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Mammoth steppe: A high-productivity phenomenon
Abstract
At the last deglaciation Earth's largest biome, mammoth-steppe, vanished. Without knowledge of the productivity of this ecosystem, the evolution of man and the glacial–interglacial dynamics of carbon storage in Earth's main carbon reservoirs cannot be fully understood. Analyzes of fossils 14C dates and reconstruction of mammoth steppe climatic envelope indicated that changing climate wasn't a reason for extinction of this ecosystem. We calculate, based on animal skeleton density in frozen soils of northern Siberia, that mammoth-steppe animal biomass and plant productivity, even in these coldest and driest of the planet's grasslands were close to those of an African savanna. Numerous herbivores maintained ecosystem productivity. By reducing soil moisture and permafrost temperature, accumulating carbon in soils, and increasing the regional albedo, mammoth-steppe amplified glacial–interglacial climate variations. The re-establishment of grassland ecosystems would slow permafrost thawing and reduce the current warming rate. Proposed methods can be used to estimate animal density in other ecosystems.
... Kozhevnikov and Ukraintseva, 1999;Yurtsev, 2001;Zimov et al., 2009), or 'mammoth steppe' (e.g. Guthrie, 1982Guthrie, , 1990Zimov et al., 2012), extended across the region (e.g. Kaplan et al., 2003;Sher et al., 2005;Bezrukova et al., 2010;Kuzmina, 2015;Chytrý et al., 2019). ...
... It remains debated whether the prevailing flora comprised a dry, productive grassland (e.g. Guthrie, 1982Guthrie, , 2001Zimov et al., 2012), sparsely vegetated Arctic herb communities (e.g. Cwynar, 1982), or a range of communities dominated by forbs and graminoids, with rare dwarf shrubs (e.g. ...
... Pollen records from northern Eurasia typically suggest a predominance of graminoids (e.g. Guthrie, 2001;Yurtsev, 2001;Zimov et al., 2012), whereas a large-scale sedaDNA survey of 242 sediment samples from 21 sites across the Arctic by Willerslev et al. (2014) questioned the predominance of graminoids, suggesting instead that the importance of forbs in the full-glacial flora has been underestimated. The samples analysed by Willerslev et al. (2014) originated from a range of depositional settings and individually represent only short snapshots in time. ...
A 24,000-year record of plant community dynamics, based on pollen and ancient DNA from the sediments (sedaDNA) of Lake Bolshoye Shchuchye in the Polar Ural Mountains, provides detailed information on the flora of the Last Glacial Maximum (LGM) and also changes in plant community composition and dominance. It greatly improves on incomplete records from short and fragmented stratigraphic sequences found in exposed sedimentary sections in the western Russian Arctic. In total, 162 plant taxa were detected by sedaDNA and 115 by pollen analysis. Several shifts in dominance between and within plant functional groups occurred over the studied period, but most taxa appear to have survived in situ. A diverse arctic-alpine herb flora characterised the interval ca. 24,000e17,000 cal years BP and persisted into the Holocene. Around 17,000 cal years BP, sedges (e.g. Carex) and bryophytes (e.g. Bryum, Aula-comnium) increased. The establishment of shrub-tundra communities of Dryas and Vaccinium sp., with potentially some Betula pubescens trees (influx~290 grains cm 2 year À1), followed at ca. 15,000 cal years BP. Forest taxa such as Picea and ferns (e.g. Dryopteris fragrans, Gymnocarpium dryopteris) established near the lake from ca. 10,000 cal years BP, followed by the establishment of Larix trees from ca. 9000 cal years BP. Picea began to decline from ca. 7000 cal years BP. A complete withdrawal of forest tree taxa occurred by ca. 4000 cal years BP, presumably due to decreasing growing-season temperatures, allowing the expansion of dwarf-shrub tundra and a diverse herb community similar to the present-day vegetation mosaic. Contrary to some earlier comparative studies, sedaDNA and pollen from Lake Bol-shoye Shchuchye showed high similarity in the timing of compositional changes and the occurrence of key plant taxa. The sedaDNA record revealed several features that the pollen stratigraphy and earlier palaeorecords in the region failed to detect; a sustained, long-term increase in floristic richness since the LGM until the early Holocene, turnover in grass and forb genera over the Pleistocene-Holocene transition , persistence of a diverse arctic-alpine flora over the late Quaternary, and a variable bryophyte flora through time. As pollen records are often limited by taxonomic resolution, differential productivity and dispersal, sedaDNA can provide improved estimates of floristic richness and is better able to distinguish between different plant assemblages. However, pollen remains superior at providing quantitative estimates of plant abundance changes and detecting several diverse groups (e.g. Poaceae, Cyperaceae, Asteraceae) which may be underreported in the sedaDNA. Joint use of the two proxies provided unprecedented floristic detail of past plant communities and helped to distinguish between long-distance transport of pollen and local presence, particularly for woody plant taxa.
... Ruminant, anseriform, and lemming species that consume at least 98% of the tundra phytomass are objects of intensive research as a key component of Arctic ecosystems (Tokmakova, 1974;Bogacheva, 1975;Klekowski and Opalinski, 1986;Ims and Fuglei 2005) with transformation rate being noticeable even against the background of global changes (Battisti and Naylor, 2009;Zimov et al., 2012). ...
... First, in comparison with ruminants, the abundance of lemmings and anseriforms wintering outside the island is very variable over time, including because of the more successful goose breeding in lemming years (Prop and Quinn, 2003;Syroechkovskii, 2013). Second, the island was not noted to have a phytomass excess (Stishov, 2004;Nature chronicles …, 2010Nature chronicles …, -2018, to destruct which in the Arctic without warm-blooded animals is very difficult (Tokmakova, 1974;Bogacheva, 1975;Klekowski and Opalinski, 1986;Zimov et al., 2012). The community diversity increase with ruminants only made the phytomass utilization more even and, possibly, more efficient. ...
... The latter version describes mainly succession features in the herbivore community transformation on Wrangel Island. If this is possible in other Artic areas, where the restoration of large herbivore populations is successful, the assumptions about their key role in the ecosystem recycling increasing, including assumptions about the super-productivity of the periglacial "mammoth" steppes of the Pleistocene (Sher et al., 2005;Zimov, 2005;Zimov et al., 2012), suffers losses. ...
... These authors argue that the Betulaand Salix-dominated shrub tundra was inhospitable to grazing megafauna because lowgrowing shrubs develop strong antiherbivory compounds, making them inedible or toxic to many mammals that lack a rumen to aid digestion (28). Other researchers have suggested that the decline in populations of grazing megafauna preceded shrub expansion, and that the spread of shrub tundra was caused by the resulting reduction in browsing pressure, vegetation trampling, and snow clearance (2,29). These studies argue that grazers, and particularly megaherbivores (mammals of >1,000 kg), such as mammoth, acted as keystone species and were essential to the continuation of the steppe-tundra (1). ...
... In records with high-resolution sampling [e.g., Birch Lake (19)], this difference is small; however, in most records, sampling resolution is ≤1 pollen spectrum every 10 cm, which may represent >500 y of sediment accumulation (SI Appendix, Table S1). With this approach, we aim to establish whether shrub expansion began prior to turnover in megafauna communities, as predicted by Guthrie (6,8), or after populations of keystone species collapsed, as suggested by Zimov et al. (2,29). As these hypotheses predict events in the opposite order, it allows us to assess whether the Late Pleistocene extinction of grazing megafauna species was a response to, or the cause of, steppe-tundra decline. ...
... Instead, the timing of shrub expansion corresponds with both Arctic-wide and regional warming and/or wetting trends that occurred during the Bølling-Allerød chronozone. These findings indicate that the role of keystone herbivores was secondary to the role of climate in preserving the steppe-tundra ecosystem and are inconsistent with the hypothesis that a decline in ecosystemmaintaining herbivore populations preceded the expansion of shrub tundra and drove ecosystem cascades (2,29). ...
The collapse of the steppe-tundra biome (mammoth steppe) at the end of the Pleistocene is used as an important example of top-down ecosystem cascades, where human hunting of keystone species led to profound changes in vegetation across high latitudes in the Northern Hemisphere. Alternatively, it is argued that this biome transformation occurred through a bottom-up process, where climate-driven expansion of shrub tundra ( Betula , Salix spp.) replaced the steppe-tundra vegetation that grazing megafauna taxa relied on. In eastern Beringia, these differing hypotheses remain largely untested, in part because the precise timing and spatial pattern of Late Pleistocene shrub expansion remains poorly resolved. This uncertainty is caused by chronological ambiguity in many lake sediment records, which typically rely on radiocarbon ( ¹⁴ C) dates from bulk sediment or aquatic macrofossils—materials that are known to overestimate the age of sediment layers. Here, we reexamine Late Pleistocene pollen records for which ¹⁴ C dating of terrestrial macrofossils is available and augment these data with ¹⁴ C dates from arctic ground-squirrel middens and plant macrofossils. Comparing these paleovegetation data with a database of published ¹⁴ C dates from megafauna remains, we find the postglacial expansion of shrub tundra preceded the regional extinctions of horse ( Equus spp.) and mammoth ( Mammuthus primigenius ) and began during a period when the frequency of ¹⁴ C dates indicates large grazers were abundant. These results are not consistent with a model of top-down ecosystem cascades and support the hypothesis that climate-driven habitat loss preceded and contributed to turnover in mammal communities.
... In the case of eastern Beringia (unglaciated regions of Yukon, Canada and Alaska, U.S.A.), Guthrie 16 , Mann et al. 28,29 , and Rabanus-Wallace et al. 30 argue that the expansion of woody shrubs and peatlands following an increased moisture regime during the late Pleistocene was the leading contributor to the loss of megafaunal grazers, including mammoth, horse, and bison. By contrast, Zimov et al. 23,31 contend that megafaunal extirpations preceded a rise in woody shrubs, with the loss of keystone megaherbivores having led to the disappearance of the graminoid and forb dominated, mammoth-steppe biome 5,[31][32][33] . Disentangling the relative timings of ecological restructuring versus megafaunal population declines often exceeds the resolution 34 of Quaternary records. ...
... In the case of eastern Beringia (unglaciated regions of Yukon, Canada and Alaska, U.S.A.), Guthrie 16 , Mann et al. 28,29 , and Rabanus-Wallace et al. 30 argue that the expansion of woody shrubs and peatlands following an increased moisture regime during the late Pleistocene was the leading contributor to the loss of megafaunal grazers, including mammoth, horse, and bison. By contrast, Zimov et al. 23,31 contend that megafaunal extirpations preceded a rise in woody shrubs, with the loss of keystone megaherbivores having led to the disappearance of the graminoid and forb dominated, mammoth-steppe biome 5,[31][32][33] . Disentangling the relative timings of ecological restructuring versus megafaunal population declines often exceeds the resolution 34 of Quaternary records. ...
... It is thought to have been the most extensive terrestrial biome on Earth during the late Pleistocene, stretching from the Iberian Peninsula eastward across Eurasia and into Canada 31,50-52 , although the extent and character of this ecosystem remains controversial for some 53 . This paradoxically productive 54,55 highlatitude mosaic biome supported a diverse abundance of large bodied fauna 31,50,52 , facilitating higher biotic productivity (energy and nutrient turnover) than many habitats existing at high latitudes today 23,56 . ...
The temporal and spatial coarseness of megafaunal fossil records complicates attempts to to disentangle the relative impacts of climate change, ecosystem restructuring, and human activities associated with the Late Quaternary extinctions. Advances in the extraction and identification of ancient DNA that was shed into the environment and preserved for millennia in sediment now provides a way to augment discontinuous palaeontological assemblages. Here, we present a 30,000-year sedimentary ancient DNA (sedaDNA) record derived from loessal permafrost silts in the Klondike region of Yukon, Canada. We observe a substantial turnover in ecosystem composition between 13,500 and 10,000 calendar years ago with the rise of woody shrubs and the disappearance of the mammoth-steppe (steppe-tundra) ecosystem. We also identify a lingering signal of Equus sp. (North American horse) and Mammuthus primigenius (woolly mammoth) at multiple sites persisting thousands of years after their supposed extinction from the fossil record.
... Most archaeological evidence for Neanderthals is from MIS 3, a period characterized by stadials and interstadials, which lasted from~60 to 27 ka (Tzedakis et al., 2013). During this time, much of the landscape was open steppe with vegetation dominated by Artemisia, Gramineae and Cyperaceae (Guthrie 2006;Zimov et al., 2012). Wood charcoal recovered from La Grotte Walou in Belgium indicates the presence of trees up to~29 ka (Tzedakis et al., 2013) including Pinus spp. ...
... The 'mammoth steppe,' which developed around 125 ka, is understood to have comprised primarily Artemisia, Gramineae, and Cyperaceae (Zimov et al., 2012). Artemisia is a genus of bitter-tasting aromatic herbs and shrubs with strong chemical constituents that can be poisonous and also have medicinal value. ...
