Arid regions are especially vulnerable to climate change and land use. More than one-third of Earth's population relies on these ecosystems. Modern observations lack the temporal depth to determine vegetation responses to climate and human activity, but paleoecological and archaeological records can be used to investigate these relationships. Decreasing rainfall across the Late Holocene provides a case study for vegetation response to changing hydroclimate. Rock hyrax (Procavia capensis) middens preserve paleoenvironmental indicators in arid environments where traditional archives are unavailable. Pollen from modern middens collected in Dhofar, Oman, demonstrates the reliability of this archive. Pollen, stable isotope (δ13C, δ15N), and microcharcoal data from fossil middens reveal changes in vegetation, relative moisture, and fire from 4000 cal yr BP to the present. Trees limited to moister areas (e.g., Terminalia) today existed farther inland at ~3100 cal yr BP. After ~2900 cal yr BP, taxa with more xeric affiliations (e.g., Senegalia) had increased. Coprophilous fungal spores (Sporormiella) and grazing indicator pollen revealed an amplified signal of domesticate grazing at ~1000 cal yr BP. This indicates that trees associated with semiarid environments were maintained in the interior desert during ~3000–4000 yr of decreasing rainfall and that impacts of human activity intensified after the transition to a drier environment.

A remarkable specimen of the actinopterygian fish Pachycormus macropterus from the Early Jurassic (Toarcian) Posidonienschiefer Formation of Germany exceptionally preserves an unusually large ammonite inside its gut. The ammonite was swallowed by the fish, likely by accident, and represents the first direct evidence for an actinopterygian fish consuming an ammonoid. Exceptional aragonite preservation of the conch retaining partial nacreous lustre, combined with only minor acid etching of the shell, strongly indicates that the ammonite was ingested immediately prior to and was directly responsible for the fish’s death. The fish’s stomach provided a microenvironment protecting the aragonite from chemical dissolution.

The Late Holocene Dry Period (LHDP) was a one-plus millennial megadrought (3100–1800 cal BP) that delivered challenges and windfalls to Indigenous communities of the central Great Basin (United States). New pollen and sedimentation rate studies, combined with existing tree-ring data, submerged stump ages, and lake-level evidence, demonstrate that the LHDP was the driest Great Basin climate within the last 6,000 years—more extreme than the well-known Medieval Climatic Anomaly. New evidence reported here documents that most Great Basin archaeological sites south of 40° N latitude were abandoned during the long dry phase of the LHDP (3100–2200 cal BP), sometimes reoccupied during a wet interval (2200–2000 cal BP), and abandoned again during the most extreme drought (2000–1800 cal BP). Even in the face of epic drought, this is a story of remarkable survivance by some people who adjusted to their drought-stricken landscape where they had lived for millennia. Some moved on, but other resilient foragers refused to abandon their homeland, taking advantage of glacier-fed mountain springs with cooler alpine temperatures and greater moisture retention at high altitude, a result of early Neoglaciation conditions across many Great Basin ranges, despite epic drought conditions in the lowlands.

Detailed sedimentological, geochemical, palynological, and aquatic-microfossil analyses on a new composite profile (Para-Reference Profile Schöningen 13 II and Zeugenblock 13 II [2018]) exposed at the archaeological excavation site of Schöningen 13 II reflect several phases of newly recorded lake level fluctuations and vegetation changes. A pronounced deforestation and the expansion of grasses and herbal plant communities characterize the first steppe (open woodland) phase, which follows the interglacial forest communities. A succeeding tripartite woodland phase predominantly marked by Betula and Pinus is followed by another rather dry steppe phase and a second woodland period, which includes the famous archaeological “spear horizon” 13 II-4ab. Transition into a cold period is indicated by progressive desiccation of the lake and a shift to a steppe/tundra vegetation. Novel 3D images of the 10 most characteristic phases of the Reinsdorf sequence have been constructed based on the botanical data (macro remains as well as palynomorphs), terrestrial vertebrate faunal, geochemical, sedimentological, and previously established data from aquatic microfossils. In addition, a tentative correlation between the post-interglacial phases of the Reinsdorf sequence and Marine Isotope Substages 9d–9a, based on biostratigraphical as well as sedimentological data, is proposed.

