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Saturday, 18 May 2013

Land abandonment and the decline of the Yellow-bellied toad in Liguria, northern Italy

Across Europe, centuries of interactions between low-intensity human activities, such as extensive small-scale farming, and the surrounding environment have created what we now call “cultural landscapes”, which provide important ecosystem services and often support a rich biodiversity. However, since the second half of the 20th century several countries have witnessed large-scale social changes that have led to modifications in these landscape dynamics. There is growing evidence that this can also entail an impact to biodiversity, as the intermediate disturbance that can benefit species is lost or replaced by more disruptive activities (such as intensive vs. extensive farming: MacDonald 2000).

These same dynamics may be a leading factor in the disappearance of the yellow-bellied toad Bombina pachypus from peninsular Italy (Figure 1). The species has declined in the last thirty years and is now listed as Endangered by the IUCN. However, the causes of this decline are still unclear: in Liguria, northern Italy, habitat loss is believed to be the main driver, with recent systematic monitoring for the amphibian fungal disease chytridiomycosis failing to detect signs of this devastating pathogen (Canessa et al, in press).

Figure 1. The Apennine Yellow-bellied toad Bombina pachypus (photo: A. Arillo)   
In a recent study, we monitored sites across the region that were known to host the species until 2005: these were a combination of artificial sites (stone washtubs) and natural sites (small mountain creeks). We found that only five years later, in 2010, more than 50% of the populations had disappeared. When we searched for common traits among the sites where local extinctions had occurred, we found they had high densities of predators (dragonflies and newts), low insulation and dense vegetation. These in turn were linked to disturbance, with more frequent flooding and desiccation cycles beneficial in removing vegetation and predators and favouring tadpole survival.

In natural sites, flooding and desiccation are natural processes, and where they continue the species still occurs in relatively large numbers. On the other hand, in artificial sites disturbance is provided by traditional management (cleaning and dredging) (Figure 2): after land parcels or traditional practices are abandoned, sites degrade rapidly and become unsuitable. Significantly, in our study all artificial sites that had been abandoned by farmers immediately prior to or after 2005 did not host toad populations when we re-sampled them. Artificial sites that were still maintained (and therefore disturbed) were still occupied by the species. 

Figure 2. The transition between a maintained artificial water body (left) and an abandoned one unsuitable for yellow-bellied toads (right) can occur within a few years (photos: S. Canessa)
This preference for disturbed sites matches observations for other yellow-bellied toads in Europe (Warren and Büttner, 2008), provides significant information for local conservation actions, and suggests the need to link ecological and socio-economic objectives: for example, in Liguria current efforts for the conservation of the yellow-bellied toad focus on the integration of traditional practices and biodiversity conservation in new forms of human activities, such as sustainable farming or eco-tourism. On the basis of this study, the Regional Park of Monte Marcello – Magra is coordinating a project, funded by the regional administration of Liguria, which includes the recovery of several semi-natural sites and the creation of new artificial sites that can be used by local farmers whilst providing suitable habitat for the species.

The conservation of culture and biodiversity needs is deeply connected in many parts of Europe: this requires an approach that is somewhat contradictive of the usual point of view of human activities as inherently negative. However, where large scale processes such as land abandonment are involved, they may be difficult to reverse by conservation funding alone. However, where traditional practices are still widespread, it is imperative that social and environmental planning should take into account the impacts on biodiversity that the abandonment of such practices may entail.

Canessa, S.a, Oneto, F.b, Ottonello, D.b, Arillo, A.b and Salvidio, S.b (2013). Land abandonment may reduce disturbance and affect the breeding sites of an endangered amphibian in northern Italy. Oryx, 47(2): 280-287
a ARC Centre of Excellence for Environmental Decisions, School of Botany, University of Melbourne, 3010 Victoria, Australia  
b Dipartimento di Scienze della Terra, dell’Ambiente e della Vita, University of Genoa, Genoa, Italy

Cited references
Canessa, S., Martel, A. and Pasmans, F. (in press). No detection of chytrid in first systematic screening of Bombina variegata pachypus (Anura: Bombinatoridae) in Liguria, northern Italy. Acta Herpetologica.
MacDonald, D., Crabtree, J.R., Wiesinger, G., Dax, T., Stamou, N., Fleury, P., Gutierrez-Lazpita, J. and Gibon, A. (2000) Agricultural abandonment in mountain areas of Europe: environmental consequences and policy response. Journal of Environmental Management, 59: 47-69.
Warren, S.D. , Büttner, R. (2008): Relationship of endangered amphibians to landscape disturbance. The Journal of Wildlife Management 72: 738-744.

Contributed by Stefano Canessa, ARC Centre of Excellence for Environmental Decisions, School of Botany, University of Melbourne, 3010 Victoria, Australia
E-mail: canessas@unimelb.edu.au
Personal blog: http://www.canessas.wordpress.com

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