Evidence for plants rarely survives on Paleolithic sites, while animal bones and biomolecular analyses suggest animal produce was important to hominin populations, leading to the perspective that Neanderthals had a very-high-protein diet. But although individual and short-term survival is possible on a relatively low-carbohydrate diet, populations are unlikely to have thrived and reproduced without plants and the carbohydrates they provide. Today, nutritional guidelines recommend that around half the diet should be carbohydrate, while low intake is considered to compromise physical performance and successful reproduction. This is likely to have been the same for Paleolithic populations, highlighting an anomaly in that the basic physiological recommendations do not match the extensive archaeological evidence. Neanderthals had large, energy-expensive brains and led physically active lifestyles, suggesting that for optimal health they would have required high amounts of carbohydrates. To address this anomaly, we begin by outlining the essential role of carbohydrates in the human reproduction cycle and the brain and the effects on physical performance. We then evaluate the evidence for resource availability and the archaeological evidence for Neanderthal diet and investigate three ways that the anomaly between the archaeological evidence and the hypothetical dietary requirements might be explained. First, Neanderthals may have had an as yet unidentified genetic adaptation to an alternative physiological method to spare blood glucose and glycogen reserves for essential purposes. Second, they may have existed on a less-than-optimum diet and survived rather than thrived. Third, the methods used in dietary reconstruction could mask a complex combination of dietary plant and animal proportions. We end by proposing that analyses of Paleolithic diet and subsistence strategies need to be grounded in the minimum recommendations throughout the life course and that this provides a context for interpretation of the archaeological evidence from the behavioral and environmental perspectives.
... The BLB extended approximately from the Lena River, Russia, in the west and the Mackenzie River, Yukon, Canada, in the east (Elias and Crocker, 2008) (Fig. 1). The Beringian ecosystem was primarily that of a mammoth steppe, a graminoid-dominated ecosystem that supported a community of large herbivorous mammals, dominated by mammoths (Mamamuthus primigenius), horses (Equus sp.), and steppe bison (Bison priscus) (Guthrie, 2001;Mann et al., 2013;Shapiro and Cooper, 2003;Zimov et al., 2012). The mammoth steppe supported large populations of these herbivores, many of which had larger body sizes than their descendants today at similar latitudes (Zimov et al., 2012). ...
... The Beringian ecosystem was primarily that of a mammoth steppe, a graminoid-dominated ecosystem that supported a community of large herbivorous mammals, dominated by mammoths (Mamamuthus primigenius), horses (Equus sp.), and steppe bison (Bison priscus) (Guthrie, 2001;Mann et al., 2013;Shapiro and Cooper, 2003;Zimov et al., 2012). The mammoth steppe supported large populations of these herbivores, many of which had larger body sizes than their descendants today at similar latitudes (Zimov et al., 2012). Bison, in particular, had larger body sizes and horns than present-day American bison (Bison bison) , and were present throughout most of Eurasia and North America in what has been termed "The Bison Belt" (Guthrie, 1989). ...
Detailed paleoecological evidence from Arctic Alaska’s past megafauna can help reconstruct paleoenvironmental conditions and can illustrate ecological adaptation to varying environments. We examined a rare, largely articulated and almost complete skeleton of a steppe bison (Bison priscus) recently unearthed in Northern Alaska. We used a multi-proxy paleoecological approach to reconstruct the past ecology of an individual representing a key ancient taxon. Radiocarbon dating of horn keratin revealed that the specimen has a finite radiocarbon age ~46,000 ± 1000 cal yr BP, very close to the limit of radiocarbon dating. We also employed Bayesian age modeling of the mitochondrial genome, which estimated an age of ~33,000e87,000 cal yr BP. Our taphonomic investigations show that the bison was scavenged post-mortem and infested by blowflies before burial. Stable carbon and oxygen isotope (d13C and d15N) analyses of sequentially sampled horn keratin reveal a seasonal cycle; furthermore, high d15N values during its first few years of life are consistent with patterns observed in modern bison that undertook
dispersal. We compared sequential analyses of tooth enamel for strontium isotope ratios (87Sr/86Sr) to a spatial model of 87Sr/86Sr values providing evidence for dispersal across the landscape. Synthesis of the paleoecological findings indicates the specimen lived during interstadial conditions. Our multi-proxy, paleoecological approach, combining light and heavy isotope ratios along with genetic
information, adds to the broader understanding of ancient bison ecology during the Late Pleistocene, indicating that ancient bison adopted different degrees of paleo-mobility according to the prevailing
paleoecological conditions and climate.
... Grasses were not dominant locally around the lake. Generally, graminoids dominate landscapes such as the mammoth steppe (Guthrie, 1990;Zimov et al., 2012). According to the sedaDNA record, the lake vicinity during the Late Pleistocene was mostly covered by forb taxa from Asteraceae and Dryas with shrubby habitats hosting a high proportion of shrub willows. ...
... Furthermore, because forbs may be more nutrient-rich and more easily digested than grasses, this could explain how numerous large animals were sustained (Cornelissen et al., 2004). The presence of abundant megafauna could have caused significant trampling and enhanced gap-based recruitment which would have facilitated the spread of forbs (Owen-Smith, 1987;Zimov et al., 2012). ...
Relationships between climate, species composition, and species richness are of particular importance for understanding how boreal ecosystems will respond to ongoing climate change. This study aims to reconstruct changes in terrestrial vegetation composition and taxa richness during the glacial Late Pleistocene and the interglacial Holocene in the sparsely studied southeastern Yakutia (Siberia) by using pollen and sedimentary ancient DNA (sedaDNA) records. Pollen and sedaDNA metabarcoding data using the trnL g and h markers were obtained from a sediment core from Lake Bolshoe Toko. Both proxies were used to reconstruct the vegetation composition, while metabarcoding data were also used to investigate changes in plant taxa richness. The combination of pollen and sedaDNA approaches allows a robust estimation of regional and local past terrestrial vegetation composition around Bolshoe Toko during the last ∼35,000 years. Both proxies suggest that during the Late Pleistocene, southeastern Siberia was covered by open steppe-tundra dominated by graminoids and forbs with patches of shrubs, confirming that steppe-tundra extended far south in Siberia. Both proxies show disturbance at the transition between the Late Pleistocene and the Holocene suggesting a period with scarce vegetation, changes in the hydrochemical conditions in the lake, and in sedimentation rates. Both proxies document drastic changes in vegetation composition in the early Holocene with an increased number of trees and shrubs and the appearance of new tree taxa in the lake’s vicinity. The sedaDNA method suggests that the Late Pleistocene steppe-tundra vegetation supported a higher number of terrestrial plant taxa than the forested Holocene. This could be explained, for example, by the “keystone herbivore” hypothesis, which suggests that Late Pleistocene megaherbivores were able to maintain a high plant diversity. This is discussed in the light of the data with the broadly accepted species-area hypothesis as steppe-tundra covered such an extensive area during the Late Pleistocene.
... This flexibility explains why horses are represented not only in interstadial and stadial faunas, but possibly even in interglacial ones (Von Koenigswald, 2003;Saarinen et al., 2016). Furthermore, reindeer material is less likely to be preserved compared to other herbivores in the present collection, as their thin-walled humeri and radii were easily eroded or gnawed away by predators and scavengers (Van der Jagt, 2005;Zimov et al., 2012). ...
... The geology at the site suggests these herbivores are to be associated with cold climatic conditions during the Late Pleistocene, and in particular with the Weichselian Glacial (DINOloket, 2020). They were occupants of the 'mammoth steppe', the cold, dry grass steppe that extended over much of the Northern Hemisphere during the Late Pleistocene (Zimov et al., 2012). ...
More than 900 vertebrate bones, ranging from Late Pleistocene to Holocene in age, have been identified in a collection that was recovered by a single dredging operation for the construction of artificial lakes near Lent (Nijmegen, province of Gelderland, the Netherlands). The Late Pleistocene assemblage comprises mainly Weichselian glacial fauna such as mammoths, reindeer and bison. Some Eemian fauna is represented as well, e.g. straight-tusked elephant. The abundance of certain species over others suggests that preservation bias had a considerable impact on this assemblage, while its time-averaged nature resulted in overrepresentation of certain species. A case study is here conducted on a fragmentary skull of a subadult woolly mammoth bull with embedded blowfly puparia. Some of these puparia are fully developed, indicating prolonged exposure of the mammoth carcass.
... Controversy has persisted for decades over the nature of the Mammoth Steppe, a distinctive, now-vanished biome dominated by large mammal grazers 1, 19,32 . Some studies, emphasizing the abundance of grazers (and the absence of large browsers), suggest that broad swaths of the unglaciated Late Pleistocene Arctic were covered by an extensive steppe dominated by low-sward herbaceous plants that were well-suited for megafaunal grazers 19,32 . ...
... Controversy has persisted for decades over the nature of the Mammoth Steppe, a distinctive, now-vanished biome dominated by large mammal grazers 1, 19,32 . Some studies, emphasizing the abundance of grazers (and the absence of large browsers), suggest that broad swaths of the unglaciated Late Pleistocene Arctic were covered by an extensive steppe dominated by low-sward herbaceous plants that were well-suited for megafaunal grazers 19,32 . Others, on the basis of pollen and plant macrofossil records, suggest that Arctic vegetation during this period was regionally diverse and included both tundra and steppe taxa 3,33 . ...
During the last glacial–interglacial cycle, Arctic biotas experienced substantial climatic changes, yet the nature, extent and rate of their responses are not fully understood1–8. Here we report a large-scale environmental DNA metagenomic study of ancient plant and mammal communities, analysing 535 permafrost and lake sediment samples from across the Arctic spanning the past 50,000 years. Furthermore, we present 1,541 contemporary plant genome assemblies that were generated as reference sequences. Our study provides several insights into the long-term dynamics of the Arctic biota at the circumpolar and regional scales. Our key findings include: (1) a relatively homogeneous steppe–tundra flora dominated the Arctic during the Last Glacial Maximum, followed by regional divergence of vegetation during the Holocene epoch; (2) certain grazing animals consistently co-occurred in space and time; (3) humans appear to have been a minor factor in driving animal distributions; (4) higher effective precipitation, as well as an increase in the proportion of wetland plants, show negative effects on animal diversity; (5) the persistence of the steppe–tundra vegetation in northern Siberia enabled the late survival of several now-extinct megafauna species, including the woolly mammoth until 3.9 ± 0.2 thousand years ago (ka) and the woolly rhinoceros until 9.8 ± 0.2 ka; and (6) phylogenetic analysis of mammoth environmental DNA reveals a previously unsampled mitochondrial lineage. Our findings highlight the power of ancient environmental metagenomics analyses to advance understanding of population histories and long-term ecological dynamics.
... Especially large-shelled taxa, such as Agalactochilus and Megalotachea did not pass the Pliocene--Pleistocene boundary. It is most likely that the climatic deterioration and the subsequent development of the Pleistocene mammoth steppe (Zimov et al., 2012) played a major role in shaping the terrestrial gastropod faunas. As mentioned above, a detailed palaeoecological analysis of the fauna is needed to decipher discrete ecological and climatical parameters to explain the observed extinctions. ...
We present a critical review of the fossil record of Cenozoic terrestrial gastropods of Europe utilizing a literature- based dataset comprising 1597 species from 584 sites. Net diversity (expressed as species, genus and family richness) and β-diversity (as species, genus and family turnover) reveal several major disruptive phases. Turnovers occurred at the Ypresian–Lutetian and Eocene–Oligocene boundaries, and extinction events took place at the Oligocene–Miocene, Burdigalian–Langhian and Pliocene–Pleistocene boundaries. These biotic shifts correlate largely with global climatic events such as the Ypresian–Lutetian transition from Hothouse to Warmhouse, the Oi-1 glaciation at the Eocene–Oligocene boundary and with the onset of the Pleistocene glacials at the Pliocene-Pleistocene boundary. Phases of diversification during the Lutetian, Burdigalian and Pliocene seem to be linked to phases of relative climate stability. At least five immigration events are reflected by the appearance of exotic elements in European faunas during the Ypresian, Bartonian, Rupelian, Burdigalian and Langhian. Many of them correlate with the formation of terrestrial pathways and major migration events in mammals. Furthermore, we provide an overview of the stratigraphic ranges of families and genera in the European fossil record and discuss the timing of the first appearances of extant genera and species, setting important constraints for future molecular phylogenies.
Pfefferiola nov. nom. pro Oppenheimiella Pfeffer, 1930, non Meunier, 1893, Hochheimia nov. nom. pro Palaeotrichia Nordsieck, 2014, non Guinot, 1976 and “Gibbulinella” sandbergeri nov. nom. pro Pupa simplex Sandberger, 1870, non Gould, 1840 are introduced as new replacement names.
... Это также указывает на формирование жил в условиях заболоченных полигональных ландшафтов, где происходит разложение органики как растительного, так и животного происхождения. Известно, что в позднем плейстоцене на севере Якутии высокая активность мамонтовой фауны и поступление в почву большого количества продуктов их жизнедеятельности [32] Заключение О сновными выводами проведенного исследования являются: 1) содержание ионов Na + , Библиография позднеплейстоценовых жилах, исследованных на севере Якутии в районе пос.Черский и Станчиковский Яр, очень низкое и в среднем не превышает 5 мг/л; 2) наиболее высокие значения отмечены для иона Ca2+ -в среднем от 6,4 мг/л в голоценовой жиле до 8-19 мг/л -в позднеплейстоценовых жилах. Это соответствует преобладанию иона Ca2+ в современном снеге Якутии и отражает континентальный тип засоления снежного покрова и указывает на преимущественное формирование жил из талого снега; 3) отмечены высокие значения N O 3-, достигающие в голоценовой жиле и до 27 мг/л в позднеплейстоценовых жилах. ...
