmosphere, and the interplay among millions of species.

Fortunately, there are other options open to us, though they will require imagination, political will, flexibility, and an attentiveness to the realities of the planet—habits of mind at which we are unpracticed.

Some forms of geo-tweaking that might be implemented seem to me unequivocally good. Taking carbon dioxide back out of the atmosphere—that's a good idea. It's worth investigating the potential of mechanically sifting carbon dioxide out of the air and then burying it, or binding carbon directly to rocks, even though doing so at a global scale would likely have associated problems. Many of the most promising ideas for carbon dioxide drawdown are local and regional rather than global, and they make use of biological processes already well tested by evolution. Take, for example, preserving or restoring forests and peat bogs. These are good practices in and of themselves for the long-term cycling of elements crucial to life; at the same time, protecting and expanding forests can help sequester atmospheric carbon. The same goes for improving farming and ranching practices to prioritize soil health, conserving coastal wetlands, seeding and sustaining offshore kelp forests, and restoring native grasslands. Getting the atmosphere back to something like 350 parts per million of CO2 will be an integral part of making a good Anthropocene.

Another form of geo-tweaking that might come to be seen as good is a regional action with global consequences: pumping seawater onto the ice cap covering eastern Antarctica so that it freezes high on the massive Antarctic icefields. The Potsdam Institute for Climate Impact Research investigated this possibility and estimated that it would take about 7 percent of all the electricity created annually by humans to pump the necessary amount of water. That sounds like a lot, and in fact the institute concluded that such a project might not be considered "economically favorable." But right now, roughly a third of 1 percent of all the electricity generated each year by humans (about the same amount that Austria or Chile uses) is being used to create Bitcoins. In other words, for about 25 times the energy cost of a stupid speculative bubble, we might be able to save all the coastal cities and beaches of the world from being submerged. Given that the world's coastlines could be priced in the trillions of dollars—or, more accurately, simply valued as priceless—is it really too expensive to pump that upcoming flood back onto the Antarctic ice cap?

Which brings us to economics, that most dismal of sciences. Economics pretends to calculate the value of things. Yet when asked whether we can return the planet to health, capitalist economics all too often answers, "No, we can't." The project of saving the biosphere from catastrophe is considered unprofitable in the short term compared with other financial opportunities, so it won't be done, because profit rules all. And so we arrive at the old saying "It is easier to imagine the end of the world than the end of capitalism."

Our challenge, then, is to imagine harder. Because the world is not an optional investment we can choose to forgo due to its low rate of return. There is no Planet B. We have to keep this planet healthy, because it's our one and only home, our extended body. Margaret Thatcher infamously said that "there is no alternative" to corporate capitalism. But there is absolutely no alternative to maintaining life on Earth.

What I am trying to say is this: Perhaps the most important thing we can do to adapt to climate chaos and the dislocations of the Anthropocene is to rethink the assumptions and revise the rules of corporate capitalism. After all, the current economic order, while massive, isn't permanent or unchangeable. It's a human artifact: We made it over time through a series of power plays and improvisations. And that means we can remake it, if we have the courage to do so.

Just consider the phenomenon of "quantitative easing"—economists' term for the Federal Reserve's creation of about $4 trillion since the crash of 2008 to prop up the financial sector, the stock market, and the housing industry. If we can create trillions of dollars and inject that money into the economy without extraordinary repercussions, as a normal part of managing civilization, then why can't we do so to rescue civilization from itself? Such wealth could be used to pay for the carbon drawdown and ecological restoration this moment demands. Essentially, we as a society would be deciding to pay ourselves to do the work needed to create a good Anthropocene. An ecology-minded quantitative easing would be its own kind of geo-engineering. Some are calling this the Green New Deal.

Science fiction? Not necessarily. Politics is, in part, the art of imagining the future, and this is a future worth envisioning. Just picture it all. With the right financial incentives, farmers would focus as much on the yields of carbon sequestered in the soil as they once did on crop yields. Timber companies would find revenues in replanting forests—not tree plantations for a future harvest but real, biodiverse forests valued for how much carbon dioxide they inhaled and stored. Ranchers would double as wildlife stewards, paid for the number of wolves, grizzlies, and bison roaming their land as well as the cattle they raised.

Imagine a remade world founded upon health and prosperity. Imagine transportation of every kind propelled by clean energy—electric cars and scooters, for sure, but also container ships pulled by kite sails, then battery powered when navigating close to port. Imagine every lightbulb and internet download powered by the sun and the wind. Imagine engineers and technicians and heavy-equipment operators finding meaningful work building out a global clean energy infrastructure. All these technologies are off-the-shelf and shovel-ready; the only thing we haven't invented yet is the economics to pay for them.

Of course, achieving such a future will be a political struggle every step of the way. Pulling together like this will be a hard and strange improvisation, like a tightrope walk over an abyss. But human history is full of examples of how cultural norms and structures of feeling can change—sometimes quite fast. This century is sure to be one of those occasions. Hope resides in this underappreciated fact of human nature: People are often at their best in the midst of crisis and emergency.

If we manage to build the good Anthropocene, the payoffs will be incalculable. The alpine meadows will still be lush in the centuries to come. The glaciers will return, and the grizzly bears too. The Sierra Nevada will still resemble the place the Sierra Club was founded to protect, the place I remember best.

Maybe the welfare of the ecosystems in one single mountain range seems like a small matter in the larger picture. But it matters to those of us who love those mountains. And the Sierra Nevada—just like the Amazon and the seas and the still-wild tundra—can serve as an indicator habitat. If those places stay healthy, it will only be because the whole world has stayed healthy.

That is something to wish for, and to work for.

This article appeared in the January/February 2019 edition with the headline "There Is No Planet B."