Pleistocene Ecosystems Research Articles

Storm-Driven Tree Exposure and Geomorphic Change: Predicting the Distribution of Preserved Late Pleistocene Tree Stumps on the Outer Alabama Continental Shelf

The Alabama Underwater or Drowned Forest is a well-preserved Late Pleistocene (dated to 72–56 ± 8 ka, 2σ) terrestrial landform on the northern Gulf of Mexico continental shelf that provides geomorphic and ecosystem information rarely preserved during the glacial intervals. Stumps of bald cypress (Taxodium distichum (L.) Rich.) trees were exposed in ∼18 m of water following Hurricane Ivan in 2004. This research investigates geomorphic changes to the Mississippi-Alabama-Florida (MAFLA) sand sheet, which presents as shore-oblique Holocene sand ridges, and the exposure and burial of tree stumps following the passage of Hurricane Sally in 2020 using repeat sidescan and bathymetric surveys (2015–2016 and 2021). Using two newly identified tree exposure areas and their geological properties, this research also hypothesized a new location where tree stumps may be outcropping. The bathymetry indicates regions with up to ∼1 m of erosion and deposition over the five years between the two surveys. Similarly, the sidescan sonar indicates changes in the location and numbers of exposed tree stumps as well as between 47,000 and 62,500 tons of sediment erosion within the study area following Hurricane Sally. The 2015 and 2016 data found 25 tree contacts whereas the 2021 survey found 76 tree contacts and only 5 of them occurred in both surveys suggesting the tree exposures are dynamic and presumably changing with the passing of large tropical cyclones. Additionally, the hypothesized exposure location had 26 newly identified tree stump contacts within a mixed texture unit along the sand-mud boundary, confirming our understanding of the geomorphic characteristics leading to the exposure of the buried forest. This research will expand the potential areas for investigations into Late Pleistocene ecosystems and landforms and their associated climatic and ecologic conditions in the Gulf of Mexico as well as in other passive continental margins.

Well‐drained floodplain taphonomic mode of Late Pleistocene vertebrates from Northeast Argentina

ABSTRACTThe vertebrate assemblage recovered from the Toropí/Yupoí Formation (Late Pleistocene) in the Arroyo Toropí area, Bella Vista (Corrientes Province, Argentina), has been subjected to taphonomic evaluation. The fossil‐bearing levels have been dated to ~53 ka (MIS 3) based on Optically Stimulated Luminescence dating. This assemblage primarily comprises mammal remains, with a notable prevalence of herbivorous megamammals. Also, reptiles and birds have been documented. Sedimentological analysis suggests that the skeletal remains were preserved within a floodplain environment influenced by the dynamics of the adjacent fluvial system, and taphonomic features observed in the assemblage support this interpretation. The assemblage resulted from the deposition of disarticulated mammal remains and local dispersion over a relatively short period. Rapid burial is evident, but several processes such as weathering and breakage have contributed to the observed patterns. The loss of several skeletal elements within the assemblage may be attributed to sporadic water flows occurring on the floodplain. During the post‐burial stage, the specimens were affected by diagenetic processes, including filling, impregnation, deformation and breakage. In summary, the taphonomic evaluation of the Toropí/Yupoí Formation offers valuable comparison with other fossil fluvial assemblages. This research contributes to our understanding of the processes and environmental conditions that shaped this Late Pleistocene ecosystem.

Microbial degradation of Pleistocene permafrost-sealed fossil mammal remains

AbstractPaleontological remains retrieved from permafrost represent the most informative records of Pleistocene ecosystems. Different levels of past microbial activity affecting fossil material preservation are presented for two selected bone samples—an almost intactBisonsp. metacarpus (45.0 ± 5.014C ka BP) and a weatheredEquussp. metacarpus (37.8 ± 1.714C ka BP) from the recently exposed cryogenic geo-contexts in the Yana River basin, NE Yakutia. Diagenetic changes in bone porosity and chemical composition as a result of the past microbial activity were investigated by multiple analytical methods. In the bison bone, which was permafrost-sealed shortly after death of the animal and conserved for ca. 45 ka in a frozen state in a cryolithic formation, only superficial microbial degradation processes were detected. Progressive microbial attacks characterize the horse bone, which was exposed to MIS 3 sub-aerial biogenic decay and modern surficial weathering. This is evidenced by extensive bacterial micro-boring with the typical focal destructions, an increase in microbial porosity, and de-mineralized osseous zones due to waterlogged and poorly oxygenated past depositional conditions. New information contributes to better understanding of the diagenesis particularities and the associated chemical and biological agents of the fossil osteological assemblages with respect to their taphonomic and paleoenvironmental implications.

