The silent threat of methane to ecosystems: Insights from mechanistic modelling

TL;DR

The paper develops a methane–resource–consumer–detritus model to investigate how rising methane ($M$) influences trophic dynamics in aquatic and terrestrial ecosystems, incorporating temperature-dependent growth and methane toxicity. Through multiscale analysis, including nondimensionalization and geometric singular perturbation theory, it dissects fast methane dynamics from slower ecological processes, revealing fast approach to methane solubility, intermediate predator–prey interactions with multiple equilibria, and slow detritus feedback that shapes long-term outcomes. The results show a nuanced, nonmonotonic influence of methane: low-to-moderate methane can temporarily boost primary producers and consumers, while higher levels reduce coexistence, destabilize dynamics, and push the system toward regime shifts or extinction; rapid methane accumulation prolongs transients near extinction states. These findings underscore methane’s potential to drive ecosystem collapses and heightened temperature sensitivity, underscoring the urgency of understanding methane’s ecological role to inform mitigation under climate change.

Abstract

Over the past century, atmospheric methane levels have nearly doubled, posing a significant threat to ecosystems. Despite this, studies on its direct impact on species interactions are lacking. Although bioaccumulation theory explains the effects of contaminants in trophic levels, it is inadequate for gaseous pollutants such as methane. This study aims to bridge the gap by developing a methane-population-detritus model to investigate ecological impacts in aquatic and terrestrial ecosystems. Our findings show that low methane concentrations can enhance species growth, while moderate accumulation may induce sub-lethal effects over time. Elevated methane levels, however, lead to ecosystem collapse. Furthermore, prolonged exposure to the gas increases the sensitivity of species towards rising temperatures. Multiscale analysis reveals that rapid methane accumulation leads to long transients near the extinction states. We argue that high emission rates can push the system towards a critical threshold, where the ecosystem shifts to an alternative stable state characterized by elevated methane concentrations. This work highlights the urgent need for a better understanding of the fatal role of methane in ecosystems for developing strategies to mitigate its effects amid climate change.

Figures (14)

• Figure 1: Global methane emission from major source categories from 2010-2019 adapted from MethaneBudget.
• Figure 2: Schematic diagram of the model.
• Figure 3: Mechanism representing the growth of algae due to methane oxidation.
• Figure 4: (a) The critical manifold $C^1$ in the $muv$ space is shown in red for a fixed $w_0$, with the trajectory converging toward it shown in blue. Triple arrows indicate the fast flow toward $C^1$. (b) The corresponding rapid rise in methane concentration ($m$) in water is shown with respect to the fast timescale $t$.
• Figure 5: The variation in the density of algae and daphnia for different values of temperature and external input rate of methane.

Theorems & Definitions (10)

• Theorem B.1
• proof
• Theorem B.2
• proof
• Theorem B.3
• proof
• Theorem B.4
• proof
• Remark B.5
• proof