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The spatial extent of marine and terrestrial protected areas (PAs) was amongst the most intensely debated issues prior to the decision about the post-2020 Global Biodiversity Framework (GBF) of the Convention on Biological Diversity. Positive impacts of PAs on habitats, species diversity and abundance are well documented. Yet, biodiversity loss continues unabated despite efforts to protect 17% of land and 10% of the oceans by 2020. This casts doubt on whether extending PAs to 30%, the agreed target in the Kunming-Montreal GBF, will indeed achieve meaningful biodiversity benefits. Critically, the focus on area coverage obscures the importance of PA effectiveness and overlooks concerns about the impact of PAs on other sustainability objectives. We propose a simple means of assessing and visualising the complex relationships between PA area coverage and effectiveness and their effects on biodiversity conservation, nature-based climate mitigation and food production. Our analysis illustrates how achieving a 30% PA global target could be beneficial for biodiversity and climate. It also highlights important caveats: i) achieving lofty area coverage objectives alone will be of little benefit without concomitant improvements in effectiveness, ii) trade-offs with food production particularly for high levels of coverage and effectiveness are likely and iii) important differences in terrestrial and marine systems need to be recognized when setting and implementing PA targets. The CBD's call for a significant increase in protected area will need to be accompanied by clear PA effectiveness goals to reduce and revert dangerous anthropogenic impacts on socio-ecological systems and biodiversity.

The expert group on scenarios and models of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services initiated the development of the Nature Futures Framework for developing scenarios of positive futures for nature, to help inform assessments of policy options. This new scenarios and modelling Framework seeks to open up diversity and plurality of perspectives by differentiating three main value perspectives on nature – Nature for Nature (intrinsic values of nature), Nature for Society (instrumental values) and Nature as Culture (relational values). This paper describes how the Nature Futures Framework can be applied in modelling to support policy processes by identifying key interventions for change in realizing a diversity of desirable futures. First, the paper introduces and elaborates on key building blocks of the framework for developing qualitative scenarios and translating them into quantitative scenarios: i) multiple value perspectives on nature and the Nature Futures frontier representing diverse preferences, ii) incorporating mutual and key feedbacks of social-ecological systems in Nature Futures scenarios, and iii) indicators describing the evolution of social-ecological systems with complementary knowledge and data. This paper then presents three possible application approaches to modelling Nature Futures scenarios to support the i) review, ii) implementation and iii) design phases of policy processes. The main objective of this paper is to facilitate the integration of the relational values of nature in models, through improved indicators and other forms of evidence, and to strengthen modelled linkages across biodiversity, ecosystems, nature’s contributions to people, and quality of life to identify science- and knowledge-based interventions and to enhance ecological understanding for achieving sustainable futures. The paper aims at stimulating the development of new scenarios and models based on this new framework by a wide community of modelers, and the testing and possible further development of the framework, particularly in the context of future IPBES assessments.

Human impacts on the Earth’s biosphere are driving the global biodiversity crisis. Governments are preparing to agree on a set of actions intended to halt the loss of biodiversity and put it on a path to recovery by 2050. We provide evidence that the proposed actions can bend the curve for biodiversity, but only if these actions are implemented urgently and in an integrated manner.

International audience; The two most urgent and interlinked environmental challenges humanity faces are climate change and biodiversity loss. We are entering a pivotal decade for both the international biodiversity and climate change agendas with the sharpening of ambitious strategies and targets by the Convention on Biological Diversity and the United Nations Framework Convention on Climate Change. Within their respective Conventions, the biodiversity and climate interlinked challenges have largely been addressed separately. There is evidence that conservation actions that halt, slow or reverse biodiversity loss can simultaneously slow anthropogenic mediated climate change significantly. This review highlights conservation actions which have the largest potential for mitigation of climate change. We note that conservation actions have mainly synergistic benefits and few antagonistic trade-offs with climate change mitigation. Specifically, we identify direct co-benefits in 14 out of the 21 action targets of the draft post-2020 global biodiversity framework of the Convention on Biological Diversity, notwithstanding the many indirect links that can also support both biodiversity conservation and climate change mitigation. These relationships are context and scale-dependent; therefore, we showcase examples of local biodiversity conservation actions that can be incentivized, guided and prioritized by global objectives and targets. The close interlinkages between biodiversity, climate change mitigation, other nature's contributions to people and good quality of life are seldom as integrated as they should be in management and policy. This review aims to re-emphasize the vital relationships between biodiversity conservation actions and climate change mitigation in a timely manner, in support to major Conferences of Parties that are about to negotiate strategic frameworks and international goals for the decades to come.

There are many sources of uncertainty in scenarios and models of socio-ecological systems, and understanding these uncertainties is critical in supporting informed decision-making about the management of natural resources. Here, we review uncertainty across the steps needed to create socio-ecological scenarios, from narrative storylines to the representation of human and biological processes in models and the estimation of scenario and model parameters. We find that socio-ecological scenarios and models would benefit from moving away from “stylized” approaches that do not consider a wide range of direct drivers and their dependency on indirect drivers. Indeed, a greater focus on the social phenomena is fundamental in understanding the functioning of nature on a human-dominated planet. There is no panacea for dealing with uncertainty, but several approaches to evaluating uncertainty are still not routinely applied in scenario modeling, and this is becoming increasingly unacceptable. However, it is important to avoid uncertainties becoming an excuse for inaction in decision-making when facing environmental challenges.

World agriculture needs to find the right balance to cope with the trilemma between feeding a growing population, reducing its impact on biodiversity and minimizing greenhouse gas (GHG) emissions. In this paper, we evaluate a broad range of scenarios that achieve 4.3 GtCO2,eq/year GHG mitigation in the Agriculture, Forestry and Other Land-Use (AFOLU) sector by 2100. Scenarios include varying mixes of three GHG mitigation policies: second-generation biofuel production, dietary change and reforestation of pasture. We find that focusing mitigation on a single policy can lead to positive results for a single indicator of food security or biodiversity conservation, but with significant negative side effects on others. A balanced portfolio of all three mitigation policies, while not optimal for any single criterion, minimizes trade-offs by avoiding large negative effects on food security and biodiversity conservation. At the regional scale, the trade-off seen globally between biodiversity and food security is nuanced by different regional contexts.

Despite the scientific consensus on the extinction crisis and its anthropogenic origin, the quantification of historical trends and of future scenarios of biodiversity and ecosystem services has been limited, due to the lack of inter-model comparisons and harmonized scenarios. Here, we present a multi-model analysis to assess the impacts of land-use and climate change from 1900 to 2050. During the 20th century provisioning services increased, but biodiversity and regulating services decreased. Similar trade-offs are projected for the coming decades, but they may be attenuated in a sustainability scenario. Future biodiversity loss from land-use change is projected to keep up with historical rates or reduce slightly, whereas losses due to climate change are projected to increase greatly. Renewed efforts are needed by governments to meet the 2050 vision of the Convention on Biological Diversity.One Sentence SummaryDevelopment pathways exist that allow for a reduction of the rates of biodiversity loss from land-use change and improvement in regulating services but climate change poses an increasing challenge.

