High-altitude areas with extensive permafrost are crucial for the global carbon cycle because their soils store huge reserves of organic carbonHowever, these vital supplies are currently at risk. double pressure: dramatic climate warming and intensive land management, especially through livestock grazing. In these regions, surface air temperatures are rising more than twice the global average, and this trend is expected to continue until the end of the century. Until recently, however, it was not entirely clear how these factors interacted and what their ultimate impact on soil carbon stocks would be. New research is providing surprising insights into this complex interaction.

Climate change and the unexpected potential for carbon sequestration

Although it has often been assumed that warming in permafrost regions will lead to accelerated soil carbon decomposition, thereby offsetting any potential gains from increased vegetation productivity, a recent study that integrated extensive soil carbon observations, incubation experiments, and a three-pole soil carbon model provides a different perspective. Soils in these high-altitude permafrost regions are projected to continue to function as a carbon sink until 2060They are expected to absorb 261 to 292 teragrams of carbon (TgC) at a depth of one meter, depending on the warming scenario.

However, it is important to note that more than half of these additions (63–70 %) are expected in the active, readily degradable carbon poolThis suggests an increased vulnerability of soil carbon stocks to extreme weather events and disturbances such as grazing. Although permafrost thawing processes (thermokarst) can release carbon (estimated at 160 TgC, offsetting about 55 Tg of warming-induced gains), the study suggests that these processes may not reverse the overall trend of increasing soil carbon stocks in a warmer future. The research also highlights that for accurate predictions it is crucial to take into account the combined effects of multiple climate factors, such as temperature and precipitation, which can stimulate plant productivity and thus contribute to soil carbon accumulation.

The dominant role of land management: The surprise of grazing

In addition to climate change, Land management, especially livestock grazing, has a profound impact on soil carbon through feeding and trampling. The study found that Grazing, not climate change, plays dominant role in weakening soil carbon sequestrationThe impact of grazing varies surprisingly depending on soil texture and grazing intensity:

• IN soils with a coarser texture (clay content < 22 %) the total carbon stock decreased significantly with increasing grazing intensity.
• IN fine-textured soils (clay content > 22 %) carbon stocks initially increased at medium grazing intensity (up to about 50 % intensity) before they began to decline. This finding is consistent with the “grazing optimization hypothesis,” which suggests that moderate grazing can increase plant productivity and thus soil carbon supply.

Synergistic effects and the way forward

The key finding is that Soil carbon losses caused by grazing largely compensate for the accumulation caused by warmingThis means that while climate change theoretically contributes to carbon sequestration, current grazing levels – and even a shift to a more sustainable “forage-livestock balance” – could almost completely offset these climate-related gains.

Projections show that under “current grazing policies” soil carbon stocks are expected to decrease by 259 to 287 TgC by 2060. Even under the “forage-livestock balance” scenario, the loss is mitigated (to 209-238 TgC), but it is still significant. The combined effect of grazing and warming could further exacerbate the carbon loss. As a result, the net carbon sequestration in soils in these regions could be reduced to minimum 0.06 TgC per year under current grazing practices. However, a shift to a more sustainable “feed-livestock balance” would increase net carbon absorption per 1.12 TgC per year, which is more than three times the current scenario.

To maintain soil carbon sequestration in alpine areas, critically important to optimize grazingAlthough complete elimination of grazing could lead to significant carbon sequestration (approximately 5.51 TgC per year by 2060), it would disrupt local livelihoods. The study therefore highlights the need sustainable management strategies such as rotational grazing or regular fencing, which can not only prevent soil carbon depletion but also support local communities. It is also crucial incorporate grazing impacts into Earth system models, which are used for climate change forecasts. JRi

Study  was published in the journal Nature