Alison R. Holt

Occupancy-abundance relationships and spatial distribution: A review

Summary One of the most general patterns in community ecology is the positive relationship between the number of sites or areas in which a species in a taxonomic assemblage occurs regionally and its local abundance. A number of hypotheses have been proposed to explain this interspecific occupancy-abundance relationship, but it has recently been argued that the pattern is most profitably viewed as a consequence of the spatial distribution of the individuals of each species. In this paper we explore the link between spatial distribution and the occupancy-abundance relationship, with particular reference to statistical models that have been suggested to describe the pattern, and discuss its connections with a broad understanding of how organisms are distributed in space. A range of models describe observed occupancy-abundance relationships reasonably well, but are commonly not well differentiated over the range of abundances implicit in such relationships. There is little evidence that species exhibit great commonality in the form of their aggregative behaviour, but this does not matter in terms of the generation of a positive interspecific occupancy-abundance relationship. Eines der allgemeinsten Muster in der Okologie der Lebensgemeinschaften ist die Beziehung zwischen der Anzahl der Standorte oder Gebiete, an oder in denen Arten einer taxonomischen Gruppe vorkommmen, und ihrer lokalen Abundanz. Es wurde eine Anzahl von Hypothesen vorgeschlagen, um diese interspezifische Anwesenheits-Abundanz-Beziehung zu erklaren. In letzter Zeit wurde jedoch angefuhrt, dass dieses Muster mit dem besten Ergebnis als eine Folge der raumlichen Verteilung der Individuen einer jeden Art zu sehen ist. In diesem Review erkunden wir die Verbindung zwischen der raumlichen Verteilung und der Anwesenheits-Abundanz-Beziehung, wobei besonderer Wert auf die statistischen Modelle gelegt wird. Zudem erortern wir in welcher Beziehung sie zu einem breiten Verstandnis der Verteilung der Organismen im Raum steht. Eine Reihe von Modellen beschreibt die Anwesenheits-Abundanz-Beziehung relativ gut; sie sind aber meistens uber den Bereich der Abundanzen, die in diesen Beziehungen vorkommen, nicht ausreichend differenziert. Es gibt nur wenige Beweise dafur, dass die Arten eine grose Gemeinsamkeit in der Form ihres aggregierenden Verhaltens aufweisen. Das spielt jedoch keine Rolle in Beziehung auf die Erzeugung einer positiven interspezifischen Anwesenheits-Abundanz-Beziehung.

Protected areas facilitate species’ range expansions

The benefits of protected areas (PAs) for biodiversity have been questioned in the context of climate change because PAs are static, whereas the distributions of species are dynamic. Current PAs may, however, continue to be important if they provide suitable locations for species to colonize at their leading-edge range boundaries, thereby enabling spread into new regions. Here, we present an empirical assessment of the role of PAs as targets for colonization during recent range expansions. Records from intensive surveys revealed that seven bird and butterfly species have colonized PAs 4.2 (median) times more frequently than expected from the availability of PAs in the landscapes colonized. Records of an additional 256 invertebrate species with less-intensive surveys supported these findings and showed that 98% of species are disproportionately associated with PAs in newly colonized parts of their ranges. Although colonizing species favor PAs in general, species vary greatly in their reliance on PAs, reflecting differences in the dependence of individual species on particular habitats and other conditions that are available only in PAs. These findings highlight the importance of current PAs for facilitating range expansions and show that a small subset of the landscape receives a high proportion of colonizations by range-expanding species.

Meta-analysis of the effects of predation on animal prey abundance: evidence from UK vertebrates.

Background Controlling vertebrate predators is one of the most widespread forms of wildlife management and it continues to cause conflict between stakeholders worldwide. It is important for managers and policy-makers to make decisions on this issue that are based on the best available scientific evidence. Therefore, it is first important to understand if there is indeed an impact of vertebrate predators on prey, and then to quantify this impact. Methodology/Principal Findings Using the UK as a case study, we use a meta-analytical approach to review the available evidence to assess the effect of vertebrate predation on animal prey abundance. We find a significant effect of predators on prey abundance across our studies. On average, there is a 1.6 fold increase in prey abundance in the absence of predation. However, we show significant heterogeneity in effect sizes, and discuss how the method of predator control, whether the predator is native or non-native, and aspects of study design, may be potential causes. Conclusions/Significance Our results allow some cautious policy recommendations to be made regarding the management of predator and prey populations. Meta-analysis is an important tool for understanding general patterns in the effect of predators on prey abundance across studies. Such an approach is especially valuable where management decisions need to be made in the absence of site-specific information.