Plant traits – the morphological, anatomical, physiological, biochemical and phenological characteristics of plants – determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystems properties and derived benefits and detriments to people. Plant trait data thus represent the essential basis for a vast area of research spanning evolutionary biology, community and functional ecology, biodiversity conservation, ecosystem and landscape management and restoration, biogeography to earth system modeling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community. Increasingly the TRY database also supports new frontiers of trait-based research, including identi:cation of data gaps and subsequent mobilization or measurement of new data. To support this development, in this article we take stock of trait data compiled in TRY and analyze emerging patterns of data coverage, representativeness, and gaps. Best species coverage is achieved for categorical traits (stable within species) relevant to determine plant functional types commonly used in global vegetation models. For the trait ‘plant growth form’ complete species coverage is within reach. However, most traits relevant for ecology and vegetation modeling are characterized by intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment: completeness at global scale is impossible and representativeness challenging. Due to the sheer amount of data in the TRY database, machine learning for trait prediction is promising - but does not add new data. We therefore conclude that reducing data gaps and biases by further and more systematic mobilization of trait data and new in-situ trait measurements must continue to be a high priority. This can only be achieved by a community effort in collaboration with other initiatives.

We examine issues to consider when reframing conservation science and practice in the context of global change. New framings of the links between ecosystems and society are emerging that are changing peoples’ values and expectations of nature, resulting in plural perspectives on conservation. Reframing conservation for global change can thus be regarded as a stage in the evolving relationship between people and nature rather than some recent trend. New models of how conservation links with transformative adaptation include how decision contexts for conservation can be reframed and integrated with an adaptation pathways approach to create new options for global‐change‐ready conservation. New relationships for conservation science and governance include coproduction of knowledge that supports social learning. New processes for implementing adaptation for conservation outcomes include deliberate practices used to develop new strategies, shift world views, work with conflict, address power and intergenerational equity in decisions, and build consciousness and creativity that empower agents to act. We argue that reframing conservation for global change requires scientists and practitioners to implement approaches unconstrained by discipline and sectoral boundaries, geopolitical polarities, or technical problematization. We consider a stronger focus on inclusive creation of knowledge and the interaction of this knowledge with societal values and rules is likely to result in conservation science and practice that meets the challenges of a postnormal world.

Fil: Díaz, Sandra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Diversidad Biológica y Ecología. Instituto Multidisciplinario de Biología Vegetal; Argentina. Fil: Díaz, Sandra. Consejo Nacional de Investigaciones Científicas y Técnica. Instituto Multidisciplinario de Biología Vegetal; Argentina. Fil: Zafra Calvo, Noelia. Future Earth; España. Fil: Purvis, Andy. Natural History Museum; Reino Unido. Fil: Verburg, Peter H. VU University Amsterdam. Institute for Environmental Studies: Países Bajos. Fil: Obura, David. Coastal Oceans Research and Development Indian Ocean; Kenia. Fil: Leadley, Paul. Université Paris-Sud. Ecologie Systématique Evolution; Francia. Fil: Chaplin Kramer, Rebecca. Stanford University. Natural Capital Project; Estados Unidos. Fil: De Meester, Luc. Leibniz Institut für Gewässerökologie und Binnenfischerei; Alemania. Fil: Dulloo, Ehsan. Bioversity International; Mauricio. Fil: Martín- López, Berta. Leuphana University of Lüneburg. Faculty of Sustainability; Alemania. Fil: Shaw, Rebecca. The World Wide Fund for Nature; Estados Unidos. Fil: Visconti, Piero. International Institute for Applied Systems Analysis. Ecosystem Services and Management Program; Austria. Fil: Broadgate, Wendy. Future Earth; Suecia. Fil: Bruford, Michael W. Cardiff University. School of Biosciences and Sustainable Places Institute; Reino Unido. Fil: Burgess, Neil D. UN Environment Programme World Conservation Monitoring Centre; Reino Unido. Fil: Cavender Bares, Jeannine. University of Minnesota. Department of Ecology, Evolution and Behavior; Estados Unidos. Fil: DeClerck, Fabrice. EAT Foundation; Noruega. Fil: Fernández Palacios, José María. Universidad de La Laguna. Instituto Universitario de Enfermedades Tropicales y Salud Pública de Canarias; España. Fil: Garibaldi, Lucas A. Universidad Nacional de Río Negro. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural. Río Negro, Argentina. Fil: Garibaldi, Lucas A. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural. Río Negro, Argentina. Fil: Hill, Samantha L. L. UN Environment Programme World Conservation Monitoring Centre; Reino Unido. Fil: Isbell, Forest. University of Minnesota. Department of Ecology, Evolution and Behavior; Estados Unidos. Fil: Khoury, Colin K. International Center for Tropical Agriculture; Colombia. Fil: Krug, Cornelia B. University of Zurich. Department of Geography; Suiza. Fil: Liu, Jianguo. Michigan State University; Estados Unidos. Fil: Maron, Martine. The University of Queensland; Australia. Fil: McGowan, Philip J. K. Newcastle University. School of Natural and Environmental Sciences; Reino Unido. Fil: Pereira, Henrique M. German Centre for Integrative Biodiversity Research; Alemania. Fil: Reyes García, Victoria. Catalan Institution for Research and Advanced Studies; España. Fil: Rocha, Juan. Future Earth; Suecia. Fil: Rondinini, Carlo. Sapienza University of Rome. Department of Biology and Biotechnologies. Global Mammal Assessment Program; Italia. Fil: Shannon, Lynne. University of Cape Town. Department of Biological Sciences; Sudáfrica. Fil: Shin, Yunne-Jai. University of Cape Town. Department of Biological Sciences; Sudáfrica. Fil: Snelgrove, Paul V. R. Memorial University of Newfoundland. Departments of Ocean Sciences and Biology; Canada. Fil: Spehn, Eva M. Swiss Academy of Sciences. Swiss Biodiversity Forum; Suiza. Fil: Strassburg, Bernardo. Pontifical Catholic University. Department of Geography and the Environment. Rio Conservation and Sustainability Science Centre; Brasil. Fil: Subramanian, Suneetha M. United Nations University. Institute for the Advanced Study of Sustainability; Japón. Fil: Tewksbury, Joshua J. University of Colorado; Estados Unidos. Fil: Watson, James E. M. Wildlife Conservation Society; Estados Unidos. Fil: Zanne, Amy E. George Washington University. Department of Biological Sciences; Estados Unidos. Global biodiversity policy is at a crossroads. Recent global assessments of living nature (1, 2) and climate (3) show worsening trends and a rapidly narrowing window for action. The Convention on Biological Diversity (CBD) has recently announced that none of the 20 Aichi targets for biodiversity it set in 2010 has been reached and only six have been partially achieved (4). Against this backdrop, nations are now negotiating the next generation of the CBD's global goals [see supplementary materials (SM)], due for adoption in 2021, which will frame actions of governments and other actors for decades to come. In response to the goals proposed in the draft post-2020 Global Biodiversity Framework (GBF) made public by the CBD (5), we urge negotiators to consider three points that are critical if the agreed goals are to stabilize or reverse nature's decline. First, multiple goals are required because of nature's complexity, with different facets—genes, populations, species, deep evolutionary history, ecosystems, and their contributions to people—having markedly different geographic distributions and responses to human drivers. Second, interlinkages among these facets mean that goals must be defined and developed holistically rather than in isolation, with potential to advance multiple goals simultaneously and minimize trade-offs between them. Third, only the highest level of ambition in setting each goal, and implementing all goals in an integrated manner, will give a realistic chance of stopping—and beginning to reverse—biodiversity loss by 2050.

