Past Climate Change Research Articles

ForamEcoGEnIE 2.0: incorporating symbiosis and spine traits into a trait-based global planktic foraminiferal model

Abstract. Planktic foraminifera are major marine calcifiers in the modern ocean, regulating the marine inorganic carbon pump, and generating marine fossil archives of past climate change. The foraminifera contain ecogroups with and without spines and algal symbionts, creating functional trait diversity which expands their ecological niches. Here, we incorporate symbiosis and spine traits into the symbiont-barren non-spinose foraminifer functional type in EcoGEnIE to represent all the extant foraminifera species. We calibrated the modelled new traits using Latin hypercube sampling (LHS) and identified the optimal model parameters from an ensemble of 1200 runs compared with global observations from core-top sediment samples, sediment traps, and plankton nets. The model successfully describes the global distribution and seasonal abundance variation of the four major foraminiferal functional groups. The model reproduces the dominance of the symbiont-obligate group in subtropical gyres and of the symbiont-barren types in the productive subpolar oceans. Global annual mean biomass and foraminifer-derived carbon export rate are correctly predicted compared to data, with biomass ranging from 0.001 to 0.010 mmol C m−3 and organic carbon export 0.002–0.031 mmol C m−2 d−1. The model captures the seasonal peak time of biomass and organic carbon export but struggles to reproduce the amplitude of both in productive areas. The sparseness and uneven distribution of observations and the model's limitation in upwelling regions likely contribute to this discrepancy. Our model overcomes the lack of major groups in the previous ForamEcoGEnIE 1.0 version and offers the potential to explore foraminiferal ecology dynamics and its impact on biogeochemistry in modern, future, and paleogeographic environments.

Genetic structure and population history of a peat swamp forest tree species, Shorea albida (Dipterocarpaceae), in Brunei Darussalam.

Southeast Asia supports high biodiversity, in a mosaic of forest types formed by the expansion and contraction of habitats through past climate changes. Among the region's forest types, the geographical distribution of peat swamp forests has fluctuated intensely over the past 120,000 years. Most peat swamp forests in Southeast Asia are found in coastal regions and formed within the last 7,000 years after a decline in sea level. However, some peat swamps were initiated earlier on substrates of slightly higher elevation, and these peat swamps might have been refugia for peat swamp species in the last glacial period and the high sea level period. We assessed genetic diversity, genetic structure and divergence time of current genetic groups for Shorea albida in Brunei, an endemic tree species of Bornean peat swamp forests, using 18 microsatellite markers. Genetic diversity was not lower than has been found in other Shorea species, possibly because of the high density of S. albida in Brunei. Although overall genetic divergence between populations was low, two populations (Ingei and Labi Road 3) were distinct from the other populations. Analysis using DIYABC estimated that three genetic groups (Ingei, Labi Road 3 and others) diverged simultaneously from their ancestral population, whose effective size was very small, about 7,500 years ago, corresponding to a recent sea level peak in the Belait-Baram river basin. In that high sea level period, some higher-elevation lands remained, and peat formation had already started in this region. We propose that the current genetic structure of S. albida in Brunei was formed from small refugial populations that survived the period of higher sea level in these higher-elevation areas. Because of their relatively high genetic diversity, Brunei's S. albida populations should become an important genetic resource for the recovery of genetically healthy populations in other parts of northwest Borneo.

Pleistocene megafaunal extinction in the grasslands of Junín‐Peru

AbstractAimTo determine the timing of megafaunal extinction in the high plains of Peru and also to determine if the timing was delayed in grasslands compared with previously published forested settings to dissociate the effects of succession from human or climatic impacts.LocationThe Junín Plateau, Peru.TaxonFlowering plants and Ascomycetes.MethodsThe sediments used in this analysis were collected from the edge of Lake Junín, Peru. Eleven ages derived from 14C accelerator mass spectrometry provide a chronology. We provide a paleoecological reconstruction of past climate and vegetation change, fire history and megafaunal herbivore presence from c. 20,000–7000 years ago based on fossil pollen, charcoal and Sporormiella spores. Data were analysed using multivariate analysis and Bayesian change point analysis.ResultsMegafaunal populations appear to have been positively impacted by dry climatic oscillations until c. 15,200 years ago. A reduction in Sporormiella abundance between 13,000 and 12,300 years before the present coincides with increased charcoal abundance and is identified as the period of megafaunal population collapse leading to extinction. The timing of the extinction does not differ substantially from that observed in wooded Andean settings.Main ConclusionThe timing of the collapse of megafaunal populations in high grasslands was very similar to that of lower, now‐forested settings. Upticks in fire activity, during what is generally seen to be a wet period, formed the backdrop to extinction and are strongly associated with human activity.

