Geochronological database and classification system for age uncertainties in Neotropical pollen records.

The newly updated inventory of palaeoecological research in Latin America offers an important overview of sites available for multi-proxy and multi-site purposes. From the collected literature supporting this inventory, we collected all available age model metadata to create a chronological database of 5116 control points (e.g. 14C, tephra, fission track, OSL, 210Pb) from 1097 pollen records. Based on this literature review, we present a summary of chronological dating and reporting in the Neotropics. Difficulties and recommendations for chronology reporting are discussed. Furthermore, for 234 pollen records in northwest South America, a classification system for age uncertainties is implemented based on chronologies generated with updated calibration curves. With these outcomes age models are produced for those sites without an existing chronology, alternative age models are provided for researchers interested in comparing the effects of different calibration curves and age-depth modelling software, and the importance of uncertainty assessments of chronologies is highlighted. Sample resolution and temporal uncertainty of ages are discussed for different time windows, focusing on events relevant for research on centennial- to millennial-scale climate variability. All age models and developed R scripts are publicly available through figshare, including a manual to use the scripts

Climate variability and human impact in South America during the last 2000 years: synthesis and perspectives from pollen records

An improved understanding of present-day climate variability and change relies on high-quality data sets from the past 2 millennia. Global efforts to model regional climate modes are in the process of being validated against, and integrated with, records of past vegetation change. For South America, however, the full potential of vegetation records for evaluating and improving climate models has hitherto not been sufficiently acknowledged due to an absence of information on the spatial and temporal coverage of study sites. This paper therefore serves as a guide to high-quality pollen records that capture environmental variability during the last 2 millennia. We identify 60 vegetation (pollen) records from across South America which satisfy geochronological requirements set out for climate modelling, and we discuss their sensitivity to the spatial signature of climate modes throughout the continent. Diverse patterns of vegetation response to climate change are observed, with more similar patterns of change in the lowlands and varying intensity and direction of responses in the highlands. Pollen records display local-scale responses to climate modes; thus, it is necessary to understand how vegetation–climate interactions might diverge under variable settings. We provide a qualitative translation from pollen metrics to climate variables. Additionally, pollen is an excellent indicator of human impact through time. We discuss evidence for human land use in pollen records and provide an overview considered useful for archaeological hypothesis testing and important in distinguishing natural from anthropogenically driven vegetation change. We stress the need for the palynological community to be more familiar with climate variability patterns to correctly attribute the potential causes of observed vegetation dynamics. This manuscript forms part of the wider LOng-Term multi-proxy climate REconstructions and Dynamics in South America – 2k initiative that provides the ideal framework for the integration of the various palaeoclimatic subdisciplines and palaeo-science, thereby jump-starting and fostering multidisciplinary research into environmental change on centennial and millennial timescales

Community owned solutions for fire management in tropical ecosystems:case studies from Indigenous communities of South America

Fire plays an increasingly significant role in tropical forest and savanna ecosystems, contributing to greenhouse gas emissions and impacting on biodiversity. Emerging research shows the potential role of Indigenous land use practices for controlling deforestation and reducing CO2 emissions. Analysis of satellite imagery suggests that Indigenous lands have the lowest incidence of wildfires, significantly contributing to maintaining carbon stocks and enhancing biodiversity. Yet, acknowledgement of Indigenous peoples’ role in fire management and control is limited, and in many cases dismissed, especially in policy-making circles. In this paper, we review existing data on Indigenous fire management and impact, focusing on examples from tropical forest and savanna ecosystems in Venezuela, Brazil and Guyana. We highlight how the complexities of community owned solutions for fire management are being lost as well as undermined by continued efforts on fire suppression and firefighting, and emerging approaches to incorporate Indigenous fire management into market, incentive-based for climate change mitigation. Our aim is to build a case for supporting Indigenous fire practices within all scales of decision-making by strengthening Indigenous knowledge systems to ensure more effective and sustainable fire management

Multi‐dimensional biodiversity hotspots and the future of taxonomic, ecological and phylogenetic diversity: A case study of North American rodents