In 2020, a unique bone assemblage was found at the Late Paleolithic site Volchia Griva. Its base is made of a distal mammoth femur minus epiphysis, in which a cavity has been hollowed out. Impact notches along the edges of the cavity and holes in the metaphysis prove the human-made nature of this specimen. A portion of a polar fox cranium, half of a fox hemimandible, a fox tooth, and a large mammal rib fragment were enclosed in the cavity. The mammoth femur was previously used as a retoucher, as evinced by the impressions and cut marks. Incisions were detected on the polar fox cranium, indicating skinning. According to two 14C dates, the age of the remains is 19.3–19.1 ka BP. Palynological analysis of the cavity fill shows a forb-grass steppe at that time. The assemblage, which has no known analogues, is a reflection of prehistoric culture. This extraordinary find most likely is evidence of the ritual behavior of people who lived in the south of Western Siberia during the last glacial maximum. The assemblage was accompanied by a large number of fox remains, and lithic artifacts identical to bladelet-based Late Paleolithic industries of Siberia and the Middle Urals.

Layers 12 and 13 of the Chongphadae Cave site located northwest of the central part of the Korean Peninsula include human fossils, fireplaces, a great number of lithic artefacts, and mammal remains. These layers represent new evidence for the paleoenvironment, human occupation, and activities in this region during the late MIS 3 and MIS 2, associated with global cold and dry climate, respectively. Most of lithic artefacts collected are flake tools. Raw material selection, lithic reduction technology, and lithic industry represent peculiar local characteristics. Our analysis of faunal assemblages also suggests that the Chongphadae region had a rich ecosystem capable of forming a diverse mammalian fauna including ungulates (mainly deer and horses) during this period. It is likely that the mosaic landscapes, including grasslands, forests, rivers, and wetlands, provided a favorable environment for humans, as well as mammals and plants, and the occupants of the site actively hunted and gathered in a relatively temperate environment. Our study suggests that the central Korean Peninsula was not severely affected by global dry and cold events such as LGM, although it was a somewhat humid and cold environment during the late MIS 3 and MIS 2. The central Korean Peninsula may have existed as an unknown refugium (or area of endemism) in northeastern Asia during this time.

This paper describes the results of research at Volchia Griva, the largest site in Asia containing mammoth fauna in situ. It is situated in the south of the West Siberian Plain in the Baraba forest-steppe zone, and occupies an area of several hectares. Analysis of sediments and taphonomy of the site allows us to suggest that thousands of megafaunal remains were buried here in mud pits and erosional depressions. The favorable geochemical landscape of Volchia Griva attracted animals during periods of mineral starvation. This is reflected in the high mortality in two intervals, ca. 20–18 14C ka BP and ca. 17–11 14C ka BP. The results of palynological analysis of samples from the upper part of the Volchia Griva section made it possible to reconstruct the history of landscape changes of the Baraba Lowland during the MIS 2. Forb-mesophytic meadows were common at the beginning of this period, with taiga type forests. At ca. 20 14C ka BP, an abrupt and significant aridization of the climate occurred, which led to the degradation of forests. The mammoth steppe was widely developed, dominated by forb-grass association and with areas of alkali meadows and soils. Such conditions existed probably until the mid-Holocene.

