Papers by Jens-Christian Svenning
Across the last ~50,000 years (the late Quaternary) terrestrial vertebrate faunas have experience... more Across the last ~50,000 years (the late Quaternary) terrestrial vertebrate faunas have experienced severe losses of large species (megafauna), with most extinctions occurring in the Late Pleistocene and Early to Middle Holocene. Debate on the causes has been ongoing for over 200 years, intensifying from the 1960s onward. Here, we outline criteria that any causal hypothesis needs to account for. Importantly, this extinction event is unique relative to other Cenozoic (the last 66 million years) extinctions in its strong size bias. For example, only 11 out of 57 species of megaherbivores (body mass ≥1,000 kg) survived to the present. In addition to mammalian megafauna, certain other groups also experienced substantial extinctions, mainly large nonmammalian vertebrates and smaller but megafauna-associated taxa. Further, extinction severity and dates varied among continents, but severely affected all biomes, from the Arctic to the tropics. We synthesise the evidence for and against climatic or modern human (Homo sapiens) causation, the only existing tenable hypotheses. Our review shows that there is little support for any major influence of climate, neither in global extinction patterns nor in fine-scale spatiotemporal and mechanistic evidence. Conversely, there is strong and increasing support for human pressures as the key driver of these extinctions, with emerging evidence for an initial onset linked to pre-sapiens hominins prior to the Late Pleistocene. Subsequently, we synthesize the evidence for ecosystem consequences of megafauna extinctions and discuss the implications for conservation and restoration. A broad range of evidence indicates that the megafauna extinctions have elicited profound changes to ecosystem structure and functioning. The late-Quaternary megafauna extinctions thereby represent an early, large-scale human-driven environmental transformation, constituting a progenitor of the Anthropocene, where humans are now a major player in planetary functioning. Finally, we conclude that megafauna restoration via trophic rewilding can be expected to have positive effects on biodiversity across varied Anthropocene settings. Terrestrial large-bodied animals (megafauna) play important roles in ecosystems and human cultures. However, their diversity and abundance have declined severely across the last ~50,000 years. This late-Quaternary megafauna extinction pattern stands out from previous Cenozoic extinctions in three ways. (1) These losses were global and severe. (2) They were strongly biased toward larger-bodied species, with other organisms experiencing only very limited extinction in this period. Illustrating this pattern, only 11 out of 57 species of megaherbivores (mean body mass ≥1,000 kg) survived through to 1,000 AD. (3) This faunal simplification is unique on a ≥30-million-year time scale, with diverse megafauna guilds being the norm throughout this entire timeframe, excepting recent millennia. Further, temporal staggering is a defining feature of these losses, with extinctions concentrated in widely different time windows in different areas. The debate on the cause, or causes, of the late-Quaternary extinctions has been ongoing for over 200 years. Though most current work accepts at least a contributory role for modern humans, the topic remains controversial. We outline multiple characteristics of the late-Quaternary extinctions that, in order to merit support, any hypothesis needs to account for, and based thereon conclude the existing evidence strongly supports a dominant role of Homo sapiens and is inconsistent with climate as a substantial cause. We discuss the known and likely ecological consequences of the late-Quaternary megafauna extinctions, with the combined evidence indicating that the disappearance of so many large animal species constitutes a fundamental re-shaping of terrestrial ecosystem worldwide.
