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The mean state of the tropical Pacific ocean-atmosphere climate, in particular its east-west asymmetry, has profound consequences for regional climates and for the El Niño/Southern Oscillation variability. Here we present a new high-resolution paleohydrological record using the stable-hydrogen-isotopic composition of terrestrial-lipid biomarkers (δDwax) from a 1,400-year-old lake sedimentary sequence from northern Philippines. Results show a dramatic and abrupt increase in δDwax values around 1630 AD with sustained high values until around 1900 AD. We interpret this change as a shift to significantly drier conditions in the western tropical Pacific during the second half of the Little Ice Age as a result of a change in tropical Pacific mean state tied to zonal sea surface temperature (SST) gradients. Our findings highlight the prominent role of abrupt shifts in zonal SST gradients on multidecadal to multicentennial timescales in shaping the tropical Pacific hydrology of the last millennium, and demonstrate that a marked transition in the tropical Pacific mean state can occur within a period of a few decades.

In 2021, the International Union for Conservation of Nature (IUCN) introduced a novel method for assessing species recovery and conservation impact: the IUCN Green Status of Species. The Green Status standardizes recovery using a metric called the Green Score, which ranges from 0% to 100%. This study focuses on one crucial step in the Green Status method—the division of a species’ range into so-called “spatial units”—and evaluates whether different approaches for delineating spatial units affect the outcome of the assessment (i.e., the Green Score). We compared Green Scores generated using biologically based spatial units (the recommended method) to Green Scores generated using ecologically based or country-based spatial units for 29 species of birds and mammals in Europe. We found that while spatial units delineated using ecoregions and countries (fine-scale) produced greater average numbers of spatial units and significantly lower average Green Scores than biologically based spatial units, coarse-scale spatial units delineated using biomes and countries above a range proportion threshold did not differ significantly from biologically based results for average spatial unit number or average Green Score. However, case studies focusing on results for individual species (rather than a group average) showed that, depending on characteristics of the species’ distribution, even these coarse-scale delineations of ecological or country spatial units often over- or under-predict the Green Score compared to biologically based spatial units. We discuss cases in which the use of ecologically based or country-based spatial units is recommended or discouraged, in hopes that our results will strengthen the new Green Status framework and ensure consistency in application.

Late Pliocene and Early Pleistocene epochs 3.6 to 0.8 million years ago 1 had climates resembling those forecasted under future warming 2 . Palaeoclimatic records show strong polar amplification with mean annual temperatures of 11–19 °C above contemporary values 3 , 4 . The biological communities inhabiting the Arctic during this time remain poorly known because fossils are rare 5 . Here we report an ancient environmental DNA 6 (eDNA) record describing the rich plant and animal assemblages of the Kap København Formation in North Greenland, dated to around two million years ago. The record shows an open boreal forest ecosystem with mixed vegetation of poplar, birch and thuja trees, as well as a variety of Arctic and boreal shrubs and herbs, many of which had not previously been detected at the site from macrofossil and pollen records. The DNA record confirms the presence of hare and mitochondrial DNA from animals including mastodons, reindeer, rodents and geese, all ancestral to their present-day and late Pleistocene relatives. The presence of marine species including horseshoe crab and green algae support a warmer climate than today. The reconstructed ecosystem has no modern analogue. The survival of such ancient eDNA probably relates to its binding to mineral surfaces. Our findings open new areas of genetic research, demonstrating that it is possible to track the ecology and evolution of biological communities from two million years ago using ancient eDNA. Analysis of two-million-year-old ancient environmental DNA from the Kap København Formation in North Greenland shows there was an open boreal forest with diverse plant and animal species, of which several taxa have not previously been detected at the site, representing an ecosystem that has no present-day analogue.

During the last glacial–interglacial cycle, Arctic biotas experienced substantial climatic changes, yet the nature, extent and rate of their responses are not fully understood1,2,3,4,5,6,7,8. 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.

