Counting the Dead: 17 Million Vertebrates Directly Killed by the 2020’s Wildfires in the Pantanal Wetland, Brazil

Abstract

Anthropogenic factors have significantly influenced the frequency, duration, and intensity of meteorological drought in many regions of the globe, and the increased frequency of wildfires is among the most visible consequences of human-induced climate change. Despite its role in determining biodiversity outcomes in different ecosystems, wildfires can cause negative impacts on wildlife. We conducted ground surveys along line transects to estimate the first-order impact of the 2020 wildfires on vertebrates in the Pantanal wetland, Brazil. We adopted the distance sampling technique to estimate the densities and the number of dead vertebrates in the 39,030 square kilometers affected by fire. Our estimates indicate that at least 16.952 million vertebrates were killed immediately by the fires in the Pantanal, demonstrating the impact of such an event in wet savanna ecosystems. The Pantanal case also reminds us that the cumulative impact of widespread burning would be catastrophic, as fire recurrence may lead to the impoverishment of ecosystems and the disruption of their functioning. To overcome this unsustainable scenario, it is necessary to establish proper biomass fuel management to avoid cumulative impacts caused by fire over biodiversity and ecosystem services.

Animal mortality during fire

“…That such low proportions of animals were killed in the fires considered in the studies we compiled does not necessarily mean that some fires, especially fires of high severity and large extent, do not kill many animals. Indeed, a recent study based on systematic counts of burnt corpses indicates that millions of vertebrate animals were killed in a ~40,000 km 2 area exposed to fires in the Pantanal, South America (Tomas et al, 2021). and prohibitively expensive transmitters.…”

“…vs. animals that emigrated outward from the firegrounds immediately prior to or following the fire's passage). Likewise, some recent studies have documented the-sometimes very high-numbers of animals killed in fires (Tomas et al, 2021), but we do not directly consider such studies because they lack a before-after component, so cannot provide evidence of proportional population losses, or survival rates of individual animals, in fire.…”

Dimensions of the 2020 wildfire catastrophe in the Pantanal wetland: the case of the municipality of Poconé, Mato Grosso, Brazil

“…Regarding the data of wildfire occurrence in 2020 (Tomas et al, 2021;ICV, 2020), the burned areas in the Pantanal of the municipality of Poconé make up 22% of the total area affected by fire in the whole biome and 40% of what was burned in the portion of the Pantanal that lies in the state of Mato Grosso. This extension of the wildfires in Poconé highlights the dimension of the impacts of fires on the whole biome, regardless of the macrohabitat characteristics, which explains the high mortality of fauna estimated by Tomas et al (2021). Most of these animals did not have the opportunity to escape from their original macrohabitats or reach or move to other habitats, causing this collapse in the Pantanal's biodiversity.…”

“…In 2020, the whole state was strongly affected by fires. In the whole Pantanal biome, a total of 3.9 million hectares were burned (Tomas et al, 2021), which represents almost 30% of its total area. According to ICV (2020), in Mato Grosso, proportionally, the Pantanal was the most impacted biome and, among all municipalities of Mato Grosso, Poconé was the most affected.…”

“…The consequences of fires are immeasurable and go from impacts on the biota to economic loss on husbandry, fishing, and biodiversity-supported ecotourism. Tomas et al (2021) calculated that 17 million vertebrates died as a direct consequence of the fires in the whole Pantanal biome in 2020. In that same year, the Encontro das Águas State Park, which is considered the largest jaguar refuge in the world (Tortato et al, 2017), had more than 90% of its area affected by fire (ICV, 2020).…”