Forest Loss and the Biodiversity Threshold: An Evaluation Considering Species Habitat Requirements and the Use of Matrix Habitats

Abstract

Habitat loss is the main driver of the current biodiversity crisis, a landscape-scale process that affects the survival of spatially-structured populations. Although it is well-established that species responses to habitat loss can be abrupt, the existence of a biodiversity threshold is still the cause of much controversy in the literature and would require that most species respond similarly to the loss of native vegetation. Here we test the existence of a biodiversity threshold, i.e. an abrupt decline in species richness, with habitat loss. We draw on a spatially-replicated dataset on Atlantic forest small mammals, consisting of 16 sampling sites divided between forests and matrix habitats in each of five 3600-ha landscapes (varying from 5% to 45% forest cover), and on an a priori classification of species into habitat requirement categories (forest specialists, habitat generalists and open-area specialists). Forest specialists declined abruptly below 30% of forest cover, and spillover to the matrix occurred only in more forested landscapes. Generalists responded positively to landscape heterogeneity, peaking at intermediary levels of forest cover. Open area specialists dominated the matrix and did not spillover to forests. As a result of these distinct responses, we observed a biodiversity threshold for the small mammal community below 30% forest cover, and a peak in species richness just above this threshold. Our results highlight that cross habitat spillover may be asymmetrical and contingent on landscape context, occurring mainly from forests to the matrix and only in more forested landscapes. Moreover, they indicate the potential for biodiversity thresholds in human-modified landscapes, and the importance of landscape heterogeneity to biodiversity. Since forest loss affected not only the conservation value of forest patches, but also the potential for biodiversity-mediated services in anthropogenic habitats, our work indicates the importance of proactive measures to avoid human-modified landscapes to cross this threshold.

An assessment of leaf-litter and epigaeic ants (Hymenoptera: Formicidae) living in different landscapes of the Atlantic Forest Biome in the State of Bahia, Brazil

“…In each plot, we disposed 10 sampling sites along a transect at intervals of 10 meters. At each site, we disposed four pitfall traps formed by plastic buckets of 35 liters distributed in Y (originally used for vertebrate collection [see Estavillo et al, 2013] and connected by a canvas strip close to the ground of 50 cm length and 15 cm height). Each pitfall was filled (one third of its volume) with a fixative liquid solution.…”

Dung beetle (Coleoptera: Scarabaeinae) persistence in Amazonian forest fragments and adjacent pastures: biogeographic implications for alpha and beta diversity

“…Depending on the type and amount of forest cover, the adjacent matrix may exert a strong pressure on species selection, acting as a ''filter'' and selecting species with greater ability to disperse, or to remain in isolated forest patches (Umetsu et al 2008;Estavillo et al 2013). Therefore, matrix-tolerant species are less vulnerable to fragmentation and habitat isolation (Antongiovanni and Metzger 2005).…”

Personality and behavioural syndrome in Necromys lasiurus (Rodentia: Cricetidae): notes on dispersal and invasion processes

“…Henriques and Alho 1991;Bonvicino et al 2002;Santos and Henriques 2010). The species occurs in all sorts of open areas and is currently abundant in anthropogenic vegetation (agriculturally managed and pasture areas) and in very disturbed areas within the Atlantic Forest biome in ecotone zones (Bonvicino et al 2002(Bonvicino et al , 2008Estavillo et al 2013), expanding regionally its distribution to these newly disturbed areas produced by anthropic activities. This fact prompts us to suggest that N. lasiurus could be considered a reasonable natural ethological model to invasion processes studies, despite not being considered an invasive 1 species sensu stricto.…”