It’s Not Just Global Warming Destroying Forests—It’s About Moisture

Soil Moisture Determines Nitrogen Emissions

For years, the scientific community was convinced that climate change would lead to increased nitrogen emissions into the atmosphere. Consequently, this was expected to fuel global warming, deepen environmental pollution, and weaken forests by stripping them of a key nutrient essential for tree growth.

However, the latest research challenges this scenario. Scientists have shown that under certain conditions, a rise in temperature can actually lead to a reduction in nitrogen emissions, particularly in arid regions. This discovery shifts our current understanding of the relationship between global warming and forest health.

Testing Temperatures in the Field

An international team of researchers, including experts from the Institute of Applied Ecology and the University of California, conducted a large-scale simulation. They raised the temperature of a soil fragment by 2 degrees Celsius—exactly the average temperature increase predicted by mid-century forecasts.

Crucially, the experiment was not conducted in a laboratory. The research took place in a natural environment where the actual process of climate change is occurring. These field conditions were decisive for the credibility of the results.

Nitrogen Decrease, Not Increase

According to the article published in the scientific journal PNAS, warming a section of the forest resulted in a 19% drop in nitric oxide emissions. A similar trend was observed for nitrous oxide, a potent greenhouse gas, which decreased by 16%.

“These results flip our previous assumptions on their head. We always thought that warming would accelerate microbial processes and release more nitrogen. That might be true in controlled laboratory settings. However, in the field, especially in dry conditions, microorganisms slow down because the soils dry out,”

– said Professor Pete Homyak for the University of California news portal.

This has real implications for how we understand the complex dynamics of global warming and forest health.

Nitrogen Governs a Forest’s Ability to Store Carbon

Forests are among the most important natural ecosystems on Earth. They absorb significantly more carbon dioxide than they emit, playing a vital role in air purification. However, to fulfill this function effectively, trees need nitrogen—one of the key elements required for growth.

If the warming process accelerates nitrogen loss from the soil, the forest’s capacity to store carbon weakens as a result. In this context, the findings from the researchers are significant, though their application has its limits when assessing overall global warming and forest health.

Warming Acts Differently in Dry vs. Wet Forests

In forests where annual rainfall does not exceed 1,000 millimeters, the heating of the Earth leads to soil desiccation and reduced gas emissions. However, in wetter regions, the situation is different. There, rising temperatures accelerate nitrogen loss—exactly as earlier laboratory studies suggested.

“This is a very important clarification. Climate models that ignore soil moisture are missing a key piece of the story,”

– Homyak added.

Dry Soils Limit Nitrogen Loss

While the research provides valuable data, it does not fully explain all the mechanisms shaping the impact of global warming and forest health. Even where nitrogen remains in dry soil, it does not necessarily translate into faster tree growth. According to the researchers, persistent drought plays the deciding role.

The results of this study are not a reason for climate optimism, but they serve as an important lesson for science. Future analyses must account for the simultaneous impact of temperature and moisture on ecosystems to obtain a fuller and more reliable picture of the ongoing changes.

Read this article in Polish: To nie globalne ocieplenie niszczy lasy. Chodzi o wilgoć