Predicting the future of an endemic endangered Andean bird species with a niche-based-model nested into a dynamic vegetation model

The slopes of the Andes are recognized as supporting the highest avian diversity in the world combined with high endemism rate but also more than 20 % of threatened species. Frugivores birds, even rare species, are known as major providers of seed dispersal service. In Bolivia, the large Red-fronted Macaw (Ara rubrogenys Lafresnaye, 1847) is one of the 15 endemic species of this country. Its natural habitat is mainly semi-deciduous dry forest but this habitat is most often severely degraded. Climate change is an additional threat over tropical mountain birds and this particular species, since some scenarios suggest warming as high as 7.5°C by 2080 and significant variations in the precipitation regime and available soil water.
To infer the future of bird species under warming climate, many authors use niche-based models (NBM), in which they combine effects of climate variables, alone or in combination with other environmental variables. A more elaborated approach consists in also including biotic interactions, notably the availability of particular plant species. While NBM with climate variables are now considered as a standard method to predict plant species distribution under future climate, this approach fails to consider the effect of increasing CO2 concentration in air on plant physiology. Contrariwise, dynamic vegetation models (DVM) are commonly able to reproduce this effect, although the uncertainties on the CO2 are large.
This study assesses the potential impact of climate change on the range of A. rubrogenys, by combining within a NBM climate variables, relief and biotic variables, i.e. plant species resource. Plant resource is computed with a DVM and a NBM to compare the methodologies and to evaluate potential effects of CO2 on plant species distribution and indirect impacts on the bird.