AimWe investigate geographic patterns across taxonomic, ecological and phylogenetic diversity to test for spatial (in)congruency and identify aggregate diversity hotspots in relationship to present land use and future climate. Simulating extinctions of imperilled species, we demonstrate where losses across diversity dimensions and geography are predicted.LocationNorth America.Time periodPresent day, future.Major taxa studiedRodentia.MethodsUsing geographic range maps for rodent species, we quantified spatial patterns for 11 dimensions of diversity: taxonomic (species, range weighted), ecological (body size, diet and habitat), phylogenetic (mean, variance, and nearest‐neighbour patristic distances, phylogenetic distance and genus‐to‐species ratio) and phyloendemism. We tested for correlations across dimensions and used spatial residual analyses to illustrate regions of pronounced diversity. We aggregated diversity hotspots in relationship to predictions of land‐use and climate change and recalculated metrics following extinctions of IUCN‐listed imperilled species.ResultsTopographically complex western North America hosts high diversity across multiple dimensions: phyloendemism and ecological diversity exceed predictions based on taxonomic richness, and phylogenetic variance patterns indicate steep gradients in phylogenetic turnover. An aggregate diversity hotspot emerges in the west, whereas spatial incongruence exists across diversity dimensions at the continental scale. Notably, phylogenetic metrics are uncorrelated with ecological diversity. Diversity hotspots overlap with land‐use and climate change, and extinctions predicted by IUCN status are unevenly distributed across space, phylogeny or ecological groups.Main conclusionsComparison of taxonomic, ecological and phylogenetic diversity patterns for North American rodents clearly shows the multifaceted nature of biodiversity. Testing for geographic patterns and (in)congruency across dimensions of diversity facilitates investigation into underlying ecological and evolutionary processes. The geographic scope of this analysis suggests that several explicit regional challenges face North American rodent fauna in the future. Simultaneous consideration of multi‐dimensional biodiversity allows us to assess what critical functions or evolutionary history we might lose with future extinctions and maximize the potential of our conservation efforts.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154236/1/geb13050.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154236/2/geb13050_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154236/3/geb13050-sup-0001-Supinfo1.pd

Warming, drought, and disturbances lead to shifts in functional composition: a millennial‐scale analysis for Amazonian and Andean sites

Tropical forests are changing in composition and productivity, probably in response to changes in climate and disturbances. The responses to these multiple environmental drivers, and the mechanisms underlying the changes, remain largely unknown. Here, we use a functional trait approach on timescales of 10,000 years to assess how climate and disturbances influence the community-mean adult height, leaf area, seed mass, and wood density for eight lowland and highland forest landscapes. To do so, we combine data of eight fossil pollen records with functional traits and proxies for climate (temperature, precipitation, and El Niño frequency) and disturbances (fire and general disturbances). We found that temperature and disturbances were the most important drivers of changes in functional composition. Increased water availability (high precipitation and low El Niño frequency) generally led to more acquisitive trait composition (large leaves and soft wood). In lowland forests, warmer climates decreased community-mean height probably because of increased water stress, whereas in highland forests warmer climates increased height probably because of upslope migration of taller species. Disturbance increased the abundance of acquisitive, disturbance-adapted taxa with small seeds for quick colonization of disturbed sites, large leaves for light capture, and soft wood to attain fast height growth. Fire had weak effects on lowland forests but led to more stress-adapted taxa that are tall with fast life cycles and small seeds that can quickly colonize burned sites. Site-specific analyses were largely in line with cross-site analyses, except for varying site-level effects of El Niño frequency and fire activity, possibly because regional patterns in El Niño are not a good predictor of local changes, and charcoal abundances do not reflect fire intensity or severity. With future global changes, tropical Amazonian and Andean forests may transition toward shorter, drought- and disturbance-adapted forests in the lowlands but taller forests in the highlands

