Klaus Henle

Predictors of species sensitivity to fragmentation

We reviewed empirical data and hypotheses derived from demographic, optimal foraging, life-history, community, and biogeographic theory for predicting the sensitivity of species to habitat fragmentation. We found 12 traits or trait groups that have been suggested as predictors of species sensitivity: population size; population fluctuation and storage effect; dispersal power; reproductive potential; annual survival; sociality; body size; trophic position; ecological specialisation, microhabitat and matrix use; disturbance and competition sensitive traits; rarity; and biogeographic position. For each trait we discuss the theoretical justification for its sensitivity to fragmentation and empirical evidence for and against the suitability of the trait as a predictor of fragmentation sensitivity. Where relevant, we also discuss experimental design problems for testing the underlying hypotheses. There is good empirical support for 6 of the 12 traits as sensitivity predictors: population size; population fluctuation and storage effects; traits associated with competitive ability and disturbance sensitivity in plants; microhabitat specialisation and matrix use; rarity in the form of low abundance within a habitat; and relative biogeographic position. Few clear patterns emerge for the remaining traits from empirical studies if examined in isolation. Consequently, interactions of species traits and environmental conditions must be considered if we want to be able to predict species sensitivity to fragmentation. We develop a classification of fragmentation sensitivity based on specific trait combinations and discuss the implications of the results for ecological theory.

Advantages of Volunteer-Based Biodiversity Monitoring in Europe

Without robust and unbiased systems for monitoring, changes in natural systems will remain enigmatic for policy makers, leaving them without a clear idea of the consequences of any environmental policies they might adopt. Generally, biodiversity-monitoring activities are not integrated or evaluated across any large geographic region. The EuMon project conducted the first large-scale evaluation of monitoring practices in Europe through an on-line questionnaire and is reporting on the results of this survey. In September 2007 the EuMon project had documented 395 monitoring schemes for species, which represents a total annual cost of about 4 million euro, involving more than 46,000 persons devoting over 148,000 person-days/year to biodiversity-monitoring activities. Here we focused on the analysis of variations of monitoring practices across a set of taxonomic groups (birds, amphibians and reptiles, mammals, butterflies, plants, and other insects) and across 5 European countries (France, Germany, Hungary, Lithuania, and Poland). Our results suggest that the overall sampling effort of a scheme is linked with the proportion of volunteers involved in that scheme. Because precision is a function of the number of monitored sites and the number of sites is maximized by volunteer involvement, our results do not support the common belief that volunteer-based schemes are too noisy to be informative. Just the opposite, we believe volunteer-based schemes provide relatively reliable data, with state-of-the-art survey designs or data-analysis methods, and consequently can yield unbiased results. Quality of data collected by volunteers is more likely determined by survey design, analytical methodology, and communication skills within the schemes rather than by volunteer involvement per se.

EU agricultural reform fails on biodiversity

Extra steps by Member States are needed to protect farmed and grassland ecosystems In December 2013, the European Union (EU) enacted the reformed Common Agricultural Policy (CAP) for 2014–2020, allocating almost 40% of the EUs budget and influencing management of half of its terrestrial area. Many EU politicians are announcing the new CAP as “greener,” but the new environmental prescriptions are so diluted that they are unlikely to benefit biodiversity. Individual Member States (MSs), however, can still use flexibility granted by the new CAP to design national plans to protect farmland habitats and species and to ensure long-term provision of ecosystem services.