Cambridge prisms. Extinction, Mar 22, 2024
Across the last~50,000 years (the late Quaternary) terrestrial vertebrate faunas have experienced... more Across the last~50,000 years (the late Quaternary) terrestrial vertebrate faunas have experienced severe losses of large species (megafauna), with most extinctions occurring in the Late Pleistocene and Early to Middle Holocene. Debate on the causes has been ongoing for over 200 years, intensifying from the 1960s onward. Here, we outline criteria that any causal hypothesis needs to account for. Importantly, this extinction event is unique relative to other Cenozoic (the last 66 million years) extinctions in its strong size bias. For example, only 11 out of 57 species of megaherbivores (body mass ≥1,000 kg) survived to the present. In addition to mammalian megafauna, certain other groups also experienced substantial extinctions, mainly large nonmammalian vertebrates and smaller but megafauna-associated taxa. Further, extinction severity and dates varied among continents, but severely affected all biomes, from the Arctic to the tropics. We synthesise the evidence for and against climatic or modern human (Homo sapiens) causation, the only existing tenable hypotheses. Our review shows that there is little support for any major influence of climate, neither in global extinction patterns nor in fine-scale spatiotemporal and mechanistic evidence. Conversely, there is strong and increasing support for human pressures as the key driver of these extinctions, with emerging evidence for an initial onset linked to pre-sapiens hominins prior to the Late Pleistocene. Subsequently, we synthesize the evidence for ecosystem consequences of megafauna extinctions and discuss the implications for conservation and restoration. A broad range of evidence indicates that the megafauna extinctions have elicited profound changes to ecosystem structure and functioning. The late-Quaternary megafauna extinctions thereby represent an early, large-scale human-driven environmental transformation, constituting a progenitor of the Anthropocene, where humans are now a major player in planetary functioning. Finally, we conclude that megafauna restoration via trophic rewilding can be expected to have positive effects on biodiversity across varied Anthropocene settings. Impact statement Terrestrial large-bodied animals (megafauna) play important roles in ecosystems and human cultures. However, their diversity and abundance have declined severely across the last 50,000 years. This late-Quaternary megafauna extinction pattern stands out from previous Cenozoic extinctions in three ways. (1) These losses were global and severe. (2) They were strongly biased toward larger-bodied species, with other organisms experiencing only very limited extinction in this period. Illustrating this pattern, only 11 out of 57 species of megaherbivores (mean body mass ≥1,000 kg) survived through to 1,000 AD. (3) This faunal simplification is unique on a ≥30-million-year time scale, with diverse megafauna guilds being the norm throughout this entire timeframe, excepting recent millennia. Further, temporal staggering is a defining feature of these losses, with extinctions concentrated in widely different time windows in different areas. The debate on the cause, or causes, of the late-Quaternary extinctions has been ongoing for over 200 years. Though most current work accepts at least a contributory role for modern humans, the topic remains controversial. We outline multiple characteristics of the late-Quaternary extinctions that, in order to merit support, any hypothesis needs to account for, and based thereon conclude the existing evidence strongly supports a dominant role of Homo sapiens and is inconsistent with climate as a substantial cause. We discuss the known and likely ecological consequences of the late-Quaternary megafauna extinctions, with the combined evidence indicating that the disappearance of so many large animal species constitutes a fundamental reshaping of terrestrial ecosystem worldwide.
Ecological Applications, May 14, 2019
Effective planning and nature management require spatially accurate and comprehensive measures of... more Effective planning and nature management require spatially accurate and comprehensive measures of the factors important for biodiversity. Light detection and ranging (LIDAR) can provide exactly this, and is therefore a promising technology to support future nature management and related applications. However, until now studies evaluating the potential of LIDAR for this field have been highly limited in scope. Here, we assess the potential of LIDAR to estimate the local diversity of four species groups in multiple habitat types, from open grasslands and meadows over shrubland to forests and across a large area (~43,000 km 2), providing a crucial step toward enabling the application of LIDAR in practice, planning, and policy-making. We assessed the relationships between the species richness of macrofungi, lichens, bryophytes, and plants, respectively, and 25 LIDAR-based measures related to potential abiotic and biotic diversity drivers. We used negative binomial generalized linear modeling to construct 19 different candidate models for each species group, and leave-one-region-out cross validation to select the best models. These best models explained 49%, 31%, 32%, and 28% of the variation in species richness (R 2) for macrofungi, lichens, bryophytes, and plants, respectively. Three LIDAR measures, terrain slope, shrub layer height and variation in local heat load, were important and positively related to the richness in three of the four species groups. For at least one of the species groups, four other LIDAR measures, shrub layer density, medium-tree layer density, and variations in point amplitude and in relative biomass, were among the three most important. Generally, LIDAR measures exhibited strong associations to the biotic environment, and to some abiotic factors, but were poor measures of spatial landscape and temporal habitat continuity. In conclusion, we showed how well LIDAR alone can predict the local biodiversity across habitats. We also showed that several LIDAR measures are highly correlated to important biodiversity drivers, which are notoriously hard to measure in the field. This opens up hitherto unseen possibilities for using LIDAR for cost-effective monitoring and management of local biodiversity across species groups and habitat types even over large areas.