Phylotranscriptomics Shed Light on Intrageneric Relationships and Historical Biogeography of Ceratozamia (Cycadales).

Ceratozamia Brongn. is one of the species-rich genera of Cycadales comprising 38 species that are mainly distributed in Mexico, with a few species reported from neighboring regions. Phylogenetic relationships within the genus need detailed investigation based on extensive datasets and reliable systematic approaches. Therefore, we used 30 of the known 38 species to reconstruct the phylogeny based on transcriptome data of 3954 single-copy nuclear genes (SCGs) via coalescent and concatenated approaches and three comparative datasets (nt/nt12/aa). Based on all these methods, Ceratozamia is divided into six phylogenetic subclades within three major clades. There were a few discrepancies regarding phylogenetic position of some species within these subclades. Using these phylogenetic trees, biogeographic history and morphological diversity of the genus are explored. Ceratozamia originated from ancestors in southern Mexico since the mid-Miocene. There is a distinct distribution pattern of species through the Trans-Mexican Volcanic Belt (TMVB), that act as a barrier for the species dispersal at TMVB and its southern and northern part. Limited dispersal events occurred during the late Miocene, and maximum diversification happened during the Pliocene epoch. Our study provides a new insight into phylogenetic relationships, the origin and dispersal routes, and morphological diversity of the genus Ceratozamia. We also explain how past climatic changes affected the diversification of this Mesoamerica-native genus.

The performance of protected-area expansions in representing tropical Andean species: past trends and climate change prospects

Protected area (PA) extent has increased significantly over the last 150 years globally, but it is yet unclear whether progress in expanding coverage has been accompanied by improved performance in ecological representation. Here, we explore temporal trends in the performance of PA networks in representing > 16,000 vertebrate and plant species in tropical Andean countries based on species bioclimatic niche modelling. We use a randomization analysis to assess whether representation gains over time (1937–2015) are the expected consequence of increasing the overall area of the network or the result of better designed networks. We also explore the impact of climate change on protected-area representation based on projected species distributions in 2070. We found that PAs added in the last three to four decades were better at representing species diversity than random additions overall. Threatened species, amphibians and reptiles are the exception. Species representation is projected to decrease across PAs under climate change, although PA expansions over the last decade (2006–2015) better represented species' future bioclimatic niches than did sites selected at random for most evaluated groups. These findings indicate an unbalanced representation across taxa, and raises concern over under-represented groups, including threatened species, and species’ representation under climate change scenarios. However, they also suggest that decisions related to locating protected areas have become more strategic in recent decades and illustrate that indicators tracking representativeness of networks are crucial in PA monitoring frameworks.

Dynamic properties of the pinyon pine syngameon.

This article is a Commentary on Buck et al. (2023), 237: 2435–2449.

Climate change, human health, and resilience in the Holocene

Climate change is an indisputable threat to human health, especially for societies already confronted with rising social inequality, political and economic uncertainty, and a cascade of concurrent environmental challenges. Archaeological data about past climate and environment provide an important source of evidence about the potential challenges humans face and the long-term outcomes of alternative short-term adaptive strategies. Evidence from well-dated archaeological human skeletons and mummified remains speaks directly to patterns of human health over time through changing circumstances. Here, we describe variation in human epidemiological patterns in the context of past rapid climate change (RCC) events and other periods of past environmental change. Case studies confirm that human communities responded to environmental changes in diverse ways depending on historical, sociocultural, and biological contingencies. Certain factors, such as social inequality and disproportionate access to resources in large, complex societies may influence the probability of major sociopolitical disruptions and reorganizations—commonly known as “collapse.” This survey of Holocene human–environmental relations demonstrates how flexibility, variation, and maintenance of Indigenous knowledge can be mitigating factors in the face of environmental challenges. Although contemporary climate change is more rapid and of greater magnitude than the RCC events and other environmental changes we discuss here, these lessons from the past provide clarity about potential priorities for equitable, sustainable development and the constraints of modernity we must address.

