Forest Loss, Fragmentation and Climate Change: Mammals in a Changing Amazon Landscape
- Gomes da Rocha, Daniel
- Advisor(s): Sollmann, Rahel
The Amazon represents over half of the world’s remaining tropical forests, which host a disproportional amount of the world’s biodiversity. Like most tropical forests, the Amazon is suffering unprecedented threats, including deforestation, indiscriminate use of fire, and climate change effects. As continuous tropical forests are progressively converted to human dominated landscapes, forests become smaller and fragmented. This process happens in concert with effects of climate change that can synergistically affect forest persistence, as well as forest-associated wildlife. These processes are particularly pronounced in the southern Brazilian Amazon. The region is part of the Arc of Deforestation, the area with the highest deforestation rates in the Brazilian Amazon. Moreover, modeling experiments predict that the region will experience landscape scale vegetation conversion from forest to open habitats (known as “savannization”) due to climate change. These habitat changes are predicted to affect wildlife distribution, occurrence, demography, and persistence. In this dissertation, I present three studies that assess the impacts of deforestation and climate-driven habitat changes on Amazon wildlife, with a focus on terrestrial mammals. In the first chapter, I predicted effects of forest loss and fragmentation on the distribution of the short-eared dog (Atelocynus microtis), the only Amazon-endemic canid. I compiled the largest record database for short-eared dogs and used it in combination with species distribution models to map species habitat suitability, estimate its distribution range and predict shifts in distribution in response to predicted deforestation across the Amazon basin. I further used camera trap surveys and occupancy models to investigate how forest cover and forest fragmentation affect space use of this species in the southern Brazilian Amazon. Species distribution models suggested approximately 30% of the short-eared dog’s current distribution is expected to be lost or suffer sharp declines in habitat suitability by 2027 (within three generations) due to forest loss. This proportion might reach 40% in unprotected areas and exceed 60% in some regions of the Amazon basin. Locally, the presence of forest positively affected short-eared dog space use, while density of forest edges had a negative effect. Results from the first chapter stress that forest loss poses a serious threat to the conservation of the species in a short time frame. Hence, I propose a re-assessment of the short-eared dog’s current ‘Near Threatened’ IUCN Red List status. In chapter 2, I combined a landscape-scale camera trap survey of terrestrial mammals and ground-dwelling birds in forest fragments with community occupancy modeling to estimate species-specific and community-level responses to forest loss and fragmentation across a rapidly changing fragmented forest landscape in the southern Brazilian Amazon. I contrasted the community with that from nearby continuous forest. As expected, both the extent and connectivity of forest cover were important and positive predictors of the occurrence of many species. Despite its large degree of forest loss and fragmentation, however, the fragmented landscape still hosted a comprehensive terrestrial vertebrate community, even though several species showed declines in their occupancy probabilities relative to continuous forest. Declines were most evident in large ungulates, which are involved in key trophic processes and therefore of conservation concern. The analysis highlights that in spite of the negative effects of forest loss and fragmentation, forest fragments in human-dominated landscapes have the potential to contribute to maintaining terrestrial vertebrate diversity in the Amazon. In chapter 3, I aimed to identify the terrestrial mammal species potentially most at risk from climate-driven savannization in southern Amazonia by studying their use of natural forest and savanna habitats within four protected areas, using systematic camera trap surveys and community occupancy models. Models showed that savanna habitat affected space use of most species strongly negatively. Only species whose distribution is predominantly associated with the Brazilian savanna (Cerrado) biome ever showed strong positive responses to savanna habitat. Although less favorable than continuous forest, riparian forest had a strong negative effect on space use for only a small fraction of species, indicating that negative effects of savannization may be buffered to some extent by riparian forests, which are less sensitive to climate change. Results suggest that most of the terrestrial mammal community is potentially vulnerable to the predicted climate-change induced savannization, including several species typically considered habitat generalists. This may reduce the future ability of protected areas to safeguard populations of terrestrial mammals in the face of ongoing deforestation in the region. Overall, these studies show that forest loss and fragmentation due to global change affect wildlife in the Amazon across spatial scales (distribution-wide, regional, local) and serve as a warning that further forest loss in the southern Brazilian Amazon will negatively impact its terrestrial vertebrate community.