Rapid range shifts and megafaunal extinctions associated with late Pleistocene climate change (original) (raw)
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PALEOECOLOGY. Abrupt warming events drove Late Pleistocene Holarctic megafaunal turnover
Science (New York, N.Y.), 2015
The mechanisms of Late Pleistocene megafauna extinctions remain fiercely contested, with human impact or climate change cited as principal drivers. We compared ancient DNA and radiocarbon data from 31 detailed time series of regional megafaunal extinctions and replacements over the past 56,000 years with standard and new combined records of Northern Hemisphere climate in the Late Pleistocene. Unexpectedly, rapid climate changes associated with interstadial warming events are strongly associated with the regional replacement or extinction of major genetic clades or species of megafauna. The presence of many cryptic biotic transitions before the Pleistocene/Holocene boundary revealed by ancient DNA confirms the importance of climate change in megafaunal population extinctions and suggests that metapopulation structures necessary to survive such repeated and rapid climatic shifts were susceptible to human impacts.
Proceedings of the National Academy of Sciences, 2004
Mid-Pleistocene vertebrates in North America are scarce but important for recognizing the ecological effects of climatic change in the absence of humans. We report on a uniquely rich mid-Pleistocene vertebrate sequence from Porcupine Cave, Colorado, which records at least 127 species and the earliest appearances of 30 mammals and birds. By analyzing >20,000 mammal fossils in relation to modern species and independent climatic proxies, we determined how mammal communities reacted to presumed glacial–interglacial transitions between 1,000,000 and 600,000 years ago. We conclude that climatic warming primarily affected mammals of lower trophic and size categories, in contrast to documented human impacts on higher trophic and size categories historically. Despite changes in species composition and minor changes in small-mammal species richness evident at times of climatic change, overall structural stability of mammal communities persisted >600,000 years before human impacts.
Abrupt warming events drove Late Pleistocene Holarctic megafaunal turnover
The mechanisms of Late Pleistocene megafauna extinctions remain fiercely contested, with human impact or climate change cited as principal drivers.We compared ancient DNA and radiocarbon data from 31 detailed time series of regional megafaunal extinctions and replacements over the past 56,000 years with standard and new combined records of Northern Hemisphere climate in the Late Pleistocene. Unexpectedly, rapid climate changes associated with interstadial warming events are strongly associated with the regional replacement or extinction of major genetic clades or species of megafauna. The presence of many cryptic biotic transitions before the Pleistocene/Holocene boundary revealed by ancient DNA confirms the importance of climate change in megafaunal population extinctions and suggests that metapopulation structures necessary to survive such repeated and rapid climatic shifts were susceptible to human impacts.
Paleoenvironmental change in central Texas: the palynological evidence
1998
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Geophysical Monograph Series, 2000
Databases of ecological and cultural records, especially of pollen diagrams, record climate variability of several time scales during the Holocene and late glacial. Results from lake and wetland ecosystems geographically extend the evidence of rapid climate change obtained from ice cores and ocean sediments. Continental and regional climate curves for North America, based on pollen diagrams from the North American Pollen Database, illustrate abrupt changes on the order of every~1000 years during the past 12 kyr, and major times of change in North American pollen records are coherent with vegetation changes across Europe. Novel analyses of the database show that even taxa that are widespread and with presumably broad climate tolerances were affected by abrupt climate changes such as the Younger Dryas and illustrate the complexity of ecosystem response to these changes. Reconstructions of freshwater as well as terrestrial ecosystems across northern Canada also show how climate variability affects terrestrial and freshwater ecosystem-level properties such as nutrient cycling. These results can be used to reconstruct the spatial patterns of abrupt climate change, as well as the impacts of climate change on ecosystem and cultures.
Late Pleistocene climate change, nutrient cycling, and the megafaunal extinctions in North America
Quaternary Science Reviews, 2011
This study proposes an ecological mechanism for the terminal Pleistocene population collapse and subsequent extinction of North American megafauna. Observations of modern ecosystems indicate that feedback mechanisms between plant nutrient content, nitrogen cycling, and herbivore–plant interactions can vary between a nutrient accelerating mode favoring increased herbivore biomass and a nutrient decelerating mode characterized by reduced herbivore biomass. These alternate modes are determined largely by plant nitrogen content. Plant nitrogen content is known to be influenced by atmospheric CO2 concentrations, temperature, and precipitation. It is argued that Lateglacial climate change, particularly increases in atmospheric CO2, shifted herbivore–ecosystem dynamics from a nutrient accelerating mode to a nutrient decelerating mode at the end of the Pleistocene, leading to reduced megafaunal population densities. An examination of Sporormiella records – a proxy for megaherbivore biomass – indicates that megafaunal populations collapsed first in the east and later in the west, possibly reflecting regional differences in precipitation or vegetation structure. The fortuitous intersection of the climatically driven nitrogen sink, followed by any one or combination of subsequent anthropogenic, environmental, or extra-terrestrial mechanisms could explain why extinctions took place at the end of the Pleistocene rather than during previous glacial–interglacial cycles.► 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.