Assessing changes in global fire regimes

PAGES, Past Global Changes, is funded by the Swiss Academy of Sciences and the Chinese Academy of Sciences and supported in kind by the University of Bern, Switzerland. Financial support was provided by the U.S. National Science Foundation award numbers 1916565, EAR-2011439, and EAR-2012123. Additional support was provided by the Utah Department of Natural Resources Watershed Restoration Initiative. SSS was supported by Brigham Young University Graduate Studies. MS was supported by National Science Centre, Poland (grant no. 2018/31/B/ST10/02498 and 2021/41/B/ST10/00060). JCA was supported by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 101026211. PF contributed within the framework of the FCT-funded project no. UIDB/04033/2020. SGAF acknowledges support from Trond Mohn Stiftelse (TMS) and University of Bergen for the startup grant ‘TMS2022STG03’. JMP participation in this research was supported by the Forest Research Centre, a research unit funded by Fundação para a Ciência e a Tecnologia I.P. (FCT), Portugal (UIDB/00239/2020). A.-LD acknowledge PAGES, PICS CNRS 06484 project, CNRS-INSU, Région Nouvelle-Aquitaine, University of Bordeaux DRI and INQUA for workshop support.Background The global human footprint has fundamentally altered wildfire regimes, creating serious consequences for human health, biodiversity, and climate. However, it remains difficult to project how long-term interactions among land use, management, and climate change will affect fire behavior, representing a key knowledge gap for sustainable management. We used expert assessment to combine opinions about past and future fire regimes from 99 wildfire researchers. We asked for quantitative and qualitative assessments of the frequency, type, and implications of fire regime change from the beginning of the Holocene through the year 2300. Results Respondents indicated some direct human influence on wildfire since at least ~ 12,000 years BP, though natural climate variability remained the dominant driver of fire regime change until around 5,000 years BP, for most study regions. Responses suggested a ten-fold increase in the frequency of fire regime change during the last 250 years compared with the rest of the Holocene, corresponding first with the intensification and extensification of land use and later with anthropogenic climate change. Looking to the future, fire regimes were predicted to intensify, with increases in frequency, severity, and size in all biomes except grassland ecosystems. Fire regimes showed different climate sensitivities across biomes, but the likelihood of fire regime change increased with higher warming scenarios for all biomes. Biodiversity, carbon storage, and other ecosystem services were predicted to decrease for most biomes under higher emission scenarios. We present recommendations for adaptation and mitigation under emerging fire regimes, while recognizing that management options are constrained under higher emission scenarios. Conclusion The influence of humans on wildfire regimes has increased over the last two centuries. The perspective gained from past fires should be considered in land and fire management strategies, but novel fire behavior is likely given the unprecedented human disruption of plant communities, climate, and other factors. Future fire regimes are likely to degrade key ecosystem services, unless climate change is aggressively mitigated. Expert assessment complements empirical data and modeling, providing a broader perspective of fire science to inform decision making and future research priorities.Peer reviewe

An early start for the Panama land bridge

The birth of the Panama land bridge, which connects the Americas, has been associated with one of the biggest biological exchanges in Earth history as numerous species migrated from one continent to the other (1). Nevertheless, the timing of formation of the land bridge is still much debated (2). On page 226 of this issue, Montes et al. (3) propose that the Central American Seaway, which separated South and North America, closed about 15 to 13 million years ago, more than 10 million years earlier than previously thought (4), with important implications for ocean circulation, climate, and biotic exchange

Examining spatially varying relationships between coca crops and associated factors in Colombia, using geographically weight regression.

This article addresses the expansion of illicit crops (coca) and the associated socio-institutional and geographical drivers in Colombia between 2001 and 2008. The analysis is based on a Geographically Weighted Regression (GWR) models and shows that the relationships between the analyzed variables and the coca crops are not constant over space. Similarly, it is demonstrated that the factors commonly associated with the expansion of coca crops are not constant with respect to time, as changes can be seen between the years of the study (2001 and 2008). The article finds that the models that include the local reality offer the best way of understanding the factors associated with the expansion of illicit coca crops in Colombia, a fundamental step in the formulation of effective policies in the reduction of crops for illicit use (coca)