A loess-paleosol record of climate and vegetation change during the past 27,000 years from South-East of the Caspian Sea, Iran

Loess and paleosols are valuable terrestrial archives of past climate change in arid and semiarid Asia, yet most of the available records are located in central Asia and China, with only few records from western Asia. Here we report on a loess-paleosol sequence retrieved from the Gorgan Plain Southeast of the Caspian Sea that extends back to ca. 27,000 years ago. By combining palynological and micromorphological data with granulometry and magnetic properties in different horizons, we infer past changes in soil formation and vegetation composition, and the related climatic conditions. In order to set up a more reliable chronological framework, we applied luminescence and radiocarbon dating. Our results suggest a dry and cold glacial period characterized by steppe vegetation and loess deposition until about 24,000 years ago. Climate conditions during the Last Glacial Maximum (19–23,000 years ago) were relatively wet followed by a drying trend towards the end of the deglaciation. Our record suggests a relatively wet early Holocene but remains inconclusive for the late Holocene due to concurrent anthropogenic impact. We argue that changes in wintertime temperature and precipitation have been decisive in shaping the vegetation and soil formation in our study area during the Holocene, whereas changes in the position of the westerlies together with sea-level fluctuations of the Caspian Sea controlled the regional climate during the last glacial period.

Annual Report 2013

Earth scientists at CAGE together with colleagues from The Geological Survey of Norway and Akvaplan-niva aim to assess the role of Arctic gas hydrate in past, present and future climate change. For past or present reconstructions we study samples from the sub seabed, the seabed, the water column and the atmosphere and for the future outlook we aim to use modeling with experts from atmospheric science. To accomplish these goals, CAGE contributes to enhanced collaborations and relationships with university and industry research teams at national and international levels.

Improving the routine analysis of siderite for δ13 C and δ18 O in environmental change research.

The carbon (δ13 C) and oxygen (δ18 O) isotope composition of siderite (FeCO3 ) is used widely to understand and quantify geochemical processes to reconstruct past climate and environmental change. However, few laboratories follow precisely the same protocol for the preparation and analysis of siderite-bearing materials, which combined with the absence of international reference materials and mineral-specific acid fractionation factors, leads potentially to significant differences in isotope data generated by individual laboratories. Here we examine procedures for the isotope analysis of siderite and discuss factors potentially contributing to inconsistencies in sample measurement data. Isotope analysis of siderite is first assessed using similar versions of the classical off-line, sealed vessel acid digestion method by comparing data sets obtained from intercomparison materials measured at two participating laboratories. We then compare data from the classical method against those generated using an automated preparation technique using data produced from an independent set of test materials. Measurement of siderite δ13 C is generally both repeatable and reproducible, but measurement of δ18 O may be subject to large (~1‰), method-dependent bias for siderite reacted at differing temperatures (70°C and 100°C) under classical and automated CO2 preparation conditions. The potential for poor oxygen isotope measurement reproducibility is amplified by local differences in sample preparation protocols and procedures used to calibrate measurement data to international reference scales. We offer suggestions for improving the repeatability and reproducibility of δ13 C and δ18 O analysis on siderite. The challenge of producing consistent isotope data from siderite can only be resolved by ensuring the availability of siderite reference materials to facilitate identical treatment as a basis for minimising method-dependent contributions to data inconsistency between laboratories.

