Positive effects of fire on ant and bee communities?

A study by the Higher Council for Scientific Research (CSIC) in Spain 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 forest fires in areas facing the Mediterranean, at least in coniferous systems, are not as negative as one might think and that this could have some positive effects, especially on ant communities. .

We live in a time in which the natural regime of forest fires has been replaced by an anthropic regime (of human origin), characterized by more severe fires, of greater extension and that occur with greater intensity and frequency.

This was denounced by José Manuel Vidal Cordero, pre-doctoral researcher at the Doñana Biological Station (EBD) of the CSIC and first author of the study. For this reason, according to the researcher, it is of vital importance to know how organisms respond to this current regime of forest fires and thus have data to face the challenge that this entails for the conservation of biodiversity.

In order to carry out this study, different approaches were used to, in this way, have a more complete and integrated vision of the effects of fire on biodiversity. On the one hand, two different study animal groups were used, ants and bees, and different types of responses to fire were also evaluated, both taxonomic and functional, such as the richness in the variety of species and their abundance, or functional traits. that the species present, such as “diurnality”, the type of nesting or the number of fecund queens that a colony of a certain species can house. In addition, the study was carried out on a spatio-temporal scale in which 35 pine forests affected by forest fires distributed throughout Andalusia were sampled, from recently burned areas to areas where there were fires more than 40 years ago.

One of the questions that the team wanted to answer was whether the fire simplified the complexity of the ecosystem, causing a reduction in the diversity of species or, on the contrary, making it possible to create new niches. The data seemed to confirm the second: the richness of ant and bee species had increased in the areas affected by the fire compared to the unburned areas. “These results were independent of the time elapsed since the fire, which indicates that these effects could last for a long time,” explains Vidal Cordero.

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

This study opens the door to investigate other additional characteristics of the fires that could affect the recovery of biodiversity and that have not yet been taken into account in this study, such as the intensity or severity of the fires, as well as other management options. of the burned areas after the fire.

The desert ant (Cataglyphis velox) lives in North Africa and southern Europe and usually nests in the sand and under rocks. (Photo: J. Manuel Vidal Cordero / CSIC)

Fire, promoter of the richness and diversity of ants and bees

“Our study shows that fire has both short-term and longer-lasting effects on ant and bee communities. While some functional traits are only modified in the short term, the richness of species and other functional traits are maintained for many years after the fire”, sums up the researcher. According to the results that are extracted from this work, the 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 forest fires,” he concludes.

The study has relied, in addition to the EBD team, with the collaboration of the Insect Biology Research Institute, the François Rabelais University of Tours and the Paris-Saclay University, both in France.

The study is entitled “Long-term recovery of Mediterranean ant and bee communities after fire in southern Spain”. And it has been published in the academic journal Science of The Total Environment. (Source: CSIC)