Spatial niche modelling of five endemic cacti from the Brazilian Caatinga: Past, present and future.

Climate change, together with human activities, impacts on natural and human systems on all continents and poses a major threat to biodiversity, especially in environments with a high rate of endemism and where species are profoundly adapted to specific environmental conditions, as is the case of the seasonally dry tropical forests, noticeably the Caatinga, an exclusively Brazilian biome. The objective of this study was to build spatial niche models of five species of Cactaceae (Arrojadoa penicillata, Brasilicereus phaeacanthus, Pereskia aureiflora, Stephanocereus leucostele and Tacinga inamoena) endemic to the Caatinga and with different traits, to evaluate the impact of climate change on their geographical distribution. The species records and environmental variable values were overlaid on a grid of 6818 cells with 0.5° spatial resolution. Niche models were obtained for five types of general circulation models between ocean and atmosphere and 12 different ecological models. The ensemble ecological niche model was calculated at present and projected to past (last glacial maximum – LGM, 21 000; and mid‐Holocene – Hol, 6000 years ago) and future climate conditions (average of 2080), under the effect of climate change, in the greenhouse gas emission scenario RCP4.5. The distribution pattern of the studied species indicates an area with less environmental suitability in the LGM, followed by an expansion that began in the Hol and continued until the present period. In the future (2080), the models predicted a retraction of areas of environmental suitability, in which P. aureiflora and B. phaeacanthus, given their more restricted, marginal habitat and woody habit, present a great risk of extinction, whilst S. leucostele, A. penicillata and T. inamoena present a smaller reduction in suitable area, partly reflecting their spreading, less woody habit. Regional conservation actions for Cactaceae species and their habitat need to take these findings into account if we are to ensure the survival of these species. [ABSTRACT FROM AUTHOR]