The subject of this research is the Late Pleistocene and Holocene ice wedges exposed near Chersky settlement, lower Kolyma River, and in the yedoma strata of the Stanchikovsky Yar on the Maly Anyuy River. In the yedoma of the Stanchikovsky Yar, multi-tiered syngenetic ice wedges were exposed at different levels – from 10 to 35 m above river level. Ice wedge in the lower tier was sampled in detail. In the yedoma strata near Chersky relatively small fragments of ice wedges up to 1.5 m wide and up to 2 m high were exposed. 1.5-2 km from Chersky within the lacusrtine-paludal depression Holocene ice wedges were exposed. Ice wedges in these three sections was sampled to clarify the geochemical conditions of their formation. It is shown that concentration of Na+, K+, Mg2+, Cl- and SO42- in Holocene and Late Pleistocene ice wedges is very low and mean values do not exceed 5 mg/L. The highest values were obtained for Ca2+, which corresponds to the predominance of this ion in the modern snow of Yakutia and indicates that ice wedges were formed mainly from melted snow. Rather high values of NO3-, reaching 14-27 mg/L, are quite likely due to the swampy environment within polygonal landscapes, where organic matter of both plant and animal origin is decomposed. For comparison, in the water of the Kolyma and Maly Anyu rivers, concentration of nitrates is quite low and does not exceed 0.3 mg/L.
... However, after the last glacial period, about 10 thousand years ago (on the boundary between the Pleistocene and Holocene epochs), climatic warming allowed expanding human habitat to the north, and people who migrated to these locations actively engaged in hunting these animals, resulting in substantial ecosystem changes. According to one hypothesis (Zimov et al., 2012), human-induced changes in the ecosystem influenced changes in the region's flora. Because of the resulting sharp decrease in the herbivore population, the steppe plants were left uneaten and accumulated in the soil, forming a heatinsulating layer, resulting in less permafrost thawing. ...
This book is an attempt to understand the impact of Climate Change on the Arctic human societies from the indigenous perspectives, by focusing on the peoples living in the Republic of Sakha (Yakutia) of the Russian Federation. Historically, and also today, the livelihood of the Sakha people is closely related to permafrost. Scientific evidence shows that the thawing of the permafrost through climate change is causing severe problems on a global scale, which is alarming both international organizations and global citizens. Scientific studies confirming actual changes to the local environment, and the communities in permafrost areas are published continuously in academia. However, it is questionable whether scientists are adequately communicating this information to both the general public and the local populations. Climate change is a global phenomenon; however, it often manifests itself as regional and local natural disasters, which makes that it is essential to view climate change from a regional perspective. Therefore, focusing on particular regions and examining specific situations in detail provides a more accurate picture of the global situation.
http://www.amazon.co.jp/dp/B08ZMH66R2
... Вымирание сокращающихся и полностью или частично изолированных популяций дикого северного оленя (Rangifer tarandus) на северной окраине ареала наносит этому виду непоправимый ущерб и критически сказывается на функционировании арктических экосистем в целом, приобретая, таким образом, глобальное значение (Абатуров, 1979;Ims, Fuglei, 2005;Zimov et al., 2012;Metcalfe, Olofsson, 2015). Среди основных причин этого сокращения рассматривались нелегальная добыча, потеря местообитаний и ограничение миграций в ходе освоения Арктики, деградация пастбищ под влиянием одомашненных оленей и преследование оленеводами, болезни, хищники и климатические изменения, например многоснежье и гололеды (Филонов, 1983; Глушков, 1987; Перовский, 1988; Глушков, Граков, 1989; Володина, 2010; Ломанова, Баранов, 2014; Горчаковский, 2015). ...
... The climate of the Yukon during the late Pleistocene was generally cooler and drier than today (Zazula et al., 2006b;Zimov et al., 2012), which allowed for the development of open, largely treeless habitats dominated by steppe-like grasslands (Zimov et al., 1995;Zazula et al., 2003). The northern Yukon Territory was part of the mammoth steppe, a megacontinental ecosystem characterized by the presence of herbivorous megafauna (>44 kg) (Harington, 2011;Jürgensen et al., 2017;Schwartz-Narbonne et al., 2019). ...
We investigate if and how diets of gray wolves from the Yukon Territory, Canada, have changed from the Pleistocene (>52.8 ka BP to 26.5 ka BP [±170 y BP]) to the recent Holocene (1960s) using dental microwear analysis of carnassial teeth and stable isotope analyses of carbonates (δ¹³CCO3 and δ¹⁸OCO3) and collagen (δ¹³Ccol and δ¹⁵Ncol) from bone. We find that dental microwear patterns are similar between the Pleistocene and Holocene specimens, indicating that there has been no change in carcass utilization behaviours, where flesh, not bone, is primarily consumed. Based on minimal changes in δ¹³CCO3 and δ¹³Ccol values, we find that, over thousands of years, Yukon gray wolves have remained generalist predators feeding upon several large ungulate species. Interestingly, δ¹⁵Ncol values suggest that the extinction of megafaunal species at ~11.7 Ka induced a shift from a diet comprised primarily of horse (Equus sp.) to one based on cervids (i.e. moose and caribou). Survival of large-bodied cervids, such as caribou (Rangifer tarandus), was likely key to wolf survival. Although gray wolves survived the end Pleistocene megafauna extinction and demonstrate a degree of ecological flexibility, we suggest that failure to preserve major elements of their current niche (e.G. caribou) may result in continued population declines, especially in the face of increasing anthropogenic influences.
... An essential element of this vanished ecosystem was an enormous ungulate biomass. Calculations of ungulate biomass derived from the fossil record of the mammoth steppe (Zimov et al., 2012) can reach values equivalent to ungulate productivity in African savanna ecosystems. However, taking the external factors that limit the carrying capacity of an ecosystem into account, ungulate biomass production in the mammoth steppe of the northern latitudes must have been relatively low, especially in relation to interglacial ecosystems (Rodríguez et al., 2014;Kind ler et al., 2020). ...
The article presents the diagnosis and aetiology of an arthropathological horse (Equus sp.) radius from the Middle Palaeolithic site of Pfeddersheim (Rhine-Hesse, Germany). For the contextualisation of the results the chronological and archaeological frame of the site, the taphonomic history of the faunal assemblage and site formation are summarised. A fracture of the ulna caused a malposition of the humeroradial joint, that developed into a degenerative arthrosis with severe grooving of the articular surface of the radius, extension of the joint by new bone formation and exostosis around the epiphysis. The progression of the disease from the trauma to the final grade of arthrosis and how it affected the horse's life is portrayed. Eventually, the horse fell prey to a large carnivore. Finally, the palaeoecological significance of this very specific palaeopathological finding is discussed.
... Woolly mammoths were distributed in open steppe-like environments across the high latitudes of the Northern Hemisphere (Guthrie, 2006). They were primarily grazers, with a diet dominated by graminoids and herbs (Willerslev et al., 2014;Zimov et al., 2012), though some authors suggest a degree of mixed-feeding of graze and browse (Rivals et al., 2010;Saunders et al., 2010). Woolly mammoth populations on the North American mainland declined steeply starting at 14 ka and were extirpated by 12.1 ka (Guthrie, 2006;MacDonald et al., 2012;Widga et al., 2017). ...
Aim
Identifying how climate change, habitat loss, and corridors interact to influence species survival or extinction is critical to understanding macro‐scale biodiversity dynamics under changing environments. In North America, the ice‐free corridor was the only major pathway for northward migration by megafaunal species during the last deglaciation. However, the timing and interplay among the late Quaternary megafaunal extinctions, climate change, habitat structure, and the opening and reforestation of the ice‐free corridor have been unclear.
Location
North America.
Time period
15–10 ka.
Major taxa studied
Woolly mammoth (Mammuthus primigenius).
Methods
For central North America and the ice‐free corridor between 15 and 10 ka, we used a series of models and continental‐scale datasets to reconstruct habitat characteristics and assess habitat suitability. The models and datasets include biophysical and statistical niche models Niche Mapper and Maxent, downscaled climate simulations from CCSM3 SynTraCE, LPJ‐GUESS simulations of net primary productivity (NPP) and woody cover, and woody cover based upon fossil pollen from Neotoma.
Results
The ice‐free corridor may have been of limited suitability for traversal by mammoths and other grazers due to persistently low productivity by herbaceous plants and quick reforestation after opening 14 ka. Simultaneously, rapid reforestation and decreased forage productivity may have led to declining habitat suitability in central North America. This was possibly amplified by a positive feedback loop driven by reduced herbivory pressures, as mammoth population decline led to the further loss of open habitat.
Main conclusions
Declining habitat availability south of the Laurentide Ice Sheet and limited habitat availability in the ice‐free corridor were contributing factors in North American extinctions of woolly mammoths and other large grazers that likely operated synergistically with anthropogenic pressures. The role of habitat loss and attenuated corridor suitability for the woolly mammoth extinction reinforce the critical importance of protected habitat connectivity during changing climates, particularly for large vertebrates.
... When Neanderthals still occupied much of Europe, the continent was largely a steppe-tundra, or Mammoth Steppe (Guthrie, 1990), characterised by the great diversity of large mammals, which required diets high in available energy and nutrients (Guthrie, 1982), effectively creating a large mosaic of environments (Johnson, 2009). In fact, Zimov et al. (2012) estimated the Mammoth Steppe to have an animal biomass and plant productivity close to those of African savannah environments. The consequence of this is that the Effective Temperature, as employed by Binford (1980) and Kelly (2013), at the European latitudes as a variable that defines the primary productivity and available animal biomass does not apply to the Palaeolithic. ...
A database of Neanderthal raw material transports and fauna from assemblages across Europe has been compiled with the aim to explore the evolution of the Neanderthals’ mobility behaviour with regard to the environment from the beginning of the Late Saalian (191 ka BP) to the demise of Neanderthals (40 ka BP). Mobility, as observed from the lithic transports in the Palaeolithic, is often interpreted as mirroring the social organisation of a group. As the study of Neanderthal mobility normally focuses on the maximum transport distances of lithics, such a methodology is seen as inadequate because three equifinal processes (subsistence activity, social transactions, and semi-random lithic scavenging) can account for these distances. Here, two different indicators of Neanderthal mobility are created based on the transport distances, quantities, and number of utilised raw material sources. The first one is the overall mobility, which represents the sum of the effort made to acquire all lithics from all sources. The second indicator is the mean effort per raw material, which quantifies the average effort made to acquire the different raw materials present in that assemblage.
By analysing Neanderthal mobility in terms of these two variables, it is shown that Neanderthal social organisation evolves from the Saalian to the Early and Late Weichselian. This change is interpreted as reflecting diversification of their subsistence behaviour and as reflecting a tendency to optimise their foraging behaviour through decision making. In subsequent statistical analyses, it is demonstrated that there are no real differences in Neanderthal mobility between the east and the west, and that Neanderthals appear to have preferred semi-open landscapes, but somewhat avoided montane regions. The presence of the Mammoth Steppe was not noted as having either a negative or a positive impact on Neanderthals’ level of mobility. The apparent preference for semi-open landscapes and the variation in the different environments implies that they were top carnivores that may have exercised encounter-based hunting, which may explain their body type and injury patterns identified previously.
... This idea is designed to slow the thawing of the Arctic permafrost (Macias-Fauria et al., 2020;Zimov et al., 2009Zimov et al., , 2012. The method is to introduce large herbivores into the permafrost region which would: (1) smash down trees, eat the young shrub and tree shoots, increasing winter and spring albedo; (2) trample the snow pack increasing its density and lowering its insulating capacity in winter thereby cooling the permafrost; and (3) increase the carbon storage capacity of the vegetation layer by fertilizing grasses, removing moss cover and improving surface drainage. ...
Targeted geoengineering aims to tackle a global scale impact of climate warming by addressing local or regional systemic interventions. We consider three examples: conserving the West Antarctic ice sheet by limiting rates of ice discharge or increasing snow accumulation, thereby reducing global sea level rise; transforming the Arctic permafrost zone into steppe grassland; raising the albedo of Arctic sea ice. There are important differences between targeted interventions and archetypal solar geoengineering, which ideally would have global governance structures, while some targeted interventions may be done entirely under the accepted purview of small numbers of nation states. For example, the West Antarctic ice sheet is governed by the consultative members of the Antarctic Treaty. Of the interventions we look at, only ice sheet conservation seems viable and efficient relative to solar geoengineering. Many important treaties and conventions rely on the precautionary approach. While at first glance this principle seems to argue against targeted interventions, we argue that it may in fact do the opposite. Given the existence of irreversible thresholds in many natural systems, the precautionary approach may be better upheld by a targeted intervention that prevents a system from changing in ways that cannot be undone.
The article is available at https://onlinelibrary.wiley.com/doi/epdf/10.1111/1758-5899.12867 and https://www.globalpolicyjournal.com/articles/climate-change-energy-and-sustainability/targeted-geoengineering-local-interventions
... The biome developed after fragmentation of taiga forests during mid-Pleistocene (Kahlke, 2014), and harboured a mixture of northern tundra and continental steppe faunas, including mammalian megaherbivores (Chytrý et al., 2019;Ricankova et al., 2014;Zazula et al., 2003). Owing to megafauna presence, the mammoth steppe consisted of mosaic of habitats and maintained the open vegetation structure even during humid interglacials (Johnson, 2009;Sandom et al., 2014;Zimov et al., 2012). In the current interglacial, the Holocene, herds of large herbivores disappeared from major parts of the Holarctic as a consequence of human hunting and/or climate change, which allowed for major expansion of woodlands (e.g., Araujo et al., 2017). ...