Recent assessment reports by the Intergovernmental Panel on Climate Change (IPCC) and the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) have highlighted the risks to humanity arising from the unsustainable use of natural resources. Thus far, land, freshwater, and ocean exploitation have been the chief causes of biodiversity loss. Climate change is projected to be a rapidly increasing additional driver for biodiversity loss. Since climate change and biodiversity loss impact human societies everywhere, bold solutions are required that integrate environmental and societal objectives. As yet, most existing international biodiversity targets have overlooked climate change impacts. At the same time, climate change mitigation measures themselves may harm biodiversity directly. The Convention on Biological Diversity’s post-2020 framework offers the important opportunity to address the interactions between climate change and biodiversity and revise biodiversity targets accordingly by better aligning these with the United Nations Framework Convention on Climate Change Paris Agreement and the Sustainable Development Goals. We identify the considerable number of existing and proposed post-2020 biodiversity targets that risk being severely compromised due to climate change, even if other barriers to their achievement were removed. Our analysis suggests that the next set of biodiversity targets explicitly addresses climate change-related risks since many aspirational goals will not be feasible under even lower-end projections of future warming. Adopting more flexible and dynamic approaches to conservation, rather than static goals, would allow us to respond flexibly to changes in habitats, genetic resources, species composition, and ecosystem functioning and leverage biodiversity’s capacity to contribute to climate change mitigation and adaptation. We acknowledge the support by Rainer Krug, Hien Ngo, and Max Gueze in parts of the literature review. Pierre Lopez drew Fig. 1, using spatial data layers provided by Aidin Niamir (https://doi.org/10.5281/zenodo.3975694).

Scenario-based modelling is a powerful tool to describe relationships between plausible trajectories of drivers, possible policy interventions, and impacts on biodiversity and ecosystem services. Model inter-comparisons are key in quantifying uncertainties and identifying avenues for model improvement but have been missing among the global biodiversity and ecosystem services modelling communities. The biodiversity and ecosystem services scenario-based inter-model comparison (BES-SIM) aims to fill this gap. We used global land-use and climate projections to simulate possible future impacts on terrestrial biodiversity and ecosystem services using a variety of models and a range of harmonized metrics. The goal of this paper is to reflect on the steps taken in BES-SIM, identify remaining methodological challenges, and suggest pathways for improvement. We identified five major groups of challenges; the need to: 1) better account for the role of nature in future human development storylines; 2) improve the representation of drivers in the scenarios by increasing the resolution (temporal, spatial and thematic) of land-use as key driver of biodiversity change and including additional relevant drivers; 3) explicitly integrate species- and trait-level biodiversity in ecosystem services models; 4) expand the coverage of the multiple dimensions of biodiversity and ecosystem services; and finally, 5) incorporate time-series or one-off historical data in the calibration and validation of biodiversity and ecosystem services models. Addressing these challenges would allow the development of more integrated global projections of biodiversity and ecosystem services, thereby improving their policy relevance in supporting the interlinked international conservation and sustainable development agendas.

Aims In human-dominated ecosystems, the presence of a given species is the result of both the ecological suitability of the site and human impacts such as land-use choices. The influence of land-use choices on the predictions of species distribution models (SDMs) has, however, been often neglected. Here, we provide a theoretical analysis of the land-use selection bias affecting classical SDMs in the case of either presence-only or presence–absence datasets. Land-use selection bias in the predictions of SDMs is then quantified for four widespread European tree species. Location Continental France. Methods We describe a bivariate selection model (BSM) that estimates simultaneously the economics of land-use choices and species responses to bioclimatic variables. The land-use equation, based on an econometric model of landowner choices, is joined to an equation of species responses to bioclimatic variables. Results We found a significant land-use selection bias in all the species studied. The sign and the magnitude of the bias varied among species and were strongly related to the type of dataset used in the SDM calibration (presence-only or presence–absence). In addition, the BSM estimates the spatial covariance between the probability of presence and the presence of compatible land use. We found that, depending on the species, sites with high ecological suitability could present a high probability of compatible land use (positive covariance) or a low probability (negative covariance). Main conclusion We showed that the use of classical SDMs in human-dominated areas can lead to strong miss-estimations of actual species distributions and could therefore prevents sound projections of the effects of climate change. The proposed BSM represents a crucial step to account for the economic forces shaping species distribution in anthropized areas and paves the way for a direct assessment of trade-offs and opportunities that may arise in a context of global change.

A major challenge today and into the future is to maintain or enhance beneficial contributions of nature to a good quality of life for all people. This is among the key motivations of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), a joint global effort by governments, academia, and civil society to assess and promote knowledge of Earth's biodiversity and ecosystems and their contribution to human societies in order to inform policy formulation. One of the more recent key elements of the IPBES conceptual framework (1) is the notion of nature's contributions to people (NCP), which builds on the ecosystem service concept popularized by the Millennium Ecosystem Assessment (MA) (2). But as we detail below, NCP as defined and put into practice in IPBES differs from earlier work in several important ways. First, the NCP approach recognizes the central and pervasive role that culture plays in defining all links between people and nature. Second, use of NCP elevates, emphasizes, and operationalizes the role of indigenous and local knowledge in understanding nature's contribution to people.

