Forest fragmentation and its associated edge-effects reduce tree species diversity, size, and structural diversity in Madagascar’s transitional forests

Abstract

Tropical forests are being cleared at an accelerating rate, despite being one of the most important habitats for global biodiversity. Many remaining tropical forest tracts are now highly degraded and fragmented, which presents a major problem for sensitive and threatened forest-dwelling species that depend on this habitat for survival. In this study, we assessed the impacts of forest fragmentation, and its associated edge-effects, on tree species diversity, tree size, and structural diversity within the transitional forests of north west Madagascar. Using data collected from 9,619 trees within 200 vegetation plots, we calculated species diversity indices, a range of dendrometry measurements, and Shannon-Weaver diversity indices of structure, which we compared among core and edge areas of a continuous forest and a fragmented forest. We found that species diversity, tree size, and structural diversity was significantly reduced in fragmented forest, and within forest edge areas in comparison to core, continuous forest. We also observed species diversity and structural diversity to be strongly influenced by the total size, core area size, and shape of forest fragments. Whilst we found fragmentation and edge-effects to individually impact tree species diversity, size and structural diversity, fragmentation and edge-effects are strongly correlated and affect natural forest synergistically. Our results provide evidence that forest fragmentation seriously degrades habitat quality and integrity of transitional forests, which is of great concern for the threatened species that inhabit them. Urgent conservation efforts are needed to halt ongoing forest fragmentation throughout the tropics, and reforestation and restoration efforts are required to reconnect isolated forest patches and to reduce forest edge area.

Effects of forest fragmentation on the dietary ecology and activity of a nocturnal lemur community in North West Madagascar

“…As our study‐species can adapt their feeding behavior to available food sources, they likely did not need to allocate a significantly larger portion of their activity toward feeding or foraging for suitable food (but see results for L. sahamalaza and M. sambiranensis ). Second, our study‐species are present within both core and edge areas of each forest (but see Hending, Randrianarison, et al, 2022), and densities appear somewhat consistent throughout. Encounter rates with conspecifics is therefore likely to be similar among study areas for each species, resulting in similar levels of social behavior within each forest and within both core and edge areas.…”

“…We also spread our survey effort for each species evenly throughout the study‐period, as available plant and invertebrate food items would likely vary significantly throughout the year and between seasons. As M. sambiranensis was only confirmed to inhabit Anabohazo forest at the time of our study (Hending, Randrianarison, et al, 2022), we were not able to collect any data for this species from Ankarafa. We conducted our behavioral follows for the first half of the night only, as there is little qualitative evidence of differences in activity level and feeding behavior in nocturnal lemurs between the first and second halves of the night (Dammhahn & Kappeler, 2008; Mandl et al, 2018).…”

Forest fragmentation and edge effects impact body condition, fur condition and ectoparasite prevalence in a nocturnal lemur community

“…, 2014 ), and the fragmented Ankarafa forest, a 1020 Ha forest comprising many fragments of varying size, shape and forest edge-core ratios ( Supplementary File S1 ). Secondly, vegetation plots measuring tree species diversity, size and forest structural diversity ( Hending et al. , 2023a ), and transects measuring the variation of microclimatic and abiotic variables (temperature, humidity and light intensity) from the forest edge into the forest core ( Mandl et al.…”

Unravelling the dynamics: Large mammal occupancy modelling in a West African tropical forest

“…Human activities, such as logging and agriculture, significantly contribute to these issues (Scanes, 2018). Roads and agriculture disrupt once-intact canopies, making species vulnerable to predators, competitors, and invasive species, impacting both biodiversity and human communities reliant on forests (Hending et al, 2023). Comprehensive conservation approaches are imperative to address biodiversity preservation and the coexistence of human societies and ecosystems.…”

“…Isolated patches restrict wildlife mobility, creating barriers to essential activities like breeding and foraging, resulting in inbreeding, genetic isolation, and increased extinction risk (Hending et al, 2023).…”