Historical Land Use Has a Major Role on Carbon Cycling

Understanding carbon cycling is important for better understanding climate change and future climate predictions. Now, scientists have discovered that historical land use has a major role on carbon cycling, which means we may need to look to the past to predict the future.

Environmental monitoring programs over the past 30 years have seen an increase in the organic carbon concentration in many Swedish lakes. This increase has consequences for water quality and for the functioning of aquatic ecosystems. The hypothesis for this increase include recovery from acidification, modern changes in land use and climate change.  However, these hypotheses don't include insights into long-term changes.

Intrigued by these changes, scientists took a closer look at these lakes. They analyzed lake sediments, and took a peak back in time.

"For analyses of sediment records from a number of lakes across central Sweden, we find that organic carbon concentrations further back in time-as much as 10,000 years ago-were at higher levels comparable to those we measure today," said Carsten Meyer-Jacob, one of the researchers, in a news release. "However, in response to forest grazing of livestock and summer forest farming that accelerated during the 1400 and 1500s the levels of carbon declined by half."

Within this system of summer forest farming, much of the landscape was exploited. This type of land use led to changes in the cycling of organic matter, which affected carbon storage and led to reduced concentrations of carbon in adjacent lakes.

"Climate change and changes in the acidification of lakes are important processes for the environment today, but long-term changes in how we have used the landscape over hundreds over even thousands of years have also left their imprint," said Richard Bindler, one of the researchers.

The findings are published in the journal Proceedings of the National Academy of Sciences.

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