David A. Burney

Pleistocene Rewilding: An Optimistic Agenda for Twenty‐First Century Conservation

Large vertebrates are strong interactors in food webs, yet they were lost from most ecosystems after the dispersal of modern humans from Africa and Eurasia. We call for restoration of missing ecological functions and evolutionary potential of lost North American megafauna using extant conspecifics and related taxa. We refer to this restoration as Pleistocene rewilding; it is conceived as carefully managed ecosystem manipulations whereby costs and benefits are objectively addressed on a case‐by‐case and locality‐by‐locality basis. Pleistocene rewilding would deliberately promote large, long‐lived species over pest and weed assemblages, facilitate the persistence and ecological effectiveness of megafauna on a global scale, and broaden the underlying premise of conservation from managing extinction to encompass restoring ecological and evolutionary processes. Pleistocene rewilding can begin immediately with species such as Bolson tortoises and feral horses and continue through the coming decades with elephants and Holarctic lions. Our exemplar taxa would contribute biological, economic, and cultural benefits to North America. Owners of large tracts of private land in the central and western United States could be the first to implement this restoration. Risks of Pleistocene rewilding include the possibility of altered disease ecology and associated human health implications, as well as unexpected ecological and sociopolitical consequences of reintroductions. Establishment of programs to monitor suites of species interactions and their consequences for biodiversity and ecosystem health will be a significant challenge. Secure fencing would be a major economic cost, and social challenges will include acceptance of predation as an overriding natural process and the incorporation of pre‐Columbian ecological frameworks into conservation strategies.

Fossil evidence for a diverse biota from Kaua`i and its transformation since human arrival

Coring and excavations in a large sinkhole and cave system formed in an eolianite deposit on the south coast of Kaua‘i in the Hawaiian Islands reveal a fossil site with remarkable preservation and diversity of plant and animal remains. Radiocarbon dating and investigations of the sediments and their fossil contents, including diatoms, invertebrate shells, vertebrate bones, pollen, and plant macrofossils, provide a more complete picture of prehuman ecological conditions in the Hawaiian lowlands than has been previously available. The evidence confirms that a highly diverse prehuman landscape has been completely transformed, with the decline or extirpation of most native species and their replacement with introduced species. The stratigraphy documents many late Holocene extinctions, including previously undescribed species, and suggests that the pattern of extirpation for snails occurred in three temporal stages, corresponding to initial settlement, late prehistoric, and historic impacts. The site also records land-use changes of recent centuries, including evidence for deforestation, overgrazing, and soil erosion during the historic period, and biological invasion during both the Polynesian and historic periods. Human artifacts and midden materials demonstrate a high-density human presence near the site for the last four centuries. Earlier evidence for humans includes a bone of the prehistorically introduced Pacific rat (Rattus exulans) dating to 822 yr BP (calendar year [cal yr] AD 1039–1241). Vegetation at the site before human arrival consisted of a herbaceous component with strand plants and graminoids, and a woody component that included trees and shrubs now mostly restricted to a few higher, wetter, and less disturbed parts of the island. Efforts to restore lowland areas in the Hawaiian Islands must take into account the evidence from this study that the prehuman lowlands of dry leeward Kaua‘i included plants and animals previously known only in wetter and cooler habitats. Many species may be restricted to high elevations today primarily because these remote locations have, by virtue of their difficult topography and climate, resisted most human-induced changes more effectively than the coastal lowlands.

Sporormiella and the late Holocene extinctions in Madagascar

Fossil spores of the dung fungus Sporormiella spp. in sediment cores from throughout Madagascar provide new information concerning megafaunal extinction and the introduction of livestock. Sporormiella percentages are very high in prehuman southwest Madagascar, but at the site with best stratigraphic resolution the spore declines sharply by ≈1,720 yr B.P. (radiocarbon years ago). Within a few centuries there is a concomitant rise in microscopic charcoal that probably represents human transformation of the local environment. Reduced megaherbivore biomass in wooded savannas may have resulted in increased plant biomass and more severe fires. Some now-extinct taxa persisted locally for a millennium or more after the inferred megafaunal decline. Sites in closed humid forests of northwest Madagascar and a montane ericoid formation of the central highlands show only low to moderate Sporormiella percentages before humans. A subsequent rise in spore concentrations, thought to be evidence for livestock proliferation, occurs earliest at Amparihibe in the northwest at ≈1,130 yr B.P.

