Tropical Soils May Accelerate Climate Change by Releasing Massive Amounts of CO₂, New Study Reveals
For decades, tropical rainforests have been celebrated as formidable carbon sinks that significantly mitigate climate change by absorbing atmospheric carbon dioxide. However, groundbreaking research led by the U.S. Forest Service, in close collaboration with Chapman University, challenges this well-established narrative. Published recently in Nature Communications, the study reveals that as global temperatures rise, the soils of tropical forests may switch roles—from carbon sinks to substantial carbon sources—potentially accelerating climate change through an intensified positive feedback loop.
This revelation derives from unprecedented experimental work focusing on soil respiration—the process through which soil organisms release CO₂ as they metabolize organic material. The study deployed state-of-the-art infrared heating technology to simulate a future warming scenario by raising atmospheric temperatures by 4 degrees Celsius within a Puerto Rican tropical rainforest. The results uncovered an astonishing increase in soil respiration, with CO₂ emissions elevated between 42% and 204% in warmed plots, representing some of the highest soil respiration rates ever recorded in any terrestrial ecosystem worldwide.
The implications of such a dramatic increase in CO₂ release from tropical soils are profound. Tropical forests collectively cover only about 7% of the Earth’s land surface, yet their soils store immense quantities of carbon—more than the amount held in the atmosphere and all terrestrial vegetation combined. If warming continues to drive these soils to emit CO₂ instead of sequestering it, the global carbon budget could be severely impacted, undermining current climate change mitigation strategies reliant on forest preservation and carbon sequestration.
Central to the study’s findings is the role of soil microbial communities. The researchers demonstrated that microbes—rather than tree roots—are the primary drivers of this enhanced respiration. These microscopic organisms accelerate their metabolic rates in response to warmer temperatures, breaking down organic matter more rapidly and emitting higher volumes of carbon dioxide in the process. This microbial sensitivity to heat not only transforms the soil from a carbon reservoir into a carbon emitter but also poses challenges to modeling future climate scenarios accurately.
This investigation, part of the Tropical Responses to Altered Climate Experiment (TRACE), marks the first time experimental warming has been applied in a tropical rainforest context at this scale. The project integrates faculty expertise and undergraduate research participation from Chapman University, highlighting the importance of collaborative, hands-on scientific inquiry. By directly manipulating the thermal environment of a complex, biodiverse ecosystem, scientists gleaned critical insights into soil-atmosphere carbon dynamics under warming conditions projected for the latter half of this century.
The discovery confronts prior assumptions about tropical ecosystems’ resilience amid climate change. Historically, models suggested tropical forests would remain carbon sinks, owing to high productivity rates and robust plant growth offsetting carbon losses. Yet the newfound primacy of soil microbes in CO₂ emissions forces a reevaluation of tropical carbon budgets, necessitating adjustment of climate projections globally. This biological feedback loop implies warming may not just be a linear driver but an accelerating force in Earth’s climate system.
Moreover, the study emphasizes the urgency of incorporating belowground processes into ecological and climate models. While aboveground vegetation dynamics have been extensively studied, the contribution of soil biota to carbon cycling has often been underestimated or simplified. This research provides strong empirical evidence that subsurface biological activity possesses the potential to drastically reshape atmospheric carbon levels, complicating the narrative of tropical ecosystems as unequivocal climate allies.
Beyond theoretical and modeling considerations, the practical ramifications of this feedback loop are concerning. Rising atmospheric CO₂ levels from tropical soil respiration could exacerbate global warming’s consequences. Accelerated warming may amplify sea-level rise, intensify severe weather patterns, threaten biodiversity, and disrupt critical ecosystem services—including agriculture and water supplies—ultimately jeopardizing food security and public health on a global scale.
Dr. Christine Sierra O’Connell, an assistant professor of biological sciences at Chapman University and a lead author of the study, articulated the gravity of these findings: “We are witnessing a troubling shift. The very systems we rely on to stabilize the climate may now be pushing us in the opposite direction.” Her perspective underscores a crucial turning point in climate science, where revisions in ecosystem feedback understanding are imperative for policymaking and adaptive strategies.
The multi-institutional research team drew expertise from several prestigious agencies, including the USDA Forest Service, U.S. Geological Survey, University of Vermont, Morton Arboretum, and Michigan Technological University. Their collective efforts underscore the value of interdisciplinary collaboration in tackling complex environmental challenges. This research not only enriches scientific knowledge but also provides critical data necessary for international climate assessments and the formulation of effective environmental policy.
In addition to its profound climatic significance, the study enhances our fundamental understanding of tropical rainforest ecology. By revealing how microbial processes respond dynamically to warming, the research contributes to a more nuanced appreciation of ecosystem functional responses, biogeochemical cycles, and the delicate balance that governs carbon fluxes within Earth’s richest biomes.
As global temperature trajectories remain on an upward trend, this pioneering research drives home the urgency of decarbonization and innovative climate interventions. It calls for intensified monitoring of tropical soil carbon pools, the integration of belowground processes in Earth system models, and stringent efforts to mitigate anthropogenic greenhouse gas emissions before these natural amplifiers overwhelm mitigation gains.
Subject of Research: Soil respiration response to warming in tropical rainforests and its impact on carbon cycling and climate feedbacks.
Article Title: Warming induces unexpectedly high soil respiration in a wet tropical forest
News Publication Date: 16-Sep-2025
Web References: DOI: 10.1038/s41467-025-62065-6
Keywords: Climatology, Forests, Tropical soil carbon cycling, Soil respiration, Climate feedback loops, Tropical rainforests, Microbial metabolism, Global warming, Carbon emissions, Ecosystem carbon dynamics
