Learning from the past
Leiden archaeologists investigate how people in the past impacted their environment. Together with scientists, environmental scientists, and humanities experts, they use this information to draw conclusions about the present – and show what we can learn from it for the future.
As far back as 20,000 to 30,000 years ago, towards the end of the last ice age, European people were already leaving their mark on the landscape. ‘Hunters impacted the landscape on a large scale by using fire, which probably even at that time had important consequences for vegetation, fauna and climate,’ explains Jan Kolen, Professor of Landscape Archaeology and Cultural Heritage. ‘We think that they even burned down forests on purpose to create a more varied landscape, with more game species, herbs and fruit-bearing plants.’
Kolen believes that this may have been a first step towards a significant human impact on the environment and ecosystem. This influence in any case began with the rise of agriculture, which set in motion the large-scale deforestation of Europe between 10,000 and 5,000 years ago.
Leiden researchers collaborate in this field with researchers from other universities such as Delft, Rotterdam and Lausanne. The researchers use archaeological findings – from careful excavation of human occupation sites and objects – supplemented with modern technologies. For example, they separate microparticles of charcoal from the soil, which allows them to date and where possible name the wood. They extract DNA from ancient animal skulls to investigate domestication. And they use satellite images to trace back historical land usage.
Their goal is to recognise and uncover underlying patterns. ‘This goes beyond historical interest alone,’ Kolen stresses. ‘We use this knowledge to understand the present and formulate solutions for the future.’ To achieve this goal Kolen seeks collaboration with fellow researchers from very different disciplines, such as the humanities and governance. ‘How do people see their role in the landscape, and how can you communicate about this with the general public and policy makers. These are typically questions that can be answered from a variety of perspectives,’ he says.
Interventions in the landscape, as noted by Kolen and his colleagues, often happen insidiously over time – until the system suddenly reaches a tipping point. Nobody at the time can predict the consequences. ‘By linking present and past you can show such effects more clearly,’ says Kolen. This makes it possible to learn to estimate this impact – and therefore prevent it.
As an example he mentions the gradual erosion in hilly loess landscapes like those in Zuid-Limburg. This erosion began in the Roman era, with deforestation. Then in the thirteenth century, the loess plateaus were exploited on a large scale for agriculture. ‘After World War II things quickly degenerated,’ explains Kolen. ‘Small-scale terraces with different types of grain made way for large fields that were no longer planted along the contour lines of the landscape, but downhill with row crops such as corn.’ This led to a tipping point. Now there is no more leeway. With every rain shower, soil flows down the hill, and heavy rain causes mudslides. All this has led to a strong decrease in fertility and biodiversity in this type of landscape. Kolen: ‘And the effect is irreversible.’
But what can we do with this knowledge now? ‘Prevent it from happening again,’ he says. ‘Not immediately agree to risky, large-scale interventions in the landscape and ecosystems, without first doing the research, giving it serious thought and looking ahead.’ What we need to do, according to Kolen, is to plough and sow parallel to the contours of the hillsides, and restore historical terraces and elevations. And make sure that biodiversity is preserved, even when introducing changes and modifications. ‘More biodiversity, with smaller-scale human use of land and historically based “rewilding” and nature development, makes a landscape more resilient.’
In some cases, Kolen argues for restoring historical agricultural elements. Elements such as terraces, floodplains, forgotten irrigation systems, and upstream water meadows are all close-knit systems created to retain water for as long as possible. ‘We have found traces of these on satellite images,’ says Kolen. ‘And in the archives we’ve found information on how they work. You can revitalise these systems to increase the holding capacity of upstream river systems. This way archaeology, historical geography and historical ecology suddenly become very relevant.’