Glacial lake sediments exposed at two sites in Skagit Valley, Washington, encase abundant macrofossils dating from 27.7 to 19.8 cal ka BP. At the last glacial maximum (LGM) most of the valley floor was part of a regionally extensive arid boreal (subalpine) forest that periodically included montane and temperate trees and open boreal species such as dwarf birch, northern spikemoss, and heath. We used the modern distribution and climate of 14 species in 12 macrofossil assemblages and a probability density function approach to reconstruct the LGM climate. Median annual precipitation (MAP) at glacial Lake Concrete (GLC) was ~50% lower than today. In comparison, MAP at glacial Lake Skymo (GLS) was only ~10% lower, which eliminated the steep climate gradient observed today. Median January air temperature at GLC was up to 10.8°C lower than today at 23.5 cal ka BP and 8.7°C lower at GLS at 25.1 cal ka BP. Median July air temperature declines were smaller at GLC (3.4°C–5.0°C) and GLS (4.2°C–6.3°C). Warmer winters (+2°C to +4°C) and increases in MAP (+200 mm) occurred at 27.7, 25.9, 24.4, and 21.2–20.7 cal ka BP. These changes accord with other regional proxies and Dansgaard–Oeschger interstades in the North Atlantic.

Understanding how raptors select prey is important to determine taphonomic biases both in modern and paleo pellet assemblages. We tested whether pellets more closely represent raptor dietary specialization or local small mammal diversity by sampling pellets from seven raptor species across four study sites in Yellowstone National Park, Wyoming, USA. We identified small mammal craniodental elements from each pellet and tested for differences among small mammal assemblages for each raptor species and study site. We found that reconstructed avian predator diets clustered significantly by site but not by predator species. Bray-Curtis diet dissimilarities were also significantly lower when comparing different raptor species within a site than when comparing the same raptor species across different sites. Our results suggest that raptors choose to eat a diversity of small mammal species close to their roosts rather than fly long distances to specialize on a particular prey species. Neontologists and paleoecologists alike can therefore be confident that raptor pellets faithfully represent local small mammal diversity.

Greenock Swamp wetland complex is one of few remaining natural wetlands in the Great Lakes region and, at 89 km2 in areal extent, is currently the largest hardwood swamp in southern Ontario, Canada. We present here pollen and sediment records from a kettle hole (Schmidt Lake) and adjacent Thuja occidentalis swamp to reconstruct regional paleoclimate and vegetation history, and to assess the timing and development of the swamp ecosystem and associated carbon stocks. Pollen-inferred paleoclimate reconstructions show the expected warming in the Early Holocene, and indicate the Mid-Holocene initiation of lake-effect snow. This enhanced snowfall may have maintained high water tables in the adjacent wetland since ca. 8300 years ago, promoting the establishment of a swamp dominated by Thuja occidentalis. Carbon accumulation rates in a >2-m-long peat core collected from a Thuja occidentalis stand adjacent to Schmidt Lake are 30–40 g C/m2/yr, which is higher than the average of northern high-latitude peatlands. Using topographic and hydrological parameters, we estimated that mean swamp peat thicknesses could exceed 2 m. Thus, this study encourages future investigations on temperate swamps from the perspective of hitherto underestimated Holocene carbon sinks and shows the importance of regional hydroclimate in supporting swamp ecosystems.

Mollusk and ostracode assemblages from the distal Old River Bed delta (ORBD) contribute to our understanding of the Lake Bonneville basin Pleistocene-Holocene transition (PHT) wetland and human presence on the ORBD (ca. 13,000–7500 cal yr BP). Located on U.S. Air Force-managed lands of the Great Salt Lake Desert (GSLD) in western Utah, USA, the area provided 30 samples from 12 localities. The biological assemblages and the potential water sources using 87Sr/86Sr analyses showed wetland expansion and contraction across the PHT, including the Younger-Dryas Chronozone (YDC). The record reflects cold, freshwater conditions, which is uncharacteristic of the Great Salt Lake Desert, after recession of Lake Bonneville. Lymnaea stagnalis jugularis, Cytherissa lacustris, and possibly Candona sp. cf. C. adunca, an endemic and extinct species only reported from Lake Bonneville, suggest cold-water environments. Between 13,000–12,400 cal yr BP, a shallow lake formed, referred to as the Old River Bed delta lake, fed by Lake Gunnison, as shown by 87Sr/86Sr ratios of 0.71024–0.71063 in mollusk fossils collected at the ORBD, characteristic of the Sevier basin. These findings add paleoenvironmental context to the long-term use of the ORBD by humans in constantly changing wetland habitats between 13,000–9500 cal yr BP.

