How many people can the Earth support? In his new book, “A Planet of 3 Billion,”Dr. Christopher Tucker invites readers to ponder this question. In this context, many define “support” as how much food and water the Earth can generate to sustain the human population. However, Tucker defines “support” as Earth’s carrying capacity, including humanity’s need for nourishment and its tendency to burden and sometimes destroy the ecosystems it relies upon. Tucker explores the historical and ecological footprint of humanity through a political, cultural, and economic lens—and yields some uncomfortable truths.
What led you to write this book?
I want to start a conversation about the world’s problems. Other than some niche Scientific American articles, nobody is asking, “How many people can the Earth support?”I want people to understand Earth’s “carrying capacity”and that our current population goes well beyond it—to realize we have an ecological footprint and what that is.
What is Earth’s current “carrying capacity”and how did you determine it?
I reviewed several existing methodologies on Earth’s carrying capacity, and then took my own analysis to come up with the number 3 billion. I ground my analysis in geographical (spatiotemporal) analysis. I precede that analysis with 200,000 years of mapping humanity’s ecological destruction, trying to put the last century or so in spatiotemporal context. With our current “production function,” as an economist would call it, the number is actually between 1 and 2 billion; mainly because of our growing, persistent, and accumulating geography of waste. But, as a technological optimist, I believe innovations will let us survive at 3 billion without maintaining long-term ecological debt.
How do you explain ecological debt and how it has changed?
Thousands of years ago, Earth’s population was extremely small.People generated the goods and services they needed with no real impact on ecosystems. However, humanity’s ecological impacts from industrialization and the waste we generate started having a real, accumulating influence. We’ve accrued an enormous ecological debt as a society. We have endocrine disruptors generated at an industrial scale, which never existed in the previous 200,000 years. We depend upon Earth to generate all these ecosystem goods and services for us to survive. Yet every year we see another species dead or another water problem in a region. So, our debt is getting worse, not better. And there will be a tipping point.
How does spatiotemporal data reveal humanity’s ecological impact?
At the very beginning of the book, I introduce “shifting baseline syndrome.”Thisis our own experience as we came into the world and it already was what it was. I may complain about things that I observed that I don’t like or improvements that I do like. But I only know what was there in 1973 or when I woke up to the world in the late ’70s. Shifting baseline syndrome is a huge problem, and a lack of spatiotemporal data magnifies its impact.
With spatiotemporal data, you look at where there were trees a thousand years ago, and you assume trees weren’t where they’re not now. But, for example, Iceland was a giant forest, and now there are almost zero trees because they were cut down and burnt by people who needed firewood in the cold. Spatiotemporal data provides the opportunity for people to get on the same page and understand things in a common historical framework and a standard narrative.
Why is there no dominant narrative concerning human geography and humanity’s ecological footprint?
We have these centuries-old journalistic and academic categories in which we separate science and economics from politics. So, you’ll have an economics reporter, a politics reporter, and a science reporter exploring different subjects. But the things humans are inducing on our planet are a mix of all three. We’ve sliced up how we talk about our world by narrow disciplines. And we’re telling self-referential stories that don’t relate to the bigger question: “What is the fate of the planet and our species?”
My book is one-part science, one-part history, one-part economics, one-part geography, one-part politics, and one-part ethics. You need to think about all of these together because doing so forces you to look at how things are laid out geographically over time. It leads you to ask uncomfortable questions that aren’t part of these narrow, fractured narratives.
How does the “Invisible Hand of Economics” play a role in this topic?
The way some economists teach is that there is an, “invisible hand”that guides an economy and therefore everything will be good. And so, what you might call free-market individuals will grab on to that concept and say, “Keep the government out of it. Everything’s going to be fine because of the invisible hand.” There is this empty world theory where you can never have too much, you can never use too many resources. In many economic circles in Washington, D.C., they still talk about the free market and the invisible hand, and how everything’s just fine. But these downsides (i.e.,humanity’s ecological footprint and carrying capacity) need to be understood and can be mapped. You can’t manage what you don’t map. For example, with satellite data you can see the progression of deforestation.
How does climate change relate to this discussion?
How most of the population discusses climate change is problematic. Climate change is bad, twice as bad as people think it is. We only talk about half of the problem, like sea-level rise. We will adapt to sea-level rise. It’ll cost trillions of dollars, but we can move away from the seashore. What we don’t discuss is the absorption of carbon into the oceans, which causes acidification and annihilates plankton, and depletes oxygen on Earth. As I said, climate change is twice as bad as people think it is. But it is only one-tenth of the problem.
Can we determine Earth’s current lifespan?
Everybody wants to see the trend line—to know that in 2050 or 2100 or 2150 it’ll be “this”bad. The problem is all of these things are non-linear. We talk about unanticipated consequences because we don’t know how all of these systems interact. We are facing a precipitous collapse, and the only way to lower that probability is to work down our ecological debt.
How do we reach “carrying capacity”or reduce humanity’s ecological footprint?
The answer is women’s empowerment, women’s education, women’s integration into the workforce, and access to family planning technologies worldwide.Wherever that has happened, you see negative fertility. There are many things that need to be done to work off our growing, persistent, accumulating geography of waste—re-wild large tracts of the planet to bring back historic wildernesses. However, there are also key things that need to be done, such as reimagining the field of economics for an era of regrowth. Without new ideas, we cannot make the changes our society will need in order to save our planet and our species.
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