LANDSCAPE PALEOECOLOGY AND MEGAFAUNAL EXTINCTION IN SOUTHEASTERN NEW YORK STATE

Stratigraphic palynological analyses of four late Quaternary deposits com- prise a landscape-level study of the patterns and processes of megafaunal extinction in southeastern New York State. Distinctive spores of the dung fungus Sporormiella are used as a proxy for megafaunal biomass, and charcoal particle analysis as a proxy for fire history. A decline in spore values at all sites is closely followed by a stratigraphic charcoal rise. It is inferred that the regional collapse of a megaherbivory regime was followed by landscape transformation by humans. Correlation with the pollen stratigraphy indicates these devel- opments began many centuries in advance of the Younger Dryas climatic reversal at the end of the Pleistocene. However, throughout the region, the latest bone collagen dates for Mammut are considerably later, suggesting that megaherbivores lasted until the beginning of the Younger Dryas, well after initial population collapse. This evidence is consistent with the interpretation that rapid overkill on the part of humans initiated the extinction process. Landscape transformation and climate change then may have contributed to a cascade of effects that culminated in the demise of all the largest members of North Americas mammal fauna.

Dating of modified femora of extinct dwarf Hippopotamus from Southern Madagascar: Implications for constraining human colonization and vertebrate extinction events

Two significant events in the late Holocene history of Madagascar were (a) the arrival of people, and (b) the loss of nearly two dozen species of land vertebrates in the socalled “subfossil extinctions”. The consensus is that the faunal losses occurred shortly subsequent to human arrival, but the timing of these events is poorly constrained. The minimum age for initial human presence on the island may now be set at approximately 2000 bp, on the basis of AMS 14C dates for human-modified femora of extinct dwarf hippos from SW Madagascar. Assuming that this date also marks the beginning of deleterious human interactions with the subfossil fauna, and assuming that this fauna became completely extinct by 900 bp, the width of the anthropogenic “extinction window” may have been as long as c. 1000 a. This estimate, nearly twice the length of previous ones, is close to the unadjusted minimum for the duration of the terminal Pleistocene extinction event in the Americas. Whether or not this length of time comports with theoretical expectations of a “blitzkrieg” pattern of losses is uncertain, but greater refinement in dating the end of the subfossil extinctions is unlikely to produce radically shorter estimates of duration.

Rates, Patterns, and Processes of Landscape Transformation and Extinction in Madagascar

Inferring cause and effect from the fossil record is not a wholly satisfying enterprise. The evidence is stale. Many useful details are missing, perhaps never to be found. Sequential events may be collapsed together, inverted, or mixed with evidence from other times. Few relevant parameters can be measured directly. Paleoecologists must forge ahead despite these obstacles, however, as extinction and environmental change are subjects too important to ignore.

Using ancient DNA to study the origins and dispersal of ancestral Polynesian chickens across the Pacific

Significance Ancient DNA sequences from chickens provide an opportunity to study their human-mediated dispersal across the Pacific due to the significant genetic diversity and range of archaeological material available. We analyze ancient and modern material and reveal that previous studies have been impacted by contamination with modern chicken DNA and, that as a result, there is no evidence for Polynesian dispersal of chickens to pre-Columbian South America. We identify genetic markers of authentic ancient Polynesian chickens and use them to model early chicken dispersals across the Pacific. We find connections between chickens in the Micronesian and Bismarck Islands, but no evidence these were involved in dispersals further east. We also find clues about the origins of Polynesian chickens in the Philippines. The human colonization of Remote Oceania remains one of the great feats of exploration in history, proceeding east from Asia across the vast expanse of the Pacific Ocean. Human commensal and domesticated species were widely transported as part of this diaspora, possibly as far as South America. We sequenced mitochondrial control region DNA from 122 modern and 22 ancient chicken specimens from Polynesia and Island Southeast Asia and used these together with Bayesian modeling methods to examine the human dispersal of chickens across this area. We show that specific techniques are essential to remove contaminating modern DNA from experiments, which appear to have impacted previous studies of Pacific chickens. In contrast to previous reports, we find that all ancient specimens and a high proportion of the modern chickens possess a group of unique, closely related haplotypes found only in the Pacific. This group of haplotypes appears to represent the authentic founding mitochondrial DNA chicken lineages transported across the Pacific, and allows the early dispersal of chickens across Micronesia and Polynesia to be modeled. Importantly, chickens carrying this genetic signature persist on several Pacific islands at high frequencies, suggesting that the original Polynesian chicken lineages may still survive. No early South American chicken samples have been detected with the diagnostic Polynesian mtDNA haplotypes, arguing against reports that chickens provide evidence of Polynesian contact with pre-European South America. Two modern specimens from the Philippines carry haplotypes similar to the ancient Pacific samples, providing clues about a potential homeland for the Polynesian chicken.