Decoding geochemical signals of the Schwalbenberg Loess-Palaeosol-Sequences — A key to Upper Pleistocene ecosystem responses to climate changes in western Central Europe

Loess deposits are the most extent continental archives of climatic- and environmental change and represent important components of local and global dust systems. Consequently, their geochemistry provides an excellent basis for studying climate oscillations on land and how these affect processes in the terrestrial system. It is, however, challenging to assess information archived in loess records due to complexities in their formation, causing interfering geochemical signatures. In particular, the use of element ratios to derive weathering indices may be complicated since dust sources change through time, and since ecosystems respond differently to changing conditions. Whilst this complexity appears as limiting factor, the explanatory potential of proxies increases when the diversity of geochemical processes is acknowledged. To make use of this potential, we integrate the decadic logarithm of element ratios indicative for provenance shifts, mineral sorting during transport and sediment reworking as well as weathering into multivariate statistical analysis. We test, if the sensitivity of Principal Component Analyses (PCA) and Linear Discriminant Analysis (LDA) can be increased by applying both to sub-datasets of diagnostic Stratigraphic Units (SU) of the Schwalbenberg Loess-Palaeosol-Sequences (Middle Rhine valley, Germany). The selected site recorded sub-millennial Upper Pleistocene ecological changes in an unprecedented resolution for Central European LPS. Differences in operating functions of PCA and LDA and our age model highlight timing and intensity of provenance shifts, sediment relocation, decalcification, redox dynamic and clay-mineral formation associated with Atlantic-driven climate oscillations. Based on this we provide evidence for the accretionary character of interstadial palaeosols caused by a close interplay of dust input and soil formation. Automated re-detection of SU across the site using LDA functions contributes important insights into slope dynamics through regional erosion events. Overall, our approach provides a key for tracing ecological changes during climate oscillations across continents.

Amphibian body size and species richness as a proxy for primary productivity and climate: The Orce wetlands (Early Pleistocene, Guadix-Baza Basin, SE Spain)

Amphibians are considered excellent indicators of ecological and climatic changes with a remarkable phenotypic plasticity. The study of such adaptative capacities is central to understanding the climate and environmental changes that occurred during the Early-Middle Pleistocene Transition, at around 1.2 Ma, when the persistence of subtropical ecosystems in Europe came to an end, and several reptile and tree taxa were extirpated. The SE Spain sites in the Guadix-Baza Basin offer an exceptional opportunity for studying this change, in addition to the significant findings made in this area in the field of human evolution. We have analysed the body size of the most well-represented amphibian species in the sites, the Iberian waterfrog, Pelophylax perezi . In order to reconstruct past body sizes from fossil samples, a regression model from current osteological collections has been generated. Also, diversity of the herpetofauna community was studied at different levels as richness or species number. Finally, to study the relationships between body size, richness, climate and productivity, OLS regression models and Pearson correlations were applied. Also for this purpose, a productivity indicator was designed based on the addition of the two most productive ecosystems from previous habitat reconstruction. Amphibian body size appears to be negatively associated with primary productivity, reaching minimum values during the interglacial stages, when species richness increased. In contrast, during glacial periods characterised by greater aridity and fewer resources, amphibian body size increased while species richness decreased. Main explanations proposed to justify this pattern are the “water-availability hypothesis” and a trade-off between somatic growth and reproductive opportunities for females. The study of herpetofaunal diversity shows a clear correlation to regional plant diversity and primary productivity. The results of this work indicate that species richness and amphibian body size are valuable proxies that can complement current environmental and climate reconstruction methods. • Somatic growth and reproduction: the trade-off which determines amphibian body size. • Amphibian body size decreases towards more productive ecosystems. • Primary productivity determines species richness. • Frog body size is defined as a new indicator of Pleistocene ecosystem conditions.