Aim Global sea-level rise (SLR) could be as much as 1.8 metres by 2100, which will impact coastal wetland communities and threatened species. We evaluated the likely outcomes of SLR for wetland communities using a process-based simulation model and coupled this with a metapopulation model for a threatened native rodent (Xeromys myoides). Furthermore, we tested the amplified impacts of SLR, urban growth and introduced predators on X. myoides persistence. Location South-east Queensland, Australia. Methods We adapted the Sea Level Affects Marshes Model to subtropical Australia. We used LiDAR elevation data, field data to parameterize surface accretion and shallow subsidence, and local knowledge to configure wetland transitions. SLR was simulated based on the IPCC B1 and A1FI scenarios, as well as the maximal limit of 1.8 m by 2100. Further, we coupled our demographic model to projected shifts in wetland habitat, and estimates of future wetland loss to urban expansion and feral cat (Felis catus) predation. Results Our models project a general decline in wetland communities under SLR, with a noted exception of mangroves. Under the A1FI scenario, SLR allows mangroves to migrate inland, with urban development acting as an obstruction in some areas. Mangrove expansion provides an unexpected benefit for dependent X. myoides populations, although the inclusion of predation and habitat loss due to urban development still suggests extirpation in c. 50 years. Main conclusions Through this case study, we illustrate the usefulness of process-based SLR models in understanding outcomes for wetland communities and dependent species. Our models will underscore decision-making in a dynamic system, with global applications for urban planning, conservation prioritization and wildlife management.

Because bones are particularly resistant to decay, quantifying how their persistence changes across environments enables us to constrain the durations that dead individuals generally contribute to eDNA archives. The magnitude of temporal mixing in eDNA must, therefore, largely depend on the decay durations of bones and other tissues. Because DNA cannot be directly dated, the degree of temporal mixing cannot be estimated for an individual eDNA sample. Mammoth body fossils found in Northeast Siberia, Northwest and Central Siberia, and northern North America (n = 101, 468, and 394, respectively; Supplementary Methods and Supplementary Data 3) are known semi-continuously from around 50 cal kyr bp until their last occurrences. [...]their predicted extinction intervals12 (Supplementary Methods) are tightly constrained (Fig. 2). On the basis of the temperature of the most recent mammoth DNA-bearing site (MAT = -13.3 °C), we would expect bone persistence times of between 2.26 and 4.19 kyr (mean and upper 95% confidence intervals for never buried bones) to more than 8.0 kyr (upper 95% CI for potentially never buried bones). [...]using eDNA time series at face value implies that bones of the last mainland Siberian mammoths might still be persisting on today's landscapes.

Tropical rainforests comprise the world's oldest and most biodiverse biome, covering over 10% of Earth surface and providing livelihoods for over 300 million people. The upcoming consequences of anthropogenic climate change on tropical rainforests remain poorly understood. This is particularly true of the lowland tropical rainforests of Southeast Asia, aka Dipterocarp rainforests, in relation to the projected changes in El Niño/Southern Oscillation dynamics (ENSO). To address this important knowledge gap, this thesis aims to elucidate the ecological responses of Dipterocarp rainforests to past ENSO changes using a sediment-based multiproxy palaeoecological approach. A suite of fossil proxies (e.g. lipid biomarkers, pollen, charcoal) from a Philippine lacustrine sequence spanning the last 1,400 years were used to generate records of precipitation, fire, nutrient availability and plant dynamics. These records were used to explore the effects of major environmental drivers on the structure and functioning of Dipterocarp rainforests, specifically their dominant tree family, Dipterocarpaceae, and their pioneer plant taxa. The results suggest that Dipterocarp rainforests have been exposed to a prolonged period of enhanced ENSO regime during the second half of the Little Ice Age (~AD 1650-1900), yet there was no apparent effect of this climatic variability on the biomass of Dipterocarp trees. In contrast, the findings indicate that major fluctuations in phosphorus availability at the study site have had a significant influence on the biomass of Dipterocarp trees, though it remains uncertain which aspect of their biomass was primarily affected. Finally, my results propose that changes in ENSO conditions can significantly affect the abundance of pioneer taxa, with the nature and magnitude of that effect depending heavily on the level of fire activity. This thesis examined for the first time the vegetation responses of Dipterocarp rainforests to large-scale climatic changes in the past. The findings presented here provide new insights into the likely structure and functioning of this globally important ecosystem in a warming world, and provide a context for understanding its resilience to current and future environmental change.