Towards sustainable land use: identifying and managing the conflicts between human activities and biodiversity conservation in Europe

Conflicts between biodiversity conservation and human activities are becoming increasingly apparent in all European landscapes. The intensification of agricultural and silvicultural practices, land abandonment and other land uses such as recreation and hunting are all potential threats to biodiversity that can lead to conflicts between stakeholder livelihoods and biodiversity conservation. To address the global decline in biodiversity there is, therefore, a need to identify the drivers responsible for conflicts between human activities and the conservation of European biodiversity and to promote the management of these conflicts. Here, the drivers of biodiversity conflicts are analysed in a European context for five habitat types: agricultural landscapes, forests, grasslands, uplands and freshwater habitats. A multi- disciplinary approach to conflict management is described, with active stakeholder involvement at every stage of conflict identification and management as well as a range of other approaches including stakeholder dialogue and education, consumer education, improvement of political and legislative frameworks, financial incentives, and planning infrastructure.

Species survival in fragmented landscapes

Preface. Part I: Case Studies on Species Survival in Fragmented Landscapes. Part II: A Review of Species Survival in Fragmented Habitats: Theory and Approaches. Part III: The FIFB Project. FIFB: Conceptual Frame. FIFB: The Hilly Landscape of Halle - Main Study Area. FIFB: Survival of Plants in Fragmented Landscapes. FIFB: Survival of Vertebrates in Fragmented Landscapes. FIFB: Survival of Butterflies in Fragmented Landscapes. FIFB: Survival of Grasshoppers and Bush Crickets in Fragmented Landscapes. FIFB: Survival of Snails in Fragmented Landscapes. FIFB: Genetics, Habitat Models, and Implementation. Part IV: Summary Conclusions.

Species survival in fragmented landscapes: where are we now?

We present a brief introduction to current attempts to understand and mitigate the effects of fragmentation on species survival. We provide a short overview of the contributions of empiricists, modellers, and practitioners in this issue of Biodiversity and Conservation, which were initiated during a workshop held in Australia in February 2002 on the topic ‘Species Survival in Fragmented Landscapes: Where are we now?’. These contributions address the themes ‘uncertainty in research and management’, ‘tools for quantifying risk and predicting species sensitivity to fragmentation’, and ‘tools for reassembling fragmented landscapes’. A final contribution provides a synthesis across the contributions and highlights the most important areas for future research on species survival in fragmented landscapes.

The role of density regulation in extinction processes and population viability analysis

We review the role of density dependence in the stochastic extinction of populations and the role density dependence has played in population viability analysis (PVA) case studies. In total, 32 approaches have been used to model density regulation in theoretical or applied extinction models, 29 of them are mathematical functions of density dependence, and one approach uses empirical relationships between density and survival, reproduction, or growth rates. In addition, quasi-extinction levels are sometimes applied as a substitute for density dependence at low population size. Density dependence further has been modelled via explicit individual spacing behaviour and/or dispersal. We briefly summarise the features of density dependence available in standard PVA software, provide summary statistics about the use of density dependence in PVA case studies, and discuss the effects of density dependence on extinction probability. The introduction of an upper limit for population size has the effect that the probability of ultimate extinction becomes 1. Mean time to extinction increases with carrying capacity if populations start at high density, but carrying capacity often does not have any effect if populations start at low numbers. In contrast, the Allee effect is usually strong when populations start at low densities but has only a limited influence on persistence when populations start at high numbers. Contrary to previous opinions, other forms of density dependence may lead to increased or decreased persistence, depending on the type and strength of density dependence, the degree of environmental variability, and the growth rate. Furthermore, effects may be reversed for different quasi-extinction levels, making the use of arbitrary quasi-extinction levels problematic. Few systematic comparisons of the effects on persistence between different models of density dependence are available. These effects can be strikingly different among models. Our understanding of the effects of density dependence on extinction of metapopulations is rudimentary, but even opposite effects of density dependence can occur when metapopulations and single populations are contrasted. We argue that spatially explicit models hold particular promise for analysing the effects of density dependence on population viability provided a good knowledge of the biology of the species under consideration exists. Since the results of PVAs may critically depend on the way density dependence is modelled, combined efforts to advance statistical methods, field sampling, and modelling are urgently needed to elucidate the relationships between density, vital rates, and extinction probability.

The tales of two geckos: does dispersal prevent extinction in recently fragmented populations?

