Human activity causes carbon loss in deserts

Some human-induced disturbances cause significant carbon loss in the soil of hyper-arid environments, a Chinese study claims. Among the most impactful activities even some practices considered “sustainable” such as seasonal harvesting and irrigation

by Matteo Cavallito

The impact of human activities on hyper-arid deserts results in significant carbon loss. This phenomenon highlights the weight of the direct effects not only of typically critical events, such as fires, but also of various practices, including—surprisingly—some actions generally considered sustainable. This was revealed in a recent study by the Xinjiang Institute of Ecology and Geography of the Chinese Academy of Sciences.

“Anthropogenic disturbance is an important driver factor of global change, greatly affects the soil organic carbon (SOC) storage,” says the research published in the journal Global Change Biology. “However, the long-term impacts of anthropogenic disturbance on SOC stability in hyperarid deserts remain poorly understood.” To uncover these dynamics, the authors conducted an experiment over a 16-year period.

Up to 13% of carbon is lost in deserts

During the study, the authors continue, “we evaluated SOC dynamics in hyper-arid desert ecosystems under five treatments: no-disturbance (CK), spring harvest, autumn harvest, fire, and irrigation (simulating artificial flooding).” The analyses covered six different soil layers (0–5 cm, 5–15, 15–30, 30–60, 60–100, 100–150).

The research revealed that the impact of human activities mainly affected particulate carbon (the carbon matter found in organic material with a diameter of between approximately 0.5 and 2 mm) in the topsoil (0-15 cm) and carbon of microbial and plant origin in the subsoil (100-150 cm).

“With the increase of soil depth, the concentrations of SOC, POC, microbial-derived C, and plant-derived C continuously decreased,” the study states. Specifically, human interference with the environment has caused a 13.2% decrease in the element, with declines in particulate matter and mineral-associated matter of 16.3% and 41.1%, respectively.

Harvesting and irrigation had the greatest impact

Among the most disruptive actions, autumn harvesting and irrigation had the most serious effects, leading to losses of 20-21% compared to unaffected areas. Topsoil (0-15 cm) was particularly vulnerable, with carbon loss caused by reduced plant inputs and disruption of interactions between microbes and minerals.

“Mechanistically, plant-derived C depletion correlated with reduced plant C inputs, while microbial-derived C decline was linked to altered mineral properties (exchangeable Ca, noncrystalline oxides and free oxides) and microbial properties (enzymes, microbial biomass, fungi and bacteria),” explains the research.

The disturbances caused the ratio of particulate carbon to mineral carbon to increase by 46.2%. The higher incidence of the latter, in other words, signals “a shift toward less stable carbon pools,” explains a statement from the Chinese Academy of Sciences. Changes in microbial communities, including a decline in fungi and an increase in bacteria, also contributed to the destabilization of the element.

A delicate balance between human activities and the ecosystem

Some discoveries, therefore, may seem almost paradoxical, highlighting the surprising impact of certain interventions, starting with irrigation. “Our findings reveal that even seemingly sustainable practices, like seasonal harvesting, can drive hyper-arid deserts toward irreversible carbon depletion,” explained Akash Tariq, lead author of the study.

For this reason, he added, “Protecting these ecosystems requires a balance between local livelihoods and long-term carbon conservation strategies.”

In short, the research highlighted the delicate balance between human activities and ecosystem health in arid regions. It therefore emphasized the urgent need to adopt sustainable practices. In other words, “to integrate subsurface carbon dynamics into desert ecosystem management strategies,” the researchers concluded.