Karlsruhe Institute Of Technology Researchers Stay The Carbon Sink Is Shrinking Due To Land Use Changes

Carbon sinks on the land surface can mitigate the greenhouse effect. Scientists at the Karlsruhe Institute of Technology (KIT) and other research institutions have brought together various data sources and determined that the majority of all European carbon storage occurs through aboveground biomass in Eastern Europe. However, this carbon sink has declined, mainly due to changes in land use. The researchers report in Communications Earth & Environment . ( DOI: 10.1038/s43247-023-00893-4 )

Forests can bind large amounts of carbon on the land surface and thus make a decisive contribution to reducing net greenhouse gas emissions. For some areas, however, there is a lack of comprehensive inventories. In Eastern Europe in particular, there is only a sparse network of measuring stations, so that little was known about the carbon fluxes there and their drivers. “The Eastern European forests in particular hold great potential for a long-term carbon sink,” says Karina Winkler from the Institute for Meteorology and Climate Research – Atmospheric Environmental Research (IMK-IFU), the Alpine Campus of KIT in Garmisch-Partenkirchen. “As a result of political upheavals, however, Eastern Europe is characterized by major changes in land use. In addition, climate change is having an increasing impact on the forests there.

The studied area covers 13 countries

Researchers from the Land Use Change & Climate group at IMK-IFU, together with scientists from other European research institutions, have now recalculated the carbon stores in Eastern Europe. The examined area extends over 13 countries – from Poland in the west to the Russian Ural Mountains in the east, from Estonia in the north to Romania in the south. For the calculation, the researchers brought together various data sources: models, satellite-based biomass estimates, forest inventories and national statistics.

“We derived from the datasets that Eastern Europe is responsible for the majority of the overall European carbon storage from 2010 to 2019,” reports Winkler. The comparison of the carbon balance has shown that the land surface of Eastern Europe binds around 410 million tons of carbon in biomass per year. This corresponds to about 78 percent of the carbon sink of the whole of Europe. The largest carbon reservoirs are mainly found in the border area between Ukraine, Belarus and Russia, in the southern Ural Mountains and on the Kola Peninsula.

Logging has the greatest impact on the carbon sink in Eastern Europe

However, the data also show that carbon uptake in Eastern Europe has by no means been constant over time, but has been declining: the Eastern European carbon sink is shrinking. To determine the causes, the researchers compared the trends in carbon change with land-use factors, i.e. land conversion for agriculture, timber extraction and share of abandoned agricultural land, and with environmental factors, namely temperature, precipitation, soil moisture and carbon dioxide (CO 2 ) and nitrogen concentration in the atmosphere.

The study has shown that environmental influences, such as changes in soil moisture, have a significant impact on the overall carbon budget, but that the spatial patterns of the carbon sink in Eastern Europe can be explained primarily by changes in land use. Accordingly, timber extraction has the greatest impact on the land-based carbon sink in Eastern Europe from 2010 to 2019. The data analysis indicates that an increase in timber extraction in western Russia and a reduction in forest growth on former agricultural land led to the carbon sink in Eastern Europe declined between 2010 and 2019.

According to the researchers, it is now necessary to forecast how Eastern European forests and their important carbon reservoirs will develop in the future under the influence of changes in land use and climate change. However, the increasing number of extreme weather events and reduced water availability already gave reason to fear that the Eastern European carbon sink will continue to shrink in the future.