Featured Image Caption: Wildfires, while potentially dangerous, are an essential component of many ecosystems. (Credit: Mark Wolfe/FEMA, in the public domain, via Wikimedia Commons.)
Source Article: González, González-Trujillo, J. D., Muñoz, A., & Armenteras, D. (2022). Effects of fire history on animal communities: a systematic review. Ecological Processes., 11(1). https://doi.org/10.1186/s13717-021-00357-7
Both destructive and seemingly uncontrollable, fires capture our attentions. While once considered unambiguously harmful to natural areas, we now know that wildfires are essential for many ecosystems. Some trees, such as giant sequoias, require fire to disperse their seeds. Fire helps to cycle nutrients back into the soil, keeps invasive species out of certain habitats, and burns away debris to prevent larger, more dangerous fires.
Though fires have clear benefits, additional research is required to understand all of their consequences. As the frequency of fire events increases due to climate change and human activities, it is increasingly important to understand fires’ effects. For example, how do fires impact wildlife communities?
Meta-analyses: bringing it all together
Recently, scientists conducted a meta-analysis — a review of many previous, similar studies — on this topic. In this case, 162 studies were reviewed, each exploring the effect of fire on animal communities. By pooling data from many studies, broad conclusions may be drawn that would be impossible using one study alone.
Additionally, scientists can identify what is commonly researched, and what areas are neglected. For instance, 60% of the studies included in this meta-analysis were from North America, but only 11% were from Europe, and even fewer were from Africa. Forty percent of the studies explored how fires impacted bird populations, while only 4% focused on herpetofauna (reptiles and amphibians). When regions or species are underrepresented in research, it can be difficult to draw conclusions about them.
How do fires affect wildlife?
This study considered how wildfires impacted species richness and abundance, which are both important metrics of biodiversity. Species richness measures how many species are in an area, while species abundance measures the number of individuals per species. Together, these measurements give additional information, such as whether an area is dominated by a certain species despite many species being present.
Studies in this meta-analysis focused on several animal groups. While fire didn’t have a consistent effect on arthropods, birds, and herpetofauna, it generally decreased the abundance and richness of mammal species. This finding becomes more nuanced when “zooming in” to compare different mammal types. Recently burned African savannas were found to have an increased abundance of large herbivores (including gazelles and zebras). This is because, in this biome, many small seedlings which herbivores like to eat grow after fires. In contrast, the overall abundance and richness of small mammals tended to decrease, because burned areas have less food and shelter for these species. The loss of vegetation also makes it harder for these animals to hide from predators.
Fires significantly alter the vegetation of a habitat, often reducing canopy cover and the number of live trees. Regrowth in subsequent years may therefore include different plants compared to before the fire, such as those which usually would not have enough light to grow in a forest understory. This shift in vegetation types may help some wildlife species but harm others, and it may be more helpful to consider how individual species or more specific categories of animals might be affected. For example, birds such as woodpeckers which nest in dead trees or eat insects found within them may benefit from a fire, due to the increased prevalence of dead wood. In contrast, birds which build nests in canopies might find it difficult to find a nest location or material to build with.
This study highlighted some other factors impacting overall species richness and abundance. Both metrics tended to increase as time passed after the wildfire. Additionally, both wild and managed fires had similar effects on these measurements, suggesting that managed fires are, in this regard, adequate substitutes for natural ones.
Understanding future fires
It is clear that fires have significant effects on ecosystems which may persist long after they have burned out. Considering a large number of studies through a meta-analysis lets us identify trends that we otherwise would not be able to with a single experiment. However, fires are complicated, and their varied interactions with their environment can have many different outcomes we do not fully grasp. Do fires impact different biomes in different ways? How are animals affected by different fire frequencies and intensities? Working to better understand these connections is important to effectively plan for future fire events, both intentional and unexpected.