Soil Moisture Controls How Well Earth Stores Carbon

A new study finds that water availability, rather than temperature or minerals, determines how effectively soil holds carbon.

Updated on Nov. 3, 2026 in Environmental

Bold flat-color vector editorial illustration of layered ochre and umber soil with an upright soil core and beads of water, evoking moisture as the key to carbon storage. — Researchers found that soil moisture, not temperature or mineral content, controls how effectively Earth's soil stores carbon, in a study of 400 samples from 34 sites. AI Illustration. Upload story photo >

Researchers found that moisture, not temperature or mineral content, controls how well soil stores carbon. The study examined 400 soil core samples from 34 sites collected by the National Ecological Observatory Network and was published in the Proceedings of the National Academy of Sciences.

Why it matters

Soil is the Earth's second-biggest carbon storage locker after the ocean, so understanding what controls its carbon retention matters for the global carbon cycle. The findings suggest that a warmer, drier climate could alter how soil carbon persists, with implications for ecosystem services.

The analysis drew on 400 soil core samples from 34 sites, with the sites divided into humid and arid climate systems that showed different organic carbon decomposition rates. The study does not quantify how much carbon persistence shifts with changing moisture levels.

The players

Jeff Hatten

Jeff Hatten is a researcher at Oregon State University who led the study on soil moisture and carbon storage.

National Ecological Observatory Network

The National Ecological Observatory Network is a National Science Foundation-funded continental-scale monitoring platform that collected the soil samples used in the study.

The details

Researchers performed radiocarbon and molecular composition analyses on the core samples to examine how carbon abundance and persistence relate to moisture availability. Their initial hypothesis centered on soil minerals, but the data pointed instead to water as the controlling factor.

November 3, 2026: Article published on the study's findings

Big Picture

The study challenges the prior assumption that soil minerals drive carbon persistence, shifting attention toward water availability as the controlling variable. Earlier work had suggested wet-ecosystem soil carbon was most vulnerable to temperature shifts, and this study complicates that picture by pointing to moisture.

For anyone following climate or land management, the study suggests soil water conditions may matter more than mineral composition when assessing how much carbon soil can retain. The source does not indicate specific practical steps readers should take.

The takeaway

Soil water availability appears to be a central lever in how much carbon the land retains, which makes moisture trends an important variable to watch alongside temperature. As climate patterns shift across the United States, this finding offers a clearer lens on where soil carbon may be most at risk.