Effects of forest fragmentation on biodiversity in the Andes región = Efectos de fragmentación de los bosques sobre la biodiversidad en la Región de los Andes.

Abstract

Since rapid economic development, natural system decline and fragmentation is one of the core drivers of global change and has huge implications for ecosystem functioning and conservation. The impacts of habitat fragmentation can arise in the face of primarily biotic change, primarily abiotic change and a combination of both, including extinction, disruption of trophic interactions and increased susceptibility to disturbances (e.g. logging, fires and invasive species) (Holl and Aide 2011; Laurance et al. 2002; Letcher and Chazdon 2009; Turner 2010a). Some changes result in species extinction and system degradation retaining some original characteristics as well as novel elements, whereas larger changes will result in system replacement or collapse. Against this background, the present study aimed to analyze the effects of habitat fragmentation on different levels of biodiversity including species, community and ecosystems.Previously the majority of efforts to conserve biodiversity have been focused on species, communities or their habitat under forest fragmentation, as well as on negative influences on species declines and extinctions. However, local extinction of different types of biodiversity can occur with a temporal delay following habitat fragmentation and such delay is called extinction debt. We assumed that the distribution of many vascular plant species in the Coastal Range of south-central Chile is not in equilibrium with the present habitat distribution. One of the aims of this research was to quantify patterns of habitat loss and to detect extinction debt from relationships between current richness of different assemblage of vascular plants (considering longevity and habitat specialization) and both of past and current habitat variables. Results showed that native forests have been fragmented and reduced by 53%, with annual deforestation rate of 1.99%, in the study area between 1979 and 2011. Current richness of plant species was mostly explained by past habitat area and connectivity. Past habitat variables explained best for richness of long-lived specialist plants, which are characterized by restricted habitat specialization and slower population turnover. We also showed that habitat fragmentation has resulted in a significant reduction in long-lived plant species’ Dwelling Patch Size (DPS) between 1979 and 2011.At ecosystem level, human have changed natural systems more rapidly and extensively than in any comparable period time in human history over the past 50 years. Despite previous studies indicated highest rates of deforestation and forest fragmentation in Ecuador, there was no clear relationship between the degree of forest ecosystem fragmentation and human land use to better design conservation strategies. We quantified and graphed forest fragmentation on different spatial scales, according to the results using GUIDOS, which measures forest fragmentation and classify forests into five main categories—intact, core, perforated, edge, and patch—based on Forest Area Density (FAD) in a given forest pixels. Our results showed that forest fragmentation in 64 forest ecosystems was mostly explained by pasture between 2008 and 2014. Although forest fragmentation became the dominant process in the Coast and Andes, rapid increase of number of patchy and rare FAD was observed in the Amazon during 1990-2014.