Climate variability and human impact in South America during the last 2000 years: synthesis and perspectives from pollen records

Abstract

An improved understanding of present-day climate variability and change relies on high-quality data sets from the past 2 millennia. Global efforts to model regional climate modes are in the process of being validated against, and integrated with, records of past vegetation change. For South America, however, the full potential of vegetation records for evaluating and improving climate models has hitherto not been sufficiently acknowledged due to an absence of information on the spatial and temporal coverage of study sites. This paper therefore serves as a guide to highquality pollen records that capture environmental variability during the last 2 millennia. We identify 60 vegetation (pollen) records from across South America which satisfy geochrono-logical requirements set out for climate modelling, and we discuss their sensitivity to the spatial signature of climate modes throughout the continent. Diverse patterns of vegetation response to climate change are observed, with more similar patterns of change in the lowlands and varying intensity and direction of responses in the highlands. Pollen records display local-scale responses to climate modes; thus, it is necessary to understand how vegetation-climate interactions might diverge under variable settings. We provide a qualitative translation from pollen metrics to climate variables. Additionally, pollen is an excellent indicator of human impact through time. We discuss evidence for human land use in pollen records and provide an overview considered useful

The flickering connectivity system of the north Andean páramos

“…We recognize mountains where (a) only few events of connectivity occurred during the Pleistocene compared to fragmentation events ('fragmentation-prone mountain fingerprint'), (b) connectivity events interchanged with isolation events in an evenly manner ('mixed connectivityfragmentation mountain fingerprint'), (c) connectivity is facilitated and occurred more often than fragmentation events ('connectivity-prone mountain fingerprint'). The right panel is only based on frequency, not the duration of each event [Colour figure can be viewed at wileyonlinelibrary.com] Humboldt, 1845) where the high peaks and deep inter-Andean valleys cause strong contrasts in climate throughout the region (Flantua et al, 2016). Surface area in mountains does not decrease monotonically with elevation as has been shown previously in southern Colombia by Flantua et al (2014) and on a global scale by Elsen and Tingley (2015).…”

“…448,000 km 2 ) covers parts of Venezuela, Colombia and Ecuador (Figure a), and can be partitioned into six principal mountain ranges or ‘cordilleras’ (Figure c), namely the Sierra Nevada de Santa Marta (SNSM), Cordillera de Mérida, Eastern, Central and Western Cordillera and the Ecuadorian Cordilleras. Most of the Northern Andes is considered a highly to extremely high rugged landscape (Figure b; See mountain illustrations by Von Humboldt, ) where the high peaks and deep inter‐Andean valleys cause strong contrasts in climate throughout the region (Flantua et al., ). Surface area in mountains does not decrease monotonically with elevation as has been shown previously in southern Colombia by Flantua et al.…”

The South American monsoon variability over the last millennium in climate models

“…PAGES 2k Consortium, 2013;, Neukom et al, 2011), a stronger effort to not only reconstruct surface climate at individual locations but also focus on reconstructions of modes of variability or entire climate components such as the SAMS, which implicitly include circulation changes, is needed. Proxies such as pollen or stable hydrogen and oxygen isotopes from lakes, speleothems, and ice cores have shown potential to record larger-scale climate signals and changes in the tropical hydrological cycle over South America (Vuille and Werner, 2005;Vimeux et al, 2009;Bird et al, 2011;Vuille et al, 2012;Ledru et al, 2013;Flantua et al, 2016;Hurley et al, 2015). Multi-proxy reconstructions from such networks, which implicitly incorporate remote and large-scale circulation aspects, may therefore provide a better tool to assess the performance of climate models than reconstructions that are based solely on local precipitation estimates.…”

Late Holocene environmental changes reconstructed from stable isotope and geochemical records from a cushion‐plant peatland in the Chilean Central Andes (27°S)

“…Paleoenvironmental studies covering the past two millennia have increased significantly in recent years with the aim to improve the spatial coverage of paleoclimate proxy data and to evaluate climate and earth system models (PAGES 2k Consortium, 2017). However, both tasks often lack continuous and reliable climate records from extreme environmental locations (Flantua et al, 2016). For example, the highlands of the Central Andes of South America are characterized by steep altitudinal gradients and harsh environmental conditions such as low temperatures, high solar radiation, low oxygen content and a reduced availability of water (K€ orner, 2007) and provide only a limited number of paleoclimatic records (Villalba et al, 2009).…”