Global biodiversity targets have far-reaching implications for nature conservation worldwide. Scenarios and models hold unfulfilled promise for ensuring such targets are well founded and implemented; here, we review how they can and should inform the Aichi Targets of the Strategic Plan for Biodiversity and their reformulation. They offer two clear benefits: providing a scientific basis for the wording and quantitative elements of targets; and identifying synergies and trade-offs by accounting for interactions between targets and the actions needed to achieve them. The capacity of scenarios and models to address complexity makes them invaluable for developing meaningful targets and policy, and improving conservation outcomes.

Aim Functional traits of organisms are key to understanding and predicting biodiversity and ecological change, which motivates continuous collection of traits and their integration into global databases. Such trait matrices are inherently sparse, severely limiting their usefulness for further analyses. On the other hand, traits are characterized by the phylogenetic trait signal, trait–trait correlations and environmental constraints, all of which provide information that could be used to statistically fill gaps. We propose the application of probabilistic models which, for the first time, utilize all three characteristics to fill gaps in trait databases and predict trait values at larger spatial scales. Innovation For this purpose we introduce BHPMF, a hierarchical Bayesian extension of probabilistic matrix factorization (PMF). PMF is a machine learning technique which exploits the correlation structure of sparse matrices to impute missing entries. BHPMF additionally utilizes the taxonomic hierarchy for trait prediction and provides uncertainty estimates for each imputation. In combination with multiple regression against environmental information, BHPMF allows for extrapolation from point measurements to larger spatial scales. We demonstrate the applicability of BHPMF in ecological contexts, using different plant functional trait datasets, also comparing results to taking the species mean and PMF. Main conclusions Sensitivity analyses validate the robustness and accuracy of BHPMF: our method captures the correlation structure of the trait matrix as well as the phylogenetic trait signal – also for extremely sparse trait matrices – and provides a robust measure of confidence in prediction accuracy for each missing entry. The combination of BHPMF with environmental constraints provides a promising concept to extrapolate traits beyond sampled regions, accounting for intraspecific trait variability. We conclude that BHPMF and its derivatives have a high potential to support future trait-based research in macroecology and functional biogeography.

Aim To analyse global patterns of climate during the mid-Holocene and conduct comparisons with pre-industrial and projected future climates. In particular, to assess the exposure of terrestrial biomes and ecoregions to climate-related risks during the Holocene–Anthropocene transition starting at the pre-industrial period. Location Terrestrial ecosystems of the Earth. Methods We calculated long-term climate differences (anomalies) between the mid-Holocene (6 ka cal bp, mH), pre-industrial conditions and projections for 2100 (middle-strength A1B scenario) using six global circulation models available for all periods. Climate differences were synthesized with multivariate statistics and average principal component loadings of temperature and precipitation differences (an estimate of climate-related risks) were calculated on 14 biomes and 766 ecoregions. Results Our results suggest that most of the Earth's biomes will probably undergo changes beyond the mH recorded levels of community turnover and range shifts because the magnitude of climate anomalies expected in the future are greater than observed during the mH. A few biomes, like the remnants of North American and Euro-Asian prairies, may experience only slightly greater degrees of climate change in the future as compared with the mH. In addition to recent studies that have identified equatorial regions as the most sensitive to future climate change, we find that boreal forest, tundra and vegetation of the Equatorial Andes could be at greatest risk, since these regions will be exposed to future climates that are well outside natural climate variation during the Holocene. Conclusions The Holocene–Anthropocene climate transition, even for a middle-strength future climate change scenario, appears to be of greater magnitude and different from that between the mH and the pre-industrial period. As a consequence, community- and biome-level changes due to of expected climate change may be different in the future from those observed during the mH.

International audience; Climate change is a threat to biodiversity, and adaptation measures should be considered in biodiversity conservation planning. Protected areas (PA) are expected to be impacted by climate change and improving their connectivity with biological corridors (BC) has been proposed as a potential adaptation measure, although assessing its effectiveness remains a challenge. In Mesoamerica, efforts to preserve the biodiversity have led to the creation of a regional network of PA and, more recently, BC. This study evaluates the role of BC for facilitating plant dispersal between PA under climate change in Mesoamerica. A spatially explicit dynamic model (cellular automaton) was developed to simulate species dispersal under different climate and conservation policy scenarios. Plant functional types (PFT) were defined based on a range of dispersal rates and vegetation types to represent the diversity of species in the region. The impacts of climate change on PA and the role of BC for dispersal were assessed spatially. Results show that most impacted PA are those with low altitudinal range in hot, dry, or high latitude areas. PA with low altitudinal range in high cool areas benefit the most from corridors. The most important corridors cover larger areas and have high altitude gradients. Only the fastest PFT can keep up with the expected change in climate and benefit from corridors for dispersal. We conclude that the spatial assessment of the vulnerability of PA and the role of corridors in facilitating dispersal can help conservation planning under a changing climate.

Improving understanding of how biodiversity and ecosystems respond to environmental change is necessary to guide policy and management. To this end, the bioDISCOVERY project of the international programme on global change, Future Earth, initiates and supports international networks of scientists to advance research on monitoring and observations, scenarios and models, and assessments of biodiversity and ecosystems. bioDISCOVERY activities seek collective solutions to key research challenges, and provide support for the international science community by participating in the development of global databases. This global working-group approach is essential for directing cutting-edge science toward supporting international policies, addressing urgent environmental issues, and closing research gaps through transdisciplinary integration and mobilisation of the scientific community.