Paleoecology in an Era of Climate Change: How the Past Can Provide Insights into the Future
Paleontology in Ecology and Conservation, 2012
Anthropogenic climate change is the most prominent conservation issue of our time. Expectations are that the Earth's climate will warm~2.5-6.5 within the next century. The accompanying biological consequences will no doubt be huge. How will the diversity of life on our planet respond to rapid climate change? The best way to predict the future may be to examine the past as biota have experienced numerous episodes of climate fluctuation throughout geologic time. Some of these climatic fluctuations, particularly those of the late Quaternary, have been as rapid as those anticipated by climate warming scenarios. Analysis of the paleontological record can yield valuable information on how past climate change has shaped biodiversity in the past, and provide clues for what we may expect in the future.
2007
A b s t r a c t ) provided the first micropaleontological evidence for terrestrial mass-mortality at the Cretaceous-Tertiary (or K-T) boundary associated with the impact of a large bolide on Earth. Five years later published corroborative evidence from leaf fossils and proposed that long-term increases in precipitation, and possibly temperature, were also associated with the K-T boundary impact event. Over the subsequent two decades numerous palynological and paleobotanical studies have corroborated early evidence for mass mortality at the K-T boundary in North America and other regions of the world, refined interpretations, and suggested additional long-term environmental changes associated with the terminal Cretaceous event. In this paper we review what we consider to be some of the more important paleobotanical and palynological literature for the K-T boundary of North America and evaluate hypothesized climatic changes. Patterns of change in species diversity and patterns of life form dominance in the pollen and leaf records are consistent with a reduction in solar radiation over a period of one year to more than a century by a global cloud of dust and/or sulfate aerosols resulting from an impact at the K-T boundary. However, limited evidence exists for associated freezing temperatures or global wildfires. Changes in the physiognomy of leaf fossils, plant communities, sedimentary facies, and paleosols provide evidence for up to a four-fold increase in mean annual precipitation after the K-T boundary that may have lasted for >1 million years. Evidence from leaf margin analysis for an early Paleocene cooling of ~5 °C is restricted to the northern Western Interior and is contradicted by evidence for no temperature change or a temperature increase. Multivariate analysis of foliar physiognomy (CLAMP) suggests a temperature increase of as much as 9 °C. Preliminary evidence for a four-fold or greater increase in atmospheric pCO 2 across the K-T boundary (to >2300 ppm) is consistent with a proposed warming of 9 °C during the early Paleocene, based on the range of sensitivity of Earth-system models to increased pCO 2 . Biogeochemical modeling indicates that a one-year period of darkness, with the lower temperatures and partial biomass burning proposed by some authors, would be sufficient to shut down photosynthesis and significantly reduce terrestrial biomass. Long lasting (10 2 to 10 6 yr) increases in precipitation, temperature, and pCO 2 created favorable environmental conditions for the recovery of net primary productivity and terrestrial biomass. This may help explain why plants at the K-T boundary, while experiencing high extinction at the level of species regionally, experienced relatively little extinction at the level of genus and family, and why the K-T mass extinction event is more pronounced in the marine realm.
Effects of Global Warming on Ancient Mammalian Communities and Their Environments
Background Current global warming affects the composition and dynamics of mammalian communities and can increase extinction risk; however, long-term effects of warming on mammals are less understood. Dietary reconstructions inferred from stable isotopes of fossil herbivorous mammalian tooth enamel document environmental and climatic changes in ancient ecosystems, including C3/C4 transitions and relative seasonality. Methodology/Principal Findings Here, we use stable carbon and oxygen isotopes preserved in fossil teeth to document the magnitude of mammalian dietary shifts and ancient floral change during geologically documented glacial and interglacial periods during the Pliocene (~1.9 million years ago) and Pleistocene (~1.3 million years ago) in Florida. Stable isotope data demonstrate increased aridity, increased C4 grass consumption, inter-faunal dietary partitioning, increased isotopic niche breadth of mixed feeders, niche partitioning of phylogenetically similar taxa, and differences in relative seasonality with warming. Conclusion/Significance Our data show that global warming resulted in dramatic vegetation and dietary changes even at lower latitudes (~28°N). Our results also question the use of models that predict the long term decline and extinction of species based on the assumption that niches are conserved over time. These findings have immediate relevance to clarifying possible biotic responses to current global warming in modern ecosystems.
Climatic backdrop to the terminal Pleistocene extinction of North American mammals
Geology, 2012
North American terminal Pleistocene mammal extinctions are the subject of a long-running scientifi c debate. Although the role of climate has fi gured centrally, we lack clear knowledge of the timing and nature of terminal Pleistocene climate variability. Herein we document lengthy terminal Pleistocene drought in the southwestern United States (USA) using δ 13 C and δ 234 U effective moisture proxy data in speleothem calcite (stalagmite FS2) from Fort Stanton Cave, New Mexico, supplemented with age data from pool basin shelfstone speleothems from the Big Room in Carlsbad Cavern. This terminal Pleistocene drought, defi ned by a sharp rise in both δ 13 C and δ 234 U values, began just before 14.5 k.y. ago and lasted at least until 12.9 k.y. ago, when it was briefl y and only mildly interrupted by the Younger Dryas. The timing and length of this drought (~1500 yr) match the Northern Hemisphere Bølling-Allerød oscillation preserved in Greenland ice cores and exhibited in the δ 18 O record of stalagmite FS2. Rapid transition from cool moist Late Glacial to warm dry Holocenelike climatic conditions was likely unfavorable to many species of Pleistocene mammals in the southwestern USA. A climate-induced extinction implies that this last glacial cycle and its termination were more extreme than previous glacial cycles and/or glacial terminations.