Vol. 5 No. 1 (2020)

We know how many people the earth can support

Christopher Tucker
American Geographical Society
This image of the cover of this issue of The Journal of Population and Sustainability has the title in block letters on a grey-green background.

Published 2020-12-01


  • carrying capacity,
  • ecological debt,
  • runaway population growth,
  • women’s empowerment

How to Cite

Tucker, Christopher. 2020. “We Know How Many People the Earth Can Support”. The Journal of Population and Sustainability 5 (1):77–85. https://doi.org/10.3197/jps.2020.5.1.77.


A quarter century after Joel Cohen asked the essential question “How Many People can the Earth Support?”, this article offers an answer, based on new science and geographical analysis, and asserts that we have long ago exceeded our planet’s long term ecological carrying capacity that optimistically can only support 3 billion modern industrialized humans. While agreeing that strategies based on reducing consumption are sorely needed to live within our planet’s carrying capacity, the impending explosion of the global middle class promises to render consumption-only strategies inadequate, in the face of runaway population growth and the accumulation of massive ecological debt. Noting recent studies that project global population to begin to decrease in 2064 after peaking at 9.7B, it is asked why we don’t act now to accelerate this already inevitable trend with enhanced investment in women’s empowerment, education, and access to family planning technologies. This paper calls for a goal of achieving 1.5 total fertility rate (TFR) by 2030 to bend the global population curve, begin relieving the ecological burden humanity has foisted on our planet, and to decrease human population as we approach 2100 to something closer to the long term ecological carrying capacity of our planet.


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