How to value biodiversity in environmental management?

Biodiversity is globally recognised as a cornerstone of healthy ecosystems, and biodiversity conservation is increasingly becoming one of the important aims of environmental management. Evaluating the trade-offs of alternative management strategies requires quantitative estimates of the costs and benefits of their outcomes, including the value of biodiversity lost or preserved. This paper takes a decision-analytic standpoint, and reviews and discusses the alternative aspects of biodiversity valuation by dividing them into three categories: socio-cultural, economic, and ecological indicator approaches. We discuss the interplay between these three perspectives and suggest integrating them into an ecosystem-based management (EBM) framework, which permits us to acknowledge ecological systems as a rich mixture of interactive elements along with their social and economic aspects. In this holistic framework, socio-cultural preferences can serve as a tool to identify the ecosystem services most relevant to society, whereas monetary valuation offers more globally comparative and understandable values. Biodiversity indicators provide clear quantitative measures and information about the role of biodiversity in the functioning and health of ecosystems. In the multi-objective EBM approach proposed in the paper, biodiversity indicators serve to define threshold values (i.e., the minimum level required to maintain a healthy environment). An appropriate set of decision-making criteria and the best method for conducting the decision analysis depend on the context and the management problem in question. Therefore, we propose a sequence of steps to follow when quantitatively evaluating environmental management against biodiversity.     

Linking variability in climate to wetland habitat suitability: is it possible to forecast regional responses from simple climate measures?

Wetlands Ecology and Management - Temporary wetlands have value to both ecological and social systems. Interactions between local climate and the surrounding landscape result in patterns of...     

How far can a tortoise walk in open habitat before overheating? Implications for conservation

Terrestrial chelonians are threatened worldwide by habitat destruction and illegal harvesting. Tortoises are slow moving animals susceptible to dehydration and overheating during movements in open habitats. Many species inhabit arid steppes where the availability of thermally buffered refuges (e.g. burrows) is a limiting factor. Determining the maximal distance between refuges that individuals can safely traverse during the active season is thus essential. We examined the relationship between body temperature variations and movement patterns in adult Testudo graeca in the arid steppes of Morocco. Using physical and mathematical models, our results suggest that during the active season adults cannot travel more than 1 km without serious risk of overheating. However, radio-tracking suggests that free-ranging individuals are behaviourally limited to 0.5 km trips between refuges. Overall, maintaining a distance less than 0.5 km between refuges (e.g. through bush planting) is essential to limit fragmentation and to retain healthy populations. This restoration would also benefit to many other species that depend on bush-refuges.     

How do habitat amount and habitat fragmentation drive time-delayed responses of biodiversity to land-use change?

Land-use change is a root cause of the extinction crisis, but links between habitat change and biodiversity loss are not fully understood. While there is evidence that habitat loss is an important extinction driver, the relevance of habitat fragmentation remains debated. Moreover, while time delays of biodiversity responses to habitat transformation are well-documented, time-delayed effects have been ignored in the habitat loss versus fragmentation debate. Here, using a hierarchical Bayesian multi-species occupancy framework, we systematically tested for time-delayed responses of bird and mammal communities to habitat loss and to habitat fragmentation. We focused on the Argentine Chaco, where deforestation has been widespread recently. We used an extensive field dataset on birds and mammals, along with a time series of annual woodland maps from 1985 to 2016 covering recent and historical habitat transformations. Contemporary habitat amount explained bird and mammal occupancy better than past habitat amount. However, occupancy was affected more by the past rather than recent fragmentation, indicating a time-delayed response to fragmentation. Considering past landscape patterns is therefore crucial for understanding current biodiversity patterns. Not accounting for land-use history ignores the possibility of extinction debt and can thus obscure impacts of fragmentation, potentially explaining contrasting findings of habitat loss versus fragmentation studies.     

Should we account for detectability in population trends?

Capsule?Accounting for changes in detectability over time which could invalidate population trends for common and widespread breeding birds in the UK, resulted in little change in trends for the majority of species considered.

Aims?To examine whether detectability has a significant influence on population trends for common and widespread breeding birds in the UK.