Early glacier advance in New Zealand during the Antarctic Cold Reversal

ABSTRACTGlacial landscapes preserve records of past climate change. Investigating the glacier–climate system over the Late Quaternary provides information about past climate change and context for present‐day glacier response to climate warming. Using 28 beryllium‐10 (10Be) surface exposure dates and snowline reconstructions, we present glacier fluctuations and climate changes for the Antarctic Cold Reversal in the Ahuriri River catchment, Southern Alps of New Zealand (44°7′50″S, 169°38′29″E). Prominent terminal and lateral moraine features from the upper right tributary of the Ahuriri River valley have exposure ages of 14.5 ± 0.3, 13.6 ± 0.3 and 12.6 ± 0.2 ka, suggesting retreat of the glacier during the Antarctic Cold Reversal. Maximum elevation of lateral moraines (MELM) and accumulation area ratio (AAR) suggest snowline elevations at these ages were ≤700, ≤630 and ~360 m lower than today, respectively. This equates to air temperatures ≤3.9, ≤3.5 and 2.3 ± 0.7 °C lower than today (1981–2010), assuming no changes in past precipitation. Ice‐sculpted bedrock surfaces bound by a lateral moraine at nearby Canyon Creek have an age of 13.1 ± 0.3 ka, indicating the moraine correlates with those in the Ahuriri upper right tributary. MELM and AAR reconstructions from the Canyon Creek suggest that snowline elevations at 14.5–13.6 ka were ≤500 or ~380 m lower than today, corresponding to air temperatures ≤2.8 or 2.4 ± 0.7 °C lower than the present‐day (1981–2010). Our results provide insight into the structure of the Antarctic Cold Reversal in the Southern Alps, showing that the largest glacier advance occurred at the start of this interval at c. 14.5 ± 0.3 ka and was followed by gradual retreat. We hypothesize that the early cooling and glacier readvance in New Zealand at the onset of the Antarctic Cold Reversal were triggered by a latitudinal shift of the Southern Hemisphere westerly wind belt.

An aridity threshold model of fire sizes and annual area burned in extensively forested ecoregions of the western USA

Wildfire occurrence varies among regions and through time due to the long-term impacts of climate on fuel structure and short-term impacts on fuel flammability. Identifying the climatic conditions that trigger extensive fire years at regional scales can enable development of area burned models that are both spatially and temporally robust, which is crucial for understanding the impacts of past and future climate change. We identified region-specific thresholds in fire-season aridity that distinguish years with limited, moderate, and extensive area burned for 11 extensively forested ecoregions in the western United States. We developed a new area burned model using these relationships and demonstrate its application in the Southern Rocky Mountains using climate projections from five global climate models (GCMs) that bracket the range of projected changes in aridity. We used the aridity thresholds to classify each simulation year as having limited, moderate, or extensive area burned and defined fire-size distributions from historical fire records for these categories. We simulated individual fires from a regression relating fire season aridity to the annual number of fires and drew fire sizes from the corresponding fire-size distributions. We project dramatic increases in area burned after 2020 under most GCMs and after 2060 with all GCMs as the frequency of extensive fire years increases. Our adaptable model can readily incorporate new observations (e.g., extreme fire years) to directly address the non-stationarity of fire-climate relationships as climatic conditions diverge from past observations. Our aridity threshold fire model provides a simple yet spatially robust approach to project regional changes in area burned with broad applicability to ecosystem and vegetation simulation models.

CMIP5 based past and future climate change scenarios over South Bihar, India

CMIP5 based past and future climate change scenarios over South Bihar, India

Including imprecisely georeferenced specimens improves accuracy of species distribution models and estimates of niche breadth

AbstractAimMuseum and herbarium specimen records are frequently used to assess the conservation status of species and their responses to climate change. Typically, occurrences with imprecise geolocality information are discarded because they cannot be matched confidently to environmental conditions and are thus expected to increase uncertainty in downstream analyses. However, using only precisely georeferenced records risks undersampling of the environmental and geographical distributions of species. We present two related methods to allow the use of imprecisely georeferenced occurrences in biogeographical analysis.InnovationOur two procedures assign imprecise records to the (1) locations or (2) climates that are closest to the geographical or environmental centroid of the precise records of a species. For virtual species, including imprecise records alongside precise records improved the accuracy of ecological niche models projected to the present and the future, especially for species with c. 20 or fewer precise occurrences. Using only precise records underestimated loss of suitable habitat and overestimated the amount of suitable habitat in both the present and the future. Including imprecise records also improves estimates of niche breadth and extent of occurrence. An analysis of 44 species of North American Asclepias (Apocynaceae) yielded similar results.Main conclusionsExisting studies examining the effects of spatial imprecision typically compare outcomes based on precise records against the same records with spatial error added to them. However, in real‐world cases, analysts possess a mix of precise and imprecise records and must decide whether to retain or discard the latter. Discarding imprecise records can undersample the geographical and environmental distributions of species and lead to mis‐estimation of responses to past and future climate change. Our method, for which we provide a software implementation in the enmSdmX package for R, is simple to use and can help leverage the large number of specimen records that are typically deemed “unusable” because of spatial imprecision in their geolocation.