The late Pleistocene to early Holocene Champlain Sea provides a unique opportunity to study the development of marine ecosystems in a context of global climatic change. This study presents radiocarbon (14C) dates and stable isotope analyses on 15 vertebrate specimens from Champlain Sea sediments, including the Charlotte Whale, which is Vermont’s State marine fossil. Data are used in an attempt to investigate the timing of colonization and ecological dynamics in this newly formed sea. Using the average marine correction, 14C dates on four specimens likely calibrate prior to or possibly synchronous with the accepted origination date for the Champlain Sea, implying larger marine reservoir effects than the average marine correction in the vertebrate tissues. Without knowing the specific marine reservoir offsets, it is not possible to calculate the timing of colonization or its relation to concurrent climatic change. Observed lower δ13C and δ15N values in walruses, a fin whale, and a right whale support consumption of prey from lower trophic levels such as bivalve mollusks, krill, and copepods. Higher isotopic values in beluga whales and a bird, the thick-billed murre, support consuming fish, such as cod and capelin. These isotopic data show comparable values and relationships as observed in modern arctic marine ecosystems.

Climatic and environmental changes, as well as human action, have been cited as potential causes for the extinction of megafauna in South America at the end of the Pleistocene. Among megamammals lineages with Holarctic origin, only horses and proboscideans went extinct in South America during this period. This study aims to understand how the spatial extent of habitats suitable for Equus neogeus and Notiomastodon platensis changed between the last glacial maximum (LGM) and the middle Holocene in order to determine the impact that climatic and environmental changes had on these taxa. We used species distribution modeling to estimate their potential extent on the continent and found that both species occupied arid and semiarid open lands during the LGM, mainly in the Pampean region of Argentina, southern and northeastern Brazil, and parts of the Andes. However, when climate conditions changed from dry and cold during the LGM to humid and warm during the middle Holocene, the areas suitable for these taxa were reduced dramatically. These results support the hypothesis that climatic changes were a driving cause of extinction of these megamammals in South America, although we cannot rule out the impact of human actions or other potential causes for their extinction.

Analyses of macroscopic charcoal, sediment geochemistry (%C, %N, C/N, δ13C, δ15N), and fossil pollen were conducted on a sediment core recovered from Stella Lake, Nevada, establishing a 2000 year record of fire history and vegetation change for the Great Basin. Charcoal accumulation rates (CHAR) indicate that fire activity, which was minimal from the beginning of the first millennium to AD 750, increased slightly at the onset of the Medieval Climate Anomaly (MCA). Observed changes in catchment vegetation were driven by hydroclimate variability during the early MCA. Two notable increases in CHAR, which occurred during the Little Ice Age (LIA), were identified as major fire events within the catchment. Increased C/N, enriched δ15N, and depleted δ13C values correspond with these events, providing additional evidence for the occurrence of catchment-scale fire events during the late fifteenth and late sixteenth centuries. Shifts in the vegetation community composition and structure accompanied these fires, with Pinus and Picea decreasing in relative abundance and Poaceae increasing in relative abundance following the fire events. During the LIA, the vegetation change and lacustrine geochemical response was most directly influenced by the occurrence of catchment-scale fires, not regional hydroclimate.

A multiproxy Holocene record from a bog in the Hudson Bay Lowlands, northern Ontario, Canada, was used to evaluate how ecohydrology relates to carbon accumulation. The study site is located at a somewhat higher elevation and on coarser grained deposits than the surrounding peatlands. This promotes better drainage and thus a slower rate of carbon accumulation relative to sites with similar initiation age. The rate of peat vertical accretion was initially low as the site transitioned from a marsh to a rich fen. These lower rates took place during the warmer temperatures of the Holocene thermal maximum, confirming the importance of hydrological controls limiting peat accretion at the local scale. Testate amoebae, pollen, and plant macrofossils indicate a transition to a poor fen and then a bog during the late Holocene, as the carbon accumulation rate and reconstructed water table depth increased. The bacterial membrane lipid biomarker indices used to infer paleotemperature show a summer temperature bias and appear sensitive to changes in peat type. The bacterial membrane lipid biomarker pH proxy indicates a rich to a poor fen and a subsequent fen to bog transition, which are supported by pollen, macrofossil, and testate amoeba records.

