Slow response of plant species richness to habitat loss and fragmentation

Abstract

We examined the response of vascular plant species richness to long-term habitat loss and fragmentation of Estonian calcareous grasslands (alvars). The current number of habitat specialist species in 35 alvars was not explained by their current areas and connectivities but it was explained by their areas and connectivities 70 years ago (R(2) = 0.27). We estimated the magnitude of extinction debt in local communities by assuming an equilibrium species richness in 14 alvars that had lost only a small amount of area and by applying this model to the remaining alvars, in which the average area has declined from 3.64 km(2) in the 1930s to 0.21 km(2) at present. The extinction debt estimated for individual alvars was around 40% of their current species number. Our conclusions are applicable to temperate grasslands in general, which have lost much area because of agricultural intensification and cessation of traditional management.

Historical landscape structure affects plant species richness in wet heathlands with complex landscape dynamics

“…Studies of temporal dynamics in temperate, open, and seminatural habitats have systematically addressed general patterns of area decrease and isolation increase resulting from habitat fragmentation (Adriaens et al, 2006;Helm et al, 2006;Lindborg and Eriksson, 2004), whereas little attention has been paid to the potential contribution of secondary habitat origins through time (but see Arroyo-Mora et al, 2004;Jacquemyn et al, 2003). Our study demonstrated that spatial changes in wet heathlands, poor fens and bogs spanning the last 250 years resulted from two processes acting jointly: destruction and origin of habitat patches.…”

“…Piessens and Hermy (2006) suggested that a low species loss rate in highly fragmented north Belgium heathlands may be the result of an extinction debt, but provided no direct test for this hypothesis. However, some studies in semi-natural grasslands have reported evidence of an extinction debt (Gustavsson et al, 2007;Helm et al, 2006) but other studies have not provided supporting data (Adriaens et al, 2006).…”

“…This temporal distance between fragmentation (cause) and extinction (effect) may lead to an erroneous evaluation of species sensitivity to habitat fragmentation (Adriaens et al, 2006;Gustavsson et al, 2007;Helm et al, 2006;Lindborg and Eriksson, 2004). Although our target habitats are of high conservation value in Europe, no study has explicitly tested for an extinction debt in the plant communities they host.…”

“…In addition, most studies address either total (e.g. Lindborg and Eriksson, 2004) or specialist species richness (Eriksson et al, 1995;Helm et al, 2006), rarely both. The few studies that have tested for a different effect of habitat structure on generalist versus specialist species have generated inconsistent results (Honnay et al, 1999b;Jonsen and Fahrig, 1997;Krauss et al, 2004), and no generalization can yet be reached.…”

Assessment of wild boar rooting on ecological and pastoral values of alpine pyrenean grasslands

“…Alongside with this trend, a sharp decline of extensive husbandry has occurred in the last decades in favour of more productive intensive farming systems (Luick, 1998;Körner, 1999). In particular, this last trend has been related with drastic changes in the ecosystem structure, such as shrub encroachment and forest recolonization (Lasanta-Martínez et al, 2005;Lasanta-Martínez et al, 2006), what in turn may increase fire events (Carcaillet et al, 2009), reduce biodiversity (Helm et al, 2006), and boost some forest animal populations beyond an equilibrium threshold (Laiolo et al, 2004).…”