Habitats on the grid: The spatial dimension does matter for red-listing

Abstract

a b s t r a c tBesides species Red Lists, recently, a variety of frameworks have been proposed for assessing higher levels of biological organisation, i.e. ecosystems, habitats, plant communities. Most of these protocols refer to 'plant species assemblages' or 'vegetation types' as proxies for ecosystems or habitats. Indeed, the habitat concept based on plant communities has acquired a central role as a key approach for biodiversity conservation above the species level. Plant communities, like every complex biological system, hold scaledependent 'emergent' properties which vary as a function of the scale of observation. With reference to red-listing, these scale-dependent properties have far-reaching consequences for both identification and classification, as well as for representation and evaluation, and become particularly challenging when dealing with criteria regarding decline in distribution or restricted distribution. The recent discussion on the red-listing protocols has evidenced several aspects that claim special efforts for a suitable use. In the present paper, starting with the analysis of some recently proposed protocols for the red-listing of habitats and ecosystems, we discuss and test some 'emergent' properties of species assemblages, providing cues for reflection. Based on a variety of theoretical models and scientific outcomes in literature from the last decades, we theorise that plant communities own some intrinsic, ecologically based and scale-dependent spatial features, which give rise to different types of pattern of spatial occupancy. We discuss a model where, in natural conditions, the possible patterns of spatial occupancy are referred to 3 basic types: areal, linear and point. This approach is here proposed as a tool to discriminate among different broad categories of plant community-based habitat types and optimise their assessment in the red-listing process. Starting from a homogeneous data set, the proposed case studies prove that the choice of the scale affects the comprehension of the habitats' occurrence, with a substantial relapse on the estimates of their distribution size. In particular, habitats with linear and point distribution, often naturally small in size and dispersed, are more susceptible to biased evaluation of their actual distribution and consequently of their threat status. The intrinsic spatial attributes of plant communities should not be neglected in a red-listing process and claim for a 'habitat-tailored' approach. The use of different gridcell sizes and thresholds for the three main patterns of spatial occupancy here proposed, might certainly avoid inaccurate statements.

Latitudinal patterns and environmental drivers of moss layer cover in extratropical forests

“…Importantly, our analyses suggested that forest moss cover reported in the literature for temperate broadleaf forests tends to overestimate moss cover compared with the estimates obtained by systematic surveys, suggesting a potential bias towards higher moss cover values in studies focused on moss communities of temperate broadleaf forests—possibly attributable to selection of moss‐rich sites or microsites in areas where moss cover is variable but generally less abundant (Cavard et al, ). Then, the spatial heterogeneity of the moss layer might be higher compared with that of its hosting forest, as expected from the variability of spatial heterogeneity across scales (Gigante, Foggi, Venanzoni, Viciani, & Buffa, ; Palmer, ). Notably, the bias of published studies towards higher moss abundance was not present in the boreal coniferous forests, where moss was much more abundant than in the temperate broadleaf forests (cf.…”

Natura 2000 protected habitats, Massaciuccoli Lake (northern Tuscany, Italy)

“…Habitats, in the pragmatic definition given in European Directives (Commission of the European Community, 1992;European Commission, 2013;Evans, 2006Evans, , 2010, are considered to be a cornerstone of European nature conservation policy, because the maintenance of a series of habitats in good condition is one of the best ways to conserve species and biodiversity (Berg et al, 2014;Bunce et al, 2013;Evans, 2012;Gigante, Foggi, Venanzoni, Viciani, & Buffa, 2016;Kontula & Raunio, 2009;Nicholson, Keith, & Wilcove, 2009;Rodríguez et al, 2011Rodríguez et al, , 2012Rodríguez et al, , 2015.…”

Scaling range sizes to threats for robust predictions of risks to biodiversity

“…; Gigante et al. ). Gaston and Fuller () note “significant confusion in the literature over the measurement and interpretation of geographic ranges, and … that [spatial metrics used in red listing] should not be regarded as more or less accurate ways of measuring range size.” The evidence from our risk analyses should help resolve confusion between the application of AOO on one hand as a measure of occupied habitat in biogeographic analysis and on the other hand as an indicator of risk in red‐list assessments.…”

“…(), and Gigante et al. (). Authors of each of these studies claim that AOO measured at recommended scales under‐ or overestimate risks, but none attempt to quantify risks or explore how the spatial features of threats influence risks through their interactions with those of biological distributions.…”

“…; Gigante et al. ). First, we reviewed the theoretical basis for range‐size metrics in red‐list criteria.…”