Late Pleistocene climate change, nutrient cycling, and the megafaunal extinctions in North America
Highlights
► An ecological mechanism for North American late Pleistocene extinctions is proposed. ► Late Pleistocene Sporormiella records in North America are reviewed. ► Feedback between herbivores, plants, and nitrogen cycling is reviewed. ► Increased CO2 during the Lateglacial could cause a megafaunal population collapse.
Introduction
The late Pleistocene of North America is characterized by the extinction of 36 genera of large mammals (Grayson, 1991, Grayson, 2011, Barnosky et al., 2004, Grayson, 2007, Faith and Surovell, 2009). Six of these genera survived elsewhere, although within them some species were lost, and the majority became globally extinct. The losses were most severe for the largest taxa, with extinctions taking place across all genera larger than 1000 kg (e.g., Mammuthus, Mammut, Glyptotherium) and over half the genera between 32 and 1000 kg (Lyons et al., 2004a, Koch and Barnosky, 2006). Due to the limitations of the fossil record, the timing of the extinctions is debated (Grayson, 2001, Grayson, 2007, Grayson and Meltzer, 2003, Fiedel and Haynes, 2004, Faith and Surovell, 2009, Fiedel, 2009). At least 16 genera are unequivocally known from the very latest Pleistocene (Grayson, 2007, Faith and Surovell, 2009, Fiedel, 2009), although the chronology is consistent with the synchronous loss of all 36 genera at the very end of the Pleistocene, between 12,000 and 10,000 14C yrs BP (∼13,800 to 11,400 cal yrs BP) (Faith and Surovell, 2009).
At the same time that extinctions were taking place, there is evidence for dramatic shifts in the geographic range and composition of plant (Williams et al., 2001, Williams et al., 2004, Gill et al., 2009) and animal communities (FAUNMAP, 1994, FAUNMAP, 1996, Stafford et al., 1999), which includes non-analog communities (Williams et al., 2001, Gill et al., 2009), and increased biomass burning (Robinson et al., 2005, Gill et al., 2009, Marlon et al., 2009). This time period also encompasses the Younger Dryas cold interval (Alley, 2000, Rasmussen et al., 2006), the arrival of Clovis hunter–gatherers in North America (Meltzer, 2004, Waters and Stafford, 2007) and a proposed – although highly contested (Paquay et al., 2009, Surovell et al., 2009, Daulton et al., 2010, Haynes et al., 2010, Holliday and Meltzer, 2010, Scott et al., 2010) – extra-terrestrial impact event (Firestone et al., 2007, Kennett et al., 2008, Kennett et al., 2009, Melott et al., 2010).
To account for the massive loss of North America’s Pleistocene megafauna (animals > 44 kg), a number of hypothesis have been forwarded. These include human hunting pressure (Martin, 1967, Martin, 1984, Martin, 2005, Martin and Steadman, 1999, Alroy, 2001, Lyons et al., 2004a), environmental change (Graham and Lundelius, 1984, Guthrie, 1984, King and Saunders, 1984), or some combination of both (Barnosky et al., 2004). Alternative explanations include an extra-terrestrial impact (Firestone et al., 2007, Kennett et al., 2008, Kennett et al., 2009, Paquay et al., 2009, Surovell et al., 2009, Daulton et al., 2010, Haynes et al., 2010, Holliday and Meltzer, 2010, Melott et al., 2010, Scott et al., 2010), disease (MacPhee and Marx, 1997, Lyons et al., 2004b), or vegetation change stemming from the loss of keystone mega-herbivores (Owen-Smith, 1987). This study discusses how the interplay between Lateglacial climate change, nutrient cycling, and plant–herbivore interactions could have played a deciding role in the demise of North America’s Pleistocene megafauna.