New insights into cave hyena ethology and the implications for territorial competition with hominins in Late Pleistocene north‐west Europe: the case of Caverne Marie‐Jeanne (Belgium)

AbstractMegacarnivore behaviours shape ecological dynamics between their prey and competitors and therefore play a key role in structuring ecosystems. In Late Pleistocene Eurasia, hominins and hyenas were sympatric predators. Since the first discoveries of Crocuta c. spelaea in the 19th century, this ‘bone‐crushing’ species has been identified at most Palaeolithic sites and has inspired many taphonomic studies. Nonetheless, there is still very little known about its reproductive, social and spatial behaviours. We believe that exploring the complexity of the cave hyena's ethology is a way to better understand spatial relationships and niche sharing/partitioning between hominins and other top predators in Pleistocene ecosystems. This paper focuses on the study of Caverne Marie‐Jeanne Layer 4 (Hastière, Belgium), one of the best‐preserved palaeontological sites in the region. The exceptional number of hyena neonates in this assemblage (minimum number of individuals >300) has led us to describe, for the first time, a Late Pleistocene hyena birth den that was reused over a long period of time around 47.6–43k a bp. By bridging the gap between archaeology and palaeontology, we explore the potential of carnivore socio‐spatial organisation and denning habits as an ecological proxy and discuss how these new unique data could help us further understand hominins’ spatial strategy in southern Belgium.

Demographic changes in Pleistocene sea turtles were driven by past sea level fluctuations affecting feeding habitat availability.

Pleistocene environmental changes are generally assumed to have dramatically affected species’ demography via changes in habitat availability, but this is challenging to investigate due to our limited knowledge of how Pleistocene ecosystems changed through time. Here, we tracked changes in shallow marine habitat availability resulting from Pleistocene sea level fluctuations throughout the last glacial cycle (120–14 thousand years ago; kya) and assessed correlations with past changes in genetic diversity inferred from genome‐wide SNPs, obtained via ddRAD sequencing, in Caribbean hawksbill turtles, which feed in coral reefs commonly found in shallow tropical waters. We found sea level regression resulted in an average 75% reduction in shallow marine habitat availability during the last glacial cycle. Changes in shallow marine habitat availability correlated strongly with past changes in hawksbill turtle genetic diversity, which gradually declined to ~1/4th of present‐day levels during the Last Glacial Maximum (LGM; 26–19 kya). Shallow marine habitat availability and genetic diversity rapidly increased after the LGM, signifying a population expansion in response to warming environmental conditions. Our results suggest a positive correlation between Pleistocene environmental changes, habitat availability and species’ demography, and that demographic changes in hawksbill turtles were potentially driven by feeding habitat availability. However, we also identified challenges associated with disentangling the potential environmental drivers of past demographic changes, which highlights the need for integrative approaches. Our conclusions underline the role of habitat availability on species’ demography and biodiversity, and that the consequences of ongoing habitat loss should not be underestimated.

Palaeoenvironments of the MIS 15 site of Cava di Breccia - Casal Selce 2 (central Italian Peninsula) and niche occupation of fossil ungulates during Middle Pleistocene interglacials

ABSTRACT The Ponte Galeria area within the city of Rome has yielded numerous fossiliferous localities that represent a reference point for the study of the European Middle Pleistocene ecosystems. Within Ponte Galeria a rich collection of fossil mammals has been unearthed from Cava di Breccia – Casal Selce 2 (MIS 15) thus the site represents an optimal laboratory to investigate the palaeoenvironments of a defined territory during the Middle Pleistocene. We investigate the feeding behaviours of the ungulate community of Cava di Breccia – Casal Selce 2 to reconstruct the MIS 15 habitats and also compare the data with those of the nearby site of Fontana Ranuccio (MIS 11) which shares similar faunal composition with Cava di Breccia – Casal Selce 2 to test if ungulates occupied the same niches during two different interglacials. Open habitats with scattered woodlands characterised the Ponte Galeria area during MIS 15, whereas woodlands were more widespread during MIS 11 at Fontana Ranuccio. Ungulates display similar diets in both localities, suggesting that cervids, large bovids and equids adopted the same niche partitioning strategies during both interglacials.