Scenarios are powerful tools toenvision how nature might respondto different pathways of futurehuman development and policy choices1.Most scenarios developed for globalenvironmental assessments have exploredimpacts of society on nature, such asbiodiversity loss, but have not includednature as a component of socioeconomicdevelopment2. They ignore policyobjectives related to nature protectionand neglect nature?s role in underpinningdevelopment and human well-being.This approach is becoming untenablebecause targets for human developmentare increasingly connected with targetsfor nature, such as in the United Nations?Sustainable Development Goals. The nextgeneration of scenarios should explorealternative pathways to reach theseintertwined targets, including potentialsynergies and trade-offs between natureconservation and other developmentgoals, as well as address feedbacks betweennature, nature?s contributions to people,and human well-being. The developmentof these scenarios would benefit from theuse of participatory approaches, integratingstakeholders from multiple sectors (forexample, fisheries, agriculture, forestry)and should address decision-makersfrom the local to the global scale3, therebysupporting assessments being undertakenby the Intergovernmental Platformon Biodiversity and EcosystemServices (IPBES). Fil: Rosa, Isabel M. D.. German Centre For Integrative Biodiversity Research; Alemania. Martin-universitat Halle-wittenberg; Alemania Fil: Pereira, Henrique M.. German Centre For Integrative Biodiversity Research; Alemania. Martin-universitat Halle-wittenberg; Alemania. Universidad de Porto; Portugal Fil: Ferrier, Simon. Csiro Land And Water; Australia Fil: Alkemade, Rob. Pbl Netherlands Environmental Assessment Agency; Países Bajos Fil: Acosta, Lilibeth A.. University Of The Philippines Los Banos; Filipinas Fil: Akcakaya, H. Resit. Stony Brook University; Estados Unidos Fil: Den Belder, Eefje. Pbl Netherlands Environmental Assessment Agency; Países Bajos. Wageningen University And Research Centre; Países Bajos Fil: Fazel, Asghar M.. Eco Institute Of Environmental Science And Technology; Irán. University Of Environment; Irán Fil: Fujimori, Shinichiro. International Institute For Applied Systems Analysis; Austria. National Institute For Environmental Studies Of Japan; Japón Fil: Harfoot, Mike. United Nations Environment Programme World Conservation Monitoring Centre; Reino Unido Fil: Harhash, Khaled A.. Egyptian Environmental Affairs Agency; Egipto Fil: Harrison, Paula A.. Lancaster University; Reino Unido Fil: Hauck, Jennifer. Coknow Consulting; Alemania. Helmholtz Centre for Environmental Research; Alemania Fil: Hendriks, Rob J. J.. Ministry Of Economic Affairs; Países Bajos Fil: Hernández, Gladys. Centre For World Economy Studies; Cuba Fil: Jetz, Walter. Imperial College London; Reino Unido. University of Yale; Estados Unidos Fil: Karlsson Vinkhuyzen, Sylvia I.. Wageningen University And Research Centre; Países Bajos Fil: Kim, Hyejin. National Institute Of Ecology; Corea del Sur Fil: King, Nicholas. North-west University; Sudáfrica Fil: Kok, Marcel T. J.. Pbl Netherlands Environmental Assessment Agency; Países Bajos Fil: Kolomytsev, Grygoriy O.. Schmalhausen Institute of Zoology of National Academy of Sciences of Ukrain; Ucrania Fil: Lazarova, Tanya. Pbl Netherlands Environmental Assessment Agency; Países Bajos Fil: Leadley, Paul. Université Paris Sud; Francia Fil: Lundquist, Carolyn J.. National Institute Of Water And Atmospheric Research; Nueva Zelanda. The University of Auckland; Nueva Zelanda Fil: García Márquez, Jaime. Humboldt-Universität zu Berlin; Alemania Fil: Meyer, Carsten. German Centre For Integrative Biodiversity Research; Alemania. University of Yale; Estados Unidos Fil: Navarro, Laetitia M.. German Centre For Integrative Biodiversity Research; Alemania. Martin-universitat Halle-wittenberg; Alemania Fil: Nesshöver, Carsten. Helmholtz Centre for Environmental Research; Alemania. German Centre for Integrative Biodiversity Research; Alemania Fil: Ngo, Hien T.. Ipbes Secretariat; Alemania Fil: Ninan, Karachepone N.. Centre For Economics, Environment And Society; India Fil: Palomo, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Pereira, Laura M.. Stockholms Universitet; Suecia Fil: Peterson, Garry D.. Stockholms Universitet; Suecia Fil: Pichs, Ramon. Centre For World Economy Studies; Cuba Fil: Popp, Alexander. Potsdam Institute for Climate Impact Research; Alemania Fil: Purvis, Andy. Natural History Museum; Reino Unido Fil: Ravera, Federica. Consejo Superior de Investigaciones Científicas. Centre de Recerca Ecológica I Aplicacions Forestals; España. University Of Évora; Portugal. Universitat Central De Catalunya; España Fil: Rondinini, Carlo. Università degli studi di Roma "La Sapienza"; Italia Fil: Sathyapalan, Jyothis. Centre For Economic And Social Studies; India Fil: Schipper, Aafke M.. Pbl Netherlands Environmental Assessment Agency; Países Bajos Fil: Seppelt, Ralf. Coknow Consulting; Alemania. Martin Luther University Halle-Wittenberg; Alemania Fil: Settele, Josef. German Centre for Integrative Biodiversity Research; Alemania. Helmholtz Centre for Environmental Research; Alemania Fil: Sitas, Nadia. The Council For Scientific And Industrial Research; Sudáfrica Fil: Van Vuuren, Detlef. Pbl Netherlands Environmental Assessment Agency; Países Bajos

We examine issues to consider when reframing conservation science and practice in the context of global change. New framings of the links between ecosystems and society are emerging that are changing peoples' values and expectations of nature, resulting in plural perspectives on conservation. Reframing conservation for global change can thus be regarded as a stage in the evolving relationship between people and nature rather than some recent trend. New models of how conservation links with transformative adaptation include how decision contexts for conservation can be reframed and integrated with an adaptation pathways approach to create new options for global-change-ready conservation. New relationships for conservation science and governance include coproduction of knowledge that supports social learning. New processes for implementing adaptation for conservation outcomes include deliberate practices used to develop new strategies, shift world views, work with conflict, address power and intergenerational equity in decisions, and build consciousness and creativity that empower agents to act. We argue that reframing conservation for global change requires scientists and practitioners to implement approaches unconstrained by discipline and sectoral boundaries, geopolitical polarities, or technical problematization. We consider a stronger focus on inclusive creation of knowledge and the interaction of this knowledge with societal values and rules is likely to result in conservation science and practice that meets the challenges of a postnormal world.

Model-based projections of shifts in tree species range due to climate change are becoming an important decision support tool for forest management. However, poorly evaluated sources of uncertainty require more scrutiny before relying heavily on models for decision-making. We evaluated uncertainty arising from differences in model formulations of tree response to climate change based on a rigorous intercomparison of projections of tree distributions in France. We compared eight models ranging from niche-based to processbased models. On average, models project large range contractions of temperate tree species in lowlands due to climate change. There was substantial disagreement between models for temperate broadleaf deciduous tree species, but differences in the capacity of models to account for rising CO2 impacts explained much of the disagreement. There was good quantitative agreement among models concerning the range contractions for Scots pine. For the dominant Mediterranean tree species, Holm oak, all models foresee substantial range expansion.

Plant traits – the morphological, anatomical, physiological, biochemical and phenological characteristics of plants and their organs – determine how primary producers respond to environmental factors, affect other trophic levels, influence ecosystem processes and services and provide a link from species richness to ecosystem functional diversity. Trait data thus represent the raw material for a wide range of research from evolutionary biology, community and functional ecology to biogeography. Here we present the global database initiative named TRY, which has united a wide range of the plant trait research community worldwide and gained an unprecedented buy-in of trait data: so far 93 trait databases have been contributed. The data repository currently contains almost three million trait entries for 69 000 out of the world's 300 000 plant species, with a focus on 52 groups of traits characterizing the vegetative and regeneration stages of the plant life cycle, including growth, dispersal, establishment and persistence. A first data analysis shows that most plant traits are approximately log-normally distributed, with widely differing ranges of variation across traits. Most trait variation is between species (interspecific), but significant intraspecific variation is also documented, up to 40% of the overall variation. Plant functional types (PFTs), as commonly used in vegetation models, capture a substantial fraction of the observed variation – but for several traits most variation occurs within PFTs, up to 75% of the overall variation. In the context of vegetation models these traits would better be represented by state variables rather than fixed parameter values. The improved availability of plant trait data in the unified global database is expected to support a paradigm shift from species to trait-based ecology, offer new opportunities for synthetic plant trait research and enable a more realistic and empirically grounded representation of terrestrial vegetation in Earth system models.

