Cumulative effects of land use, altered fire regime and climate change on persistence ofCeanothus verrucosus, a rare, fire‐dependent plant species

Abstract

Mediterranean ecosystems are among the highest in species richness and endemism globally and are also among the most sensitive to climate and land-use change. Fire is an important driver of ecosystem processes in these systems; however, fire regimes have been substantially changed by human activities. Climate change is predicted to further alter fire regimes and species distributions, leading to habitat loss and threatening biodiversity. It is currently unknown what the population-level effects of these landscape-level changes will be. We linked a spatially explicit stochastic population model to dynamic bioclimate envelopes to investigate the effects of climate change, habitat loss and fragm entation and altered fire regime on population abundances of a long-lived obligate seeding shrub, Ceanothus verrucosus, a rare endemic species of southern California. We tested a range of fire return intervals under the present and two future climate scenarios. We also assessed the impact of potential anthropogenic land-use change by excluding land identified as developable by local governments. We found that the 35-50 year fire return interval resulted in the highest population abundances. Expected minimum population abundance (EMA) declined gradually as fire return interval increased, but declined dramatically for shorter fire intervals. Simulated future development resulted in a 33% decline in EMA, but relatively stable population trajectories over the time frame modeled. Relative changes in EMA for alternative fire intervals were similar for all climate and habitat loss scenarios, except under the more severe climate scenario which resulted in a change in the relative ranking of the fire scenarios. Our results show climate change to be the most serious threat facing obligate seeding shrubs embedded in urban landscapes, resulting in population decline and increased local extirpation, and that likely interactions with other threats increase risks to these species. Taking account of parameter uncertainty did not alter our conclusions.

Local-scale disturbances can benefit an endangered, fire-adapted plant species in Western Mediterranean heathlands in the absence of fire

“…The transformation of heathlands into forests is also the result of active afforestation campaigns (Andres & Ojeda, 2002). The combination of fire suppression and anthropogenic disturbances should increase local extinction risk of pyrophytic species (Bartolomé et al, 2005;Lawson et al, 2010;Fagúndez, 2013). Nonetheless, species responding to indirect fire-related germination cues, such as light increase from vegetation removal, may still find refuges from local extinction in habitats where disturbances such as shrub slashing mimic the fire effect of elimination of the aboveground vegetation (Pavlovic 1994;Quintana-Ascencio et al, 2007).…”

“…Many of these post-fire http://dx.doi.org/10.1016/j.biocon.2015.04.010 0006-3207/Ó 2015 Elsevier Ltd. All rights reserved. dwelling species are hence highly sensitive to alterations in fire frequency (Quintana-Ascencio, 2003;Lawson et al, 2010).…”

Land Use, Climate Change, and Ecosystem Services

“…An example of a study explicitly linking landscapes to climate change and plant species is by Lawson et al (2010). This study links a spatially explicit stochastic population model to dynamic bioclimate envelopes to investigate cumulative effects of land use, changed fire regime, and climate change on persistence of a rare, fire-dependent plant species (Ceanothus verrucosus) of southern California.…”

demoniche – an R‐package for simulating spatially‐explicit population dynamics

“…Th e demoniche software has three options to model the link between the environment and the species. For example, the niche suitability can be derived from ecological niche models or bioclimatic envelope models (Keith et al 2008), future climate scenarios (Hunter et al 2010), land use (Lawson et al 2010), landscape topology, presence of another species, or a composite of values. One way to link population growth to the environment is by defi ning a carrying capacity -the maximum number of individuals that can be sustained in a patch.…”