Quaternary Research (2018), 89, 103–118. Copyright © University of Washington. Published by Cambridge University Press, 2017. doi:10.1017/qua.2017.60 The collapse of megafaunal populations in southeastern Brazil Marco F. Raczka a *, Mark B. Bush a , Paulo Eduardo De Oliveira b,c a Department of Biological Sciences, Florida Institute of Technology, Melbourne, Florida 32901, USA b Department of Sedimentary and Environmental Geology, Institute of Geosciences, University of São Paulo, São Paulo 05508-080, Brazil c Department of Botany, The Field Museum of Natural History, Chicago, Illinois 60605, USA (RECEIVED December 2, 2016; ACCEPTED July 5, 2017) Abstract Whether humans or climate change caused the extinction of megafaunal populations is actively debated. Caves in the Lagoa Santa provide mixed assemblages of megafauna and human remains; however, it remains uncertain the extent to which humans and megafauna interacted or overlapped temporally. Here we present the first paleoecological record from lowland South America that tracks the decline of megafauna and its ecological implications. We provide a data set for pollen, charcoal, and Sporormiella, from two lakes in southeastern Brazil that span the last 23,000 yr. The data showed reduced abundances of Sporormiella and an inferred megafaunal population decline that began 18,000 yr ago, with the functional extinction occurring between 12,000 and 11,500 yr ago. Population declines coincided with wet events. The age of the final megafaunal decline is within the range of the first human occupation of the region. Our data are consistent with climate causing the population collapse, with humans preventing population recovery and inducing extinction. We did not observe some of the ecological repercussions documented at other sites and attributed to the megafaunal extinction. Habitat-specific ecological consequences of the extinction add to the heterogeneity of late Pleistocene and early Holocene landscapes. Keywords: Charcoal; Climate change; Human; Megafauna; Pleistocene; Pollen; Sporormiella INTRODUCTION The deglacial period, ca. 22,000–12,500 before present, was a period of rapid change in composition and structure of terrestrial environments that coincided with a major extinc- tion of large mammals (Alroy, 2001; Barnosky et al., 2004; Koch and Barnosky, 2006; Fiedel, 2009; Barnosky and Lindsey, 2010; Villavicencio et al., 2016). At the end of the Pleistocene, ~59 species of megafauna, accounting for 79.6% of animals weighing >44 kg went extinct in South America (Barnosky et al., 2004; Wroe et al., 2004). In fact, the only large herbivore in Brazil that survived this mass extinction event was the tapir (tapirus terrestris) (Steadman et al., 2005). The proportion of megafauna lost from the South America fauna was higher than on any other continent (Bar- tlett et al., 2016), and the loss of grazers and browsers may have contributed to changes in vegetation cover (Doughty et al., 2016). Representatives of megafauna were major ecosystem engineers crucial for ecosystem functions such as seed dispersal (Janzen and Martin, 1982; Giombini et al., 2016; Sridhara et al., 2016), reduction of fuel load (Knapp et al., 1999), and nutrient cycling (Feeley and Terborgh, 2005; Doughty et al., 2013). The loss of these animals may have induced transformations in the landscape, including the formation of no-analog communities (Gill et al., 2009), and had repercussions that are still felt today (Owen-Smith, 1987; Doughty et al., 2013). The cause of the megafaunal extinction has been debated for many decades (e.g., Martin, 1973; Barnosky et al., 2004; Cione et al., 2009; Feranec et al., 2011). Multiple conflicting hypotheses have been proposed ranging from widespread autoimmune diseases (Stevens, 1997) to a meteorite impact that triggered abrupt climatic changes such as the rapid cool- ing of the Young Dryas Event ca. 12,500 calibrated 14 C years before present (hereafter cal yr BP) (Firestone et al., 2007). The two most widely cited hypotheses are that humans induced the extinction (Martin, 1973; Mosimann and Martin, 1975; Brook and Bowman, 2004; Koch and Barnosky, 2006) or that it was caused by climatic changes (Coltorti et al., 1998; Cione et al., 2003). Of these causes, extraterrestrial impact (Firestone et al., 2007) seems the least likely (Kerr, 2007), and the other three need not be mutually exclusive. A modern analog to megafaunal loss is perhaps found in the decline of amphibians that results from the effects of human-induced SPECIAL ISSUE Tribute to Daniel Livingstone and Paul Colinvaux * Corresponding author at: Department of Biological Sciences, Florida Institute of Technology, Melbourne, Florida 32901, USA. E-mail address: mraczka2009@my.fit.edu (M.F. Raczka). 103 https://www.cambridge.org/core/terms. https://doi.org/10.1017/qua.2017.60 Downloaded from https://www.cambridge.org/core. University of Texas Libraries, on 09 Apr 2018 at 18:02:28, subject to the Cambridge Core terms of use, available at