Lithologic features of near-surface layers of the Quaternary cover as a key to understanding of environmental constraints for the Quaternary ground squirrel species

ABSTRACT Here, we propose the modern soil map as a source for creating spatial context for agent-based modelling of the historical expansion and dispersal of ground squirrel species. On the basis of this soil map, we produced a lithologic map of the near-surface layers of the Quaternary cover. Units of this new lithologic map (i.e. certain kinds of substrate) were assessed in context of preferability by certain ground squirrel species. Then, these (basic) preference rates were modified for the case of valley slopes (positive impact of valley slopes) and for the case of loess-and-soil accumulation (also positive impact). The hypothesis of the positive impact of loess and soil accumulation is supported by following facts: range shrinking of Spermophilus species in the Holocene; stability of the range boundary between Spermophilus pygmaeus and Spermophilus suslicus in the Middle and Late Pleistocene and the ability of the Pleistocene ecosystems to support high animal biomass even during cold epochs.

Evidence of a significant marine plant diet in a Pleistocene caribou from Haida Gwaii, British Columbia, through compound-specific stable isotope analysis

The Northwest Coast of Canada was likely an important location for glacial refugia in the Late Pleistocene. Recently, a caribou (Rangifer tarandus) antler fragment was reported from Graham Island dating prior to the Fraser Glaciation (MIS 3; 48,200–45,200 cal yr BP). The high carbon and nitrogen stable isotope values found in the bulk collagen samples of this caribou prompted further investigation into its diet and palaeoecological context. Today, caribou in British Columbia face rapid population and range decline, and have been placed on threatened and endangered species lists by both the U.S. and Canadian governments. Further insights into this species and its responses to changing environmental conditions can both improve our understanding of the Late Pleistocene ecosystems of the Northwest Coast and add relevant data to modern conservation issues. We employed compound-specific carbon and nitrogen stable isotope analysis to the individual amino acids of antler collagen to better understand the isotopic signal of this specimen. Our results suggest a significant marine plant contribution to the caribou's spring–summer diet, potentially reflecting an intensive foraging behavior observed in some modern-day Rangifer tarandus populations under conditions of terrestrial resource restriction.

Fox dietary ecology as a tracer of human impact on Pleistocene ecosystems.

Nowadays, opportunistic small predators, such as foxes (Vulpes vulpes and Vulpes lagopus), are well known to be very adaptable to human modified ecosystems. However, the timing of the start of this phenomenon in terms of human impact on ecosystems and of the implications for foxes has hardly been studied. We hypothesize that foxes can be used as an indicator of past human impact on ecosystems, as a reflection of population densities and consequently to track back the influence of humans on the Pleistocene environment. To test this hypothesis, we used stable isotope analysis (δ13C, δ15N) of bone collagen extracted from faunal remains from several archaeological sites located in the Swabian Jura (southwest Germany) and covering a time range over three important cultural periods, namely the Middle Palaeolithic (older than 42,000 years ago) attributed to Neanderthals, and the early Upper Palaeolithic periods Aurignacian and Gravettian (42,000 to 30,000 years ago) attributed to modern humans. We then ran Bayesian statistic systems (SIBER, mixSIAR) to reconstruct the trophic niches and diets of Pleistocene foxes. We observed that during the Middle Palaeolithic period, when Neanderthals sparsely populated the Swabian Jura, the niches occupied by foxes suggest a natural trophic behavior. In contrast, during the early Upper Palaeolithic periods, a new trophic fox niche appeared, characterized by a restricted diet on reindeer. This trophic niche could be due to the consumption of human subsidies related to a higher human population density and the resulting higher impact on the Pleistocene environment by modern humans compared to Neanderthals. Furthermore, our study suggests that, a synanthropic commensal behavior of foxes started already in the Aurignacian, around 42,000 years ago.

