For decades, environmental researchers and scientists have warned us about the effects of global warming and human activities on the planet. For some, it’s difficult to believe their little activity has any impact; others think it’s all a hoax. However, recently, scientists have discovered a new way to peer into the past local environment through hazelnuts.
Have you ever paused to think about what the past looked like before agriculture? Was it heavily forested or an open and pasture-like environment? The answers to these questions were found in hazelnuts. Scientists from the University of Oxford and Lund University in Sweden used hazelnut carbon isotope values to find out forest densities in the past, how they have changed, and how humans have interacted with the landscape over millennia.
Finding information on past landscapes
Before analyzing hazelnuts collected from various archaeological sites, scientists first established that varying light levels can affect the carbon isotope levels of hazelnuts. They collected samples from three areas with varying light levels in southern Sweden. They then analyzed the hazelnuts’ carbon quantities and established a relationship between these values and the light levels the trees were exposed to.
Once they had these reference points, they moved to hazelnuts collected from archaeological sites in Sweden. They analyzed shell fragments from four Mesolithic sites and 11 sites from the Neolithic to the Iron Age Period. The Mesolithic Period (also called the Middle Stone Age) is dated around 10,000 B.C. to 8,000 B.C., while the Neolithic Period (New Stone Age) is dated around 7,000 B.C. to 1,700 B.C. On the other hand, the Iron Age lasted between 1,200 B.C. and 550 B.C. So the scientists analyzed hazelnuts from a period of around 9,000 years.
The scientists analyzed several samples from each archaeological site to eliminate any biases.
Why hazelnuts?
People in northern Europe have been using hazelnuts as a source of nourishment and materials for millennia. They are an excellent source of energy and protein, a non-perishable source of food, and their shells can be an excellent fuel source.
Like all living things, hazelnuts contain carbon in different isotope values or forms. These isotope values are influenced by the rate of photosynthesis, which is, in turn, heavily influenced by the amount of sunlight the hazelnut trees get. It means that if the scientists find that hazelnuts from a particular site had higher carbon isotope values, the site used to be an open or pasture-like place — the hazelnut trees didn’t have to compete for sunlight like in heavily forested areas.
From denser forests to pasture-like landscapes
The researchers discovered that nuts harvested from the Mesolithic period came from heavily forested areas. They found that the hazelnuts were collected from more open environments as time progressed. From this analysis, they gleaned that the landscapes had changed significantly into open landscapes by the Iron Age.
“By analyzing the carbon in hazelnuts recovered from archaeological sites in southern Sweden, from Mesolithic hunter-gatherer campsites through to one of the largest and richest Iron Age settlements in northern Europe, we show that hazelnuts were harvested from progressively more open environments,” lead author Amy Styring of the University of Oxford said.
Their findings are consistent with other environmental reconstructions done from pollen analyses. However, scientists believe hazelnuts give them a clearer picture of past landscapes because pollen can be scarce in most archaeological sites.
“In future work, we would like to directly radiocarbon date and measure the carbon isotopes of hazelnut shells from a wider range of archaeological sites and settings,” said Dr Styring. “This will provide much more detailed insight into woodlands and landscapes in the past, which will help archaeologists better understand the impact of people on their environment and perhaps help us to think differently about woodland use and change today.”
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