Articles | Volume 23, issue 3
https://doi.org/10.5194/bg-23-1199-2026
https://doi.org/10.5194/bg-23-1199-2026
Research article
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10 Feb 2026
Research article | Highlight paper |  | 10 Feb 2026

Future diversity and lifespan of metazoans under global warming and oxygen depletion

Kunio Kaiho

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Relationship between extinction magnitude and climate change during major marine and terrestrial animal crises
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Biogeosciences, 19, 3369–3380, https://doi.org/10.5194/bg-19-3369-2022,https://doi.org/10.5194/bg-19-3369-2022, 2022
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Cited articles

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Abe, Y., Abe-Ouch, A., Sleep, N. H., and Zahnle, K. J.: Habitable zone limits for dry planets, Astrobiol., 11, 443–460, 2011. 
Alexander, J. K., Mills, B. J. W., Merdith, A. S., Lenton, T. M., and Poulton, S. W.: Extreme variability in atmospheric oxygen levels in the late Precambrian, Sci. Adv., 8, eabm8191, https://doi.org/10.1126/sciadv.abm8191, 2022. 
Arauúo, M. B., Ferri-Yáñez, F., Bozinovic, F., Marquet, P. A., Valladares, F., and Chown, S. L.: Heat freezes niche evolution, Ecol. Lett., 16, 1206–1219, https://doi.org/10.1089/ast.2010.0545, 2013. 
Balter, V., Renaud, S., Girard, C., and Joachimski, M. M.: Record of climate-driven morphological changes in 376 Ma Devonian fossils, Geology, 36, 907–910, https://doi.org/10.1130/G24989A.1, 2008. 
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Kaiho uses historic records of diversification, starting with the early evolution of metazoans from cnidarian ancestors 700-500 mya, to predict the future of metazoan life on Earth. In analyzing past records of diversification, environmental drivers beyond the typically considered meteorite impacts and volcanism, such as variations in solar irradiance and inherent climatic fluctuations, are included as major additional drivers. These analyses lead to the proposal that metazoan life will likely go extinct on Earth within the next 700 million years. This extinction will be driven by long-term increases in physiological stress resulting from warming due to increasing solar radiation, as well as decreasing O2 and increasing CO2 concentrations in Earth’s atmosphere. While gradual changes in the Earth system will likely cause a decline in metazoan prevalence, the final thrust to extinction will likely require a global-scale geological or astronomical event.
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Life on Earth has changed over millions of years, shaped by shifting climates and natural disasters. This study explores how future environmental changes—like rising temperatures and reduced oxygen—may gradually reduce animal diversity on land and in the oceans. It predicts most complex animals could disappear in about 0.9 to 1 billion years, offering new insights into the far future of life on Earth.
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