The effects of human disturbance on vascular epiphyte in the Brazilian Atlantic Forest

Abstract

The high pressure that anthropogenic activities places on tropical forests are pushing species and communities to the brink of local, regional or global extinctions. However, the consequences of the loss of species and their ecosystem functions are not well known. My thesis addresses the causes and consequences of human disturbance on vascular epiphytes in the Brazilian Atlantic forest (BAF). I sampled understory and canopy, across a gradient of habitat loss, i.e. pastureland, human-modified forests (HMFs) and old-growth forest. I found that habitat loss has driven a net loss of 91% of species exclusive to old-growth, and 90% of individuals. I also found the edge effect to be a ubiquitous landscape process extending at least 500 m within forests habitats, leaving just 19.4% of the whole of the BAF suitable for forest-dependant epiphytes. However, whilst endemic species (habitat specialised species) are more prone to disappear as consequence of habitat loss, species with larger dispersal ranges and the ability to colonize different forest types flourish or endure the harsh conditions after disturbance. Consequently, HMFs have low functional richness and low functional redundancy, meaning low resilience, whereas old-growth forests exhibit high ecological resilience. Habitat transformation also leads to the loss of a large set of ecosystem functions related to pollination and water cycling across strata. Hence preserving large continuous forests are probably the only pragmatic conservation strategy for vascular epiphytes in highly human-modified landscapes. However, human-modified forests still provide limited ecosystem functions that may increase because of initiatives to improve habitat amount.