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Justice in a World of Limits
Contribution to GTI Forum The Population Debate Revisited

Aaron Karp

I am among those who believe that population growth is a serious issue that does not receive the attention it deserves, and that this is largely the result of a taboo around discussing it. If we are to lift that taboo, which is a prerequisite for taking action at scale, we should first listen to the counterarguments and then address them as completely as possible. One in particular that has been expressed in this discussion is that efforts to reduce further population expansion distract us from real issues, like lowering consumption per person in wealthy countries. Making a clear case for the significant role of population growth in our existential problems should speak to this argument. Ian Lowe’s nuanced essay contributes to that case, and I wanted to offer additional perspectives and data I find compelling.

Some basic ideas shape my view. One is that regardless of the form of ecological overshoot we focus on—climate change, biodiversity loss, topsoil erosion, freshwater depletion, etc.—the unifying cause is the scale of human consumption, which currently stretches beyond the limits of our finite planet. Total consumption is the product of consumption per person and the number of people, and unless the contribution of the latter is truly negligible, our crises are too dire to ignore it. The population has been growing by one billion people about every twelve years for the last five decades, even as the growth rate has dropped. I have a difficult time thinking of that trend as insignificant or that it is reasonable to expect it to stabilize on its own with no large ecological consequences as expansion continues. It is also clear that we need to establish a non-growing economy to have any hope of respecting ecological limits, but we cannot maintain it with a growing population.

Scientific perspectives are also compelling. In November 2019, over 11,000 scientists from around the world declared that Earth faces a climate emergency and asserted the need to stabilize the human population as one of six “critical” steps to address the crisis. As Ian Lowe noted, the Intergovernmental Panel on Climate Change (IPCC) is clear on the main drivers of increasing emissions over time: economic and population growth. The latest mitigation report observes that “[t]echnological improvements...have shown [a] persistent pattern over the last few decades but gains have been outpaced by increases in affluence (GDP per capita) and population growth, leading to continued emissions growth.” While economic growth was responsible for 2.3 percent annual emissions growth from fossil fuel combustion over the past decade, population growth increased emissions by 1.2 percent annually; a factor with half the impact of affluence is not insignificant. Emissions before the year 2000 were driven in more equal measure by both factors and at times even led by population growth.

When breaking down our mitigation options, the report says, “The key gap in knowledge therefore is how these drivers of emissions can be mitigated by demand management, alternative economic models, population control and rapid technological transition.” But though the IPCC acknowledges the significant role of population growth in the increase of emissions over time, efforts to curb it are almost never explicitly discussed in the report. Many in the climate science community therefore contribute to the taboo around addressing the issue. That is a serious problem when the report’s authors identify “high levels of global population growth” as one of the “high mitigation challenges” that “may render modelled pathways that limit warming to 2°C (> 67%) or lower infeasible.”

For those who understandably focus on the need for immediate emissions reductions, let us recognize that while addressing population growth cannot solve climate change, leaving it unchecked could push the required mitigation rate much higher and perhaps out of reach. We are not going to reduce emissions by achieving a gradual decrease in population over the next few years. But by working to stabilize the population, we can greatly diminish the eventual expansion, and in so doing give other necessary solutions like renewable energy supply increases and consumption reductions a chance to reduce emissions as quickly as we need.

Learning to Have Difficult Conversations about Justice on a Finite Planet

Despite efforts to establish population growth as a priority for ecological activism, many thoughtful people remain wary of the idea of addressing it. The overriding concern is that any attempt to stabilize the population is almost certain to lead to injustice. That view may be less open to change solely in response to evidence about population’s role in our crises; rather, it calls for a deeper discussion of ethics. Only a few thoughts can be provided in this short essay.

Some see the potential for injustice only on one side. However, moral issues arise not only when we consider limiting population growth, but also when we don’t. The well-being of future generations and non-human life is dependent on how much finite ecological space we appropriate today, and population size is a key determinant. Is it more moral to let populations grow?

Others fear that discussing the ecological impacts of population growth inevitably emboldens eco-fascist ideologues. But if we believe there can be no responsible conversation about population size and therefore remain silent, we create that reality by completely ceding the topic to malicious actors.

Moral issues abound when considering a transition from seemingly limitless societies to ones that respect ecological limits. Population is just one (crucial) issue. We must learn how to have productive discussions about what justice looks like on a planet in overshoot, and nuance is a critical component.

We have yet to fully reckon with the fact that human rights have costs. This idea may be overlooked in societies with the highest fossil fuel use because these fuels empower us to completely reshape our surroundings, quickly travel any distance, and allow an individual to easily perform the equivalent of thousands of hours of human labor. We cannot necessarily expect the same suite of rights we are accustomed to in a society with cheap and abundant energy in one without these advantages. Many people believe in the power of technology to solve overshoot while improving well-being for all. But what if that view is too optimistic? What if, for example, renewables are unable to provide the same scale of energy use as fossil fuels?

We often underestimate the extent to which society must change in order to become sustainable and the significant limits that we will need to place on our consumption at least during the transition, if not on a permanent basis. This, too, will be called unjust. All efforts to create rapid and deep change carry risks of causing hardship and stoking authoritarianism. The longer that we delay this transition, the less avoidable these risks become. Many aspects of the transition will inevitably bring about accusations of injustice, but we will need to discuss them and take action anyway. We must be willing to explore new notions of justice and rights compatible with a limited world.

The overconsumption that drives today’s ecological crises arises from multiple sources, and reining it in requires us to address many of those sources. Several approaches are therefore necessary and insufficient, including implementing more efficient technologies, redesigning our societies to deliver services with less underlying energy and resource use, organizing campaigns to shift our culture away from consumerism and towards an embrace of sufficiency, transforming our extremely unequal and consumption-maximizing economy into one focused on equity and meeting needs, and stabilizing the size of the human population. Some people will of course focus on one of these factors more than the rest. That shouldn’t be the basis of unnecessary division among the too few working on these issues. The stakes are too high to not fairly consider the role of each potential source of the existential issues facing us.

We chip away at the taboos that impede the path to a sustainable society as we commit to analyzing and discussing our problems with an open mind and assuming positive intent by others who also want to construct that path. This conversation is a step in that direction.

Aaron Karp
Aaron Karp is an activist writing a book about why our ecological crises demand economic and cultural transformation and how the climate movement can lay the groundwork for these changes. He writes at

Cite as Aaron Karp, "Justice in a World of Limits," contribution to GTI Forum "The Population Debate Revisited," Great Transition Initiative (August 2022),

As an initiative for collectively understanding and shaping the global future, GTI welcomes diverse ideas. Thus, the opinions expressed in our publications do not necessarily reflect the views of GTI or the Tellus Institute.

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