Elsevier

Anthropocene

Volume 15, September 2016, Pages 49-59
Anthropocene

Human and climatically induced environmental change in the Mediterranean during the Medieval Climate Anomaly and Little Ice Age: A case from central Italy

https://doi.org/10.1016/j.ancene.2016.01.003Get rights and content

Abstract

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.

Introduction

Global concern over future climate change and its potential impact on society has placed a focus on understanding the relationship between climate and human activity. There is no doubt that climate influences human activities through extremes such as droughts, freezes, and floods, as well as periods of stasis such as prolonged periods of mild or inclement climate Lamb, 1982, Ladurie, 1967, Ladurie, 1971, Pfister and Brázdul, 1999, Pfister and Brázdul, 2006). However, human use of the environment takes place within a local socio-economic context, and while some land use decisions may be constrained by climatic limitations, a broad set of human (e.g. culture and technology) and environmental factors influence land use practices. There is now general recognition that paleoenvironmental change within the Anthropocene is the complex result of both human activity and climate (Dearing et al., 2008, Coombes et al., 2009, Munoz et al., 2010, McCormick et al., 2012), and that unicausal explanations of cultural expansion or collapse are overly simplistic (Dincauze, 2000, O’Sullivan, 2008, Aimers, 2011, Izdebski et al., 2015). Reconstructing human-induced paleoenvironmental change remains a challenge because sources describing human use of the landscape are limited, and distinguishing human impacts from climatic impacts is not a trivial problem. To the extent that we can combine high-resolution physical proxies of paleoenvironmental reconstruction with detailed historical records from the same locality we have the potential to gain new insights into the role of climate and human activities in impacting environmental systems (Berglund, 2003, Dearing et al., 2008, Coombes et al., 2009, Harris, 2013, Izdebski et al., 2015, Kemp et al., 2015). To achieve this we approach local climate changes within an historical framework of longue durée (Leed, 2010).

The Medieval Climate Anomaly (MCA), between ∼900–1350 AD (Graham et al., 2011) and the subsequent Little Ice Age (LIA), between ∼1400 and 1850 AD (Mann, 2002) are arguably the two most important periods of recent climate change that impacted societies, particularly in Europe where the climatic influences have been extensively documented (Lamb, 1982, Ladurie, 1971, Pfister and Brázdul, 1999, Pfister and Brázdul, 2006). The Medieval period was also a time of dramatic socio-economic change with the development of new economic models, expansion of the role of the church through monasteries, and shifting political influences (Hodges, 2012). Europe is one of the few places with extensive written documents for >1000 years, providing an opportunity to compare the historical record of socio-economic activity with the physical proxy record of environmental and climate change. A rich documentary record exists in the Rieti region of central Italy, through monastic writings and community records (Leggio, 1986, Leggio, 1989, Leggio, 1992, Leggio, 1994, Leggio, 1995, Leggio, 2007, Leggio and Marinelli, 1995, Lorenzetti, 1989, Lorenzetti, 1990, Lorenzetti, 1994, Lorenzetti, 2009). In this paper we take advantage of the trove of medieval documents from the Rieti region in central Italy and compare this with a high-resolution paleoenvironmental reconstruction using multiple proxies from sediment cores recovered in the Rieti basin to interpret landscape change within the context of both climatic change and historical development. Our goal is to use this case to document abrupt environmental change in relation to the local history and regional climate in an effort to evaluate the extent to which these changes might be explained by socioeconomic factors, climate change, or the complex interaction of the two.

