by Maithili Joshi
In South East Queensland, Australia Pavlacky et al.(2014) conducted a study on the vulnerability of birds, rainforest ecosystems, and the biological impacts in response to deforestation in local and regional areas. The central idea is the to investigate the life history and forest structure to rank the vulnerability of avian species, while also looking at species loss along different kinds of forest structure and landscape change. The objectives are evaluating the effects of life history traits on the patch occupancy and vulnerability of rainforest birds, determining the relative effects of stand, landscape, and patch structure on species richness, and evaluating the relative contributions of deforestation and fragmentation to species richness.
Packlacky et al. categorized 46 different rainforest patches into three different rainforest types: upland notophyll vine forest, lowland notophyll vine forest, and araucarian notophyll-microhyll vine forest. They counted bird species along transects, recording time of day, date, and year. Life history traits of the birds were used to hypothesize the influence of extinction risk; These tasks included extent of occurrence, body mass, dispersal strategy, clutch size, feeding behavior, and population density. The scale of habitat, defined as “the spatial extent of ecological process”, was also analyzed.
Land cover data, statistical analysis and model developments were used to study local landscapes, emigration and immigration patterns, and rainforest cover types. It was found that species with low population size were more vulnerable to fragmentation and deforestation than abundant species. When looking at behavioral specialization, there are high rates of extinction for species that live in terrestrial, understory, and canopy regions. Dispersal is another important factor which helped identify that sedentary species exhibited higher vulnerability than migratory or nomadic movements. Lastly, body mass analyses suggested that smaller species are more vulnerable to deforestation than are larger species. In looking at species richness and landscape structure, it was concluded that supporting avian communities is related to rainforest conditions at the stand sale, forest composition at landscape scale, and rainforest configuration at patch scale. There is evidence that bird assemblage responded to stand basal area, meaning that maintaining stand basal area is essential in minimizing the impacts of invasive plant species. This suggests that declining stand basal area and the degradation of forest structure could be one explanation of reduced species of birds.
There is a positive effect of maintaining forest cover in the surrounding landscape in order to maintain landscape connectivity, increase species richness, and increase occupancy of these birds. Further, it was found that vegetation composition could also improve habitat connectivity. As a result, it is important to improve stand condition in order to keep high species richness.
Finally, in looking at the effects of deforestation and fragmentation, they concluded that fragmentation exacerbates the effects of deforestation. In conclusion, maintaining high species richness, and biodiversity will be achieved by improving the structure of the rainforest.
Pavlacky Jr., D.C., Possinghan, H. P., Goldizen, A. W. Integrating life history traits and forest structure to evaluate the vulnerability of rainforest birds along gradients of deforestation and fragmentation in eastern Australia. Biol. Conserv. (2014), http://dx.doi.org/10.1016/j.biocon.2014.10.020