Summary 1. The invasion of grasslands by woody species is often associated with changes in environmental conditions, but few studies have addressed the impact of climate change on the competitive interactions between tree seedlings and herbaceous vegetation. We examined patterns of growth and morphology in Fraxinus excelsior seedlings germinating in the presence or absence of grass competition ( Dactylis glomerata ) at either low (380 p.p.m.) or high (645 p.p.m.) atmospheric carbon dioxide (CO 2 ), and at two levels of nitrogen (N) nutrition. 2. Elevated CO 2 had a positive effect on Fraxinus dry mass irrespective of N treatment, but the magnitude of growth response was small. In contrast, Dactylis dry mass showed a significant CO 2 × N interaction: no apparent response to elevated CO 2 in the low N treatment compared with a 25% dry mass increase in the high N, high CO 2 treatment. 3. Dactylis and Fraxinu s showed greater responses to N compared with CO 2 in terms of dry mass, morphology and biomass allocation. The direction of Fraxinus responses to N varied depending on the trait examined and the grass competition treatment. 4. Both the competitive intensity (C int ) and the importance of the competition (C imp ) experienced by Fraxinus seedlings increased with an increase in N availability. Contrary to expectations, elevated CO 2 had no significant effect on either C int or C imp . 5. Plant plasticity may have important implications for the long-term success of tree seedlings in grasslands. Our results suggest that the combination of both grass and tree seedling responses to CO 2 may have indirect benefits for the persistence of woody invaders in high-nutrient grasslands under future atmospheric conditions.

Biological monitoring has a long history in freshwaters, where much of the pioneering work in this field was developed over a 100 years ago—but few of the traditional monitoring tools provide the global perspective on biodiversity loss and its consequences for ecosystem functioning that are now needed. Rather than forcing existing monitoring paradigms to respond to questions they were never originally designed to address, we need to take a step back and assess the prospects for novel approaches that could be developed and adopted in the future. To resolve some of the issues with indicators currently used to inform policymakers, we highlight new biological monitoring tools that are being used, or could be developed in the near future, which (1) consider less-studied taxonomic groups, (2) are standardised across regions to allow global comparisons, and (3) measure change over multiple time points. The new tools we suggest make use of some of the key technological and logistical advances seen in recent years—including remote sensing, molecular tools, and local-to-global citizen science networks. We recommend that these new indicators should be considered in future assessments of freshwater ecosystem health and contribute to the evidence base for global to regional (and national) assessments of biodiversity and ecosystem services: for example, within the emerging framework of the Intergovernmental Platform on Biodiversity and Ecosystem Services.

The impact of elevated atmospheric CO2 concentrations on the nitrogen cycle was evaluated in a 2-month experiment in monospecific grassland microcosms (Holcus lanatus L.) grown on reconstituted grassland soil. The responses of the N pools in the plants, soil, and soil microbes were studied. The impact of high CO2 on key stages of the N cycle, especially nitrification and denitrification processes, were also measured. Our study showed a strong plant response to high CO2: total biomass increased by 76% (P < 0.001) and root length density increased by 77% (P = 0.010). However, total plant N was not significantly modified by high CO2, because the percent N in the plant decreased by 40% (P < 0.001). We observed a large decrease in soil NO3– concentration under elevated CO2 (–50%; P = 0.002). Soil ammonium concentrations were much less affected by CO2 enrichment, and only in resin bags (–8%, P = 0.019). Soil nitrifying enzyme activity (NEA) had a tendency to increase (+17%; P = 0.061) and denitrifying enzyme activity (DEA) decreased (-12%; P = 0.013). We found evidence of increased microbial N sink (microbial N increased by 17%, P = 0.004). This and other studies suggest that rising CO2 often reduces soil nitrate concentrations, which may lead to decreased nitrate leaching. Elevated CO2 led to environmental conditions that were less favourable for denitrification in our study.

We present a multisite analysis of the relationship between plant diversity and ecosystem functioning within the European BIODEPTH network of plant-diversity manipulation experiments. We report results of the analysis of 11 variables addressing several aspects of key ecosystem processes like biomass production, resource use (space, light, and nitrogen), and decomposition, measured across three years in plots of varying plant species richness at eight different European grassland field sites. Differences among sites explained substantial and significant amounts of the variation of most of the ecosystem processes examined. However, against this background of geographic variation, all the aspects of plant diversity and composition we examined (i.e., both numbers and types of species and functional groups) produced significant, mostly positive impacts on ecosystem processes. Analyses using the additive partitioning method revealed that complementarity effects (greater net yields than predicted from monocultures due to resource partitioning, positive interactions, etc.) were stronger and more consistent than selection effects (the covariance between monoculture yield and change in yield in mixtures) caused by dominance of species with particular traits. In general, communities with a higher diversity of species and functional groups were more productive and utilized resources more completely by intercepting more light, taking up more nitrogen, and occupying more of the available space. Diversity had significant effects through both increased vegetation cover and greater nitrogen retention by plants when this resource was more abundant through N2 fixation by legumes. However, additional positive diversity effects remained even after controlling for differences in vegetation cover and for the presence of legumes in communities. Diversity effects were stronger on above- than belowground processes. In particular, clear diversity effects on decomposition were only observed at one of the eight sites. The ecosystem effects of plant diversity also varied between sites and years. In general, diversity effects were lowest in the first year and stronger later in the experiment, indicating that they were not transitional due to community establishment. These analyses of our complete ecosystem process data set largely reinforce our previous results, and those from comparable biodiversity experiments, and extend the generality of diversity–ecosystem functioning relationships to multiple sites, years, and processes.

The objective of this study was to determine what patterns, if any, existed in the response of nitrifying enzyme activity (NEA), denitrifying enzyme activity (DEA), soil microbial N and soil inorganic N to elevated CO2 across a broad range of grassland environments. We studied the response of these N pools and microbial activities in four CO2-enrichment sites of the MEGARICH project (Managing European Grasslands as a Sustainable Resource in a Changing Climate). CO2 treatment was studied in factorial combination with a cutting frequency treatment at two sites and with a temperature treatment at one site. Our study showed that microbial biomass N, NEA, DEA and extractable soil [NH4 1 ] and [NO3 ] were generally not affected by elevated CO2 in these grassland ecosystems after several years of treatment, nor by cutting frequency or temperature at the sites that included these treatments. Exceptions to this were that DEA and soil [NO3 ] decreased by 22% and 45%, respectively, at the French site at elevated CO2. We discuss the possible explanations for this lack of response.

