A Niche-Based Framework to Assess Current Monitoring of European Forest Birds and Guide Indicator Species' Selection

Amy S I Wade,Simon J Butler,Petr Vorisek,Taoyang Wu,Ian J Burfield,Boris Barov,Ken Norris,Richard D Gregory,Louis-Felix Bersier

doi:10.1371/journal.pone.0097217

Abstract

Concern that European forest biodiversity is depleted and declining has provoked widespread efforts to improve management practices. To gauge the success of these actions, appropriate monitoring of forest ecosystems is paramount. Multi-species indicators are frequently used to assess the state of biodiversity and its response to implemented management, but generally applicable and objective methodologies for species' selection are lacking. Here we use a niche-based approach, underpinned by coarse quantification of species' resource use, to objectively select species for inclusion in a pan-European forest bird indicator. We identify both the minimum number of species required to deliver full resource coverage and the most sensitive species' combination, and explore the trade-off between two key characteristics, sensitivity and redundancy, associated with indicators comprising different numbers of species. We compare our indicator to an existing forest bird indicator selected on the basis of expert opinion and show it is more representative of the wider community. We also present alternative indicators for regional and forest type specific monitoring and show that species' choice can have a significant impact on the indicator and consequent projections about the state of the biodiversity it represents. Furthermore, by comparing indicator sets drawn from currently monitored species and the full forest bird community, we identify gaps in the coverage of the current monitoring scheme. We believe that adopting this niche-based framework for species' selection supports the objective development of multi-species indicators and that it has good potential to be extended to a range of habitats and taxa.

Highlights

The majority of European forests are semi-natural ecosystems, heavily influenced by anthropogenic management and exploitation [1,2]
58 species are currently covered by PECBMS, together exploiting 172 of the 191 resources types used by the full community
The average sensitivity score of the optimal combination within each indicator set size category decreased with increasing indicator set size to a minimum value of 16.4 for SENSITIVE, which included 40 species (Fig. 2, Table S5); beyond this, average sensitivity scores increased and the indicator became less sensitive with increasing set size

Summary

Introduction

The majority of European forests are semi-natural ecosystems, heavily influenced by anthropogenic management and exploitation [1,2]. To assess the success of resultant modifications to management practice in counteracting the detrimental impacts of existing or emergent drivers of biodiversity decline, appropriate monitoring of forest ecosystems is paramount. Ecological indicators are a useful and widely adopted tool for assessing biodiversity health and ecological change [7,8]. They measure trends of a proportion of the ecological community with the aim of providing a representative portrayal of the state of the wider community. The characteristics of a good indicator have been widely discussed and a number of key attributes have been identified [8,9]. Applicable and objective methodologies for species’ selection are frequently lacking, as are methods for assessing whether existing indicators are fit for purpose

Methods

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Discussion

Conclusion