Methods?Using data collected over 16 years of the UK Breeding Bird Survey (1994–2009) and focusing on a random sample of 20 common and widespread bird species, we examine the extent to which controlling for temporal change in detectability would influence national population trends.

Results?Population trends were significantly different for only 2 of the 20 species, Common Blackbird and Winter Wren. This difference corresponds to an apparent fall off in detectability of these species between 2005 and 2009. For the remaining species, controlling for detectability resulted in no significant difference in population trends.

Conclusions?The importance of detectability should be examined as part of any long-term monitoring programme. However, currently we do not find sufficient support for routinely incorporating detectability into population trends for widespread and abundant breeding birds in the UK.     

How to know about waters? Finnish traditional knowledge related to waters and implications for management reforms

Finnish lakes, rivers, the Baltic and wetlands–our aquatic ecosystems–are surveyed, assessed and studied using natural sciences and ecological data. We argue that this approach is leaving out a key repository of information–the traditional knowledge of waters. By reviewing aspects, qualities and depth of knowledge across Finland from mid-boreal ecosystems in Eastern Finland to large Saimaa lake system to Western Finnish lakes we demonstrate a potentially reformative approach to aquatic assessments. Cultural indicators, baseline data from oral histories, linguistic diversity and behaviour of species on lakes based on traditional knowledge observations have the potential to greatly enhance our understanding of ecosystem health. Of special importance are the spawning locations of fish known through traditional knowledge, but often ignored by science-based assessments.

     

How does temporal variation in habitat connectivity influence metapopulation dynamics?

Metapopulation persistence depends on connectivity between habitat patches. While emphasis has been placed on the spatial dynamics of connectivity, much less has been placed on its short‐term temporal dynamics. In many terrestrial and aquatic ecosystems, however, transient (short‐term) changes in connectivity occur as habitat patches are connected and disconnected due, for example, to climatic or hydrological variability. We evaluated the implications of transient connectivity using a network‐based metapopulation model and a series of scenarios representing temporal changes in connectivity. The transient loss of connectivity can influence metapopulation persistence, and more strongly autocorrelated temporal dynamics affect metapopulation persistence more severely. Given that many ecosystems experience short‐term and temporary loss of habitat connectivity, it is important that these dynamics are adequately represented in metapopulation models; failing to do so may yield overly optimistic‐estimates of metapopulation persistence in fragmented landscapes.     

How resilient are Andean montane forest bird communities to habitat degradation?

The threatened forest habitats of the tropical Andes are reportedly being modified and destroyed 30% faster than their lowland tropical counterparts, but impacts on the hyper-diverse resident avifauna have received little systematic study. We present a baseline analysis of the effects of habitat modification on birds in a lower montane forest landscape in Ecuador, comparing avian community composition in landscape elements subjected to different levels of human modification: primary forest, secondary forest, edge habitat and agricultural land. We use data from a point count survey of 300 counts at 150 sites to test whether community composition and density of birds with different reported habitat preferences and foraging strategies change among landscape elements. Species richness and diversity were lowest in agricultural land, but on some measures, equally low in primary forest. Richness and diversity peaked in secondary forest and edge habitat, but ordination and density analysis revealed clear differences in their species composition. While secondary forest contained mostly forest-preferring species, edge habitat harboured a mix of forest and open-land birds. There was a clearly structured gradient in species composition across landscape elements, with densities of habitat specialists, foraging guilds and families varying considerably from primary forest to agricultural land. Agricultural land was characterised by an assemblage of widespread, abundant species very different from that in core forest habitats. As such, while the majority of montane forest birds appear resilient to a certain level of habitat modification, they cannot persist, and are displaced, where forest has been cleared outright. We argue that, for Andean montane forests, preservation of mature secondary forest offers flexibility in supplementing preserved primary forest areas to provide sufficient habitat for the persistence of this incredibly diverse but severely threatened bird community.     

Does cutting herbicide rates threaten the sustainability of weed management in cropping systems?