Aim
Biogeographical studies on the entire ranges of widely distributed species can change our perception of species’ range dynamics. We studied the effects of Pleistocene glacial cycles on current butterfly species distributions, aiming to uncover complex biogeographic patterns in the Holarctic, a region dramatically affected by Cenozoic climate change.
Location
Eurasia and North America.
Taxon
Boloria chariclea, Agriades optilete, Carterocephalus palaemon, Oeneis jutta.
Methods
We reconstructed the biogeographic history of four butterfly species differing in habitat preferences (B. chariclea – tundra, A. optilete – bogs, C. palaemon – temperate grasslands, O. jutta – taiga), using one mitochondrial and two nuclear DNA markers and species distribution modelling.
Results
Except for B. chariclea, all species originated in Eurasia. The open habitat species A. optilete and C. palaemon formed widely distributed east‐west genetic clusters in continental Asia and clusters separated from them in Europe. Genetic clusters of the taiga species O. jutta were not geographically separated in Eurasia, suggesting Pleistocene fragmentation and recent reconnection. The glaciated North America was recolonized from Beringian and southerly situated refugia by all four species.
Main conclusions
The Pleistocene mammoth steppe allowed a widespread continuous distribution of open habitat butterflies, while in contrast the distribution of a taiga‐specialist species was more limited. In the mostly flat and continental North Asia, the butterflies of various types of open habitats survived ice age in widely distributed east‐west belts. In the mountainous and oceanic regions of Europe, Beringia and west North America, all four species persisted in contracted areas during the glacials. After deglaciation, they expanded their ranges and formed contact zones among populations. To conclude, the harsh climate of the glacials did not represent an obstacle for butterflies. Instead, different habitat specialists selected their own ways to thrive in the dynamic conditions of Quaternary glacial periods.
... During much of the Late Pleistocene epoch, Siberia, Alaska and northern Canada were connected, forming a dry and largely treeless landmass known as Beringia (Hopkins, 1959;Hopkins et al., 1982). The landscape was dominated by emblematic megafauna such as woolly mammoths and steppe bison, and in terms of biomass some authors have compared this period to the current African savannah (Zimov et al., 2012). Mammals had a major role in shaping vegetation community and structure by reducing vegetation density, enhancing nutrient turnover, dispersing seeds and reducing fire potential (Guthrie, 2001;Hester et al., 2006;Johnson, 2009). ...
... Gene editing is not only an efficient, perhaps sometimes necessary means to certain ends-it will alter how we and future humans will feel about nature as it is increasingly populated by gene-edited creatures, even if these serve as our agents for species conservation or ecosystem restoration. For some of us, it is very appealing to "resurrect" species that could remake past landscapes and ecosystems that we mourn, from the American chestnut-dominated forests of central and eastern North America (86-88) to the mammoth steppes of Beringia (89,90). If we restrict human activities and free enough space and time so that these species can evolve and reconfigure ecological systems on their own, we could possibly maintain aspects of wildness and wilderness important to the prophets (80) among us today. ...
CRISPR-Cas gene editing tools have brought us to an era of synthetic biology that will change the world. Excitement over the breakthroughs these tools have enabled in biology and medicine is balanced, justifiably, by concern over how their applications might go wrong in open environments. We do not know how genomic processes (including regulatory and epigenetic processes), evolutionary change, ecosystem interactions, and other higher order processes will affect traits, fitness, and impacts of edited organisms in nature. However, anticipating the spread, change, and impacts of edited traits or organisms in heterogeneous, changing environments is particularly important with “gene drives on the horizon.” To anticipate how “synthetic threads” will affect the web of life on Earth, scientists must confront complex system interactions across many levels of biological organization. Currently, we lack plans, infrastructure, and funding for field science and scientists to track new synthetic organisms, with or without gene drives, as they move through open environments.
... www.nature.com/scientificreports/ Today, wild herbivore density is relatively low, with only domestic horses, and reindeer in the north occurring in larger herds 13,14 . Higher densities of grazers are only reached in game parks, where supplementary feeding sustains these herds. ...
The Siberian mammoth steppe ecosystem changed dramatically with the disappearance of large grazers in the Holocene. The concept of Pleistocene rewilding is based on the idea that large herbivore grazing significantly alters plant communities and can be employed to recreate lost ecosystems. On the other hand, modern rangeland ecology emphasizes the often overriding importance of harsh climates. We visited two rewilding projects and three rangeland regions, sampling a total of 210 vegetation relevés in steppe and surrounding vegetation (grasslands, shrublands and forests) along an extensive climatic gradient across Yakutia, Russia. We analyzed species composition, plant traits, diversity indices and vegetation productivity, using partial canonical correspondence and redundancy analysis. Macroclimate was most important for vegetation composition, and microclimate for the occurrence of extrazonal steppes. Macroclimate and soil conditions mainly determined productivity of vegetation. Bison grazing was responsible for small-scale changes in vegetation through trampling, wallowing and debarking, thus creating more open and disturbed plant communities, soil compaction and xerophytization. However, the magnitude of effects depended on density and type of grazers as well as on interactions with climate and site conditions. Effects of bison grazing were strongest in the continental climate of Central Yakutia, and steppes were generally less affected than meadows. We conclude that contemporary grazing overall has rather limited effects on vegetation in northeastern Siberia. Current rewilding practices are still far from recreating a mammoth steppe, although large herbivores like bison can create more open and drier vegetation and increase nutrient availability in particular in the more continental Central Yakutian Plain.
... Apart from the increased exposure of organic matter to mineral soil through physical mixing, soil fauna play a dominant role for overall ecosystem functioning [87]. In the Arctic, where it has been proposed that large herbivores played a major role in prehistoric times in shaping ecosystems [88,89], the soil community is currently not adapted to large herbivore-rich systems, which may have functional repercussions [89]. For example, experimental introduction of soil-mixing earthworms in the Arctic has shown that they can effectively alleviate plant nutrient limitations and increase greening [90]. ...
There is growing interest in aligning the wildlife conservation and restoration agenda with climate change mitigation goals. However, the presence of large herbivores tends to reduce aboveground biomass in some open-canopy ecosystems, leading to the possibility that large herbivore restoration may negatively influence ecosystem carbon storage. Belowground carbon storage is often ignored in these systems, despite the wide recognition of soils as the largest actively-cycling terrestrial carbon pool. Here, we suggest a shift away from a main focus on vegetation carbon stocks, towards inclusion of whole ecosystem carbon persistence, in future assessments of large herbivore effects on long-term carbon storage. Failure to do so may lead to counterproductive biodiversity and climate impacts of land management actions.
... Permafrost landscape studies can benefit this development. Recently, suggestions for permafrost temperature management by controlled grazing to ensure permafrost sustainability and reduce greenhouse gas emissions have attracted interest [147,[160][161][162]. ...
The results of permafrost landscape studies on northeastern Eurasia are presented in this review. The assessment of permafrost vulnerability to disturbances and global warming was the basis for the development of these studies. The permafrost landscape, considering the morphological features of the landscape and the permafrost together, is a timely object of study. The theoretical developments of Soviet physical geographers and landscape scientists are the basis for permafrost landscape studies. Over the past four decades, numerous permafrost landscape studies have been carried out on northeastern Eurasia (and Russia). Considering the results of these studies is the main objective of this article. The analysis of the problems of permafrost landscape identification, classification, and mapping and the study of their dynamics and evolution after disturbances and long-term development were carried out. Permafrost landscape studies employ the research methods of landscape science and geocryology. Environmental protection and adaptation of socioeconomic conditions to modern climate warming will determine the prospects for studying permafrost landscapes.
... During much of the Late Pleistocene epoch, Siberia, Alaska and northern Canada were connected, forming a dry and largely treeless landmass known as Beringia (Hopkins, 1959;Hopkins et al., 1982). The landscape was dominated by emblematic megafauna such as woolly mammoths and steppe bison, and in terms of biomass some authors have compared this period to the current African savannah (Zimov et al., 2012). Mammals had a major role in shaping vegetation community and structure by reducing vegetation density, enhancing nutrient turnover, dispersing seeds and reducing fire potential (Guthrie, 2001;Hester et al., 2006;Johnson, 2009). ...
The study of faecal samples to reconstruct the diets and habitats of extinct megafauna has traditionally relied on pollen and macrofossil analysis. DNA metabarcoding has emerged as a valuable tool to complement and refine these proxies. While published studies have compared the results of these three proxies for sediments, this comparison is currently lacking for permafrost preserved mammal faeces. Moreover, most metabarcoding studies have focused on a single plant-specific DNA marker region. In this study, we target both the commonly used chloroplast trnL P6 loop as well as nuclear ribosomal ITS (nrITS). The latter can increase taxonomic resolution of plant identifications but requires DNA to be relatively well preserved because of the target length (∼300–500 bp). We compare DNA results to pollen and macrofossil analyses from permafrost and ice-preserved faeces of Pleistocene and Holocene megafauna. Samples include woolly mammoth, horse, steppe bison as well as Holocene and extant caribou. Most plant identifications were found using DNA, likely because the studied faeces contained many vegetative remains that could not be identified using macrofossils or pollen. Several taxa were, however, identified to lower taxonomic levels uniquely with macrofossil and pollen analysis. The nrITS marker provides species level taxonomic resolution for commonly encountered plant families that are hard to distinguish using the other proxies (e.g. Asteraceae, Cyperaceae and Poaceae). Integrating the results from all proxies, we are able to accurately reconstruct known diets and habitats of the extant caribou. Applying this approach to the extinct mammals, we find that the Holocene horse and steppe bison were not strict grazers but mixed feeders living in a marshy wetland environment. The mammoths showed highly varying diets from different non-analogous habitats. This confirms the presence of a mosaic of habitats in the Pleistocene ‘mammoth steppe’ that mammoths could fully exploit due to their flexibility in food choice.
... Besides the tundra, relatively high levels of underrepresentation were also found in the taiga and the broadleaf deciduous forest biomes, which could be related to the extreme fragmentation levels underwent by these biomes during Pleistocene glacial phases, when tundra, steppe and desert expanded across the globe, relegating forest ecosystems to very limited locations (Ray and Adams 2001;Behl 2011;Beyer et al. 2020), which might not be large enough to maintain minimum viable populations of stenobiomic species of these biomes, particularly among the larger species. The fact that tundra specialists also reached high values of underrepresentation might suggest that continental ice-sheet expansion and development of the tundra-steppe biome, also known as mammoth steppe (Zimov et al. 2012;Bråthen et al. 2021), might have an important role in the demise of tundra faunas, despite the globally colder climate, due to the preponderance of dryer conditions. ...
... Additional proxy reconstructions from Asia are needed to evaluate the spatial pattern of LGM temperature change there. The mild conditions reconstructed for Beringia may have been important for maintaining the highlyproductive mammoth-steppe tundra (Zimov et al., 2012) and sustaining human occupation of Beringia through the LGM (Goebel et al., 2008;Vachula et al., 2019). Our finding of relatively weak summertime cooling during the LGM could support the hypothesis that the orographic effect of the Laurentide Ice Sheet was to steer relatively warm air into the region (Otto-Bliesner et al., 2006;Briner and Kaufman, 2008;Bartlein et al., 2011). ...
The Late-Quaternary climate of Beringia remains unresolved despite the region's role in modulating glacial-interglacial climate and as the likely conduit for human dispersal into the Americas. Here, we investigate Beringian temperature change using an ∼32,000-year lacustrine record of leaf wax hydrogen isotope ratios (δ²Hwax) from Arctic Alaska. Based on Monte Carlo iterations accounting for multiple sources of uncertainty, the reconstructed summertime temperatures were ∼3 °C colder (range: −8 to +3 °C) during the Last Glacial Maximum (LGM; 21-25 ka) than the pre-industrial era (PI; 2–0.1 ka). This ice-age summer cooling is substantially smaller than in other parts of the Arctic, reflecting altered atmospheric circulation and increased continentality which weakened glacial cooling in the region. Deglacial warming was punctuated by abrupt events that are largely synchronous with events seen in Greenland ice cores that originate in the North Atlantic but which are also controlled locally, such as by the opening of the Bering Strait between 13.4 and 11 ka. Our reconstruction, together with climate modeling experiments, indicates that Beringia responds more strongly to North Atlantic freshwater forcing under modern-day, open-Bering Strait conditions than under glacial conditions. Furthermore, a 2 °C increase (Monte Carlo range: −1 to +5 °C) over the anthropogenic era reverses a 6 °C decline (Monte Carlo range: −10 to 0 °C) through the Holocene, indicating that recent warming in Arctic Alaska has not surpassed peak Holocene summer warmth.
... In cold biomes, herbivores reduce winter snow cover through trampling and foraging. This activity exposes soil microbial communities to cold winter temperatures, which reduces their activity 89,90 and creates drier soil conditions during the spring thaw 91 , both of which result in lower methane and N 2 O emissions (N 2 O is a greenhouse gas $265 times more potent than CO 2 85 ) 92,93 . Animals also add nitrogen to the soil system, via defecation and urination, which can increase pulse N 2 O production ( Figure 1) 88 . ...