The last 85,000 years were characterized by high climate and environmental variability on the Yucatán Peninsula. Heinrich stadials are examples of abrupt climate transitions that involved shifts in regional temperatures and moisture availability. Thus, they serve as natural experiments to evaluate the contrasting responses of aquatic and terrestrial ecosystems. We used ostracodes and pollen preserved in a 75.9-m-long sediment core (PI-6, ~85 ka) recovered from Lake Petén Itzá, Guatemala, to assess the magnitude and velocity of community responses. Ostracodes are sensitive to changes in water temperature and conductivity. Vegetation responds to shifts in temperature and the ratio of evaporation to precipitation. Ostracodes display larger and more rapid community changes than does vegetation. Heinrich Stadial 5-1 (HS5-1) was cold and dry and is associated with lower ostracode and vegetation species richness and diversity. In contrast, the slightly warmer and dry conditions during HS6 and HS5a are reflected in higher ostracode species richness and diversity. Our paleoecological study revealed the greatest ecological turnover for ostracodes occurred from 62.5 to 51.0 ka; for pollen, it was at the Pleistocene/Holocene transition. Future studies should use various climate and environmental indicators from lake and marine sediment records to further explore late glacial paleoclimate causes and effects in the northern neotropics.

Accelerator mass spectrometry (AMS) dating of pollen concentrates is often used in lake sediment records where large, terrestrial plant remains are unavailable. Ages produced from chemically concentrated pollen as well as manually picked Pinaceae grains in Yellowstone Lake (Wyoming) sediments were consistently 1700–4300 cal years older than ages established by terrestrial plant remains, tephrochronology, and the age of the sediment-water interface. Previous studies have successfully utilized the same laboratory space and methods, suggesting the source of old-carbon contamination is specific to these samples. Manually picking pollen grains precludes admixture of non-pollen materials. Furthermore, no clear source of old pollen grains occurs on the deglaciated landscape, making reworking of old pollen grains unlikely. High volumes of CO2 are degassed in the Yellowstone Caldera, potentially introducing old carbon to pollen. While uptake of old CO2 through photosynthesis is minor (F14C approximately 0.99), old-carbon contamination may still take place in the water column or in surficial lake sediments. It remains unclear, however, what mechanism allows for the erroneous ages of highly refractory pollen grains while terrestrial plant remains were unaffected. In the absence of a satisfactory explanation for erroneously old radiocarbon ages from pollen concentrates, we propose steps for further study.

Stable isotopes of mammoths and mastodons have the potential to illuminate ecological changes in late Pleistocene landscapes and megafaunal populations as these species approached extinction. The ecological factors at play in this extinction remain unresolved, but isotopes of bone collagen (δ13C, δ15N) and tooth enamel (δ13C, δ18O, 87Sr/86Sr) from midwestern North America are leveraged to examine ecological and behavioral changes that occurred during the last interglacial-glacial cycle. Both species had significant C3 contributions to their diets and experienced increasing levels of niche overlap as they approached extinction. A subset of mastodons after the last glacial maximum exhibit low δ15N values that may represent expansion into a novel ecological niche, perhaps densely occupied by other herbivores. Stable isotopes from serial and microsampled enamel show increasing seasonality and decreasing temperatures as mammoths transitioned from Marine Isotope Stage (MIS) 5e to glacial conditions (MIS 4, MIS 3, MIS 2). Isotopic variability in enamel suggests mobility patterns and life histories have potentially large impacts on the interpretation of their stable isotope ecology. This study further refines the ecology of midwestern mammoths and mastodons demonstrating increasing seasonality and niche overlap as they responded to landscape changes in the final millennia before extinction.