Ideas and perspectives: Tipping into the unknown—the global consequences of biogeochemical system collapse 

Abstract. With Earth's tipping points being approached and already exceeded, human-driven disruptions of carbon (C), nitrogen (N), and phosphorus (P) cycles are forcing Earth’s biogeochemical systems toward irreversible collapse. Potential functional extinction of key regulatory processes—such as carbonate precipitation, denitrification, phosphorus burial, and methane oxidation—could lead to cascading failures, spread beyond biogeochemical domains and further contribute to destabilize planetary homeostasis. This study examines scenarios how these disruptions may interact across biogeochemical cycles, and how they might create reinforcing feedback loops that amplify climate change, accelerate ecosystem degradation, and alter atmospheric and oceanic chemistry.

Our scenarios envision carbon cycle disruptions (ocean acidification, soil carbon loss) weaken CO₂/CH₄ sequestration and boost emissions. Eutrophication and oxygen depletion threaten the nitrogen cycle, increasing nitrates and N₂O. Meanwhile, phosphorus release from hypoxic sediments sustains eutrophication and intensifies greenhouse gas emissions. Changing feedback loops may prevent the recovery of desirable biogeochemical conditions. A shift to anaerobic metabolism would favor sulfate reduction, methanogenesis, and ammonification, triggering biodiversity collapse, expanding anoxic zones, and allowing microbial extremophiles to dominate—echoing early anoxic Earth.

The loss of these regulatory functions would exacerbate global warming and push Earth’s ecosystems irreversibly into a “Hothouse Earth” regime. Immediate governance action is necessary to mitigate these risks by managing nutrient cycles, protecting carbon sinks, and incorporating biogeochemical feedbacks into climate policies. Without intervention, the accelerating extinction of key biogeochemical processes may render long-term climate protection unattainable.