Two major environmental challenges of our time are responding to climate change and reversing biodiversity decline. Interventions that simultaneously tackle both challenges are highly desirable. To date, most studies aiming to find synergistic interventions for these two challenges have focused on protecting or restoring vegetation and soils but overlooked how conservation or restoration of large wild animals might influence the climate mitigation and adaptation potential of ecosystems. However, interactions between large animal conservation and climate change goals may not always be positive. Here, we review wildlife conservation and climate change mitigation in terrestrial and marine ecosystems. We elucidate general principles about the biome types where, and mechanisms by which, positive synergies and negative trade-offs between wildlife conservation and climate change mitigation are likely. We find that large animals have the greatest potential to facilitate climate change mitigation at a global scale via three mechanisms: changes in fire regime, especially in previously low-flammability biomes with a new or intensifying fire regime, such as mesic grasslands or warm temperate woodlands; changes in terrestrial albedo, particularly where there is potential to shift from closed canopy to open canopy systems at higher latitudes; and increases in vegetation and soil carbon stocks, especially through a shift towards below-ground carbon pools in temperate, tropical and sub-tropical grassland ecosystems. Large animals also contribute to ecosystem adaptation to climate change by promoting complexity of trophic webs, increasing habitat heterogeneity, enhancing plant dispersal, increasing resistance to abrupt ecosystem change and through microclimate modification.
... Active layer thickness is associated with warming of the ground, influenced by summer temperatures, insulation from snow, 325 and vegetation density and composition (Walker et al., 2003;Skarin et al., 2020). Therefore, following Zimov et al. (2012), influencing these insulating factors should affect the active layer depth by allowing for stronger cooling of the ground in winter (Fig. 8). However, to determine any trends, repeated annual measurements of the thaw depth are needed. ...
The risk of carbon emissions from permafrost ground is linked to ground temperature and thus in particular to thermal insulation by vegetation and organic soil layers in summer and snow cover in winter. This ground insulation is strongly influenced by the presence of large herbivorous animals browsing for food. In this study, we examine the potential impact of large herbivore presence on the ground carbon storage in thermokarst landscapes of northeastern Siberia. Our aim is to understand how intensive animal grazing may affect permafrost thaw and hence organic matter decomposition, leading to different ground carbon storage, which is significant in the active layer. Therefore, we analysed sites with differing large herbivore grazing intensity in the Pleistocene Park near Chersky and measured maximum thaw depth, total organic carbon content and decomposition state by δ13C isotope analysis. In addition, we determined sediment grain size composition as well as ice and water content. We found the thaw depth to be shallower and carbon storage to be higher in intensively grazed areas compared to extensively and non-grazed sites in the same thermokarst basin. The intensive grazing presumably leads to a more stable thermal ground regime and thus to increased carbon storage in the thermokarst deposits and active layer. However, the high carbon content found within the upper 20 cm on intensively grazed sites could also indicate higher carbon input rather than reduced decomposition, which requires further studies. We connect our findings to more animal trampling in winter, which causes snow disturbance and cooler winter ground temperatures during the average annual 225 days below freezing. This winter cooling overcompensates ground warming due to the lower insulation associated with shorter heavily grazed vegetation during the average annual 140 thaw days. We conclude that intensive grazing influences the carbon storage capacities of permafrost areas and hence might be an actively manageable instrument to reduce net carbon emission from these sites.
... The relationship of animals and this ecosystem was dependent. The mammoth steppe provided food indirectly for carnivores and directly for herbivores, who grazed, trampled vegetation and fertilized the landscape, maintaining ecosystem productivity (Zimov et al., 2012). A diverse set of megaherbivore and megacarnivore species lived within this biome, and there was significant ecosystem faunal and floral homogeneity. ...
A faunal assemblage was recently recovered from the Krosinko site in Poland, marking a new site in the Warsaw–Berlin ice-marginal valley. Analysis and radiocarbon dating of the remains revealed the presence of two subassemblages: one Late Pleistocene (at least MIS 3–2) and one Holocene (MIS 1), with the former being taxonomically highly diverse. By referring to previous Polish studies, the Pleistocene mammal bone assemblage allowed us to reconstruct the biogeography of its individual components: woolly mammoths, woolly rhinoceri, horses, giant deer, red deer, fallow deer, reindeer, steppe bison, aurochses, bears, and cave lions. The biogeography was later combined with radiocarbon chronology using 21 dates from Krosinko. The wide range of radiocarbon dates (48.4–26.4 ka BP) probably reflects different chronological distributions of species resulting from the changing climate and environment as well as the diverse original sources of the bones. The remains, which constituted a single, compact geological horizon, was possibly deposited in a single geological event around 26 ka BP, as inferred from the most recently produced radiocarbon date. Radiocarbon datings of woolly rhinoceros remains have shown the species to have been present around 38 ka BP, a time that it had previously been considered to have been non-existent in Europe (with no evidence having been discovered for the period 40–34 ka BP). This result alters the stratigraphic gap range for the woolly rhinoceros in Europe to 40–38 ka BP. The clear dominance of woolly mammoth and woolly rhinoceros specimens reflects the structure of the Mammuthus–Coelodonta faunal complex. The main representatives of this complex preferred the dry and cold conditions that characterized the palaeoenvironmental conditions in Krosinko in MIS 2 and thus in Central Europe, as shown by the integration of the results of the fauna and those of the sediments in which they were deposited. These palaeoenvironmental features are related to the mammoth steppe, which was a long-lived biome in Eurasia and whose diversity influenced the faunal distribution. Thus, the species-by-species review of taxa performed in this paper, against the background of previous results from Poland, illuminates the individual responses of taxa to changing environmental conditions in response to climatic ones. These changes led to the disappearance of the mammoth steppe and near or total extinction of the fauna species inhabiting it.
... We do not have sufficient data on carnivores to trust the results for these species, yet for herbivores, grazing species were more affected than those feeding on browse or mixed diet. This correlates well to the notion that by the end of the Pleistocene the so-called mammoth steppe, a widespread habitat extending from central Europe to the Kamchatka started to vanish together with its habitat specialists, such as the mammoth or the woolly rhino (Zimov et al. 2012, Yeakel et al. 2013. Browse specialists, like the straight-tusked elephant and hippopotamus, were similarly affected by the disappearance of forested areas around 70 ka, which might have been responsible for their extinction at that time and might explain the apparent trend for increasing extinction risk with an increased amount of browse in the diet (Fig. 2). ...
The idea that several small, rather than a single large, habitat areas should hold the highest total species richness (the so-called SLOSS debate) brings into question the importance of habitat fragmentation to extinction risk. SLOSS studies are generally addressed over a short time scale, potentially ignoring the long-term dimension of extinction risk. Here, we provide the first long-term evaluation of the role of habitat fragmentation in species extinction, focusing on 22 large mammal species that lived in Eurasia during the last 200 000 years. By combining species distribution models and landscape pattern analysis, we compared temporal dynamics of habitat spatial structure between extinct and extant species, estimating the size, number and degree of the geographical isolation of their suitable habitat patches. Our results evidenced that extinct mammals went through considerable habitat fragmentation during the last glacial period and started to fare worse than extant species from about 50 ka. In particular , our modelling effort constrains the fragmentation of habitats into a narrow time window, from 46 to 36 ka ago, surprisingly coinciding with known extinction dates of several megafauna species. Landscape spatial structure was the second most important driver affecting megafauna extinction risk (ca 38% importance), after body mass (ca 39%) and followed by dietary preferences (ca 20%). Our results indicate a major role played by landscape fragmentation on extinction. Such evidence provides insights on what might likely happen in the future, with climate change, habitat loss and fragmentation acting as the main forces exerting their negative effects on biodiversity.
... For instance, in the well-studied Pleistocene Lujanian fauna in Argentina, xenarthrans would have represented almost half of the mammalian herbivore guild, with sloths alone representing almost 20% 53 . Furthermore, as large herbivores greatly impact the vegetation structure, soil moisture, and the carbon cycle of an ecosystem 54 , removal of some fossil ground sloth taxa from the continental herbivore guild would change previous estimations of the net primary production required to sustain a given number of megaherbivores, as well as the type of vegetation dominating the biome floor (e.g., grass-dominated versus moss/shrub-dominated 55 ). This would be the case in particular if, in addition to Mylodon, other fossil sloth species also had more versatile feeding behaviors than traditionally thought and would help explain the perplexing and long-assumed paucity of mammalian secondary consumers during the Cenozoic in South America. ...
Fossil sloths are regarded as obligate herbivores for reasons including peculiarities of their craniodental morphology and that all living sloths feed exclusively on plants. We challenge this view based on isotopic analyses of nitrogen of specific amino acids, which show that Darwin’s ground sloth Mylodon darwinii was an opportunistic omnivore. This direct evidence of omnivory in an ancient sloth requires reevaluation of the ecological structure of South American Cenozoic mammalian communities, as sloths represented a major component of these ecosystems across the past 34 Myr. Furthermore, by analyzing modern mammals with known diets, we provide a basis for reliable interpretation of nitrogen isotopes of amino acids of fossils. We argue that a widely used equation to determine trophic position is unnecessary, and that the relative isotopic values of the amino acids glutamate and phenylalanine alone permit reliable reconstructions of trophic positions of extant and extinct mammals.
... Fayrer-Hosken et al., 2000;Robson et al., 2017). For historical reference, palaeoecological data from Europe and Asia reveal relatively high biomass estimates, for example, the mammoth steppe is estimated to have had a megafauna biomass of 10,500 kg/km 2 (Zimov et al., 2012) and in Last interglacial Britain an equivalent of ≥2.5 fallow deer/ha were estimated for half the study locations , that is, ≥15,000 kg/ km 2 assuming 60 kg individuals. ...
Large herbivores provide key ecosystem processes, but have experienced massive historical losses and are under intense pressure, leaving current ecosystems with dramatically simplified faunas relative to the long‐term evolutionary norm. Hampered by a shifting baseline, natural levels of large‐herbivore biomass are poorly understood and seldom targeted. This ‘Decade of ecosystem restoration’ calls for evidence‐based targets for restoring the natural diversity and biomass of large herbivores. We apply the scaling of the consumer–producer relationship to a global dataset of large‐herbivore density in natural areas. The analyses reveal that African ecosystems generally have much higher large‐herbivore biomass and also the strongest consumer–producer relationship. For Europe, Asia and South America, there are no significant relationships with primary productivity indicative of impoverished faunas. Compared to expectations from the African scaling relation, large‐herbivore biomass in ecosystems outside Africa is considerably lower than expected. Synthesis and applications. Ecological restoration and rewilding entail restoration of a natural grazing process. Our findings indicate that many nature reserves are depleted in large‐herbivore biomass, judged from their primary productivity. Meanwhile, overexploitation by seasonal livestock grazing takes place in other areas. It is thus difficult, but urgent, to reach scientific consensus regarding a natural baseline for large‐herbivore biomass. Until such agreement has been reached, we recommend to manage, or rewild, large herbivores in year‐round near‐natural grazing and without predefined density targets, but following natural and fluctuating resource availability with minimal management intervention. The establishment of experimental rewilding sites with reactive herbivore management is needed to further advance our understanding of natural grazing density. Ecological restoration and rewilding entail restoration of a natural grazing process. Our findings indicate that many nature reserves are depleted in large‐herbivore biomass, judged from their primary productivity. Meanwhile, overexploitation by seasonal livestock grazing takes place in other areas. It is thus difficult, but urgent, to reach scientific consensus regarding a natural baseline for large‐herbivore biomass. Until such agreement has been reached, we recommend to manage, or rewild, large herbivores in year‐round near‐natural grazing and without predefined density targets, but following natural and fluctuating resource availability with minimal management intervention. The establishment of experimental rewilding sites with reactive herbivore management is needed to further advance our understanding of natural grazing density.
... The MRCA of these two species might have even had an uninterrupted distribution area across the periglacial steppe, which eventually underwent fragmentation in the Pleistocene during numerous expansion and contraction cycles of the (periglacial) steppe biome (Hurka et al., 2019). While primarily occupying continental Asia, pollen and macrofossil evidence of drought-adapted Artemisia and numerous Amaranthaceae representatives is found from north-western America as well (Yurtsev, 2001;Zimov et al., 2012). These two continents were connected via the Bering land bridge, which, due to extensive Pleistocene decrease of cloud cover, allowed arid-and cold-adapted vegetation to persist in this region during interglacial cycles (Dale Guthrie, 2001). ...
Atriplex is the most species-rich genus of Amaranthaceae and one of the largest C4 clades in eudicots. Distributed predominantly in the arid subtropical and temperate regions worldwide, many Atriplex species dominate the plant communities of harsh and inhospitable inland and coastal habitats. Current threats of aridification and salinisation increase the ecological and economic value of this highly stress tolerant xerophytic genus. We compiled sequence data of approximately 80% (208 spp.) of all currently recognised species and carried out a phylogenetic reconstruction using nuclear-encoded internal and external transcribed spacers. In addition, time divergence estimation analysis and ancestral area reconstruction were carried out to reconstruct the worldwide spread of Atriplex. Our results show that Atriplex originated in continental Asia during the Oligocene and dispersed from there across the world, often via long-distance dispersal from the Aralo-Caspian and the Pontic regions, or the floristic province of Turkestan. The highest alpha diversity was retrieved from arid habitats of Australia and the New World resulting from extensive radiation events of the Late Miocene and Pliocene. Most dispersal events took place into the Mediterranean region. Atriplex invaded most continents several times independently from different regions throughout the continuous cooling trend of the Neogene and the Quaternary. Despite limited resolution power of the used molecular markers, this study allows for a more comprehensive understanding of the evolutionary history of Atriplex and lays the foundation for future evolutionary studies of saltbushes.