Although habitat loss and fragmentation threaten species throughout the world and are a major threat to biodiversity, it is apparent that some species are at greater risk of extinction in fragmented landscapes than others. Identification of these species and the characteristics that make them sensitive to habitat fragmentation has important implications for conservation management. Here, we present a comparative study of the population genetic structure of two arboreal gecko species (Oedura reticulata and Gehyra variegata) in fragmented and continuous woodlands. The species differ in their level of persistence in remnant vegetation patches (the former exhibiting a higher extinction rate than the latter). Previous demographic and modelling studies of these two species have suggested that their difference in persistence levels may be due, in part, to differences in dispersal abilities with G. variegata expected to have higher dispersal rates than O. reticulata. We tested this hypothesis and genotyped a total of 345 O. reticulata from 12 sites and 353 G. variegata from 13 sites at nine microsatellite loci. We showed that O. reticulata exhibits elevated levels of structure (FST = 0.102 vs. 0.044), lower levels of genetic diversity (HE = 0.79 vs. 0.88), and fewer misassignments (20% vs. 30%) than similarly fragmented populations of G. variegata, while all these parameters were fairly similar for the two species in the continuous forest populations (FST = 0.003 vs. 0.004, HE = 0.89 vs. 0.89, misassignments: 58% vs. 53%, respectively). For both species, genetic structure was higher and genetic diversity was lower among fragmented populations than among those in the nature reserves. In addition, assignment tests and spatial autocorrelation revealed that small distances of about 500 m through fragmented landscapes are a barrier to O. reticulata but not for G. variegata. These data support our hypothesis that G. variegata disperse more readily and more frequently than O. reticulata and that dispersal and habitat specialization are critical factors in the persistence of species in habitat remnants.

Integrating ongoing biodiversity monitoring: potential benefits and methods

Halting the loss of biodiversity comes along with the need to quantify biodiversity composition and dynamics at large spatial and temporal scales. Highly standardized, international monitoring networks would be ideal, but they do not exist yet. If we are to assess changes in biodiversity now, combining output available from ongoing monitoring initiatives is the only option. However, integration of biodiversity information across schemes is still very poorly developed. In this paper, we outline practical issues to be considered when planning to combine existing monitoring information. First, we provide an overview of avenues for integration along the four dimensions that characterize a monitoring design: sample size, biological coverage, spatial coverage and temporal coverage. We also emphasize that complementarity in monitoring targets across schemes enables to describe complex processes of biodiversity dynamics, e.g. through relating species traits to the impacts of environmental changes. Second, we review some methods to overcome differences in designs among monitoring schemes, such as site selection, post-stratification and measurement error. Finally, we point out some commonly used statistical methods that are at hand for combining data or parameter estimates. We especially emphasize the possible levels of data integration (raw data, parameter estimates, or effect size estimates), and the largely under-exploited potential of meta-analysis methods and weighted analyses. This contribution aims to bolster the practice and use of integration of ongoing monitoring initiatives for biodiversity assessment.

Long-term carbon loss in fragmented Neotropical forests

Tropical forests play an important role in the global carbon cycle, as they store a large amount of carbon (C). Tropical forest deforestation has been identified as a major source of CO2 emissions, though biomass loss due to fragmentation--the creation of additional forest edges--has been largely overlooked as an additional CO2 source. Here, through the combination of remote sensing and knowledge on ecological processes, we present long-term carbon loss estimates due to fragmentation of Neotropical forests: within 10 years the Brazilian Atlantic Forest has lost 69 (±14) Tg C, and the Amazon 599 (±120) Tg C due to fragmentation alone. For all tropical forests, we estimate emissions up to 0.2 Pg C y(-1) or 9 to 24% of the annual global C loss due to deforestation. In conclusion, tropical forest fragmentation increases carbon loss and should be accounted for when attempting to understand the role of vegetation in the global carbon balance.