Section snippets
The late Pleistocene megafaunal population collapse
Davis (1987) demonstrated that Sporormiella dung fungal spores track herbivore abundances on the landscape. Sporormiella is a coprophilous fungus found only on the dung of herbivores (Ahmed and Cain, 1972). The spores are common on the dung of domestic herbivores and mega-herbivores (Ebersohn and Eicker, 1997) and are also known from the dung and gut contents of Pleistocene Mammuthus (Davis et al., 1984, Mead et al., 1986, van Geel et al., 2008). In pollen cores, Sporormiella abundances <2% of
Nutrient cycling in modern ecosystems & Lateglacial climate change
Modern ecosystems are characterized by dynamic feedback mechanisms between herbivores, plant tissue chemistry, and nutrient (nitrogen) cycling (Pastor et al., 2006). As reviewed by Pastor et al. (2006), ecosystems are broadly characterized by two primary modes of herbivore–ecosystem interactions, termed nutrient accelerating or nutrient decelerating modes (Fig. 4) (Ritchie et al., 1998). Theoretical and empirical evidence suggests that the distinction between these modes depends on forage
Conclusion
This study proposes an ecological explanation for the population collapse and subsequent extinction of North American Pleistocene megafauna. Drawing upon observations of contemporary herbivore–ecosystem dynamics, it is argued that Lateglacial environmental change, including rising CO2 concentrations and possibly elevated temperatures and precipitation, prompted a transition from a nutrient accelerating mode to a nutrient decelerating mode in North America. This transition would have been
Acknowledgments
I thank Kay Behrensmeyer, Don Grayson, and John Pastor (reviewer) for their comments on previous versions of this manuscript and helpful discussions on the topic. I also thank Mark Ritchie for pointing out useful references at the onset of this research. This research was funded by a NSF IGERT fellowship.
References (93)
The Younger Dryas cold interval as viewed from central Greenland
Quaternary Science Reviews
(2000)- et al.
Paleoclimate simulations for North America over the past 21,000 years: features of the simulated climate and comparisons with paleoenvironmental data
Quaternary Science Reviews
(1998) Spores of the dung fungus Sporormiella: increased abundance in historic settlements and before Pleistocene megafaunal extinction
Quaternary Research
(1987)Pollen analysis of Tulare Lake, California: Great Basin-like vegetation in central California during the full-glacial and early Holocene
Review of Palaeobotany and Palynology
(1999)Pollen analysis of a late-glacial and Holocene sediment core from Mono Lake, Mono County, California
Quaternary Research
(1999)- et al.
Sporormiella fungal spores, a palynological means of detecting herbivore density
Palaeogeography, Palaeoclimatology, Palaeoecology
(2006) - et al.
A premature burial: comments on Grayson and Meltzer’s “Requiem for overkill”
Journal of Archaeological Science
(2004) - et al.
A requiem for North American overkill
Journal of Archaeological Science
(2003) - et al.
Wildfire and abrupt ecosystem disruption on California’s Northern Channel Islands at the Ållerød–Younger Dryas boundary (13.0–12.9 ka)
Quaternary Science Reviews
(2008) - et al.
Climate and biome simulations for the past 21,000 years
Quaternary Science Reviews
(1998)
Dung of Mammuthus in the arid Southwest, North America
Quaternary Research
Herbivores, the functional diversity of plant species, and the cycling of nutrients in ecosystems
Theoretical Population Biology
Latest Pleistocene paleoecology of Jefferson’s ground sloth (Megalonyx jeffersonii) and elk-moose (Cervalces scotti) in northern Illinois
Quaternary Research
Do ungulates accelerate or decelerate nitrogen cycling?