This article covers the history of scientific research of the Nizhnekolymsk tundra, conducted over the period from 1970 to 1987 by the employees of the Institute of Biology of the Yakut Branch of the Academy of Sciences of USSR (Yakutsk). The subject of this research is the biochemical composition of plants from the family of sedge and grass – Егiорhorum роlуstасhiоn and Arctophila fulva) as the most common communities. It was conducted in tundra pastures in the lower reaches of the Kolyma River for rational economic management. One of the largest state owned farms of Yakutia “Nizhnekolymsky” specializes in reindeer herding – the traditional activity of indigenous peoples, was located in this area. In the past, this area was referred to as Hallerchinskaya tundra; it covered low left bank of the Kolyma River from delta to the forest boundary on the south and Konakovsky uplands in the west. Within the limits of Hallerchinskaya lowland in the rural locality of Pohodsk was located the “Nizhnekolymsky” geobotanical station. The method of models developed by staff members of the Institute of Biology was applied in monitoring the formation of aftergrass and determination of productivity reserve, as well as in selection of quadrats in the subarctic tundra. The main conclusions consists in the statement that the use of the such method for determining the phytomass reserve allowed conducting a prolonged observation over aftergrass formation in the same quadrats, and thereby discerning the natural development process towards reduction or increase of the studied species.
Herbivorous mammals are important for natural ecosystems even today, but how much stronger would there effects be without human-linked extinctions and extirpations? The ranges of many mammal species have contracted and numerous species have gone extinct due to human pressures, so herbivore impacts in even seemingly natural ecosystems likely deviate from their pre-anthropogenic state. However, such effects remain poorly understood and often unrecognized. To address this issue, we here quantified and mapped plant consumption by all terrestrial mammals in natural areas based on both current and estimated natural ranges. We then compared the estimated consumption rates to current plant net primary productivity, and summarised the results for global ecosystem types both broadly and in the wildest remaining natural areas around the world (the Last of the Wild). We found that wild mammals consume 7.3% (95% interquantile range: 0.85% - 26%) of net primary productivity in current natural areas, and that this would be much higher in the absence of extinctions and extirpations, namely 13% (95% interquantile range: 1.7% - 40%), i.e., a >50% higher consumption rate. Marked human-linked declines in herbivory were seen even in the wildest remaining natural areas, where mammals now consume a mean of 9% (95% interquantile range: 2.2% - 26%) of plant primary productivity, which is only 60% of no-extinction level. Our results show that mammalian herbivores naturally play an important part in ecosystems at a global scale, but that this effect has been strongly reduced by extinctions and extirpations.
In the alpine ecosystems across mountainous ranges, open areas are threatened by forest expansion, whether it is caused by natural succession or afforestation by human activities. During the last century, the abandonment of the grazing land and the banning of grazing by cattle in some areas, brought many pastures to become shrubby. Thus, reducing the habitat quality of various insect species. To test how these climate-change-induced effects impacted open-areas insects, we chose a dietary specialist and locally distributed butterfly, Parnassius apollo.
During its larvae stage, P. apollo (Linnaeus, 1758) strictly depends on a few species of the plant genus Sedum (Linnaeus, 1758), which rely on open areas for their life cycle.
To address this problem, we calculated species distribution models through a machine learning method, MaxEnt, using bioclimatic variables and the most used host plants, as a predictor. We predicted how the suitability of the environment has changed during the Late Pleistocene period, to detect how the alternation between interglacial-glacial periods affected Apollo’s habitat suitability. The results reveal a significant increase in habitat suitability during cold periods, especially during LGM, probably caused by the spread of the steppe habitats across the Eurasian continent. Future projections of the habitat suitability for the butterfly are not as alarming as expected, even in the worst scenarios. However, afforestation and overgrazing remain the main threats to P. apollo and thus, we encourage to enhance habitat management measures in Europe as well as in the Eastern part of the butterfly’s distribution range.
Solving the problems of sustainable existence of the biota in Northern Eurasia requires a detailed
analysis of the interactions between human and nature at the initial stage of the development of this territory.
Paleoreconstructions of the structural and functional organization of the biota in the analyzed territory at different
stages of its development constitute the necessary basis for solving the problems of preserving and restoring
natural laws, which are absolutely necessary for a deep understanding of natural mechanisms, as the main condition
for the survival of mankind. The initial stage of interaction between human and nature called “appropriating
economy” was marked by the destruction of complementary systems – the basis of the sustainable existence of
nature as a whole. The main reason is the almost complete destruction of the giant phytophagous mammoth
complex. The next period of interaction between human and nature is “the stage of the productive economy”, in
which slash-and-burn agriculture became the main method of agricultural development of forest areas in Northern
Eurasia. This type of Nature management caused a decrease in the productivity of forest ecosystems, associated with
the loss of nutrients after the burning of the stand, with the loss of soil biota and a decrease in soil fertility. Thus, the
pre-anthropogenic biota is replaced by modern fragments of anthropogenically transformed areas. Currently, when
the still preserved species and their groups cannot be maintained by nature itself, we need to develop and implement
large-scale measures to restore the biota and its climate-regulating functions as soon as possible.
During the past several decades, the paleoecology of the Mammuthus-Coelodonta Faunal Complex in the Palearctic has been thoroughly explored, especially using stable isotope analysis. Numerous studies have documented high ecological plasticity and regional heterogeneities for this fauna. However, very limited attention has focused on Northeast Asia, at the southeastern edge of the distribution of the mammoth steppe biome. In the present study, we undertook radiocarbon dating, zooarchaeology by mass spectrometry (ZooMS), and stable isotope analysis on the fossil faunas from Yanjiagang Paleolithic site, Northeast (NE) China, and from the Geographical Society Cave in the nearby Russian Far East, to explore the paleoecology of this fauna in this middle-latitude region. Isotopic (δ¹³C, δ¹⁵N) data from these two sites suggested that the woolly mammoth (Mammuthus primigenius) was a grazer feeding on grass/sedges, while the woolly rhinoceros (Coelodonta antiquitatis) and steppe bison (Bison priscus) utilized a wider range of food resources. All megaherbivores exhibited some ecological plasticity. Meanwhile, the mammal remains from Geographical Society Cave prevalently exhibited lower δ¹⁵N values than those from China, indicating variable environments and vegetation in Northeast Asia during MIS 3. Interestingly, through reevaluating the diachronic mammal distribution and ecology based on direct radiocarbon dating and ZooMS, we report the solid evidence of Bubalus, typically interpreted as a mild climate faunal element in the Pleistocene, alongside the Mammuthus-Coelodonta Fauna in Yanjiagang. This emphasizes the unique scenario of this biome in Northeast Asia, where the fauna exhibits sensitivity to synergic effects of climatic oscillations and local geographic traits. After comparing isotopic data of mammoth from different subregions of Asia, we found that NE China displayed both highest δ¹³C and δ¹⁵N values, possibly correlate with the higher temperature compared to other arctic regions. This study reveals the characteristics and complexity at the southeastern limit of the range of the mammoth steppe biome and urges more systematic studies within and outside this region.
The Kolyma region is historically famous for the unique finds of large Pleistocene fauna, yet, until very recently, absent of the time‐corresponding occupation sites. Quaternary geology and palaeontology investigations (2013–2019) in the middle reaches of the Kolyma River (NE Yakutia) have delivered new evidence on the Last Glacial (MIS 4–2) to Early Holocene sub‐arctic ecosystems and the past landscape dynamics retrieved from the fossiliferous bodies exposed from thawed grounds. The palaeoecology multi‐proxies from the MIS 3 (55–24 ka) cryolithic formations document riparian, larch‐dominated northern forests and open parklands with backwater channels, marshlands and lakes. The abundant skeletal remains of Pleistocene ungulates and carnivores, as well as relic flora point to long‐term biomass‐rich interstadial ecosystems and favourable Palaeolithic occupation habitats. Utilized animal bones, worked mammoth ivory and stone tools show the presence of pre‐modern humans in the northeast Russian Arctic >45 000 years ago. Flaked mammoth tusks suggest persistence of settlement during the Last Glacial Maximum in xeric and extremely cold (sub)arctic tundra. The postglacial climate shifts triggered major environmental and hydrological transformations. The final Pleistocene/Early Holocene warming brought restructuring of the Last Ice Age landscape and vanishing of the periglacial tundra‐steppe replaced by the present‐day larch‐dominated Siberian taiga. The mid‐Last Glacial human ecology records from the geographical limits of northeast Siberia have fundamental relevance for the reconstructions of the time trajectories and the natural conditions of peopling of Beringia.
In contrast to the modern Arctic, high-latitude ecosystems of the Late Pleistocene supported a diverse range of large mammalian herbivores, including abundant bison (Bison priscus) and horses (Equus sp.). This ‘mammoth steppe’ biome has no extant analog and modern tundra vegetation is likely incapable of supporting such a high density of large mammals. Compared to modern Arctic ecosystems, higher diversity and biomass of Late Pleistocene large mammal populations may have been sustained by more nutritious forage and/or dietary niche partitioning. We used dental microwear texture analysis and dental mesowear analysis of bison and horses (Bison priscus, Equus sp.) to characterize diet and assess the degree to which dietary differences supported co-existence of these dominant and likely competing herbivores on the mammoth steppe. Additionally, we compared microwear and mesowear of Late Pleistocene specimens to modern Alaska bison (reintroduced Bison bison athabascae and introduced Bison bison bison) and published microwear and mesowear data for extant bovids and equids. Our results demonstrate that Late Pleistocene bison and horses had less abrasive diets than modern obligate grazers, suggesting that these “grazers” of the mammoth steppe likely incorporated more forbs in their diets than modern grazers. Furthermore, Late Pleistocene bison and horses ate foods with similar textures, indicating that dietary niche partitioning alone cannot explain their co-occurrence. However, taphonomic differences between bison and horse specimens indicate potential spatial or temporal niche partitioning during the Late Pleistocene.
That humans originated from Africa is well-known. However, this is widely regarded as a chance outcome, dependant simply on where our common ancestor shared the land with where the great apes lived. This volume builds on from the 'Out of Africa' theory, and takes the view that it is only in Africa that the evolutionary transitions from a forest-inhabiting frugivore to savanna-dwelling meat-eater could have occurred. This book argues that the ecological circumstances that shaped these transitions are exclusive to Africa. It describes distinctive features of the ecology of Africa, with emphasis on savanna grasslands, and relates them to the evolutionary transitions linking early ape-men to modern humans. It shows how physical features of the continent, especially those derived from plate tectonics, set the foundations. This volume adequately conveys that we are here because of the distinctive features of the ecology of Africa.
The Bering Land Bridge (BLB) last connected Eurasia and North America during the Late Pleistocene. Although the BLB would have enabled transfers of terrestrial biota in both directions, it also acted as an ecological filter whose permeability varied considerably over time. Here we explore the possible impacts of this ecological corridor on genetic diversity within, and connectivity among, populations of a once wide‐ranging group, the caballine horses (Equus spp.). Using a panel of 187 mitochondrial and eight nuclear genomes recovered from present‐day and extinct caballine horses sampled across the Holarctic, we found that Eurasian horse populations initially diverged from those in North America, their ancestral continent, around 1.0‐0.8 million years ago. Subsequent to this split our mitochondrial DNA analysis identified two bi‐directional long‐range dispersals across the BLB ~875‐625 and ~200‐50 thousand years ago, during the Middle and Late Pleistocene. Whole genome analysis indicated low levels of gene flow between North American and Eurasian horse populations, which likely occurred as a result of these inferred dispersals. Nonetheless, mitochondrial and nuclear diversity of caballine horse populations retained strong phylogeographic structuring. Our results suggest that barriers to gene flow, currently unidentified but possibly related to habitat distribution across Beringia or ongoing evolutionary divergence, played an important role in shaping the early genetic history of caballine horses, including the ancestors of living horses within Equus ferus.
That humans originated from Africa is well-known. However, this is widely regarded as a chance outcome, dependant simply on where our common ancestor shared the land with where the great apes lived. This volume builds on from the 'Out of Africa' theory, and takes the view that it is only in Africa that the evolutionary transitions from a forest-inhabiting frugivore to savanna-dwelling meat-eater could have occurred. This book argues that the ecological circumstances that shaped these transitions are exclusive to Africa. It describes distinctive features of the ecology of Africa, with emphasis on savanna grasslands, and relates them to the evolutionary transitions linking early ape-men to modern humans. It shows how physical features of the continent, especially those derived from plate tectonics, set the foundations. This volume adequately conveys that we are here because of the distinctive features of the ecology of Africa.
Large herbivore grazing has been shown to substantially alter tundra soil and vegetation properties as well as carbon fluxes, yet observational evidence to quantify the impact of herbivore introduction into Arctic permafrost ecosystems remains sparse. In this study we investigated growing season CO2 and CH4 fluxes with flux chambers on a former wet tussock tundra inside Pleistocene Park, a landscape experiment in Northeast Siberia with a 22 year history of grazing. Reference data for an undisturbed system were collected on a nearby ungrazed tussock tundra. Linked to a reduction in soil moisture, topsoil temperatures at the grazed site reacted one order of magnitude faster to changes in air temperatures compared to the ungrazed site and were significantly higher, while the difference strongly decreased with depth. Overall, both GPP (gross primary productivity, i.e. CO2 uptake by photosynthesis) and Reco (ecosystem respiration, i.e. CO2 release from the ecosystem) were significantly higher at the grazed site with notable variations across plots at each site. The increases in CO2 component fluxes largely compensated each other, leaving NEE (net ecosystem exchange) similar across grazed and ungrazed sites for the observation period. Soil moisture and CH4 fluxes at the grazed site decreased over the observation period, while in contrast the constantly water-logged soils at the ungrazed site kept CH4 fluxes at significantly higher levels. Our results indicate that grazing of large herbivores promotes topsoil warming and drying, effectively accelerating CO2 turnover while decreasing methane emissions. Our experiment did not include autumn and winter fluxes, and thus no inferences can be made for the annual NEE and CH4 budgets at tundra ecosystems.