Enamel isotopes reveal late Pleistocene ecosystem dynamics in southeastern North America

The end of the late Pleistocene (∼10,000 years ago) witnessed the extinction of over seventy percent of North America’s megafaunal genera. Although this pattern has been extensively investigated, its causal mechanisms remain elusive. Much of this difficulty is related to the spatial and temporal discontinuity of sites dating to the period leading up to the extinctions. In this study, we present new stable carbon and oxygen isotope data from Mammuthus columbi and Bison latifrons teeth collected from a well-dated Last Glacial Maximum (∼20,000 rcybp) locality called Clark Quarry in coastal Georgia, USA. This site lies in direct proximity to where Sir Charles Lyell collected the type specimen of M. columbi in 1846 and therefore is of added historical significance. We compare these data to those from similarly aged (Sangamonian interglacial and Wisconsin glacial intervals) localities from Florida and demonstrate the presence of a vegetation gradient with elevated levels of C3 vegetation at higher latitudes. Serially-sampled δ13C and δ18O values suggest that Clark Quarry Mammuthus and Bison changed their diet seasonally with the incorporation of elevated quantities of C4 vegetation during warmer periods. Our data indicate more exaggerated seasonal dietary variability in these taxa at Clark Quarry relative to those collected from the Sangamonian interglacial locality of Waccasassa River in Florida, providing additional evidence for the significant influence of glacial dynamics in structuring North American ecosystems. These high-resolution ecological patterns should be incorporated into hypotheses focused on extinction dynamics in southeastern North America and more broadly.

Insights into the evolution of the young Lake Ohrid ecosystem and vegetation succession from a southern European refugium during the Early Pleistocene

Mediterranean mid-altitude sites are critical for the survival of plant species allowing for elevational vegetation shifts in response to high-amplitude climate variability. Pollen records from the southern Balkans have underlined the importance of the region in preserving plant diversity over at least the last half a million years. So far, there are no records of vegetation and climate dynamics from Balkan refugia with an Early Pleistocene age. Here we present a unique palynological archive from such a refugium, the Lake Ohrid basin, recording continuously floristic diversity and vegetation succession under obliquity-paced climate oscillations. Palynological data are complemented by biomarker, diatom, carbonate isotope and sedimentological data to identify the mechanisms controlling shifts in the aquatic and terrestrial ecosystems within the lake and its catchment. The study interval encompasses four complete glacial-interglacial cycles (1365–1165 ka; MIS 43–35). Within the first 100 kyr of lake ontogeny, lake size and depth increase before the lake system enters a new equilibrium state as observed in a distinct shift in biotic communities and sediment composition. Several relict tree genera such as Cedrus, Tsuga, Carya, and Pterocarya played an important role in ecological succession cycles, while total relict abundance accounts for up to half of the total arboreal vegetation. The most prominent biome during interglacials is cool mixed evergreen needleleaf and deciduous broadleaf forests, while cool evergreen needleleaf forests dominate within glacials. A rather forested landscape with a remarkable plant diversity provide unique insights into Early Pleistocene ecosystem resilience and vegetation dynamics.

The importance of ecotonic habitats in the spatial organization of the Late Pleistocene ecosystems of Yakutia

The mosaic of the existing vegetation cover of Yakutia in the Late Pleistocene is due to a combination of arid climate, as well as because of permafrost spreading and frequent fires. The combination of these factors creates necessary conditions for the formation of ecotone natural systems represented by dissipative plant communities. Sparse plant communities are characterized by the absence or weak expression of phytocenotic bonds. Their formation occurs stochastically under the absolute influence of external factors and is genetically entirely dependent on the surrounding vegetation, which acts as a donor of patient and ruderal species. Such processes were characteristic of the Late Pleistocene ecosystems of the Northern Hemisphere. A low productivity of such biotopes did not allow them to act as the main pastures for the representatives of the mammoth megafauna, apart from the saiga and bighorn sheep, but contributed to the increase in the biodiversity of the late Pleistocene ecosystems.