Understanding the relative roles of local and regional processes in determining local species diversity is now of strong relevance in basic ecology. To address this question, we have tested the influence of immigration on species diversity dynamics in a three-year experiment using herbaceous plant communities. We manipulated the intensity of seed rain (i.e., immigration) and the relative contribution of each species to the seed rain. For each of three levels of intensity of immigration (seed rain), we considered three cases, in which immigration was either negatively correlated, positively correlated, or uncorrelated with local competitive ability. Our experiment illustrates how both immigration and local competition contribute to explaining species diversity in herbaceous plant communities. Communities were more diverse when they received more seeds and when immigration was inversely correlated or uncorrelated with local competitive ability. Only species of intermediate or low competitive ability responded positively to the seed-addition treatment. Community-level functional properties were not strongly modified by immigration: immigration treatments did not differ in total above-ground biomass and plant cover, soil surface occupation was higher at high immigration intensities. A comparison of our results with theoretical models of plant community structure suggests that the mechanisms underlying the species dynamics in our communities were probably a mixture of colonization-extinction and competitive weighted lottery.

We examined the effects of decreasing plant diversity and functional group identity on root biomass, soil bulk density, soil nitrate and ammonium concentrations, microbial basal respiration, density of predaceous and non-predaceous nematodes, earthworm biomass and density and Shannon–Wiener indices of earthworm diversity in a temperate grassland. Plant species and functional group diversity did not have significant effects on any of these measured variables. However, functional group identity of the plants did significantly affect root biomass and soil abiotic factors. In addition, root biomass, Shannon–Wiener indices of earthworm diversity and density of epigeic earthworms were significantly higher in the presence of legumes, while we found no correlation between functional group identity and other groups of soil biota. We also found several significant relationships among root biomass density, soil microbial basal respiration, nematodes and earthworms. Thus, how can the lack of correlation between soil variables and plant diversity manipulation be explained? Firstly, plant litter input and historical land use have long-term effects on soil properties, which suggests effects of plant diversity manipulation might only be manifested over the long-term. However, we found significant relationships between root biomass density and soil biota suggesting that changes in root biomass density with declining plant diversity could lead to changes in soil biota that might be detectable despite large temporal lags in the soil system. Secondly, we did not find significant effects of plant diversity on root biomass but we found that it was significantly related to the identity of functional groups. Thirdly, we observed complex interactions among trophic levels of soil organisms, which may counteract and buffer effects of changes in plant diversity on soil biota. Fourth, our results suggest that belowground properties might be much more influenced by the identity (and litter quality) of plant functional groups than plant species diversity per se.

We examine the relationship between plant diversity and ecosystem properties in a Mediterranean grassland. Five legumes, three grasses and two forb species are grown in monocultures and compared with mixtures that include these ten species. Trifolium angustifolium L. (a legume), Lolium rigidum Gaudin (a grass), and Centaurea solstitialis L. (a forb), are replicated in monocultures. Plant cover, root length and biomass, and concentrations of soil nitrate and ammonium are measured in all plots in March and May. Aboveground biomass is measured at a final harvest in late May to early June. Root biomass is significantly higher in the species mixtures than the average of the monocultures. Plant cover and root length are marginally significantly higher (0.05 < P ≤ 0.1) in the mixtures compared to the average of the monocultures. Soil inorganic nitrogen concentrations and aboveground biomass do not significantly differ between the average of the monocultures and the mixtures. Aboveground biomass in T. angustifolium monocultures is significantly higher than in the mixtures, and on average the legume monocultures do not differ significantly from the mixtures. Root length and biomass in L. rigidum monocultures are higher than in the mixtures in March. Nitrate concentrations (which are negatively correlated with root length and biomass) are the lowest in C. solstitialis in May. Thus, we have evidence that some of the measures of ecosystem performance decline in the average of the monocultures when compared with the mixtures, but mixtures never outperform or do more poorly than the best performing monocultures.

The topics assessed in this chapter were last assessed by the IPCC in 2007, principally in WGII AR4 Chapters 3 (Kundzewicz et al., 2007) and 4 (Fischlin et al., 2007), but also in WGII AR4 Sections 1.3.4 and 1.3.5 (Rosenzweig et al., 2007). The WGII AR4 SPM stated “Observational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases,” though they noted that documentation of observed changes in tropical regions and the Southern Hemisphere was sparse (Rosenzweig et al., 2007). Fischlin et al. (2007) found that 20 to 30% of the plant and animal species that had been assessed to that time were considered to be at increased risk of extinction if the global average temperature increase exceeds 2°C to 3°C above the preindustrial level with medium confidence, and that substantial changes in structure and functioning of terrestrial, marine, and other aquatic ecosystems are very likely under that degree of warming and associated atmospheric CO2 concentration. No time scale was associated with these findings. The carbon stocks in terrestrial ecosystems were considered to be at high risk from climate change and land use change. The report warned that the capacity of ecosystems to adapt naturally to the combined effect of climate change and other stressors is likely to be exceeded if greenhouse gas (GHG) emission continued at or above the then-current rate.

Global and regional climate model (GCM and RCM) outputs are often used as climate forcing for ecological impact models, and this potentially results in large cumulative errors because information and error are passed sequentially along the modeling chain from GCM to RCM to impact model. There are also a growing number of Earth system modeling platforms in which climate and ecological models are dynamically coupled, and in this case error amplification due to feedbacks can lead to even more serious problems. It is essential in both cases to rethink the organization of evaluation which typically relies on independent validation at each successive step, and to rely more heavily on analyses that cover the full modeling chain and thus require stronger interactions between climate and impact modelers. In this paper, we illustrate the benefits of using impact models as an additional source of information for evaluating climate models. Four RCMs that are part of the HyMeX (Hydrological cycle in Mediterranean EXperiment) and Mediterranean CORDEX projects (MED-CORDEX) were tested with observed climatology and a process-based model of European beech (Fagus sylvatica L.) tree growth and forest ecosystem functioning that has been rigorously validated. This two part analysis i) indicates that evaluation of RCMs on climate variables alone may be insufficient to determine the suitability of RCMs for studies of climate-forest interactions and ii) points to areas of improvement in these RCMs that would improve impact studies or behavior in coupled climate-ecosystem models over the spatial domain studied. © 2015, Springer Science+Business Media Dordrecht.