Desert paleoenvironmental data from cave speleothems with examples from the Chihuahuan, Somali-Chalbi, and Kalahari deserts

Abstract Pollen-bearing lake, bog, and spring sediments are relatively scarce in many arid and semiarid regions of the world, and few are dateable beyond the 14C range. We have obtained pollen spectra from speleothems collected from caves in the Somali-Chalbi and Kalahari deserts suggesting that these deposits may be an important future source of desert paleovegetation data. As cave speleothems can be dated by the 230Th/234U method to c. 350,000 yr B.P., and by the TL and ESR methods potentially to 1 m.y. B.P., and can sometimes give paleotemperature and paleohydrologic data, they could provide a first glimpse of desert paleoenvironments during isotope stages 4–9. Ages of speleothems from the Chihuahuan, Kalahari, and Somali-Chalbi deserts suggest that there was more available moisture in the southwestern U.S.A. and in northwestern Bostwana during glacials and interstadials of the last c. 300,000 years, but that wetter conditions in the Horn of Africa corresponded with interglacials and perhaps to a lesser extent with interstadials. Pollen from three northern Somalia speleothems indicate more mesic conditions in the Horn of Africa at 10,000, 11,800, and 176,500 yr B.P., while speleothem pollen spectra from Matupi Cave in northeastern Zaire, presently surrounded by tropical rainforest, suggest a savanna grassland at this cave c. 14,000 yr B.P.

New insights into old lemurs: The trophic adaptations of the Archaeolemuridae

Modern tools of paleoecological and ecomorphological research have enabled researchers to reconstruct the lifeways of extinct species more thoroughly than ever before. We apply a variety of tools in an attempt to reconstruct the diets of the extinct archaeolemurids of Madagascar. Our data include dental use wear (examined across species and across ontogenetic series of single species), enamel microstructure, enamel thickness, and δ13C. The data are complemented by field data on the environmental contexts in which the species lived and 14C determinations that demonstrate the surprisingly late survival of archaeolemurids. Several lines of evidence converge to suggest that all archaeolemurid species were hard-object processors, but with different diets and different methods of food processing. Past reconstructions of the diet of Hadropithecus as a specialized grass consumer fail under the scrutiny of multiple lines of evidence.

Tropical Islands as Paleoecological Laboratories: Gauging the Consequences of Human Arrival

Inter-island paleoecological comparisons have provided useful information concerning the role of humans vs. background-level disturbance in tropical ecosystems. Major ecological changes have occurred since human arrival in Madagascar, the West Indies, the Hawaiian Islands, and elsewhere. Prehuman vegetation changes and disturbances have also been documented for many islands. Instructive inter-island similarities and differences have been detected in the chronology, distribution, and extent of human activities, vegetation changes, and biotic extinctions. The earliest stratigraphic proxy evidence for initial human impacts (including increased charcoal particle influx to sediments, first appearance of exotic pollen, increase in ruderal pollen, and paleolimnological evidence for cultural eutrophication of lake waters) generally confirm but sometimes predate the earliest conventional archaeological evidence for human activity. Carefully chosen sites permitting the close integration of palynological, paleontological, and archaeological data from a variety of island settings with differing geographic and historical contingencies can enable investigators to more fully evaluate the importance of a range of human and ecological variables in determining the overall character and dynamics of ecosystems.