Evolution of herbicide resistance in weeds is a growing problem across the world, and it has been suggested that low herbicide rates may be contributing to this problem. An individual-based simulation model that represents weed population dynamics and the evolution of polygenic herbicide resistance was constructed and used to investigate whether using lower herbicide rates or standard rates at reduced efficacy could reduce the sustainability of cropping systems by causing faster increases in weed population density as herbicide resistance develops. A number of different possible genetic bases for resistance were considered, including monogenic resistance and polygenic resistance conferred by several genes. The results show that cutting herbicide rates does not affect the rate at which weed densities reach critical levels when resistance is conferred exclusively by a single dominant gene. In some polygenic situations, cutting herbicide rates substantially reduces sustainability, due to a combination of faster increase in resistance gene frequency and reduced kill rates in all genotypes, while in other polygenic situations the effect is small. Differences in sustainability depend on combined strength of the resistance genes, variability in phenotypic susceptibility and rate delivered, level of control due to alternative measures, and degree of genetic dominance and epistasis. In the situation where resistance can be conferred by both a single dominant major gene or a number of co-dominant minor genes in combination, the difference made by low rates depends on the relative initial frequency of the major and minor genes. These results show that careful consideration of herbicide rate and understanding the genetic basis of resistance are important aspects of weed management.     

Does allelopathy offer real promise for practical weed management and for explaining rhizosphere interactions involving higher plants?

This paper selectively reviews developments in the study of allelopathy, principally from a chemical standpoint. Particular attention is given to recently discovered aspects of signalling within the rhizosphere rather than to direct physiological effects caused by broadly active allelopathic agents with only a brief review of the role of bulk generation of weakly biocidal material. Many of the chemicals responsible for allelopathic effects have been identified and the biosynthesis and modes of action of a number are included. The paper also highlights instances where signalling aspects of allelopathy may be exploited for practical weed control purposes, and how the study of allelopathic components of the rhizosphere metabolome might be studied more directly by means of plant genomics.     

Living on the edge: do central and marginal populations of plants differ in habitat suitability?

The performance of populations at the edge of specie’s distribution range may differ substantially from central populations. Here, we develop a modelling framework to estimate ecological niches (i.e. climatic) of four locally endangered plant species and measure the distance of marginal (geographically) populations to the species’ niche centroid in order to analyse whether marginal populations are outside of the optimal ecological niche of each species. Our results show that for three of the four studied species, which have their populations located at the margins of their distribution ranges, are also at the margins of their climate gradients. These results would support the hypothesis that marginality within the set of habitable conditions (i.e. ecological niche) may represent an important determinant on performance of some plant populations, as well as a plausible explanation to the degree of stagnancy or regression experienced by species in those regions where their populations are at the margin of their ecological niche and/or they are restricted to microrefugia with ecological conditions very different from those around them. Finally, this study aims to be a theoretical base from which to advance on, including other types of factors (e.g. biotic interactions, topography, human influence and population fluctuations through time), which will allow for a better understanding of the complex network of factors that occur in marginal plant populations.     

Is variation in tail vertebral morphology linked to habitat use in chameleons?

Chameleons (Chamaeleonidae) are known for their arboreal lifestyle, in which they make use of their prehensile tail. Yet, some species have a more terrestrial lifestyle, such as Brookesia and Rieppeleon species, as well as some chameleons of the genera Chamaeleo and Bradypodion. The main goal of this study was to identify the key anatomical features of the tail vertebral morphology associated with prehensile capacity. Both interspecific and intra-individual variation in skeletal tail morphology was investigated. For this, a 3D-shape analysis was performed on vertebral morphology using μCT-images of different species of prehensile and nonprehensile tailed chameleons. A difference in overall tail size and caudal vertebral morphology does exist between prehensile and nonprehensile taxa. Nonprehensile tailed species have a shorter tail with fewer vertebrae, a generally shorter neural spine and shorter transverse processes that are positioned more anteriorly (with respect to the vertebral center). The longer tails of prehensile species have more vertebrae as well as an increased length of the processes, likely providing a greater area for muscle attachment. At the intra-individual level, regional variation is observed with more robust proximal tail vertebrae having longer processes. The distal part has relatively longer vertebrae with shorter processes. Although longer, the small size and high number of the distal vertebrae allows the tail to coil around perches.     