Global Ecology and Biogeography, Aug 7, 2019
Global Ecology and Biogeography, Jul 17, 2017
Aims: Long-term climate stability is hypothesized to drive the emergence of species assemblages w... more Aims: Long-term climate stability is hypothesized to drive the emergence of species assemblages with large species age differences due to the accumulation of relict species and relatively newly arisen species via reduced extinction and increased speciation. Few studies have addressed these predictions and so far no study has done so for plants across the Northern Hemisphere. Here, we linked Quaternary-scale climate variability to phylogenetic age differences between the oldest and youngest group of species in tree assemblages in 100 km × 100 km grid cells across the Northern Hemisphere to test these predictions. Location: Northern Hemisphere. Methods: Last Glacial Maximum (LGM)-to-present shifts in temperature and precipitation were used as proxies for Quaternary-scale glacial-interglacial climate variability. Simultaneous autoregressive (SAR) models were used to assess the relationships between phylogenetic age differences and Quaternary-scale climate variability. Results: We found that phylogenetic age differences overall were largest in China and smallest in Europe, and they declined with increasing temperature instability as predicted, but only in Europe and North America. In China, the relatively mild Quaternary climate changes did not appear to have strongly affected phylogenetic age differences in tree assemblages. Main conclusions: Our results show that phylogenetically diverse assemblages with large phylogenetic age differences among species are associated with relatively high long-term climate stability, with intra-regional links between long-term climate variability and phylogenetic composition especially strong in the more unstable regions. These findings point to future climate change as a key risk to the preservation of the phylogenetically diverse assemblages in regions characterized by relatively high paleoclimate stability, with China as a key example.
Global Ecology and Biogeography, Aug 2, 2021
Biosketch Xue Yin is currently a PhD candidate who is interested in patterns and mechanisms assoc... more Biosketch Xue Yin is currently a PhD candidate who is interested in patterns and mechanisms associated with the disjunct plants in eastern Asia and eastern North America.
Global Ecology and Biogeography, Jul 19, 2021
Niche overlap and divergence times support niche conservatism in eastern Asia−eastern North Ameri... more Niche overlap and divergence times support niche conservatism in eastern Asia−eastern North America disjunct plants
Global Ecology and Biogeography
AimThe number of naturalized (i.e. established) alien species has increased rapidly over recent c... more AimThe number of naturalized (i.e. established) alien species has increased rapidly over recent centuries. Given the differences in environmental tolerances among species, little is known about what factors determine the extent to which the observed size of the naturalized range of a species and hence the extent to which the observed richness of naturalized species of a region approach their full potential. Here, we asked which region‐ and species‐specific characteristics explain differences between observed and expected naturalizations.LocationGlobal.Time periodPresent.Major taxa studiedVascular plants.MethodsWe determined the observed naturalized distribution outside Europe for 1,485 species endemic to Europe using the Global Naturalized Alien Flora (GloNAF) database and their expected distributions outside Europe using species distribution models. First, we investigated which of seven socio‐economic factors related to introduction pathways, anthropogenic pressures and inventory e...
