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Potential impacts to dry forest species distribution under two climate change scenarios in southern Ecuador

Abstract:

Tropical dry forest is an important ecosystem that offers different good and services to communities. However, despite their importance, these ecosystems are the least studied and have been impacted by human activity in the last decades. Moreover, future projections show an additional impact caused by climate change. For this reason, the understanding of anthropogenic and climate change impacts will help to improve adaptation strategies for a better species conservation. Consequently, we analyzed the impact of climate change and stressors on species distribution from dry forest ecosystem in southern Ecuador. We identified the variables that could help to buffer the potential impacts. Indicator species of climate change impacts were chosen using a species selection index considering an importance index value, density, rarity and altitudinal range. The selected species were Cavanillesia platanifolia, Cordia macrantha (C. macrantha), Erythrina velutina, Handroanthus chrysanthus (H. chrysanthus) and Terminalia valverdeae (T. valverdeae). Species current and future distribution models were generated with information from Herbarium ‘Reinaldo Espinosa’ of the National University of Loja and permanent plots that were established between 2005 and 2009. We used climate data from WorldClim under two climate change scenarios based on two IPCC Representative Concentration Pathways; RCP 2.6 and RCP 8.5. To know if the species distribution will be placed in regions with high sensitivity or adaptive capacity, 13 stressor variables and 3 buffers were selected. The sensitivity and adaptive capacity maps were intersected with species future distribution models under RCP 2.6 and RCP 8.5. Four of five species in the analysis showed a reduction in their future distribution: C. macrantha, T. valverdeae and H. chrysanthus. These were reduced due to increasing niche restriction. Between 18 and 26% of species future distribution area were located in zones with high sensitivity. In addition, among 14% to 46% of species future distribution area could be in sites with high adaptive capacity. In these areas, conservation strategies can serve as buffers against climate change; however, nowadays there is a conservation gap that needs to be addressed through the implementation of different strategies oriented to reinforce the adaptive capacity of these species in dry forest ecosystems. Species distribution models showed no migration to higher altitudes, but we observed a reduction in areas with high probability of presence. Additionally, sites with high likelihood of species presence have been influenced by deforestation, fragmentation, land use and other stressors, that will likely diminish their ability to adapt to climate warming and increased rainfall variability.