Long term management of duodenal ulcer in general practice: How best to use cimetidine?

Two hundred and sixty seven patients with duodenal ulceration were entered into a five year study of two strategies of treatment with cimetidine. Two thirds were treated continuously with 400 mg at bedtime supplemented by temporary increases in dosage if they had symptomatic relapses (group 1), and the remaining third were given intermittent “healing” doses for four to eight weeks if a symptomatic recurrence was judged to have occurred (group 2). Life table analysis showed that the probability of remaining free of clinically important symptoms five years after the start of treatment was 24% (95% confidence interval (CI) 15·5% to 32·6%) in group 1 compared with nil in group 2 (p<0·0001). The median values for the longest periods free from relapse for each patient were 108 weeks in group 1 and 32 weeks in group 2, respectively (p<0·0001; 95% CI of the median difference 36 to 76). Over the five years 10 patients suffered major complications, two requiring emergency surgery, while a further nine had elective surgery because of the failure of medical treatment. There were no deaths that could be attributed either to ulceration or to treatment with cimetidine.Medical management was therefore very satisfactory for most patients, though those treated continuously with cimetidine suffered considerably less from their ulcer symptoms. As 80% of patients studied relapsed during the two years after a healing course of cimetidine, continuous treatment will benefit many patients treated in general practice.     

Can settlement in natal-like habitat explain maladaptive habitat selection?

The study of habitat selection has long been influenced by the ideal free model, which maintains that young adults settle in habitat according to its inherent quality and the density of conspecifics within it. The model has gained support in recent years from the finding that conspecifics produce cues inadvertently that help prebreeders locate good habitat. Yet abundant evidence shows that animals often fail to occupy habitats that ecologists have identified as those of highest quality, leading to the conclusion that young animals settle on breeding spaces by means not widely understood. Here, we report that a phenomenon virtually unknown in nature, natal habitat preference induction (NHPI), is a strong predictor of territory settlement in both male and female common loons (Gavia immer). NHPI causes young animals to settle on natal-like breeding spaces, but not necessarily those that maximize reproductive success. If widespread, NHPI might explain apparently maladaptive habitat settlement.     

How flexible are habitat specialists? Short-term space use in obligate coral-dwelling damselfishes

Reviews in Fish Biology and Fisheries - As habitats change, highly specialised species may die or be forced to relocate. However, some obligate coral-dwelling damselfishes appear to survive the...     

How much does an individual habitat fragment contribute to metapopulation dynamics and persistence?

We derive measures for assessing the value of an individual habitat fragment for the dynamics and persistence of a metapopulation living in a network of many fragments. We demonstrate that the most appropriate measure of fragment value depends on the question asked. Specifically, we analyse four alternative measures: the contribution of a fragment to the metapopulation capacity of the network, to the equilibrium metapopulation size, to the expected time to metapopulation extinction and the long-term contribution of a fragment to colonization events in the network. The latter measure is comparable to density-dependent measures in general matrix population theory, though some differences are introduced by the fact that "density dependence" is spatially localized in the metapopulation context. We show that the value of a fragment depends not only on the properties of the landscape but also on the properties of the species. Most importantly, variation in fragment values between the habitat fragments is greatest in the case of rare species that occur close to the extinction threshold, as these species are likely to be restricted to the most favorable parts of the landscape. We expect that the measures of habitat fragment value described and analysed here have applications in landscape ecology and in conservation biology.     

How to characterize meiotic functions in plants?

Our understanding of plant meiosis is rapidly increasing thanks to the model Arabidopsis thaliana. Here we present the results of a screening for meiotic mutants carried out with a library containing 30,719 T-DNA insertion lines. An average of one mutant per 1000 lines was recovered. Several phenotypic classes could be distinguished and are presented. In parallel, 39 proteins known to be involved in meiosis in non-plant organisms were chosen and a search was performed for homologue sequences in the completed Arabidopsis thaliana genome. Approximately 30% of the meiotic related sequences showed similarities with one or several Arabidopsis putative genes. The relevance of forward versus reverse genetics in order to characterize meiotic functions is discussed.