Within the Anthropocene, human activities can play a major role in environmental change. Identifying human-caused landscape change is challenging, however, and requires combining high-resolution physical proxies with detailed historical records from the same locality. In this study we demonstrate that paleoenvironmental change is the complex result of both human activity and climatic variation. We use pollen and geochemical analyses from lake sediments in central Italy along with archival records to analyze landscape change for the last 1400 years, including the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). Between ∼870 and 925 AD deforestation coincided with intensification of agriculture associated with development of monastic estates that exploited increasingly larger land holdings as well as new settlement patterns in higher-elevation defensible locations (incastellamento). Above average temperatures probably allowed high elevation settlements to persist throughout the MCA, though social trends played a large role in the conversion of uplands into an agro-pastoral landscape. Cool temperatures and increased precipitation at the beginning of the LIA, ∼1400 AD, combined with population loss to plague of >50 percent overwhelmed the technical capabilities of the population leading to abandonment of high elevation settlements and persistent flooding of the valley. The landscape rapidly reforested and the plain reverted to wetland. In 1601, during one of the coldest periods of the LIA, new hydrologic technology allowed the community to drain the wetlands and successfully mitigate the impacts of climate change. Despite increased LIA precipitation, the basin was steadily reclaimed and converted to agriculture by 1750 AD.
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We appreciate two anonymous reviews that significantly improved the quality of the manuscript. We are grateful to the many people who helped make this study possible. Chronology development was done by Leonardo Sagnotti, Fabio Florindo and Francisco-Javier Pavón-Carrasco of the Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy and Susan Zimmerman of the Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory. Cores were processed at LACORE, Minneapolis with assistance from Anders Noren, Christina Brady, Amy Mybro and Jessica Heck. Fig. 1 base map was created by Emanuele Ziaco. Funding was provided by the National Science Foundation ( GSS-1228126 ) to Mensing and Noble, international travel awards and sabbatical leave from the University of Nevada, Reno to Mensing, the Sabina Universitas and Province of Rieti. We are grateful to Luigi Sandoletti for technical support, Giulia Sandoletti for laboratory assistance, Emanuele Presutti Saba, Emanuele Ziaco, and Gianluca Bonavigo for field and coring assistance, and DAFNE Università degli Studi della Tuscia for field transportation. Paolo Bellezza, Maurizio Sterpi at the Riserva Naturale dei Laghi Lungo e Ripasottile provided housing at the field site and boat access to Lago Lungo. Stefano Pizetti helped arrange housing in Viterbo for U.S. participants.
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- Human impacts
- Little Ice Age
- Medieval Climate Anomaly
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