Diversity and Distributions, 2020
AimPalms are an ecologically and societally important plant group, with high diversity in the Neo... more AimPalms are an ecologically and societally important plant group, with high diversity in the Neotropics. Here, we estimated the impacts of future climate change on phylogenetic diversity (PD) of Neotropical palms under varying climatic and dispersal scenarios, assessed the effectiveness of the established network of protected areas (PAs) for conserving palms PD today and in 2070, and identified priority areas for the conservation of palm species and their evolutionary history in the face of climate change.LocationNeotropics.MethodsWe used ecological niche modelling to estimate the distribution of 367 species in the present and for 2070 based on two greenhouse gas emission and two dispersal scenarios. We calculated Faith's PD within each five arc‐minute grid cell to evaluate the effectiveness of PAs relative to null models and used phylogenetic spatial prioritisation analysis to detect priority areas.ResultsWe found that even under the most optimistic climatic and dispersal scen...
Journal of Vegetation Science, 2021
QuestionsThe human‐related spread of alien plants has serious environmental and socioeconomic imp... more QuestionsThe human‐related spread of alien plants has serious environmental and socioeconomic impacts. Therefore, it is important to know which habitats are most threatened by invasion and why. We studied a wide range of European grasslands to assess: (a) which alien species are the most successful invaders in grasslands; (b) how invasion levels differ across European regions (countries or their parts) and biogeographical regions; and (c) which habitat types are the most invaded.LocationEurope.MethodsWe selected 97,411 grassland vegetation plots from the European Vegetation Archive (EVA) and assigned a native or alien status to each of the 8,212 vascular plant species found in these plots. We considered only neophytes (alien species introduced after 1500 AD), which we further divided according to their origin. We compared the levels of invasion using relative neophyte richness in the species pool, relative neophyte richness and cover per plot, and percentages of invaded plots among ...
National Science Review, 2021
Biodiversity science in China has seen rapid growth over recent decades, ranging from baseline bi... more Biodiversity science in China has seen rapid growth over recent decades, ranging from baseline biodiversity studies to understanding the processes behind evolution across dynamic regions such as the Qinghai-Tibetan Plateau. We review research, including species catalogues, biodiversity monitoring, the origins, distributions, maintenance, and threats to biodiversity, biodiversity-related ecosystem function and services, and species and ecosystems' responses to global change. Next, we identify priority topics, offer suggestions and priorities for future biodiversity research in China. These priorities include 1) the ecology and biogeography of the Qinghai-Tibetan Plateau and surrounding mountains, and that of subtropical and tropical forests across China; 2) marine and inland aquatic biodiversity, and 3) effective conservation and management to identify and maintain synergies between biodiversity and socio-economic development to fulfil China's vision for becoming an ecologica...
Global Change Biology, 2021
Climate and land cover changes are increasing threats to biodiversity globally. However, potentia... more Climate and land cover changes are increasing threats to biodiversity globally. However, potentially varying biotic sensitivity is a major source of uncertainty for translating environmental changes to extinction risks. To reduce this uncertainty, we assessed how extinction risks will be affected by future human‐driven environmental changes, focusing on 554 species from 52 disjunct plant genera between eastern Asia (EAS) and eastern North America (ENA) to control for differences in environmental sensitivity at the genus level. Species distribution models were used to estimate and compare the vulnerability of species in disjunct genera between the two regions under two climate and land cover change scenarios (RCP2.6 and RCP8.5) in the 2070s, allowing to assess the effects of differences in climate and land cover pressures. Compared with ENA, stronger pressures from climate and land cover changes along with smaller range sizes in EAS translate into a larger number and proportion of sp...
Biological Reviews, 2020
ABSTRACTTropical Africa is home to an astonishing biodiversity occurring in a variety of ecosyste... more ABSTRACTTropical Africa is home to an astonishing biodiversity occurring in a variety of ecosystems. Past climatic change and geological events have impacted the evolution and diversification of this biodiversity. During the last two decades, around 90 dated molecular phylogenies of different clades across animals and plants have been published leading to an increased understanding of the diversification and speciation processes generating tropical African biodiversity. In parallel, extended geological and palaeoclimatic records together with detailed numerical simulations have refined our understanding of past geological and climatic changes in Africa. To date, these important advances have not been reviewed within a common framework. Here, we critically review and synthesize African climate, tectonics and terrestrial biodiversity evolution throughout the Cenozoic to the mid‐Pleistocene, drawing on recent advances in Earth and life sciences. We first review six major geo‐climatic p...
