Wildfire–vegetation dynamics affect predictions of climate change impact on bird communities

Firevegetation dynamics (and not only climate) drive the variability of climate change indicators. Wildfire management and land use policies have the potential to offset or exacerbate the effects of climate change on biological communities, offering an excellent opportunity to address global change proactively.

Our recent study, recently published in Ecography, suggests that climate change indicators are strongly dependent on the interactive effects of climate change and wildfire–vegetation dynamics. The feasibility of using climate change indicators (in our case, the Community Thermal Index) to measure the likely effects of climate change hinges on our ability to accurately predict changes in community composition, that might be strongly affected (nulled or exacerbated) by drivers other than climate.

According to our fire and landscape simulations, the concomitance of land abandonment and climate warming is expected to herald larger wildfires, of higher intensity, thus jeopardising our ability to curb the increasing impact of wildfire on ecosystems. This should incite a gradual rethink of the current wildfire suppression paradigm based on the systematic suppression of all wildfires, and prompt alternative wildfire management policies aimed at reducing the impact of large forest fires [see e.g. forest biomass extraction for bioenergy].

MEthods

Fig. 1. Bird species assemblage were predicted using the spatially-explicit species assemblage modelling framework – SESAM – that applies successive filters to constrained predictions of richness and composition obtained by stacking species distribution models that hierarchically integrate climate change and wildfire–vegetation dynamics. Community Thermal Index (CTI) reports the average breeding-season temperature for all species present in a local community.

Previous research has shown that landscape-level wildfire management policies that allow small and low-intensity fires to burn under controlled, mild fire-weather conditions will likely decrease the impact of large forest fires under adverse climate conditions [see Let it burns !]. These policies have also proved to be effective tools for creating new habitats for early-successional species [e.g. on Dartford Warbler], without strong side effects on forest species, as the land abandonment processes in Southern Europe have largely counterbalanced the negative effect of wildfires in the past few decades. However, given the increasing severity of wildfire regimes, high-efficiency wildfire suppression policies (as typically implemented to date) were predicted to be more effective in mitigating climate change impact on our bird community than policies based on ‘let-burn’ strategies.

Wildfire management as opportunity to cope with climate change impacts on biological communities

This study thus showed how changes in habitat characteristics driven by wildfire–vegetation dynamics could have an important effect on the response of bird communities to climate change (Figs. 2 and 3). More importantly, our findings highlight how counteracting patterns (e.g. antagonistic effects of climate warming and land abandonment) or lagged community responses to climate warming might be enhanced by interacting and self-reinforcing processes between climate and land-cover changes, e.g. by synergistic/additive responses of the bird communities to climate warming and recurrent wildfire regimes. Our findings therefore suggest that it is crucial to consider fire–vegetation dynamics when forecasting the impact of climate change through community-based climate change indicators, especially in highly dynamic ecosystems, such as those of fire-prone areas.

 

Boxplots

Fig. 2. Boxplots representing change in community thermal index (ΔCTI) between 2000 and 2050 under each global change scenario and for each simulation, averaged for the whole study area and for areas below and above 1000 metres a.s.l.

 

In particular, we predicted that the combined effect of climate change and fire–vegetation dynamics can result in an overall increase in climate change indicators, despite the lags in responses to climate warming predicted for large parts of our study region as caused by land abandonment processes (Figs. 2 and 3). Identifying optimal wildfire management strategies is essential to enhance the resilience of biological communities to climate change without high conservation costs for open-habitat, warm-dwelling species.

maps

Fig. 3. Predictive maps showing change in the community thermal index (ΔCTI) between 2000 and 2050 under two global change scenarios: (i) business-as-usual, characterized by high levels of wildfire suppression (‘Stop all fires’), and (ii) ‘let-burn’ strategies (‘let-burn’ plus), where larger burnt areas are expected, using Climate and habitat suitability models (‘Combined’), or only habitat models (‘Habitat’).

This is especially relevant in fire-prone areas, where the direction of the net change in climate change indicator is predicted to depend on wildfire management policy implemented in the near future. In these fire-prone systems, wildfire management and land use policies have the potential to offset or exacerbate the effects of climate change on biological communities, offering an excellent opportunity to address global change proactively.

 

Regos A, Clavero M., D’Amen M, Guisan A, Brotons L. (2017). Wildfire–vegetation dynamics affect predictions of climate change impact on bird communities. Ecography.  doi/10.1111/ecog.02990.0.

 

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