The Network Governance of Urban River Corridors

Urban centers can provide important ecosystem services to society both through green spaces and river corridors. However, urbanization has impacted rivers, and as a consequence, there is increasing support for their sustainable management. The governance of urban river corridors reflects a trend toward stakeholder participation and partnership working in urban regeneration. The integration of ecological, social, and economic knowledge required for their sustainable management is achieved through networks of people and organizations that cross multiple sectors. However, little is known about the structure and function of such governance networks. We address this through a case study that explores the network structure of a multi- stakeholder collaboration tasked with developing a city-wide strategy for the sustainable management of urban river corridors in Sheffield, UK. We combine interpretive policy analysis and social network analysis to reveal the network structure and leadership characteristics of the group. We aim to explain why the group are having difficulty reaching a shared strategic vision for the river corridors and why they feel the group lacks representativeness. Our findings show that the network needs to become better connected to support an ongoing process of deliberation and negotiation for a shared vision. In addition, there is a limited diversity of stakeholders that will affect the legitimacy of the group and their ability to manage for a range of ecosystem services of benefit across society. We conclude that governance processes need to account for a diversity of actors that may change through time, and link regional and city networks to local interests.

Food production, ecosystem services and biodiversity: We can't have it all everywhere

Debate about how sustainable intensification and multifunctionality might be implemented continues, but there remains little understanding as to what extent they are achievable in arable landscapes. Policies that influence agronomic decisions are rarely made with an appreciation of the trade-offs that exist between food production, biodiversity conservation and ecosystem service provision. We present an approach that can reveal such trade-offs when used to assess current and future policy options that affect agricultural inputs (e.g. pesticides, nutrients) and practices. In addition, by demonstrating it in a pesticide policy context, we show how safeguarding a range of ecosystem services may have serious implications for UK food security. We suggest that policy change is most usefully implemented at a landscape scale to promote multifunctionality, tailoring pesticide risk assessment and incentives for management that support bundles of ecosystem services to specific landscape contexts. In some instances tough trade-offs may need to be accepted. However, our approach can ensure that current knowledge is used to inform policy decisions for progress towards a more balanced food production system.

Chapter 2:Ecosystem Services and Policy: A Review of Coastal Wetland Ecosystem Services and an Efficiency-Based Framework for Implementing the Ecosystem Approach

The Ecosystem Approach (EA) to environmental management aims to enhance human well-being within a linked social and ecological system, through protecting the delivery of benefits and services to society from ecosystems in the face of external pressures such as climate change. However, our lack of understanding of the linkages between the human and natural components of ecosystems inhibits the implementation of the EA for policy decision-making. Coastal wetland systems provide many benefits and ecosystem services to humans, including nutrient recycling, climate and water quality regulation, timber, fuel and fibre, but they are under considerable threat from population pressure and climate change. In this chapter, we review the ecosystem services provided by coastal wetlands, and the threats to these services. We then present a new integrative conceptual framework to underpin the EA. The framework is divided into three sub-systems: one relating to ecosystem functions, one to ecosystem services, and one to social development and well-being. The pathways linking these sub-systems represent transfers of state, for example, ecosystem functions being transferred into ecosystem services, or ecosystem services being transferred into benefits. The focus of our approach is on enhancing the magnitude and efficiency of these transfers, by introducing or making use of any existing catalysts and overcoming any constraints in the system. The framework represents a dynamic system for implementing the EA in which interventions can be planned and managed in an adaptive way.

Optimising UK urban road verge contributions to biodiversity and ecosystem services with cost-effective management

Urban road verges can contain significant biodiversity, contribute to structural connectivity between other urban greenspaces, and due to their proximity to road traffic are well placed to provide ecosystem services. Using the UK as a case study we review and critically evaluate a broad range of evidence to assess how this considerable potential can be enhanced despite financial, contractual and public opinion constraints. Reduced mowing frequency and other alterations would enhance biodiversity, aesthetics and pollination services, whilst delivering costs savings and potentially being publically acceptable. Retaining mature trees and planting additional ones is favourable to residents and would enhance biodiversity, pollution and climate regulation, carbon storage, and stormwater management. Optimising these services requires improved selection of tree species, and creating a more diverse tree stock. Due to establishment costs additional tree planting and maintenance could benefit from payment for ecosystem service schemes. Verges could also provide areas for cultivation of biofuels and possibly food production. Maximising the contribution of verges to urban biodiversity and ecosystem services is economical and becoming an increasingly urgent priority as the road network expands and other urban greenspace is lost, requiring enhancement of existing greenspace to facilitate sustainable urban development.

Capitalizing on nature: how to implement an ecosystem approach.

The Natural Capital Initiative (www.naturalcapitalinitiative.org.uk) held its first conference ‘Valuing our life support systems’ at Savoy Place, London, from 29 April to 1 May 2009. The aim of the conference was to discuss different perspectives on, and solutions to, the conservation and sustainable use of ecosystem services. It particularly focused on the link between the environment and the economy, and how to implement an ecosystem approach to environmental management. This event brought together scientists across the natural and social sciences, alongside representatives from government, non-governmental organizations, business and industry.