Atlantic forest bird communities provide different but not fewer functions after habitat loss

Abstract

Habitat loss often reduces the number of species as well as functional diversity. Dramatic effects to species composition have also been shown, but changes to functional composition have so far been poorly documented, partly owing to a lack of appropriate indices. We here develop three new community indices (i.e. functional integrity, community integrity of ecological groups and community specialization) to investigate how habitat loss affects the diversity and composition of functional traits and species. We used data from more than 5000 individuals of 137 bird species captured in 57 sites in the Brazilian Atlantic Forest, a highly endangered biodiversity hotspot. Results indicate that habitat loss leads to a decrease in functional integrity while measures of functional diversity remain unchanged or are even positively affected. Changes to functional integrity were caused by (i) a decrease in the provisioning of some functions, and an increase in others; (ii) strong within-guild species turnover; and (iii) a replacement of specialists by generalists. Hence, communities from more deforested sites seem to provide different but not fewer functions. We show the importance of investigating changes to both diversity and composition of functional traits and species, as the effects of habitat loss on ecosystem functioning may be more complex than previously thought. Crucially, when only functional diversity is assessed, important changes to ecological functions may remain undetected and negative effects of habitat loss underestimated, thereby imperiling the application of effective conservation actions.

Using avian functional traits to assess the impact of land-cover change on ecosystem processes linked to resilience in tropical forests

“…However, it is becoming increasingly clear that the raw number and even heterogeneity of species surviving in communities may be poor indices of functional aspects of biodiversity [12,13], including the trophic interactions needed to maintain recruitment and gene flow in rainforest trees [14,15]. Consequently, the implication of land-cover change for the health and stability of tropical forest ecosystems, and their ability to recover from human-driven perturbations, is still largely unclear [16][17][18].…”

“…One advantage of quantifying multiple functional traits as continuous variables, rather than the categories adopted by many studies [13,18], is that we can visualize the effects of land-cover change on the structure of communities. We plotted the species in multivariate trait space (hereafter termed 'morphospace') to assess the volume and density of functional traits in different land-cover categories.…”

Forest fragmentation on the national forest of irati bufferzone – Brazil

“…Este autor, Prist et al (2012) (DE COSTER et al, 2015), foi comprovado que certas espécies são restritas a fragmentos, sendo incapazes de atravessar a matriz agrícola. Para certos anfíbios e aves típicas de sub-bosque e estritamente florestais, é recomendado que sejam protegidas grandes manchas, ao invés de muitos pequenos e médios fragmentos isolados ou mesmo conectados por trampolins ou corredores estreitos (HANSBAUER et al, 2008;DE COSTER et al, 2015;ALMEIDA-GOMES et al, 2016). Seja como for, o entorno da FLONA de Irati está fragmentado, com manchas de hábitat de diversos tamanhos, e a manutenção destes torna-se importante para táxons dependentes de florestas e que exercem funções ecossistêmicas importantes.…”

“…A redução da biodiversidade como consequência da fragmentação (DE COSTER et al, 2015) ocorre por dois processos: em curto prazo, a perda de espécies é imediata após o evento, como o desmatamento; o outro, em médio e longo prazo, através do isolamento (PAGLIA et al, 2006). Ocorre então um aumento na proporção de áreas de borda; a área central de um fragmento, aquela não afetada pelo efeito de borda, pode ser a única adequada para certas espécies (op.…”

“…cit.). Assim, paisagens muito fragmentadas e com florestas em fases iniciais de regeneração não são capazes de satisfazer toda a demanda humana por serviços ecossistêmicos (FERRAZ et al, 2014;DE COSTER et al, 2015).…”