Phylogeography within the Peromyscus maniculatus species group: Understanding past distribution of genetic diversity and areas of refugia in western North America

The effects of anthropogenic climate change on biodiversity have been recognized on every continent, ocean, and across different taxonomic groups. Here, we study the range dynamics and demography of a cosmopolitan species: the deer mouse, Peromyscus maniculatus. We generated a multilocus SNP dataset using the ddRADseq protocol for 218 individuals across the geographic range within three western North American lineages of this species group. We evaluated population structure using several methods and explored the correlation between geographic and genetic distances. We modeled the demographic history using a site frequency spectrum approach and used a machine learning algorithm to infer current and past (Last Glacial Maximum; LGM) environmental suitability. Lastly, we explored the origin of population expansion for the identified lineages. The genome-wide SNP dataset was able to identify-three regionally distinct groups— 1) P. m. gambelii (southern California); 2) P. keeni (Pacific Northwest); 3) P. m. sonoriensis (a broad population spanning the Pacific Northwest through central California and across the Rocky Mountains into the Great Plains). Demographic analysis indicated the splits between the three populations occurred within the last 500 thousand years, with one very recent (late Holocene) split. Ecological niche models for each of these lineages predicted suitable environment present throughout their known ranges for current conditions, and a severe reduction of northern habitat in the past. The deer mouse has responded to past climate changes by expanding its range during interglacial periods and contracting its range during glacial periods leading to strong population differentiation. But lower magnitude climate change or other processes within the Holocene interglacial period led to population differentiation as well, which is likely still ongoing today given the substantial anthropogenic climate change and other landscape transformations caused by humans during the Anthropocene. By understanding the historical processes that led to the contemporary geographic distribution of biodiversity, we can determine the relative importance of different factors that shape biodiversity, now and into the future.

An early Miocene (∼20 Ma) paleogeographic reconstruction for paleoclimate modelling

The current Asian monsoon system is considered to have formed in the late Oligocene–early Miocene, but the mechanisms of the monsoonal system are not fully understood. A knowledge of paleogeography is essential for understanding past climatic change. A reliable paleogeographic reconstruction for the early Miocene is essential to provide key boundary conditions for early Miocene climate modelling studies. However, the temporal–spatial distribution of key geographic features such as seaways and mountain belts that control climate change differ for various published early Miocene paleogeographic reconstructions, which thus require updating with new geological data. Here we present a new reconstruction of global paleogeography for the early Miocene (∼20 Ma). We used a four-step methodology and integrated various types of geological data into a coherent plate tectonic model using GPlates and ArcGIS to reconstruct the paleogeography. Based on previous paleogeographic reconstructions and our compiled geological data, we further constrained and revised the land–sea distribution in several key regions (i.e., the Paratethys Sea, Sunda Shelf, Bohai Sea–Yellow Sea, Barents Sea–Kara Sea, and Hudson Bay); the paleodepths of the Paratethys Sea, Mediterranean Sea, and key seaways (i.e., the Atlantic–Mediterranean Gateway, eastern Tethys Seaway, Indonesian Gateway, Panama Seaway, Fram Strait, and Greenland–Scotland Ridge); and paleoelevations of high mountains and plateaus (i.e., the Tibetan Plateau, North American Cordillera, Andes, East Africa, and Antarctica). The new and improved early Miocene paleogeographic reconstruction is available for use in climate models to facilitate early Miocene climate modelling studies.

Branched glycerol dialkyl glycerol tetraether (brGDGT) distributions influenced by bacterial community composition in various vegetation soils on the Tibetan Plateau

Branched glycerol dialkyl glycerol tetraether (brGDGT) lipids are membrane-spanning lipids of some bacteria that are sensitive to environmental gradients, which makes it possible to use brGDGT proxies to estimate changes in environmental temperatures in paleoenvironmental studies. However, it is currently unknown whether the observed correlations of temperature and brGDGT distribution in natural samples are driven by directly changing bacterial membrane fluidity and permeability, or by a shift in the bacterial community. Here we present brGDGT distributions along an elevation gradient (704–3760 m) in the southeastern Tibetan Plateau, spanning gradients in temperature and vegetation. Analysis of brGDGTs shows that their distributions are significantly influenced by vegetation-intermediated soil temperature, in addition to mean annual air temperature, soil pH, and other environmental variables. Different vegetation types contribute to soil temperature and bacterial community changes. Consequently, these different groups of bacteria result in changes in the relative abundance of brGDGTs. Our results show that temperature and pH indirectly influence cyclopentane-containing brGDGTs via changes in the bacterial community. Genetic analyses reveal that in addition to Acidobacteria, Proteobacteria, Nitrospira, Bacteroidetes, Actinobacteria, and Verrucomicrobia could be potential candidates as brGDGT producers. These results indicate that changes in the vegetation and bacterial community should be taken into consideration when applying brGDGT proxies to reconstruct past changes in climate.

