Biology subjects

Backus, G. A.

Publications and source records attributed to Backus, G. A..

4 recordsLinked to original sources

bioRxiv2022

Restoring local climate refugia to enhance the capacity for dispersal-limited species to track climate change

Climate refugia are areas where species can persist through climate change with little to no movement. Among the factors associated with climate refugia are high spatial heterogeneity, such that there is only a short distance between current and future optimal climates, as well as biotic or abiotic environmental factors which buffer against variability in time. However, climate refugia may be declining due to anthropogenic homogenization of environments and degradation of environmental buffers. To quantify the potential for restoration of refugia-like environmental conditions to increase population persistence under climate change, we simulated a populations capacity to track increasing temperatures over time given different levels of spatial and temporal variability in temperature. To determine how species traits affected the efficacy of restoring heterogeneity, we explored an array of values for species dispersal ability, thermal tolerance, and fecundity. We found that species were more likely to persist in environments with higher local heterogeneity and lower environmental stochasticity. When simulating a management action that increased the local heterogeneity of a previously homogenized environment, species were more likely to persist through climate change, and population sizes were generally higher, but there was little effect with mild temperature change. The benefits of heterogeneity restoration were greatest for species with limited dispersal ability. In contrast, species with longer dispersal but lower fecundity were more likely to benefit from a reduction in environmental stochasticity than an increase in spatial heterogeneity. Our results suggest that restoring environments to refugia-like conditions could promote species persistence under climate change in addition to conservation strategies such as assisted migration, corridors, and increased protection.

ecology↗

bioRxiv2022

Quantifying the capacity for assisted migration to achieve conservation and forestry goals under climate change

Many tree species might be threatened with extinction because they cannot disperse or adapt quickly enough to keep pace with climate change. One potential, and potentially risky, strategy to mitigate this threat is assisted migration, the intentional movement of species to facilitate population range shifts to more climatically suitable locations under climate change. The ability for assisted migration to minimize risk and maximize conservation and forestry outcomes depends on a multi-faceted decision process for determining, what, where, and how much to move. To quantify how the benefits and risks of assisted migration could affect the decision-making process, we used a dynamical vegetation model parameterized with 23 tree species in the western United States. We found that most of the modeled species are likely to experience a substantial decline in biomass, potentially facing regional extinction by 2100 under the high-emission SSP5-85 climate-change scenario. Though simulations show assisted migration had little effect on the forestry goal of total biomass across all species, its effects on the conservation goal of promoting individual species persistence were far more substantial. Among eight assisted migration strategies we tested that differ in terms of life cycle stage of movement and target destination selection criteria, the approach that conserved the highest biomass for individual species involved relocating target seedlings to areas with the highest canopy openness. Although this strategy significantly reduced extinction risk for six at-risk species compared to no action, it also slightly reduced biomass of four species, due to increasing competition. Species with relatively weak tolerance to drought, fire or high temperature were the most likely candidate groups for assisted migration. This model framework could be applied to other forest ecosystems to evaluate the efficacy of assisted migration globally.

ecology↗

bioRxiv2021

Comparing management strategies for conserving communities of climate-threatened species with a stochastic metacommunity model

Many species are shifting their ranges to keep pace with climate change, but habitat fragmentation and limited dispersal could impede these range shifts. In the case of climate-vulnerable foundation species such as tropical reef corals and temperate forest trees, such limitations might put entire communities at risk of extinction. Restoring connectivity through corridors, stepping-stones, or enhanced quality of existing patches could prevent the extinction of several species, but dispersal-limited species might not benefit if other species block their dispersal. Alternatively, managers might relocate vulnerable species between habitats through assisted migration, but this is generally a species-by-species approach. To evaluate the relative efficacy of these strategies, we simulated the climate-tracking of species in randomized competitive metacommunities with alternative management interventions. We found that corridors and assisted migration were the most effective strategies at reducing extinction. Assisted migration was especially effective at reducing the extinction likelihood for short-dispersing species, but it often required moving several species repeatedly. Assisted migration was more effective at reducing extinction in environments with higher stochasticity, and corridors were more effective at reducing extinction in environments with lower stochasticity. We discuss the application of these approaches to an array of systems ranging from tropical corals to temperate forests.

ecology↗

bioRxiv2019

Identifying robust strategies for assisted migration given risks and uncertainties in a stochastic metacommunity

Assisted migration is the translocation of species beyond their historical range to locations that are expected to be more suitable under future climate change. However, a relocated population might fail to establish within its donor community if there is high uncertainty in decision making, climate, and interactions with the recipient ecological community. To quantify the benefit to persistence and risk of establishment failure of assisted migration under different management scenarios, we built a stochastic metacommunity model to simulate several species reproducing, dispersing, and competing on a temperature gradient as temperature increases over time. Without assisted migration, the species in our model were vulnerable to climate change if they had low population sizes, short dispersal, and strong poleword competition. When relocating species that exemplified these traits, assisted migration increased the long-term persistence of the species most when relocating a fraction of the donor population, even if the remaining population was very small or rapidly declining. This suggests that leaving behind a fraction of the population could be a robust approach, allowing managers to repeat assisted migration in case they move the species at the wrong place and wrong time, especially when it is difficult to identify a species optimal climate. We found that assisted migration was most beneficial to species with low dispersal ability and least beneficial to species with narrow thermal tolerances, for which assisted migration increased extinction risk on average. Lastly, while relocation did not affect the persistence of non-target species in our simple competitive model, researchers will need to consider a more complete set of community interactions to comprehensively understand invasion potential.

ecology↗