Beyond the Fragmentation Threshold Hypothesis: Regime Shifts in Biodiversity Across Fragmented Landscapes

By R. Pardini, A. Bueno, T. Gardner, P. Prado, J. Metzger. PLoS ONE, 2010

606 citations recorded by the source corpus.

Ecological systems are vulnerable to irreversible change when key system properties are pushed over thresholds, resulting in the loss of resilience and the precipitation of a regime shift. Perhaps the most important of such properties in human-modified landscapes is the total amount of remnant native vegetation. In a seminal study Andrén proposed the existence of a fragmentation threshold in the total amount of remnant vegetation, below which landscape-scale connectivity is eroded and local species richness and abundance become dependent on patch size. Despite the fact that species patch-area effects have been a mainstay of conservation science there has yet to be a robust empirical evaluation of this hypothesis. Here we present and test a new conceptual model describing the mechanisms and consequences of biodiversity change in fragmented landscapes, identifying the fragmentation threshold as a first step in a positive feedback mechanism that has the capacity to impair ecological resilience, and drive a regime shift in biodiversity. The model considers that local extinction risk is defined by patch size, and immigration rates by landscape vegetation cover, and that the recovery from local species losses depends upon the landscape species pool. Using a unique dataset on the distribution of non-volant small mammals across replicate landscapes in the Atlantic forest of Brazil, we found strong evidence for our model predictions - that patch-area effects are evident only at intermediate levels of total forest cover, where landscape diversity is still high and opportunities for enhancing biodiversity through local management are greatest. Furthermore, high levels of forest loss can push native biota through an extinction filter, and result in the abrupt, landscape-wide loss of forest-specialist taxa, ecological resilience and management effectiveness. The proposed model links hitherto distinct theoretical approaches within a single framework, providing a powerful tool for analysing the potential effectiveness of management interventions.

Subfields: Ecology, Global and Planetary Change, Nature and Landscape Conservation

View Paper: https://www.semanticscholar.org/paper/3f9e8281df92a4163426a70fd5d76e33a09ab4b1

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Citations in the corpus

Biodiversity Response To Habitat Loss And Fragmentation (2017, background): “This is not to say that patch scale metrics are not important, but rather that their effects may depend on landscape context (e.g., Pardini et al., 2010).”
Traits related to species persistence and dispersal explain changes in plant communities subjected to habitat loss (2012, background): “A majority of grassland species might, in other words, be equally and highly dispersal limited irrespective of their traits (Pardini et al., 2010), that is, in several regions even relatively large values of connectivity indicated situations of dispersal limitation.”
Landscape and patch attributes impacting medium- and large-sized terrestrial mammals in a fragmented rain forest (2013, background): “Nevertheless, these effects depend on the landscape spatial context (e.g. percentage of remaining forest cover: Arroyo-Rodrı́guez et al. 2009, Bender & Fahrig 2005, Pardini et al. 2010; matrix quality: Fahrig et al. 2011, Prugh et al. 2008; landscape connectivity: Taylor et al. 1993).”
Retention Forestry to Maintain Multifunctional Forests: A World Perspective (2012, background): “…interventions for conservation have their greatest relative effects in landscapes with intermediate amounts of remaining natural vegetation (Pardini et al. 2010), whereas others suggest that July 2012 / Vol. 62 No. 7 www.biosciencemag.org landscape-level reserves within forest production…”
Indirect effects of habitat loss via habitat fragmentation: A cross-taxa analysis of forest-dependent species (2020, background): “to be caused by an exponential increase of inter-fragment distances (Andrén, 1994; Fahrig, 2003), which is supported by a variety of studies on species richness (e.g., Andrén, 1994; Pardini et al., 2010), community dissimilarity (e.”
Positive responses of flower visiting bees to landscape heterogeneity depend on functional connectivity levels (2017, background): “This indicates that the system we observed might be governed by strong regime shifts according to landscape structure (Pardini et al., 2010; Ferreira et al., 2015).”
Forest loss or management intensification? Identifying causes of mammal decline in cacao agroforests (2014, background): “Responses of individual species and species assemblages to changes in local forest cover may depend on landscape context, which can influence landscape connectivity and the species pool (Andrén, 1994; Pardini et al., 2010).”
Ecological and evolutionary consequences of living in a defaunated world (2013, background): “scientists have focused their attention on the effects of land-use change – habitat loss, degradation and fragmentation – as one of the main drivers of biodiversity loss (Bierregaard et al., 1997; Fahrig, 2003; Pardini et al., 2010).”
Habitat fragmentation and species richness (2015, background): “To take a real example, Pardini et al. (2010) have reported on the occurrence of non-volant forest specialist small mammal species in multiple landscapes of 100 km2 in the Atlantic forest in Brazil.”
Avian biodiversity in multiple-use landscapes of the Brazilian Amazon (2013, background): “influence on local species distribution patterns (e.g. Bennett et al., 2006; Pardini et al., 2010).”
Testing the habitat amount hypothesis for South American small mammals (2017, background): “A case in point is protection laws for the Cerrado in Brazil.”
Impact of landscape composition and configuration on forest specialist and generalist bird species in the fragmented Lacandona rainforest, Mexico (2015, background): “…the region (>40% of forest cover), which means that the remaining forest patches tend to be large, presenting a high landscape connectivity, thus facilitating inter-patch animal movements (see Ewers and Didham, 2006; Fischer and Lindenmayer, 2007; Pardini et al., 2010; Villard and Metzger, 2014).”