How Many Planets Do We Need?

Some scientists say that there are certain levels of environmental damage from which it will be impossible to recover. But is that true? Will humanity be able to adapt to the new planet we have created?

How Many Planets Do We Need?

The UN has recently proposed an international set of planetary boundaries, a series of benchmarks for various environmental affects on the planet (like carbon emissions or ocean acidification) that humans must adhere to if we are to avoid overshooting the Earth’s capacity. But a number of prominent ecologists are now questioning that principle.


“Our issues are so serious that what we’re framing in this paper is to move to a paradigm of not jut what we’re doing wrong but how to use our science to contribute to solutions to this very serious problem,” says Ruth DeFries, professor of sustainable development at Columbia University, and one of the authors of a recent paper (PDF) scheduled to come out in BioPress, which calls for consideration of “planetary opportunities” such as urbanization and agricultural innovation, as the key to sustainable development. “It’s a shift in thinking of our role and the kind of research we do and … how solutions can be achieved.”

Global change researchers–scientists in fields from atmospheric physics to anthropology–fall roughly between two extremes: those that see hard biophysical thresholds as threatening to humanity’s ability to sustain itself, and a more adaptive camp that sees humans shrugging off most environmental damage. This first view demands costly curbs to human growth. The second suggests disastrous complacency. For decades (if not centuries), the “constraints” camp has been the dominant voice.

DeFries and her co-authors propose a middle path. By pursuing solution-oriented research, most of it achievable in the next 10 years, scientists may help minimize environmental damage while society continues to evolve and adapt the Earth to our needs (and desires).

Researchers have tended to focus on the global and the theoretical, rather than the local and the practical. The scale of analysis, says DeFries, must better match the decision-making. “What we’re trying to promote in this paper is some very deliberate thinking about the scale of the research that is being done,” says DeFries. Although today’s science is valuable, she says, the questions researchers are asking must be reframed to focus on “solution-oriented research to provide realistic, context-specific pathways to a sustainable future.”

The authors do not see evidence of hard biophysical limits for humans. Our species, they note, has proved extraordinarily capable of expanding that envelope. “It’s very difficult to identity what those boundaries are on a global scale,” says DeFries. “Human society has demonstrated over and over again that we find a way to adapt and solve problems, so a hard boundary doesn’t take into an account our demonstrated ability to adapt. … I don’t mean to say that there’s a solution to every problem, but humans are good problem solvers and there are no absolute boundaries.”

Urbanization is a good example of human systems responding to a planetary opportunity. By living more efficiently in larger populations, we free up rural land for ecosystem services and agriculture. Similarly, society mobilized to solve challenges throughout history, from the Great Plains’ Dust Bowl to ozone depletion and acid rain, states the study.


That doesn’t mean we will always have a soft landing. Humans can probably exceed the “safe operating space” proposed in a seminal Nature article in 2009. Some problems–such as species extinction–can never be solved: Loss of biodiversity is essentially permanent.

But in the era of the Anthropocene, when humans are the dominant biophysical force on the planet, researchers may need to look beyond strict limits, and find ways to live sustainably on a planet of our own making.

“I think that humans are part of the the whole system,” says DeFries. “It’s not about wrong and right. It’s about identifying opportunities of providing for human needs and minimizing impacts on the system.”

About the author

Michael is a science journalist and co-founder of Publet: a platform to build digital publications that work on every device with analytics that drive the bottom line. He writes for FastCompany, The Economist, Foreign Policy and others on science, economics, and the environment.