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Abstract :
[en] To quote President Barack Obama, at the United Nations Climate Change Summit in 2014, “There is one issue that will define the contours of this century more dramatically than any other, and that is the urgent threat of a changing climate”. Mounting evidence has shown the impacts a changing climate has on species, flora and fauna – it can provoke changes in distributions, physiology, phenology, and behaviours, which in turn can lead to extinctions within the natural world, and a subsequent loss of ecological processes. The Brazilian Atlantic Forest (BAF), once stretching continuously from northern Brazil to northern Argentina is now heavily fragmented, and could be a portentous indicator for other ecosystems that also experience degradation. As the forest is converted, endemic fauna and flora lose their habitats, and various functions that maintained the ecosystems are also under threat. The small-bodied, endemic Leontopithecus chrysomelas can play a starring role in our understanding on what happens to regenerative processes in heavily defaunated and degraded forests. This thesis considers potential impacts of climate change on tree species distribution in the BAF, focused on seed dispersal and plant-animal interactions as a symptom of ecosystem functionality, and finally propose a method to incorporate seed dispersal into vegetation modelling, and use the outputs to consider how to implement various conservation and policy measures.
MaxENT (Maximum Entropy model – an ecological niche-based model) results for two future scenarios in four general circulation models suggest that up to 75% of the species risk losing more than half of their original distribution. CARAIB (CARbon Assimilation in Biosphere dynamic vegetation model) simulations are more optimistic in scenarios with and without accounting for potential plant-physiological effects of increased CO2, with less than 10% of the species losing more than 50% of their range. Potential gains in distribution outside the original area do not necessarily diminish risks to species, as the potential new zones may not be easy to colonise. It will also depend on the tree species’ dispersal ability. This research highlights the importance of choosing the appropriate modelling approach and interpretation of results to understand key processes.
Our results from the field suggests that the dispersal behaviour and short daily-trajectories of L. chrysomelas (golden headed lion tamarins; GHLTs) may play a small role in regeneration of the forest because it is only a short-range disperser. Nevertheless, it probably contributes to increase the prevalence of its resource tree species locally, and thus likely to have a function in maintaining tree diversity by preventing local extinction.
In this field site, we were fortunate to have observed, sometimes only briefly, sloths, toucanets, tayras, kinkajous, hawks, various snake species (including one potentially mimicking the coral snake), and my field assistant (who had previously worked with Sapajus xanthosternus for 10+ years) confirmed that he heard vocalisations of the capuchins one morning. Additionally, the few evenings when the GHLTs were late arrivals to their sleeping sites, bats (unrecognisable to me at species level) were also seen flying around the trees. It was also always amusing to see beautifully intricate little frogs jumping up from puddles after rainy evenings. While defaunation and degradation are problems and must be confronted, it can be hopeful to know that even these areas can be home to the intrepid, beautiful, slithery, diversity that makes the BAF the hotspot it is.
The principal conclusion from both modelling and field work, is that conservation actions, both in the field, and at policy levels are mandatory for the conservation and functionality of the Brazilian Atlantic Forest.
