After a wildfire sweeps through the landscape, it may be inevitable to be shocked by the desolate scene it leaves. Yet, a recent research led by Lucas Carbone suggests that plants can flourish in these environments as never expected.

Although fire is often perceived as harmful due to the immediate damage it can cause, its presence triggers vital processes for the natural dynamics of some ecosystems. The influence of fire on these ecosystems is such that plants have developed different adaptations to take advantage of these renewed environments. 

For example, the flowering of some species is stimulated by fire, with some even flowering in less than a day after being burned. This probably occurs because the plants that can withstand the scorching pass of fire are fuelled by the flush of nutrients and the lack of competition resulting from a fire event. This unique scenario provides favourable conditions for growth and flowering, resulting in rapid and massive flower blooms that pave the way for the reestablishment of vegetation.

A recently burned area in the mountain region of Córdoba (Argentina). Photo by Lucas Carbone.

While previous studies have extensively documented the phenomenon of fire-stimulated flowering, less attention has been given to the intricate interaction between fire, plants and their pollinators. One would expect that the large number of flowers that appear after a fire event would attract many pollinators, ensuring the reproductive success of the plants. However, this has only been corroborated in a few local studies and with only a handful of species. Understanding how fire influences pollination is crucial for understanding how ecosystems respond to fire, especially nowadays, when humans have profoundly altered fire regimes in various parts of the planet. 

Massive flowering events after a wildfire in Córdoba (Argentina). Photos by Lucas Carbone.

With this in mind, a research team led by Dr. Lucas M. Carbone from the National University of Córdoba (Argentina) conducted a study to evaluate the effects of fire on pollination and reproductive success of plants at a global scale. To achieve this, they compiled data from 40 studies across ten different countries and re-analysed them all together.

The authors found that wildfires did increase pollination visits on average. This effect was mainly evident after a single fire event and during the first three years after the fire event, arguably because many plants initially responded to fire by increasing their floral display and offering more conspicuous visual cues and better floral rewards, thus attracting more pollinators.

However, this positive effect varied between different pollinator groups. Flower visitation by bees, for example, increased after the fire, while visits by flies, beetles, butterflies, and moths showed no response to the fire. Such differences probably arise because social bees tend to have larger colonies that forage more extensively for resources, allowing them to exploit post-fire environments more efficiently than other pollinator groups. 

Flowers of Eryngium horridum being visited by a wasp in a recently-burned area. Photo by Lucas Carbone.

Interestingly, the study by Carbone and his team also highlighted a positive effect of fire on plant reproduction, with plants producing more fruits and seeds after its pass. This positive effect was observed after single fire events, prescribed fires, during the late post-fire stages and pollinated by wind. 

After a fire event, different abiotic conditions, such as habitat opening, nutrient quantity, and light quantity, are altered, favouring flowering and fruiting. Plant species like wind-pollinated plants, perennial forbs, and grasses seem to be especially favoured reproduction after fire events. On the one hand, wind pollination is easier after the fire has removed the surrounding vegetation, allowing the wind to flow more freely. Similarly, perennial forbs tend to resprout and reach a minimum size quickly after the fire, probably because these plants take advantage of the high amount of nutrients in the soil and low competition to increase their reproduction, implying that the pulse of abiotic resources has tremendous relevance for plant reproduction in these environments.

However, researchers also stress the importance of the number of fire events, since, like all things in excess, a radical increase in the number of fires or the intensity of fires can lead to the effect of fire being merely destructive. For example, in ecosystems where frequent wildfires are the norm, certain species have evolved traits to withstand or rapidly regenerate after fire. Still, a significant increase in fire frequency, severity, or extent could outpace these species’ regeneration capacity, leading to potential population declines or even local extinctions. Similarly, in fire-sensitive ecosystems where fires are infrequent or of low intensity, species may lack the adaptations necessary to cope with heightened fire occurrences. In such scenarios, wildfires can result in habitat destruction, reduced food availability, or direct mortality among fire-sensitive species.

Overall, this research sheds light on the intricate relationship between wildfires, pollination, and plant reproduction in fire-prone ecosystems. By synthesising data from numerous studies across different regions and ecosystems, the study underscores fire’s critical role in shaping ecological processes and evolutionary dynamics. These findings have significant implications for understanding the environmental consequences of wildfires and for informing conservation and management strategies in fire-prone environments.

However, Carbone and his team stress the urgent need for further research to fill knowledge gaps, particularly in underrepresented regions such as tropical areas and deserts. By expanding our understanding of how wildfires impact pollination and plant reproduction in these diverse ecosystems, we can develop more effective conservation and management strategies tailored to their specific needs. One thing is sure, and that is that this research will spark new lines of research to understand better the ability of fire to shape the natural dynamics of our ecosystems.

READ THE ARTICLE

Carbone, L. M., Tavella, J., Marquez, V., Ashworth, L., Pausas, J. G., & Aguilar, R. (2024). Fire effects on pollination and plant reproduction: a quantitative review. Annals of Botany, https://doi.org/10.1093/aob/mcae033.

Victor H. D. Silva is a biologist passionate about the processes that shape interactions between plants and pollinators. He is currently focused on understanding how plant-pollinator interactions are influenced by urbanisation and how to make urban green areas more pollinator-friendly. For more information, follow him on X as @another_VDuarte

Portuguese version by Victor H. D. Silva.

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