A study led by the Doñana Biological Station reveals that species richness and diversity of ants and bees could increase after a wildfire. Some of these positive effects could persist over the long term.

Researchers from the Doñana Biological Station has evaluated the effects of fire on ant and bee communities in Mediterranean pine forests in Andalusia. Their short and long-term results could suggest that wildfires, at least in coniferous systems, are not as negative as one might think and could have positive effects, especially on ant communities.

"The natural regime of wildfires has been replaced by an anthropogenic regime, of human origin, characterized by more severe fires, of greater extension and intensity, and that occur more often", explains J. Manuel Vidal Cordero, predoctoral researcher at the Doñana Biological Station – CSIC and first author of the study. For this reason, according to the researcher, it is important to know how organisms respond to this current regime of wildfires and have data to face that this poses for the conservation of biodiversity.

To carry out this study, several approaches have been used to have a more integrated and holistic view of the effects of wildfires on biodiversity. Two taxonomic groups, ant and bee communities, and two different responses, taxonomic and functional, were assessed. In addition, the study was carried out on a spatio-temporal scale. The team sampled 35 pine forests that had experienced a wildfire at some point in the past, recently and up to 41 years ago.

One of the questions the team wanted to answer was whether fire simplifies the complexity of the ecosystem, causing a reduction in species diversity or, on the contrary, creates new niches. The data seemed to confirm the latter: ant and bee species richness had increased in fire-affected areas compared to unburned areas. "These results were independent of the time since fire, which indicates that these effects could last for a long time," says Vidal Cordero.

In addition, six of the thirteen ant functional traits analyzed differed between burned and unburned areas. For example, in burned areas, ant communities with more ground-nesting and more strictly diurnal species were observed. These differences in species traits did decrease as time since fire increased. Others, however, persisted over time. In the burned areas, a greater number of species with a higher degree of morphological differences in the worker caste (polymorphism) and also more species whose colonies have only one queen (monogynous) were detected, regardless of how much time had passed.

Future studies should investigate further additional fire characteristics that could impact community recovery, which were not considered in this study, such as fire recurrence, intensity or severity, or other management options of burned areas after fire.

Wildfire, promoter of richness and diversity of bee and ant communities

"Our study shows that fire has both short and long-term effects on ant and bee communities. While some functional traits are only modified in the short term, species richness and other functional traits are maintained for many years after the fire," summarizes the researcher. According to the results extracted from this work, rejuvenation of coniferous systems, always within a forest planning, should be considered as a promoter of the richness and diversity of these species. "It would be beneficial to develop an effective long-term monitoring system to detect changes in ecosystems and make recovery assessments after wildfires," he concludes.

The study has been published in the scientific journal Science of the Total Environment and, in addition to the Doñana Biological Statio, has the colaboration of the Research Institute of Insect Biology of the François Rabelais University of Tours y the Paris-Saclay University. This work is part of a Project of Excellence 2012 (RNM 2705) of the Andalusian Regional Government, the  Iberian Centre for Research and Forest Firefighting – CILIFO and the FIREPOCTEP project.

Reference:

Vidal-Cordero, J. M., Angulo, E., Molina, F. P., Boulay, R. & X. Cerdá (2023). Long-term recovery of Mediterranean ant and bee communities after fire in southern Spain. Science of The Total Environment 887: 164132. https://doi.org/10.1016/j.scitotenv.2023.164132

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