Ecology Letters, 2020
It has been suggested that biogeographic historical legacies in plant diversity may influence eco... more It has been suggested that biogeographic historical legacies in plant diversity may influence ecosystem functioning. This is expected because of known diversity effects on ecosystem functions, and impacts of historical events such as past climatic changes on plant diversity. However, empirical evidence for a link between biogeographic history and present‐day ecosystem functioning is still limited. Here, we explored the relationships between Late‐Quaternary climate instability, species‐pool size, local species and functional diversity, and the net primary productivity (NPP) of Northern Hemisphere forests using structural equation modelling. Our study confirms that past climate instability has negative effects on plant functional diversity and through that on NPP, after controlling for present‐day climate, soil conditions, stand biomass and age. We conclude that global models of terrestrial plant productivity need to consider the biogeographical context to improve predictions of plant...
New Phytologist, 2019
Determining where species diversify (cradles) and persist (museums) over evolutionary time is fun... more Determining where species diversify (cradles) and persist (museums) over evolutionary time is fundamental to understanding the distribution of biodiversity and for conservation prioritization. Here, we identify cradles and museums of angiosperm generic diversity across tropical Africa, one of the most biodiverse regions on Earth. Regions containing nonrandom concentrations of young (neo-) and old (paleo-) endemic taxa were identified using distribution data of 1719 genera combined with a newly generated time-calibrated mega-phylogenetic tree. We then compared the identified regions with the current network of African protected areas (PAs). At the generic level, phylogenetic diversity and endemism are mainly concentrated in the biogeographically complex region of Eastern Africa. We show that mountainous areas are centres of both neo-and paleo-endemism. By contrast, the Guineo-Congolian lowland rain forest region is characterized by widespread and old lineages. We found that the overlap between centres of phylogenetic endemism and PAs is high (> 85%). We show the vital role played by mountains acting simultaneously as cradles and museums of tropical African plant biodiversity. By contrast, lowland rainforests act mainly as museums for generic diversity. Our study shows that incorporating large-scale taxonomically verified distribution datasets and mega-phylogenies lead to an improved understanding of tropical plant biodiversity evolution.
Annual Review of Environment and Resources, 2017
This review explores what past environmental change in Africa—and African people's response t... more This review explores what past environmental change in Africa—and African people's response to it—can teach us about how to cope with life in the Anthropocene. Organized around four drivers of change—climate; agriculture and pastoralism; megafauna; and imperialism, colonialism, and capitalism (ICC)—our review zooms in on key regions and debates, including desertification; rangeland degradation; megafauna loss; and land grabbing. Multiscale climate change is a recurring theme in the continent's history, interacting with increasingly intense human activities from several million years onward, leading to oscillating, contingent environmental changes and societally adaptive responses. With high levels of poverty, fast population growth, and potentially dramatic impacts expected from future climate change, Africa is emblematic of the kinds of social and ecological precariousness many fear will characterize the future globally. African people's innovation and adaptation to con...
Annals of the Missouri Botanical Garden, 2018
Plant geography seeks to describe the patterns of species distributions and understand the underl... more Plant geography seeks to describe the patterns of species distributions and understand the underlying mechanisms. The foundation of the field is attributed to Alexander von Humboldt following the broad-scale insights he gained on his explorations of the New World two centuries ago. Today, in the age of "Big Data," advances in methods and data availability allow us to better assess the complex drivers of species distributions. In this essay, we give an overview of the relevant legacy of Humboldt in the field of plant geography. Comparing the foremost insights and approaches of Humboldt's time and of today, we highlight areas in which major changes have taken place and areas in which Humboldt's approach is still relevant. We present advances in the description and understanding of plant geography, which have changed our entire worldview to a much more dynamic one. Further, we present some of the outstanding challenges of the field, and how solving them requires going back to the "Humboldtian" approach to science, i.e., combining precise, quantitative empirical studies with a holistic approach. Finally, we discuss how our recognition of the planetary impact of humans in the Anthropocene means that much of our research is no longer exclusively driven by curiosity, but also by the societal need to make predictions of ecosystem responses to environmental change. There is thus a strong need for combining quantitative empiricism with a holistic perspective to address the complex challenges of the current epoch.
