Over the course of the year, the earth absorbs carbon dioxide and releases it again – in summer mainly through the metabolism of plants, in winter through the decomposition of biomass. But due to global warming, this natural ebb and flow, the “breath” of the earth, is becoming more and more extreme. According to a new meta-study, the earth is now breathing much faster, especially in northern latitudes. This, in turn, could further drive climate change.
Plants and soils act like the lungs of the earth: During the growing season in summer, plants absorb carbon dioxide from the air through photosynthesis and convert it into biomass. In winter, some of this carbon is released again, for example through the decomposition of dead plant material in the soil. These natural rhythms are a central part of the global carbon cycle.
Carbon cycle in turbo mode
However, the “breathing in and out” of nature is significantly increased by climate change. These seasonal CO levels are particularly extreme2-Fluctuations in arctic and boreal regions, as measured data from the past decades show. In order to better understand these trends and their causes, researchers led by Zhihua Liu from the University of Montana have now conducted a meta-study in which they compiled and systematically evaluated the results of numerous previous studies.
The result: Since the 1960s, seasonal CO2-Fluctuations in the area between the 50th and 65th parallels increased by around 50 percent. For example, Scandinavia, Siberia and the Urals are affected. But what is causing this change? “We have provided convincing evidence that more active plant growth is the main reason why the carbon cycle occurs faster in the northern regions,” explains co-author Wolfgang Buermann from the University of Augsburg.
Rising temperatures in these previously rather cool northern latitudes are extending the growing time and making plants more productive. The higher carbon dioxide content in the air acts like additional fertilization. Increased productivity accelerates CO2-Absorption in summer, but at the same time is accompanied by increased breathability in winter. As a result, global warming is shifting the balance between the absorption and release of carbon dioxide. “Scientists have been observing this trend for some time, but by combining data from multiple studies we were able to better understand the specific processes driving this change,” says Buermann.
Dangerous feedbacks
However, this “breathing trend” is problematic because it could further fuel global warming. The research team suspects that respiration could eventually outpace plant productivity, which – together with an increase in forest fires and the thawing of permafrost – could lead to higher greenhouse gas emissions from northern ecosystems and further increase global warming. “Arctic ecosystems are changing faster than any other on Earth, and the feedback effects can be enormous – making realistic CO reduction goals2emissions could seriously endanger,” emphasizes Buermann.
Source: University of Augsburg; Specialist article: Nature Reviews Earth & Environment, doi: 10.1038/s43017-024-00600-7