Hydrological and dynamical response of glaciers to climate change based on their dimensions in the Hunza Basin, Karakoram

Glaciers of different dimensions respond differently to climate change, resulting in variations in glacier dynamics and runoff. Differentiation of these responses is critical for the Karakoram region (in context to Karakoram anomalies) where glaciers contribute significantly to runoff. Herein, the Open Global Glacier Model is used to quantify these variabilities in the Hunza basin, and thereby develop a comprehensive understanding of how glaciers respond to past and future climate change. Basin glaciers were classified into six classes based on their terminus elevation and area (Z1-Z6). Annual mass balance (MB) time series were reconstructed from 1960 to 2019. The results indicate that the average MB is −0.09 ± 0.21 m w.e.a−1, which has been accelerated in 2000 s (average: −0.16 ± 0.20 m w.e.a−1). Cumulative MB between classes varies from −4.55 m w.e. (Z1) to −5.92 m w.e. (Z3), indicating that the medium classes (Z3, Z4) glaciers MB is comparatively more negative. Monthly glacier runoff explains the sensitivity of small glaciers to summer temperature, as they only contribute to runoff in the summer season. However, glacier runoff per unit area per year remains almost the same across these groups. Future climate change scenarios under CMIP6 illustrate that small (Z5/Z6) and large (Z1) glaciers will lose up to 90 % and 10 % of their volume, area, and length, respectively. The results identified that basin glacier runoff will increase till the year 2060 and will start decreasing after that to 2100. Projected glacier runoff suggests that the Basin runoff is mediated by Z4 glaciers. Whereas, the peak water supply from small size glaciers has occurred in past (Z6) or would occur in near future (Z5) while large size glaciers (Z1-Z3) runoff keeps on increasing till 2100. These findings indicate that immediate mitigation measures are required to deal with glacier change and ensure long-term water security in this region.

A Modeling Perspective on the Lingering Glacial Sea Surface Temperature Conundrum

AbstractThe strong cooling during the Last Glacial Maximum (LGM, 21 ka BP) provides a rigorous test of climate models' ability to simulate past and future climate changes. We force an atmospheric general circulation model with two recent global LGM sea surface temperature (SST) reconstructions, one suggesting a weak and the other a more pronounced cooling, and compare the simulated land surface temperatures (LSTs) to reconstructed data. Our results do not confirm either SST reconstruction. The cold SST data set leads to good agreement between simulated and observed LSTs at low latitudes, but is systematically too cold at mid‐latitudes. The opposite is true for the warm SST data set. Differences between the simulated LSTs are caused by varying land surface albedos, which is lower for the warmer SST reconstruction. The inconsistency between reconstructed and simulated climate points to a potentially significant bias in the proxy reconstructions and/or the climate sensitivity of current climate models.

The Białowieża Forest as a Key Area for Understanding the History of European Forest Bird Communities

The last remnants of pristine forests in Europe, especially in the nemoral belt of deciduous and mixed deciduous coniferous trees, are unique for understanding the history, composition and structure of plant and animal communities. This is especially true for the Białowieża forest, NE Poland. The biogeographical history of emblematic forest clades of birds, e.g. woodpeckers, tits and nuthatches, is analyzed from molecular phylogenies which allow to determine their pace and mode of origination and differentiation. The flyways which connect temperate and tropical realms played a major role in the origination and differentiation of many extant lineages. Then, large differences in the structure of bird communities between North American and European forests are discussed and explained in the light of the geographic configuration of major land masses and past climatic changes and upheavals throughout the Neogene. From long term in depth studies in this forest, the composition and structure of bird communities may be used as references for understanding and measuring the processes and mechanisms of change in communities of the western managed forests.