Coevolution of primitive methane cycling ecosystems and early Earth atmosphere and climate

TL;DR

This study uses a novel ecosystem-planetary model to explore how primitive methane-cycling microbial ecosystems influenced early Earth's atmosphere and climate, revealing their low productivity but significant impact on climate stability and atmospheric composition.

Contribution

The paper introduces a new model to analyze early methane-cycling ecosystems and their role in Earth's atmospheric and climatic evolution before photosynthesis.

Findings

Primitive methane ecosystems had low productivity.

Methanogenic metabolisms significantly warmed the early Earth.

Low CO:CH4 ratio is a signature of simple methane ecosystems.

Abstract

The history of the Earth has been marked by major ecological transitions, driven by metabolic innovation, that radically reshaped the composition of the oceans and atmosphere. The nature and magnitude of the earliest transitions, hundreds of million years before photosynthesis evolved, remain poorly understood. Using a novel ecosystem-planetary model, we find that pre-photosynthetic methane-cycling microbial ecosystems are much less productive than previously thought. In spite of their low productivity, the evolution of methanogenic metabolisms strongly modifies the atmospheric composition, leading to a warmer but less resilient climate. As the abiotic carbon cycle responds, further metabolic evolution (anaerobic methanotrophy) may feed back to the atmosphere and destabilize the climate, triggering a transient global glaciation. Although early metabolic evolution may cause strong climatic instability, a low CO:CH4 atmospheric ratio emerges as a robust signature of simple methane-cycling ecosystems on a globally reduced planet such as the late Hadean/early Archean Earth.