Mapping tree species vulnerability to multiple threats as a guide to restoration and conservation of tropical dry forests

Abstract

Understanding the vulnerability of tree species to anthropogenic threats is important for the efficient planning of restoration and conservation efforts. We quantified and compared the effects of future climate change and four current threats (fire, habitat conversion, overgrazing and overexploitation) on the 50 most common tree species of the tropical dry forests of northwestern Peru and southern Ecuador. We used an ensemble modelling approach to predict species distribution ranges, employed freely accessible spatial datasets to map threat exposures, and developed a trait-based scoring approach to estimate species-specific sensitivities, using differentiated trait weights in accordance with their expected importance in determining species sensitivities to specific threats. Species-specific vulnerability maps were constructed from the product of the exposure maps and the sensitivity estimates. We found that all 50 species face considerable threats, with an average of 46% of species' distribution ranges displaying high or very high vulnerability to at least one of the five threats. Our results suggest that current levels of habitat conversion, overexploitation and overgrazing pose larger threats to most of the studied species than climate change. We present a spatially explicit planning strategy for species-specific restoration and conservation actions, proposing management interventions to focus on (a) in situ conservation of tree populations and seed collection for tree planting activities in areas with low vulnerability to climate change and current threats; (b) ex situ conservation or translocation of populations in areas with high climate change vulnerability; and (c) active planting or assisted regeneration in areas under high current threat vulnerability but low climate change vulnerability, provided that interventions are in place to lower threat pressure. We provide an online, user-friendly tool to visualize both the vulnerability maps and the maps indicating priority restoration and conservation actions. K E Y W O R D S functional traits, multithreat vulnerability, restoration and conservation planning, sensitivity, tropical dry forest FREMOUT ET al. | 3553Vulnerability

AlleleShift: An R package to predict and visualize population-level changes in allele frequencies in response to climate change

“…As an approach to obtain a better handle on the transferability of AlleleShift predictions into future climates, I recommend to also estimate the suitability (and ideally the transferability, for instance via evaluation strips as proposed by Elith et al, 2005) of target species via species distribution models (SDMs). Well-documented methods of utilizing SDMs to predict shifts in species habitat are available in the literature, including recent examples that use the ensemble suitability modelling framework available in BiodiversityR (e.g., de Sousa et al, 2019;Fremout et al, 2020;Kindt, 2018;Ranjitkar et al, 2014). For organisms such as trees, correlative SDMs remain the best available method of predicting future species suitability, whereas the limitations of these methods may not be as great as has been suggested (Booth, 2018).…”

Mapping tree species for restoration potential resilient to climate change

“…In addition, while the projected suitability maps provide general indication to facilitate local decision making, species selection should take real consideration of local knowledge where possible for guiding responsable land management practices (Osorio-Salomón et al 2021). Finally, the maps developed in our study can serve beyond restoration and support the conservation of threatened tree species globally (Fremout et al 2020) and inform a variety of environmental programs.…”

Half of the world’s tree biodiversity is unprotected and is increasingly threatened by human activities

“…However, the other half of high-priority areas for tree diversity conservation are distributed in regions with moderate to high human pressures, where certain kinds of threats, e.g., fire, habitat conversion, or overgrazing, are likely to negatively impact ecosystems (16,17,45,46). Thus passive restoration, such as natural regeneration on degraded lands, is likely to be a more effective and affordable approach to recover and conserve the ecosystem structure and function (47,48), alongside using legal boundaries and designations to protect land from human pressures (49).…”