The extinction of 80% of megaherbivore (>1,000 kg) species towards the end of the Pleistocene altered vegetation structure, fire dynamics, and nutrient cycling worldwide. Ecologists have proposed (re)introducing megaherbivores or their ecological analogues to restore lost ecosystem functions and reinforce extant but declining megaherbivore populations. However, the effects of megaherbivores on smaller herbivores are poorly understood. We used long-term exclusion experiments and multispecies hierarchical models fitted to dung counts to test 1) the effect of megaherbivore (elephant and giraffe) presence-absence on the occurrence (dung presence) and use intensity (dung-pile density) of mesoherbivores (2-1,000 kg), and 2) the extent to which the responses of each mesoherbivore species was predictable based on their traits (diet and shoulder height) and phylogenetic relatedness. Megaherbivores increased the predicted occurrence and use intensity of zebras but reduced the occurrence and use intensity of several other mesoherbivore species. The negative effect of megaherbivores on mesoherbivore occurrence was stronger for shorter species, regardless of diet or relatedness. Megaherbivores substantially reduced the expected total use intensity (i.e., cumulative dung density of all species) of mesoherbivores, but only minimally reduced the expected species richness (i.e., cumulative predicted occurrence probabilities of all species) of mesoherbivores (by <1 species). Simulated extirpation of megaherbivores altered use intensity by mesoherbivores, which should be considered during (re)introductions of megaherbivores or their ecological proxies. Species' traits (in this case shoulder height) may be more reliable predictors of mesoherbivores' responses to megaherbivores than phylogenetic relatedness, and may be useful for predicting responses of data-limited species.
The occurrence and origin of dry grasslands and their rich biota in the moderately humid Central‐European climate have fascinated scientists for over a century. Modern palaeoecological and phylogeographical data support earlier hypotheses that these grasslands are late Pleistocene relicts and can therefore be considered part of the Eurasian forest–steppe biome. However, it is still unclear which factors fostered the maintenance of steppe patches in Central Europe throughout the Holocene. Here, we provide an overview of the main hypotheses, which stress, respectively, the effects of climate, edaphic conditions and disturbances. We then develop a general conceptual framework on how these three factors interact to form forest–steppe mosaics. We thereby emphasize the role of topography as a crucial control on forest–steppe patterns at the landscape scale. Topography is related to several mechanistic drivers that influence vegetation processes, such as near‐surface microclimate and soil formation. Consequently, topographic variation allows both forest and steppe patches to occur beyond their macroclimatic niche, favouring the development of forest–steppe mosaics. To illustrate our framework, we demonstrate the interactive effect of macroclimate and topography on the occurrence of steppe patches at 108 selected Central European forest–steppe sites. Although we developed our framework focusing on the current distribution of Central European forest–steppe, we suggest that it contributes to the understanding of similar transitions between temperate forest and steppe biomes in the past as well as elsewhere in the world.
Results of the methane research on late Cenozoic permafrost of Northeastern Arctic have been summarized. The data on methane content and pattern of its distribution across permafrost of different age and origin have been presented. The correlation between bivalent iron content and methane has been established. As it has been experimentally shown using 14C-traced substrates, the process of methane formation may occur within permafrost. Isotopic composition of methane's carbon (δ13C from-64 up to -99%) confirms its biological origin, while the extremely low values of δ13C indicate substantial fractionation of carbon isotopes through the process of methane formation and the possibility for this process to take place at subzero temperatures. Cultures of methane.forming bacteria Methanosarcina and Methanobacterium have been isolated from the permafrost and described.
Many mammoth remains have been radiocarbon-dated. We present here more than 360 14C dates on bones, tusks, molars and soft tissues of mammoths and discuss some issues connected with the evolution of mammoths and their environment: the problem of the last mammoth; mammoth taphonomy; the plant remains and stable isotope records accompanying mammoth fossils; paleoclimate during the time of the mammoths and dating of host sediments. The temporal distribution of the 14C dates of fossils from the northern Eurasian territory is even for the entire period from 40 to 10 ka BP.
During the Last Glacial Maximum (LGM), atmospheric CO2 concentration was 80–100 ppmv lower than in pre-industrial times. At that time steppe-tundra was the most extensive biome on Earth. Some authors assume that C storage in that biome was very small, similar to today's deserts, and that the terrestrial carbon (C) reservoir increased at the Pleistocene-Holocene transition (PHT) by 400–1300 Gt. To estimate C storage in the entire steppe-tundra biome we used data of C storage in soils of this biome that persisted in permafrost of Siberia and Alaska and developed a model that describes C accumulation in soils and in permafrost. The model shows a slow but consistent C increase in soil when permafrost appears. At the PHT, C-rich frozen loess of Europe and South of Siberia thawed and lost most of its carbon. Soil carbon decreases as tundra-steppe changes to forest, steppes and tundra. As a result, over 1000 Gt C was released to the atmosphere, oceans, and other terrestrial ecosystems. The model results also show that restoring the tundra-steppe ecosystem would enhance soil C storage, while providing other important ecosystem services.
The authors manipulated light, temperature, and nutrients in moist tussock tundra in Alaska to determine how global changes might affect community and ecosystem processes. Some of these manipulations altered nutrient availability, growth-form composition, net primary production, and species richness in less than a decade, indicating arctic vegetation at this site is sensitive to climatic change. In general, short-term (3-yr) responses were poor predictors of longer term (9-yr) changes in community composition. The longer term responses showed closer correspondence to patterns of vegetation distribution along environmental gradients. Nitrogen and phosphorus availability tended to increase with elevated temperature and in response to light attenuation. Nutrient addition increased biomass and production of deciduous shrubs but reduced growth of evergreen shrubs and nonvascular plants. Light attenuation reduced biomass of all growth forms. Elevated temperature enhanced shrub production but reduced production of nonvascular plants. The contrasting responses to temperature increase and to nutrient addition by different growth forms {open_quotes}canceled out{close_quotes} at the ecosystem level, buffering changes in ecosystem characteristics such as biomass, production, and nutrient uptake. The major effect of elevated temperature was to speed plant response to changes in soil resources and, in long term (9 yr), to increase nutrient availability. Species richness was reduced 30-50% by temperature and nutrient treatments. Declines in diversity occurred disproportionately in forbs and in mosses. During our 9-yr study (the warmest decade on record in the region), biomass of one dominant tundra species unexpectedly changed in control plots in the direction predicted by our experiments and by Holocene pollen records. This suggests that regional climatic warming may already be altering the species composition of Alaskan arctic tundra. 73 refs., 9 figs., 4 tabs.
EVIDENCE from ice cores1 indicates that concentrations of
atmospheric carbon dioxide were lower by about 75 p.p.m. during the Last
Glacial Maximum (LGM; ~18,000 years ago) than during the present
interglacial (10,000 years ago to the present). The causes of such large
changes in atmospheric CO2 remain uncertain. Using a climate
model, Prentice and Fung2 have estimated that there was
approximately the same amount of carbon in vegetation and soils during
the LGM as there was during the present (pre-industrial) interglacial.
In contrast, we present here results based on palynological, pedological
and sedimentological evidence which indicate that in fact the amount of
carbon in vegetation, soils and peatlands may have been smaller during
the LGM by ~1.3x 1012 tonnes. Thus, organic carbon in
vegetation and soils has more than doubled (from 0.96 to 2.3 x
1012 tonnes) since the LGM. Oceanic CO2 reservoirs
seem to be the only possible source of this large quantity of carbon
that has entered the terrestrial biosphere since the LGM (in addition to
that which has entered the atmosphere to give the higher interglacial
CO2 levels).
A simulation model, recent experiments, and the literature provide consistent evidence that megafauna extinctions caused by human hunting could have played as great a role as climate in shifting from a vegetation mosaic with abundant grass-dominated steppe to a mosaic dominated by moss tundra in Beringia at the end of the Pleistocene. General circulation models suggest that the Pleistocene environment of Beringia was colder than at the present with broadly similar wind patterns and precipitation but wetter soils. These and other observations suggest that the steppelike vegetation and dry soils of Beringia in the late Pleistocene were not a direct consequence of an arid macroclimate. Trampling and grazing by mammalian grazers in tundra cause a shift in dominance from mosses to grasses. Grasses reduce soil moisture more effectively than mosses through high rates of evapotranspiration. Results of a simulation model based on plant competition for water and light and plant sensitivity to grazers and nutrient supply predict that either of two vegetation types, grass-dominated steppe or moss-dominated tundra, could exist in Beringia under both current and Pleistocene climates. The model suggests that moss-dominated tundra is favored when grazing is reduced below levels that are in equilibrium with climate and vegetation. Together these results indicate that mammalian grazers have a sufficiently large effect on vegetation and soil moisture that their extinction could have contributed substantially to the shift from predominance of steppe to tundra at the Pleistocene-Holocene boundary. Our hypothesis suggests a mechanism by which the steppe ecosystem could be restored to portions of its former range. We also suggest that mammalian impacts on vegetation are sufficiently large that future vegetation cannot be predicted from climate scenarios without considering the role of mammals.
PREVIOUS studies1-5 have demonstrated that the
predictions of global climate models are highly sensitive to large
changes in vegetation cover, such as the complete removal of tropical or
boreal forests. Although these studies have illustrated the potential
effects of massive deforestation on the climate system, vegetation
changes of this scale are very unlikely to occur. Investigating past
environments may better illustrate the possible interactions between
climate and vegetation cover. For example, palaeobotanical evidence
indicates that 6,000 years ago boreal forests extended north of the
modern treeline6, apparently in response to high-latitude
warming resulting from variations in the Earth's orbit7,8.
The expanded boreal forests, which took the place of tundra, must also
have affected climate by significantly reducing the surface
albedo5. Here we use a global climate model to examine the
relative effects of orbitally-induced insolation variations and of the
northward extension of boreal forests on the mid-Holocene climate.
Orbital variations alone warm the high latitudes by 2 °C or more in
summer, autumn and winter. The subsequent northward extension of boreal
forests gives rise to an additional warming of approximately 4 °C in
spring and about 1 °C in the other seasons. This suggests that large
positive feedbacks between climate and boreal forests may have taken
place in the recent geological past.
Here we present a new data synthesis of global peatland ages, area changes, and carbon (C) pool changes since the Last Glacial Maximum, along with a new peatland map and total C pool estimates. The data show different controls of peatland expansion and C accumulation in different regions. We estimate that northern peatlands have accumulated 547 (473-621) GtC, showing maximum accumulation in the early Holocene in response to high summer insolation and strong summer - winter climate seasonality. Tropical peatlands have accumulated 50 (44-55) GtC, with rapid rates about 8000-4000 years ago affected by a high and more stable sea level, a strong summer monsoon, and before the intensification of El Niño. Southern peatlands, mostly in Patagonia, South America, have accumulated 15 (13-18) GtC, with rapid accumulation during the Antarctic Thermal Maximum in the late glacial, and during the mid-Holocene thermal maximum. This is the first comparison of peatland dynamics among these global regions. Our analysis shows that a diversity of drivers at different times have significantly impacted the global C cycle, through the contribution of peatlands to atmospheric CH4 budgets and the history of peatland CO2 exchange with the atmosphere.
Northern soils will release huge amounts of carbon in a warmer world,
say Edward A. G. Schuur, Benjamin Abbott and the Permafrost Carbon
Network.
A new calibration curve for the conversion of radiocarbon ages to calibrated (cal) ages has been constructed and internationally ratified to replace IntCal98, which extended from 0–24 cal kyr BP (Before Present, 0 cal BP = AD 1950). The new calibration data set for terrestrial samples extends from 0–26 cal kyr BP, but with much higher resolution beyond 11.4 cal kyr BP than IntCal98. Dendrochronologically-dated tree-ring samples cover the period from 0–12.4 cal kyr BP. Beyond the end of the tree rings, data from marine records (corals and foraminifera) are converted to the atmospheric equivalent with a site-specific marine reservoir correction to provide terrestrial calibration from 12.4–26.0 cal kyr BP. A substantial enhancement relative to IntCal98 is the introduction of a coherent statistical approach based on a random walk model, which takes into account the uncertainty in both the calendar age and the ¹⁴C age to calculate the underlying calibration curve (Buck and Blackwell, this issue). The tree-ring data sets, sources of uncertainty, and regional offsets are discussed here. The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed in brief, but details are presented in Hughen et al. (this issue a). We do not make a recommendation for calibration beyond 26 cal kyr BP at this time; however, potential calibration data sets are compared in another paper (van der Plicht et al., this issue). This article has been published in the journal: Radiocarbon. © 2004 by the Arizona Board of Regents on behalf of the University of Arizona. Used with permission.