Ecography, 2018
The relationship between species' niche breadth (i.e. the range of environmental conditions under... more The relationship between species' niche breadth (i.e. the range of environmental conditions under which a species can persist) and range size (i.e. the extent of its spatial distribution) has mostly been tested within geographically restricted areas but rarely at the global extent. Here, we not only tested the relationship between range size (derived from species' distribution data) and niche breadth (derived from species' distribution and co-occurrence data) of 1255 plant species at the regional extent of the European Alps, but also at the global extent and across both spatial scales for a subset of 180 species. Using correlation analyses, linear models and variation partitioning, we found that species' realized niche breadth estimated at the regional level is a weak predictor of species' global niche breadth and range size. Against our expectations, distribution-derived niche breadth was a better predictor for species' range size than the co-occurrence-based estimate, which should, theoretically, account for more than the climatically determined niche dimensions. Our findings highlight that studies focusing on the niche breadth vs range size relationship must explicitly consider spatial mismatches that might have confounded and diminished previously reported relationships.
Global Ecology and Biogeography, 2019
AimThe aim was to assess whether and to what extent the role of local landscape attributes in sha... more AimThe aim was to assess whether and to what extent the role of local landscape attributes in shaping macroscopic biodiversity patterns is sensitive to spatial and thematic resolutions of land cover data.LocationSub‐Saharan Africa and continental China.Time periodEarly 21st century.Taxa studiedTerrestrial mammals.MethodsWe conducted spatial and thematic scaling analyses to generate land cover datasets of different spatial (0.3, 0.5, 1.0 and 9.0 km) and thematic (two, three and five classes) resolutions. We calculated landscape metrics based on the resulting land cover maps and examined the power of landscape metrics for explaining species richness patterns, using non‐spatial (OLS) and spatial (SAR) linear models and random forest (RF) models. We systematically assessed the resolution dependence of explanatory power for different geographical regions, different scaling approaches and different model types. We also compared the explanatory power of landscape attributes with that of ma...
Diversity and Distributions, 2017
Aim: Understanding how climate affects species distributions remains a major challenge, with the ... more Aim: Understanding how climate affects species distributions remains a major challenge, with the relative importance of direct physiological effects versus biotic interactions still poorly understood. We focus on three species of resource specialists (crossbill Loxia finches) to assess the role of climate in determining the seasonal availability of their food, the importance of climate and the occurrence of their food plants for explaining their current distributions, and to predict changes in their distributions under future climate change scenarios. Location: Europe. Methods: We used datasets on the timing of seed fall in European Scots pine Pinus sylvestris forests (where different crossbill species occur) to estimate seed fall phenology and climate data to determine its influence on spatial and temporal variation in the timing of seed fall to provide a link between climate and seed scarcity for crossbills. We used large-scale datasets on crossbill distribution, cover of the conifers relied on by the three crossbill species and climate variables associated with timing of seed fall, to assess their relative importance for predicting crossbill distributions. We used species distribution modelling to predict changes in their distributions under climate change projections for 2070. Results: We found that seed fall occurred 1.5-2 months earlier in southern Europe than in Sweden and Scotland and was associated with variation in spring maximum temperatures and precipitation. These climate variables and area covered with conifers relied on by the crossbills explained much of their observed distributions. Projections under global change scenarios revealed reductions in potential crossbill distributions, especially for parrot crossbills. Main conclusions: Ranges of resource specialists are directly influenced by the presence of their food plants, with climate conditions further affecting resource availability and the window of food scarcity indirectly. Future distributions will be determined by tree responses to changing climatic conditions and the impact of climate on seed fall phenology.
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Papers by Jens-Christian Svenning