Describing a drowned Pleistocene ecosystem: Last Glacial Maximum vegetation reconstruction of the Palaeo-Agulhas Plain

Pleistocene ecosystems provided the stage for modern human emergence. Terrestrial vegetation communities structure resources for human foragers, providing plant food, wood for fuel and tools, and fibre, as well as habitat for animal prey. The Pleistocene distribution of vegetation communities is seldom considered as a key constraint on hunter-gatherers foraging across the landscape. We used modern vegetation patterns along the Cape south coast to develop a rule-based model of the expected vegetation for a given soil type, precipitation regime and fire regime. We then applied this ruleset to present-day environmental conditions to test and validate the model. We also scaled the climate-vegetation ruleset to account for likely effects of low atmospheric [CO2] and lower temperature in the Last Glacial Maximum (LGM) on plant water use efficiency. The model was then used to postdict vegetation patterns for the LGM using palaeo-landscape reconstruction of geological substrata and soils, and palaeoclimate simulations. This palaeoscape comprised the extensive Palaeo-Agulhas Plain (PAP), which was exposed at lower sea levels during glacial periods. Our model predicts that the PAP was dominated by limestone fynbos in its southern part, and by shale grassland with cappings of dune fynbos-thicket mosaic in the north. Shale and sandstone fynbos were restricted to the western zone, which experienced a stronger winter rainfall regime during the LGM than at present. The entire PAP was dissected by broad and shallow floodplains supporting a mosaic of woodland and grassland on fertile, alluvial soils. This savanna-like vegetation, as well as shale grassland, are poorly represented in the modern landscape, and would have been capable of supporting the diverse megafauna typical of glacial periods. These Pleistocene periods would have presented a very different resource landscape for early modern human hunter-gatherers than the interglacial landscape such as is found in the Cape coastal lowlands today.

Carrying capacity, carnivoran richness and hominin survival in Europe

Carrying capacity, the maximum biomass that an ecosystem can sustain over the long term, strongly influences several ecological processes and it is also one of the main determinants of biodiversity. Here, we estimate the carrying capacity (CC) of the late Early and early Middle Pleistocene ecosystems of Europe, using equations describing the relationship between CC and climatic variables observed in the present, as well as maps of inferred paleotemperature and paleoprecipitation. Maps of paleoclimate values were interpolated from the composite benthic stable oxygen isotope ratios and a transfer function was used to estimate ungulate carrying capacity (CCU) from the interpolated mean annual temperature and annual precipitation values. Carnivoran carrying capacity was subsequently estimated from ungulate carrying capacity and the effect of CC on the carnivoran faunas was analyzed in 12 paleocommunities from Southern Europe. Our results show that carnivoran species richness is strongly related to ungulate carrying capacity in recent ecosystems, but the late Early Pleistocene paleocommunities from Southern Europe included much richer carnivore guilds than would be expected for a recent community with a similar ungulate carrying capacity. Thus, those late Early Pleistocene ecosystems supported a high number of carnivoran species, but the carnivoran biomass they could support was relatively low. Consequently, carnivorans occurred at low densities in Southern Europe compared to the recent African savanna ecosystems, but likely also compared to coeval East African ecosystems. Consequently, the first Homo populations that arrived in Europe at the end of the late Early Pleistocene found mammal communities consisting of a low number of prey species, which accounted for a moderate herbivore biomass, as well as a diverse but not very abundant carnivore guild. This relatively low carnivoran density implies that the hominin-carnivore encounter rate was lower in the European ecosystems than in the coeval East African environments, suggesting that an opportunistic omnivorous hominin would have benefited from a reduced interference from the carnivore guild.

The last terror birds (Aves, Phorusrhacidae): new evidence from the late Pleistocene of Uruguay

We report new fossil evidence of terror bird survival until the end of the Pleistocene in Uruguay. The new specimens comprise the distal portion of right tarsometatarsus and a left humerus; the latter is assigned to the genus Psilopterus. The sedimentary context of the remains yields a characteristic Pleistocene mammalian association along with numerical age dating giving an undoubted late Pleistocene age (OSL 96,040 ± 6300 years). We also revise and discuss the systematic placement of late Pleistocene phorusrhacid material previously published. The trophic role of terror birds and other South American carnivorous birds in late Pleistocene ecosystems should be revised based on the increasing findings of avian fossil materials.