Forest Ecology and Management
The ecological implications of a Yakutian mammoth’s last meal
Quaternary Research
Revision of the genera Sporormia and Sporormiella
Canadian Journal of Botany
A multispecies overkill simulation of the end-Pleistocene megafaunal mass extinction
Science
Assessing the causes of late Pleistocene extinctions on the continents
Science
Responses of Picea mariana to elevated CO2 concentrations during growth, cold hardening and dehardening: phenology, cold tolerance, photosynthesis and growth
Tree Physiology
Grazing intensity and ecosystem processes in a northern mixed-grass prairie, USA
Ecological Applications
Timing of the Antarctic cold reversal and the atmospheric CO2 increase with respect to the Younger Dryas event
Geophysical Research Letters
Bayesian analysis of radiocarbon dates
Radiocarbon
Sporormiella and the late Holocene extinctions in Madagascar
Proceedings of the National Academy of Sciences of the U S A
Elevated CO2 reduces the nitrogen concentration of plant tissues
Global Change Biology
Biomass and nitrogen responses to grazing of upland steppe on Yellowstone’s northern winter range
Journal of Applied Ecology
Temperature, accumulation, and ice sheet elevation in central Greenland through the last deglacial transition
Journal of Geophysical Research
Physiographically sensitive mapping of climatological temperature and precipitation across the conterminous United States
International Journal of Climatology
No evidence of nanodiamonds in Younger-Dryas sediments to support an impact event
Proceedings of the National Academy of Sciences of the U S A
The Pleistocene dung blanket of Bechan Cave, Utah
Constructing retrospective gridded daily precipitation and temperature datasets for the conterminous United States
Journal of Applied Meteorology and Climatology
Determination of the coprophilous fungal fruit body successional phases and the delimitation of species association classes on dung substrates of African game animals
Botanical Bulletin of Academia Sinica
Synchronous extinction of North America’s Pleistocene mammals
Proceedings of the National Academy of Sciences of the U S A
A database documenting late Quaternary distributions of mammal species in the United States
Spatial response of mammals to late Quaternary environmental fluctuations
Science
Sudden deaths: the chronology of terminal Pleistocene megafaunal extinction
Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling
Proceedings of the National Academy of Sciences of the U S A
Effects of native grazers on N cycling in a north temperate grassland ecosystem: Yellowstone National Park
Ecology
Ecological conditions that determine when grazing stimulates grass production
Oecologia
Pleistocene megafaunal collapse, novel plant communities, and enhanced fire regimes in North America
Science
Coevolutionary disequilibrium and Pleistocene extinctions
Late Pleistocene mammalian extinctions in North America
Journal of World Prehistory
The archaeological record of human impacts on animal populations
Journal of World Prehistory
Deciphering North American Pleistocene extinctions
Journal of Anthropological Research
The Great Basin: A Natural History
Mosaics, allochemics, and nutrients: an ecological theory of late Pleistocene extinctions
The Murray Springs Clovis site, Pleistocene extinction, and the question of extraterrestrial impact
Proceedings of the National Academy of Sciences of the U S A
Cited by (37)
Diverse responses of vegetation and fire after pleistocene megaherbivore extinction across the eastern US
2022, Quaternary Science ReviewsWhen the grass wasn't greener: Megafaunal ecology and paleodroughts
2021, Quaternary Science ReviewsCitation Excerpt :Tropical forests are generally phosphate limited, but as they become drier they can become nitrogen limited (Pellegrini et al., 2016; Wang et al., 2014). These systems may have become so dry that they tipped from being in an ‘accelerating mode’ spurring productivity through rapid nutrient cycling to a ‘decelerating mode’ (Pastor et al., 2006) in which slowing nutrient cycling lowered megafaunal carrying capacity (Faith, 2011). Thus, a combination of low productivity and low-quality forage may have prevented Mammuthus from using these habitats even though they were grass-rich.
Megabeasts under the microscope: a closer look at Quaternary extinctions in the Asia-Pacific
2020, Quaternary InternationalSynthesis and assessment of the flat-headed peccary record in North America
2020, Quaternary Science ReviewsCitation Excerpt :Until these issues are addressed, the Sheriden Cave results cannot definitively signal an expanding or dwindling population prior to final extinction. The absence of support for human predation leads us to postulate that the late Glacial environmental shift from a nutrient-accelerating to a nutrient-decelerating mode of ecosystem fueling and its concomitant effect on forage quality (Faith, 2011) along with the increasing environmental seasonality (Denton et al., 2005) and insolation (Berger and Loutre, 1991) may have had devastating consequences for flat-headed peccary. GRIWM predicted extinction occurred when temperatures returned to more glacial conditions but CO2 values continued to rise and seasonality increased (Fig. 2).
Reframing the mammoth steppe: Insights from analysis of isotopic niches
2019, Quaternary Science Reviews