Complex life on Earth may last 500 million years longer than expected
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- Jacob Haqq-Misra and Eric Wolf ran simulations suggesting Earth's plant life could persist past 1.8 billion years from now — roughly 500 million years longer than the previous 1.35-billion-year estimate for when atmospheric CO2 would drop below the 10 ppm starvation threshold.
- The key difference in the model was accounting for crassulacean acid metabolism (CAM) photosynthesis, used by cacti and pineapples, which harvests CO2 more efficiently and could push the survival limit down to 1 part per million.
- Jacob Haqq-Misra of Blue Marble Space said the results show "life on Earth can do a lot more than we thought," and argued evolution could push survival even further as organisms slowly adapt to a brightening sun.
- Edward Schwieterman of UC Riverside said the models place Earth "closer to the beginning" of the complex biosphere rather than the middle or end, directly contradicting more pessimistic prior scenarios.
- Schwieterman added that the extended habitability window has a practical payoff for astronomy: if Earth is representative, "future Earth" analogs around aging sun-like stars could potentially be observed within the next two decades for biosignature detection.
- The CO2 thermostat mechanism — in which rising temperatures draw atmospheric carbon into rocks — means CO2 levels, rather than temperature, become the ultimate bottleneck for plant survival as the sun expands toward red giant phase in roughly 5 billion years.
Why it matters: If Earth is representative of habitable worlds, the 500-million-year extension of complex life's habitability window widens the time range over which astronomers could detect biosignatures around aging sun-like stars — Schwieterman noted such 'future Earth' analogs may be observable within the next two decades, making this both a longevity finding for Earth and a detection-target finding for exoplanet science.
