The response of faunal biodiversity to an unmarked road in the Western Amazon

Abstract

Roads are an increasingly common feature of forest landscapes all over the world, and while information accumulates regarding the impacts of roads globally, there remains a paucity of information within tropical regions. Here we investigate the potential for biodiversity impacts from an unmarked road within a rainforest protected area in Western Amazonia. We focus on three key taxonomic groups; amphibians, butterflies and birds, each of which have been shown to be both sensitive and reliable indicators of forest disturbance. In total, 315 amphibians of 26 different species, 348 butterflies of 65 different species, 645 birds representing 77 different species were captured using mist netting and 877 bird records representing 79 different species were recorded using point counts. We provide evidence to show that the presence of a small unmarked road significantly altered levels of faunal species richness, diversity, relative abundance and community structure. This was true to a varying degree for all three taxa, up to and potentially beyond 350 m Communicated by Dirk Sven Schmeller.Electronic supplementary material The online version of this article (into the forest interior. Responses to the road were shown to be taxon specific. We found increasing proximity to the road had a negative effect on amphibian and understorey bird communities, whilst butterfly and overall diurnal bird communities responded positively. We show that the impact on biodiversity extends up to at least 32 % of the whole reserve area; a serious impact under any scenario. This work provides support for recently voiced calls to limit networks of unmarked roads in order to realistically and effectively preserve natural levels of tropical biodiversity.

Secondary forest is utilized by Great Curassows (Crax rubra) and Great Tinamous (Tinamus major) in the absence of hunting

“…In order to ensure that any effects detected were directly related to differences in habitat type, we investigated the potential influence of 4 other key covariates that could influence habitat use by tropical game birds: roads, rivers, elevation, and camera placement on or off trails. Rainforest roads are known to widely influence biodiversity patterns as a result of hunting access, edge effects, and changes in fruit distribution patterns (Martínez-Morales 1999, Whitworth et al 2015, Gon¸calves da Silva 2017. Largebodied terrestrial birds have been found to associate with either riparian forest systems or terra firme interior forest (Martínez-Morales 1999, Haugaasen andPeres 2008).…”

Food for thought. Rainforest carrion-feeding butterflies are more sensitive indicators of disturbance history than fruit feeders

“…For example, mist nets and point count methods used to assess the response of bird communities to tropical forest disturbance in Brazil have displayed contrasting responses of bird species richness (Barlow et al 2007b). Likewise, an assessment of the impact of an unmarked road on bird biodiversity in the Ecuadorian Amazon found a negative response using mist nets, while point counts detected greater biodiversity near to the road (Whitworth et al 2015).…”

Past Human Disturbance Effects upon Biodiversity are Greatest in the Canopy; A Case Study on Rainforest Butterflies

“…[ 64 ]), address questions over much larger regions and seek to include the effects of natural heterogeneity due to locality differences in climate, soil types and general topography, so that these effects can be investigated. In contrast, in order to answer specific questions about differences between one type of treatment and another, as in the case of on-trail vs. off-trail [ 65 ], near to a road vs. far from a road [ 59 ], or high altitude vs. lower altitude [ 66 ], a within-site scale approach of the type we adopted here is often more desirable; as it eliminates large scale drivers of heterogeneity. One potential complication of a small spatial scale is that transient species may enter adjacent treatment types temporarily [ 16 ].…”

“…Such plots compare the evenness of a community, with shallow curves representing a community of many species of similar abundance, whereas steep curves represent a skewed assemblage with one or more species in substantially higher abundance than others. Significant differences in slope, and therefore significant differences in community evenness, were assessed through the use of a linear model with log relative abundance of species as the response term, and an interaction between species rank and disturbance history or vertical zone as continuous and categorical fixed effects respectively (vegan package [ 58 ], function ‘rad.zipfbrot’; see [ 36 , 59 ]). Results are reported as ΔG, which corresponds to absolute change in gradient between disturbance areas and vertical strata, whereby more negative values denote steeper curves and thus less even assemblages [ 36 , 59 ].…”