Rieti (Reate in Latin) was settled by the Sabini in the Early Iron Age ∼2800 years ago, although archaeological evidence indicates that the region was largely abandoned towards the end of the period with virtually no occupation by the time the Romans established a presence ∼300 BC (Cifani, 2003). The Rieti Basin is an intermontane depression in the Central Apennines (Fig. 1) connected with Rome by the ancient Via Salaria (Coccia et al., 1992). Water level in the basin was controlled by the elevation of a travertine sill at Marmore where the Velino River exits the basin (Calderoni et al., 1994) and local hydrologic engineering efforts have played a major role in environmental changes in the valley. During pre-Roman times the basin held one large lake, Lacus Velinus, though by early Roman time it is thought that the basin was an expansive wetland dotted with lakes (Lorenzetti, 1990, Calderoni et al., 1994). Written documents suggest that the Romans cut a channel through the travertine sill ∼270 BC to drain the basin for pasture and agriculture (Coccia et al., 1992). The basin has been continuously utilized for farming and pasture since then although maintaining drainage in the basin has been a continuous challenge. Following Roman occupation, the basin was controlled by the Ostrogoth until it fell to the Lombards in 590 AD. Monasteries have been important from an early time with the founding of the Farfa Monastery by the Benedictine Order between 550 and 560 AD and foundation of San Salvatore Maggiore Monastery within the Rieti basin in 735 AD (Leggio, 1992, Leggio, 1995). The monasteries controlled use of the lakes including fishing and shrimp production (Coccia et al., 1992). During this period the governance of the region was established through the Duchy of Spoleto (Leggio, 1992). In 774 AD Charlemagne conquered northern Italy and Rieti became the southern frontier of the Carolingian Empire. An important period of urbanization began about 1000 AD with the chartering of multiple fortified hill towns around the basin (Coccia et al., 1992). Throughout the Medieval period, community records and historic maps dating from the 16th century describe the successive phases of drainage works critical to preventing the basin from becoming a marsh (Leggio, 1992, Leggio, 1995, Leggio, 2007, Lorenzetti, 1990, Lorenzetti, 1994).

Today, four remnant lakes persist, Lago Lungo, Ripasottile, Ventina and Pieidiluco (Fig. 1). Our site, Lago Lungo, (369 a.m.s.l.) has a maximum depth of up to 7 m with a surface area of 0.78 km2 (Riccardi, 2006). The basin is cultivated for maize and cereals and the hillsides and the surrounding hill slopes are covered in coppiced stands of mixed deciduous forest dominated by oaks and hop-hornbeam. Sedimentation rates in the Apennines are among the highest across Europe (Panagos et al., 2015), averaging 10–20 tons ha−1 yr−1. Detailed description of local vegetation and geology are published in Mensing et al. (2015). The area has a Mediterranean precipitation pattern with 1117 mm annually falling predominantly in winter. Mean annual temperature varies between 4 °C in January and 21 °C in July (Fig. 4 29 in Leone, 2004). The temperature and precipitation regime is strongly controlled by the North Atlantic Oscillation (NAO) with warm dry climate predominating during positive phases of the NAO, and cool wet climate during negative phases (Hurrell, 1995, López-Moreno et al., 2011).

Section snippets

Methods

Sediment cores were recovered in 2009 and 2012 using a hand operated square-rod Livingstone corer from a floating platform anchored in the deepest part of the lake. Surface sediments were recovered with a plastic tube core specially fitted with a piston to produce minimal disturbance of the sediment-water interface. The unconsolidated surface sediments were stabilized with Zorbitrol (sodium polyacrylate absorbent powder) while the core was still in an upright position. Three overlapping cores

Results

Ninety different pollen types, nine non-pollen palynomorphs (NPP) and eleven algae types (not shown) were identified. Cluster analysis (Fig. 2) identified three eco-functional groups: Grassland and disturbance taxa; forest taxa; and cultivated plants and early pioneer forest taxa. Pinus grouped with grassland and disturbance taxa, possibly because it is not a common constituent of the local forest and appears in disturbed habitats through long-distance transport. Selected pollen and NPP are

Independent climate change reconstructions

There are no millennial-length high resolution temperature or precipitation reconstructions from peninsular Italy, therefore we rely on reconstructions from the western Mediterranean, Alps and northern Europe for independent climate records (Fig. 4). The longest precipitation series available comes from a tree-ring reconstruction of the Palmer Drought Severity Index—(PDSI) in Morocco using Cedrus atlantica (Endl. Carrière; Esper et al., 2007). A reconstructions of the NAO from speleothems in

Conclusions

Our study demonstrates that within the Anthropocene, paleoenvironmental change may be the result of the complex interaction between human activity and climatic variation. The MCA and LIA provide an important climatic backdrop to environmental change in the Rieti basin of central Italy, but examination of the socioeconomic context within which land use change took place demonstrates that the timing and magnitude of environmental impacts was closely linked to local activities. There are three

Acknowledgements

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

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