Evaluating the impact ofHomo-carnivore competition in European human settlements during the early to middle Pleistocene

AbstractFossil remains and the technological complexes recorded in archaeological sites suggest that the human presence in Europe late in the early and middle Pleistocene was discontinuous. Moreover, competition for meat with other secondary consumers could have delayed the human dispersal through Europe. However, evaluation of the extent competition intensity among secondary consumers suggests this influenced the discontinuity of the human settlement of Europe between 1.1 and 0.2 Ma. Using a mathematical model, we estimate the amount of biomass available in a community for secondary consumers. The amount of available biomass is subsequently distributed among the guild of secondary consumers according to their requirements and prey preferences. Indexes that quantify the competition intensity among secondary consumers to compare the conditions in different paleoecosystems show that the competition intensity late in the early Pleistocene, early in the middle Pleistocene, and late in the middle Pleistocene does not support the view that an increase in competition intensity constrained the expansion of human populations early in the middle Pleistocene. Somewhat paradoxically, the lowest competition intensity is estimated to have occurred early in the middle Pleistocene, most likely because of an increase in the number of large herbivore species and a decrease in the number of secondary consumers. The early Pleistocene paleoecosystems supported higher competition intensity than the middle Pleistocene ecosystems, likely because of the different configuration in the food webs of these two periods (the early and middle Pleistocene).

Refugial ecosystems in central Asia as indicators of biodiversity change during the Pleistocene–Holocene transition

Site-scale species richness (alpha diversity) patterns are well described for many present-day ecosystems, but they are difficult to reconstruct from the fossil record. Very little is thus known about these patterns in Pleistocene full-glacial landscapes and their changes following Holocene climatic amelioration. However, present-day central Asian ecosystems with climatic features and biota similar to those of the full-glacial periods may serve as proxies of alpha diversity variation through both space and time during these periods. We measured alpha diversity of vascular plants, bryophytes, macrolichens and land snails, as well as environmental variables, in 100-m2 plots located in forests and open habitats in the Russian Altai Mountains and their northern foothills. This region contains adjacent areas that possess climatic and biotic features similar to mid-latitude Europe for both the Last Glacial Maximum and contemporaneous Holocene ecosystems. We related alpha diversity to environmental variables using generalized linear models and mapped it from the best-fit models. Climate was identified as the strongest predictor of alpha diversity across all taxa, with temperature being positively correlated to number of species of vascular plants and land snails and negatively correlated to that of bryophytes and macrolichens. Factors important for only some taxa included precipitation, soil pH, percentage cover of tree layer and proportion of grassland areas in the landscape around plots. These results, combined with the high degree of similarity between the current Altai biota and dry-cold Pleistocene ecosystems of Europe and northern Asia, suggest that vascular plant and land snail alpha diversity was low during cold phases of the Pleistocene with a general increase following the Holocene climatic amelioration. The opposite trend probably existed for terricolous bryophytes and macrolichens.

The Role of Rewilding in Landscape Design for Conservation

Rewilding means returning a non-wild area back to the wild. It implies a reduction or cessation of human control in favour of allowing nature to take care of itself. The concept originated in North America, where it was initially focused on reconnecting existing wilderness areas and re-establishing populations of large carnivores and other large vertebrates. The modern literature is dominated by European studies, however, in which rewilding is seen as a management option for the increasing areas of abandoned agricultural land. Although modern rewilding looks forward to a future wildness that is not necessarily the same as the past, evidence from past ecosystems gives inspiration and support for a hands-off approach. Late Pleistocene ecosystems provide a major challenge since they show the irreplaceable roles of the now largely extinct megafauna. Large-scale rewilding will benefit some charismatic large vertebrates, but probably at the expense of many disturbance-dependent species, with the overall impact likely to differ in different regions. Other potential problems include the loss of valued biocultural landscapes and an increase in human-wildlife conflicts. Benefits may include increased recreational opportunities, enhanced ecosystem services, and greater resilience, as well as less quantifiable social benefits and spiritual values. Rewilding science needs to catch up with rewilding practice, and there is an urgent need for replicated, large-scale, long-term experiments.