The last glacial period was terminated by an abrupt warming event in the North Atlantic approximately 15,000 years before the present, and warming events of similar age have been reported from low latitudes. Understanding the mechanism of this termination requires that the precise relative timing of abrupt climate warming in the tropics versus the North Atlantic be known. Nitrogen and argon isotopes in trapped air in Greenland ice show that the Greenland Summit warmed 9 +/- 3 degrees C over a period of several decades, beginning 14,672 years ago. Atmospheric methane concentrations rose abruptly over a approximately 50-year period and began their increase 20 to 30 years after the onset of the abrupt Greenland warming. These data suggest that tropical climate became warmer or wetter (or both) approximately 20 to 80 years after the onset of Greenland warming, supporting a North Atlantic rather than a tropical trigger for the climate event.
The European Project for Ice Coring in Antarctica Dome C ice core enables us to extend existing records of atmospheric methane (CH4) and nitrous oxide (N2O) back to 650,000 years before the present. A combined record of CH4 measured along the Dome C and the Vostok ice cores demonstrates, within the resolution of our measurements, that preindustrial concentrations over Antarctica have not exceeded 773 +/- 15 ppbv (parts per billion by volume) during the past 650,000 years. Before 420,000 years ago, when interglacials were cooler, maximum CH4 concentrations were only about 600 ppbv, similar to lower Holocene values. In contrast, the N2O record shows maximum concentrations of 278 +/- 7 ppbv, slightly higher than early Holocene values.
Large uncertainties in the budget of atmospheric methane, an important greenhouse gas, limit the accuracy of climate change projections. Thaw lakes in North Siberia are known to emit methane, but the magnitude of these emissions remains uncertain because most methane is released through ebullition (bubbling), which is spatially and temporally variable. Here we report a new method of measuring ebullition and use it to quantify methane emissions from two thaw lakes in North Siberia. We show that ebullition accounts for 95 per cent of methane emissions from these lakes, and that methane flux from thaw lakes in our study region may be five times higher than previously estimated. Extrapolation of these fluxes indicates that thaw lakes in North Siberia emit 3.8 teragrams of methane per year, which increases present estimates of methane emissions from northern wetlands (< 6-40 teragrams per year; refs 1, 2, 4-6) by between 10 and 63 per cent. We find that thawing permafrost along lake margins accounts for most of the methane released from the lakes, and estimate that an expansion of thaw lakes between 1974 and 2000, which was concurrent with regional warming, increased methane emissions in our study region by 58 per cent. Furthermore, the Pleistocene age (35,260-42,900 years) of methane emitted from hotspots along thawing lake margins indicates that this positive feedback to climate warming has led to the release of old carbon stocks previously stored in permafrost.
The first reliable, securely dated full- and late-glacial pollen stratigraphy from Eastern Beringia forces the rejection of the widely held hypothesis of a steppetundra or grassland associated with extinct vertebrates and early humans. The arctic-alpine fossil flora and low pollen influx suggest a sparse tundra similar to modern herb fell-field vegetation.
The results of excavations at an early Holocene site on Zhokov Island in the De-Long Archipelago of the Siberian High Arctic are reported. The site's terrain and paleogeographic characteristics are discussed. Thirteen semisubterranean house pits were identified and excavations were carried out in two of them. The artifact assemblage reflects a Mesolithic association, with microblades, bone and antler inset tools, and groundstone adzes. Radiocarbon analyses indicate a date for the cultural layer of about 7900 BP. Faunal remains indicate a hunting economy relying mainly on reindeer and polar bear. The significance of the site in terms of the early penetration of the High Arctic by a continental hunting culture is discussed, with a commentary on the state of knowledge about early Holocene cultural complexes in northeast Siberia. -Author
During the Last Glacial Maximum (LGM) the mammoth steppe was the planet’s biggest biome. Ice rich loess-like soils of this biome covered vast northern territories. These soils are currently one of the biggest carbon reservoirs. It is likely that in this century the bigger part of these soils will thaw. This would lead to massive erosion, destruction of modern ecosystems and a large emission of carbon dioxide and methane into the atmosphere, which are produced from the decomposition of Pleistocene organics. Minimizing these effects is possible only through the restoration of ecosystems similar to the Pleistocene mammoth steppe. Skeleton densities in the permafrost show that the mammoth steppe was a highly productive ecosystem similar to African savannas. Biomass of animals in the north of Siberia was ~10t/km2. Herbivores enhanced biocyclicity, trampled moss and shrubs and maintained pastures. Therefore this ecosystem was only partially dependent on climate. Analyses of climate dynamics, vegetation and animals shows that today the climate in the north of Siberia, Alaska and Yukon are close to the optimum of the mammoth steppe, and that climate warming did not destroy this ecosystem. Rather, humans are the more likely cause. After the LGM, climate warming allowed humans to penetrate the north, where they decreased animal densities to the point where they became insufficient to maintain pastures. In this chapter we discuss questions of preservation of bones and artifacts in the permafrost, physiology and evolution of pasture ecosystems and the role of humans in this ecosystem.
During the last deglaciation (LD) a strong increase in atmospheric methane (CH4) concentrations occurred simultaneously with a rise in Greenland temperatures indicating that in the north, during this time period, strong CH4 sources ``awakened'', as additionally documented by the appearance of a strong gradient between northern (Greenland) and southern (Antarctica) hemisphere atmospheric CH4 concentrations. This rise could not be caused by wetland expansion. A reconstruction of peatland formation dynamics has indicated that wetlands on Earth were few in LD and only actively expanded 10,000 yr BP, after atmospheric CH4 concentrations began to decline. Destabilization of methane clathrates also could not be the source for atmospheric CH4 increase. Geological CH4 (including methane clathrates) has the highest deuterium content (deltaD) among all of the known sources of CH4 while atmospheric CH4 deltaD values determined for the LD were record low. To explain recorded atmospheric CH4 and its isotopic dynamics required a strong northern source, which was active only during the LD and that provided very low deltaD CH4 values. Such a source is permafrost thawing under anaerobic conditions (or better stated soils of mammoth steppe-tundra ecosystems). Permafrost thawing is the strongest, among known, wetland sources (usually over 100g CH4/m2yr) and has a unique isotopic signature (deltaD = -400 per mil (-338 to -479 per mil), delta13C = -73 per mil (-58 to -99 per mil)). The main sources of atmospheric CH4 have different isotopic signatures (delta13C, deltaD). The isotopic content of atmospheric CH4 is a simple function of the weight average for all of the sources. Inclusion of permafrost source into a budget model of the atmospheric methane and its isotopes allowed us to reconstruct the dynamics of methane's main sources. Model indicated geological source to be negligible as in LGM so and in LD and Holocene. During the glaciation, the largest methane source was megafauna, whose 1.4-1.7 billion ton biomass was larger than the modern biomass of human and domestic animals combined. During the LD, the largest methane source was the thawing of steppe-tundra soils. During the Holocene the largest CH4 source was wetlands. All these estimates correspond with the scales of permafrost degradation in the LD, megafaunal extinction and increase in fire intensity derived from charcoal within stratigraphic columns.
The total carbon inventory in the terrestrial biosphere in the last glacial maximum (LGM), 18 kyr ago, is analyzed in a series of experiments that examine the sensitivity of the inventory to vegetation distribution and carbon dynamics. The results show that for most forest vegetation types, carbon densities for the LGM are within 10% of their present-day values. Discrepancies between vegetation distributions simulated by two bioclimatic schemes are attributable to the assignation of vegetation types to climates with rare or no present-day analog. The model experiments, combined with palynogical data for regions with no present-day analog climate, yield to a decrease of 612{+-}105 Gt C compared to present day. 47 refs., 12 figs., 3 tabs.
The little known Achchagyi–Allaikha mass assemblage of mammoths and the well-known Berelyokh site (Lower Indigirka River, Arctic Siberia) were studied. Detailed study of the Achchagyi–Allaikha site provided ample data concerning its geology, stratigraphy, taphonomy, and the gender-age structure of the taphocoenosis. The Achchagyi–Allaikha assemblage included redeposited bones from numerous young (not less than 21) and some adult female mammoths, with limited quantities of Bison, Equus and Rangifer bones. Collagen from mammoth bones preserved at the Achchagyi–Allaikha site (n=6) was radiocarbon-dated at 12,490±80 to 12,400±60BP. At the Berelyokh site, eight mammoth bones were radiocarbon-dated at 12,720±100 to 11,900±50BP, one bison bone was dated at 12,380±150BP, and one mammoth bone dated at 36,500±1000 (redeposited bone included in younger sediments). The mass accumulations are synchronous and are similar in their mode of formation. The assemblage of mammoths in the Achchagyi–Allaikha and Berelyokh sites resulted from simultaneous deaths of a large number of animals (probably herd-family groups) in one or several seasons. It is very probable that the deposits in both cases were not of cultural origin. The formation of the burials is a direct consequence of short but strong climatic warming (Bølling Oscillation) that resulted in many unfavorable environmental conditions. Among these, the increase of snow cover and stronger spring floods were very notable. Bølling warming is a model of the large-scale Holocene event. Mass death of mammoths during the Bølling phase was a prelude to their final extinction.
Ice Complexes, extremely ice-rich permafrost deposits with large ice wedges, are widely distributed in the Arctic region of northeast Siberia. They present excellent archives for the reconstruction of Late Quaternary paleoenvironmental conditions in non-glaciated areas. In 1998, 1999, and 2000 Russian and German scientists worked together on the Bykovsky Peninsula southeast of the Lena Delta in order to investigate the Ice Complex and its associated sediments. Intensive cryolithological and sedimentological studies, Radiocarbon age determinations, paleobotanical studies, micropaleontological investigations, studies of mammal and insect fossils, and stable isotope analyses of ground ice were performed. Radiocarbon data have been obtained from the entire exposed sequence covering approximately the last 60,000 years. The results indicate that compared with modern time the investigated Ice Complex sequence was formed during two cooler and more arid stages of the Late Pleistocene with relatively uniform environmental conditions, separated by a stage with environmental variations and more intensive soil formation caused by climate amelioration. The Late Pleistocene environmental changes were not as strong as those occurring during the Pleistocene/Holocene transition where a sharp break is evident.
Ice Complexes, extremely ice-rich permafrost deposits with large ice wedges, are widely distributed in the Arctic region of northeast Siberia. They present excellent archives for the reconstruction of Late Quaternary paleoenvironmental conditions in nonglaciated areas. In 1998, 1999, and 2000 Russian and German scientists worked together on the Bykovsky Peninsula southeast of the Lena Delta in order to investigate the Ice Complex and its associated sediments. Intensive cryolithological and sedimentological studies, Radiocarbon age determinations, paleobotanical studies, micropaleontological investigations, studies of mammal and insect fossils, and stable isotope analyses of ground ice were performed. Radiocarbon data have been obtained from the entire exposed sequence covering approximately the last 60,000 years. The results indicate that compared with modern time the investigated Complex sequence was formed duringtwo cooler and more arid stages of the Late Pleistocene with relatively uniform environmental conditions, separated by a stage with environmental variations and more intensive soil formation caused by climate amelioration. The Late Pleistocene environmental changes were not as strong as those occurring during the Pleistocene/Holocene transition where a sharp break is evident.
Woodland loss is a major cause of biodiversity decline in African savanna parks. Decisions about whether remedial steps are possible and warranted depend on the cause. Climate, fire, elephants and human impact, often in combination, have been cited as major causes. The almost complete extinction of woodland in Amboseli National Park since 1950 has been at the centre of such debate. A 20-year study based on an experimental design to test overgrazing, pathogen, climate and elephant browsing theories of woodland loss was established in 1981. The experiment showed that elephants alone are preventing regeneration. Based on the outcome of the experiment, a woodland refuge was restored in the centre of the park to maintain biodiversity and demonstrate the management prospects for habitat restoration. A strong interaction of elephants and pastoralists, played out across the ecosystem over many decades, probably accounts for the habitat mosaic and high biological diversity of the ecosystem prior to the establishment of the national park. The restoration of biodiversity in the park will therefore depend on mimicking the shifting mosaic of habitats created by their interaction.
Loess is one of the most widespread subaerial deposits in Alaska and adjacent Yukon Territory and may have a history that goes back 3 Ma. Based on mineralogy and major and trace element chemistry, central Alaskan loess has a composition that is distinctive from other loess bodies of the world, although it is quartz-dominated. Central Alaskan loess was probably derived from a variety of rock types, including granites, metabasalts and schists. Detailed stratigraphic data and pedologic criteria indicate that, contrary to early studies, many palaeosols are present in central Alaskan loess sections. The buried soils indicate that loess sedimentation was episodic, or at least rates of deposition decreased to the point where pedogenesis could keep ahead of aeolian input. As in China, loess deposition and pedogenesis are likely competing processes and neither stops completely during either phase of the loess/soil formation cycle. Loess deposition in central Alaska took place before, and probably during the last interglacial period, during stadials of the mid-Wisconsin period, during the last glacial period and during the Holocene. An unexpected result of our geochronological studies is that only moderate loess deposition took place during the last glacial period. Our studies lead us to conclude that vegetation plays a key role in loess accumulation in Alaska. Factors favouring loess production are enhanced during glacial periods but factors that favour loess accumulation are diminished during glacial periods. The most important of these is vegetation; boreal forest serves as an effective loess trap, but sparsely distributed herb tundra does not. Thus, thick accumulations of loess should not be expected where tundra vegetation was dominant and this is borne out by modern studies near the treeline in central Alaska. Much of the stratigraphic diversity of North American loess, including that found in the Central Lowlands, the Great Plains, and Alaska is explained by a new model that emphasizes the relative importance of loess production factors versus loess accumulation factors. Published by Elsevier Science Ltd.