In 2010, the international community, under the auspices of the Convention on Biological Diversity, agreed on 20 biodiversity-related “Aichi Targets” to be achieved within a decade. We provide a comprehensive mid-term assessment of progress toward these global targets using 55 indicator data sets. We projected indicator trends to 2020 using an adaptive statistical framework that incorporated the specific properties of individual time series. On current trajectories, results suggest that despite accelerating policy and management responses to the biodiversity crisis, the impacts of these efforts are unlikely to be reflected in improved trends in the state of biodiversity by 2020. We highlight areas of societal endeavor requiring additional efforts to achieve the Aichi Targets, and provide a baseline against which to assess future progress.

The LPJ-GUESS dynamic vegetation model uniquely combines an individual- and patch-based representation of vegetation dynamics with ecosystem biogeochemical cycling from regional to global scales. We present an updated version that includes plant and soil N dynamics, analysing the implications of accounting for C–N interactions on predictions and performance of the model. Stand structural dynamics and allometric scaling of tree growth suggested by global databases of forest stand structure and development were well reproduced by the model in comparison to an earlier multi-model study. Accounting for N cycle dynamics improved the goodness of fit for broadleaved forests. N limitation associated with low N-mineralisation rates reduces productivity of cold-climate and dry-climate ecosystems relative to mesic temperate and tropical ecosystems. In a model experiment emulating free-air CO2 enrichment (FACE) treatment for forests globally, N limitation associated with low N-mineralisation rates of colder soils reduces CO2 enhancement of net primary production (NPP) for boreal forests, while some temperate and tropical forests exhibit increased NPP enhancement. Under a business-as-usual future climate and emissions scenario, ecosystem C storage globally was projected to increase by ca. 10%; additional N requirements to match this increasing ecosystem C were within the high N supply limit estimated on stoichiometric grounds in an earlier study. Our results highlight the importance of accounting for C–N interactions in studies of global terrestrial N cycling, and as a basis for understanding mechanisms on local scales and in different regional contexts.

Interactive effects of increases in atmospheric CO2 and reductions in plant species diversity were investigated in planted calcareous grassland communities in northwestern Switzerland. The experimental communities were composed of 5, 12, and 31 species assembled from the native species pool. The study aimed at testing whether the CO2 responses of ecosystems change when specific sets of species are lost from plant communities. Species were selected so that the proportion of grasses, legumes, and non-legume forb individuals remained constant across levels of diversity. The most diverse plant community had approximately the same diversity as the surrounding grassland, and species occurring in less diverse communities were subsets of the species in the more diverse communities. The factorial atmospheric-CO2 treatment was applied using 50-cm-tall, open-bottom, open-top wind screens. Plant community-level responses and the responses of the individual species were assessed over a period of five years. A signific...

Interactive effects of reductions in plant species diversity and increases in atmospheric CO2 were investigated in a long-term study in nutrient-poor calcareous grassland. Throughout the experiment, soil nitrate was persistently increased at low plant species diversity, and CO2 enrichment reduced soil [NO3 –] at all levels of plant species diversity. In our study, soil [NO3 –] was unrelated to root length density, microbial biomass N, community legume contents, and experimental plant communities differed only little in total N pools. However, potential nitrification revealed exactly the same treatment effects as soil [NO3 –], providing circumstantial evidence that nitrification rates drove the observed changes in [NO3 –]. One possible explanation for plant diversity effects on nitrification lies in spatial and temporal interspecific differences in plant N uptake, which would more often allow accumulation of NH4 + in part of the soil profile at low diversity than in more species-rich plant communities. Consequently, nitrification rates and soil [NO3 –] would increase. Elevated CO2 increased soil water contents, which may have improved NO3 – diffusion to the root surface thereby reducing soil [NO3 –]. Higher soil moisture at elevated CO2 might also reduce nitrification rates due to less aerobic conditions. The accordance of the diversity effect on soil [NO3 –] with previous experiments suggests that increased soil [NO3 –] at low species diversity is a fairly general phenomenon, although the mechanisms causing high [NO3 –] may vary. In contrast, experimental evidence for effects of CO2 enrichment on soil [NO3 –] is ambiguous, and the antagonistic interaction of plant species reductions and elevated CO2 we have observed is thus probably less universal.

Recruitment algorithms in forest gap models are examined with particular regard to their suitability for simulating forest ecosystem responses to a changing climate. The traditional formu- lation of recruitment is found limiting in three areas. First, the aggregation of different regeneration stages (seed production, dispersal, storage, germination and seedling establishment) is likely to result in less accurate predictions of responses as compared to treating each stage separately. Second, the related assumptions that seeds of all species are uniformly available and that environmental conditions are homogeneous, are likely to cause overestimates of future species diversity and for- est migration rates. Third, interactions between herbivores (ungulates and insect pests) and forest vegetation are a big unknown with potentially serious impacts in many regions. Possible strategies for developing better gap model representations for the climate-sensitive aspects of each of these key areas are discussed. A working example of a relatively new model that addresses some of these limitations is also presented for each case. We conclude that better models of regeneration processes are desirable for predicting effects of climate change, but that it is presently impossible to determine what improvements can be expected without carrying out rigorous tests for each new formulation.

1. Instantaneous leaf photosynthesis and land area-based net ecosystem CO2 exchange (NEC) are almost universally increased at elevated CO2 concentrations, at least in the short term and under high light conditions. This raises the possibility that terrestrial ecosystems sequester extra C in response to elevated CO2, and it has been hypothesized that part of this extra C is stored in soils. 2. Attempts to quantify ecosystem C sequestration experimentally are based on (i) ecosystem CO2 exchange measurements; (ii) C isotope tracking; and (iii) direct C stock measurements. 3. Because direct C stock measurements are insensitive to increases in ecosystem C storage in the range expected, and C isotope tracking is methodologically difficult because of the need to account for new and old soil C pools, NEC measurements were considered to be a more direct and unbiased method to estimate net ecosystem production and C sequestration at elevated CO2. 4. Here we present a case study in calcareous grassland under long-term CO2 enrichment in which we demonstrate that calculated C balances are extremely sensitive to systematic experimental biases inherent in any CO2 flux-based study at elevated CO2. A sensitivity analysis demonstrates that these systematic errors tend to result in severe overestimation of ecosystem C accretion under elevated CO2. 5. Carbon isotope data and soil pool C and N measurements from the same study add to the evidence that the C balance derived from CO2 flux measurements at elevated CO2 is overestimated. 6. Based on this evidence, and the wide attention given to C sequestration at elevated CO2, we suggest a critical reconsideration of the appropriateness of NEC measurement in CO2-enriched ecosystems as a basis for calculating ecosystem C balances at elevated CO2.