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HERBIVORES CAN HELP MITIGATE THE SPREAD OF MEGAFIRES



Curtis Abraham






Most experts and the media have attributed the increased frequency, intensity, and severity of large-scale wildfires (“mega-fires”) globally largely to climate change. This might be true in the case of certain types of wildfires, where increased global warming due to mounting concentrations of atmospheric greenhouse gases has caused unprecedented droughts and heat waves increasing the risk of wildfires. But what has been largely neglected (the elephant in the room so to speak) as one of several fundamental causes behind the rise of these massive infernos, other than climate change, is the decline of large herbivores in fire-prone areas. DOI: 10.1126/sciadv.1400103


Megafires are part of the blowback from the global loss of biodiversity, particularly the disappearance of large herbivores. More than 60% of the world’s largest terrestrial herbivores are at risk of vanishing forever because of extensive overhunting for meat to feed rising populations across much of the developing world https://doi.org/10.1126/sciadv.1400103

while in developed regions this has also been brought about through habitat destruction, overhunting, and habitat fragmentation.


Large herbivores such as the American bison, elk, and the White rhinoceros traditionally clipped the grass and ate the shrubs, thereby reducing the amount of natural accelerants that fuel wildfires. Additionally, their feeding habits, which included eating a variety of plants above ground and roots and tubers below the soil, also cause changes to the composition of vegetation over vast areas thereby creating diverse habitats. These varied habitats differ in their vulnerability to wildfires, which experts say affects how often large wildfires break out and the amount of heat produced by such blazes. DOI: 10.1111/1365-2664.13972;

DOI: 10.1126/science.1205106


Wild herbivores also help reduce the spread of wildfires in other ways. These creatures are among nature’s best ecological engineers-species that alter their habitat for better or worse. For instance, animal trail networks have been proven to limit the spread of low-intensity wildfires by creating firebreaks- barriers or gaps in vegetation halting the spread of wildfires. Such pathways are usually bare ground or simply areas of compressed organic debris such as leaves. Other large herbivores such as Cape buffalo and Red deer make temporary pools by creating wallows, which also act as firebreaks. https://doi.org/10.1111/acv.12269; https://doi.org/10.1080/17550871003610930


The foraging behaviors of smaller herbivores also contribute towards limiting the spread of bushfires (these smaller plant eaters are becoming increasingly important as habitat engineers due to declining populations of their larger kin). Some search for food by turning over or digging through the dried undergrowth and surface soils, and in the process bury flammable foliage thus reducing the amount of fuel for wildfires. DOI:10.1002/eap.2018;

doi.org/10.1093/biosci/biac069


However, regardless of these diverse effects herbivores have on wildfires, most researchers, conservationists, and media stories have typically focused on how such disasters are devastating some species and their habitats (media images of emaciated-looking koala bears escaping an Australian bush inferno in 2019 broke countless hearts). But these animals are not merely helpless victims but are also part of the solution in any ecological restoration strategy (i.e. rewilding and pastoralism) to avert or limit these massive blazes.


Archeological evidence indicates that the extinction of mammoths, wooly rhinos, mastodons, and other megafauna due to human population expansion and increased hunting activity during the Ice Age around 11,000 thousand years ago, led to an increase in wildfires (mega-herbivore extinctions also caused declines in predator populations and the loss of fruit-bearing trees that once depended on herbivores for dispersal).

https://www.pnas.org/doi/full/10.1073/pnas.1534700100

https://doc.rero.ch/record/210391/files/PAL_E4398.pdf

DOI: 10.1126/science.1179504





Places such as California and Australia’s southern regions, where mild wet winters and warm, dry summers prevail, have felt the brunt of these infernos almost every summer it seems. Unsurprisingly, these areas have had major declines in large herbivores. Among the twenty-nine land-dwelling mammals that have perished over the past two centuries in Australia, several of these species were ecosystem engineers whose burrowing activities increased the speed at which leafy debris decomposes. Reduced amounts of leaf matter lead to a decreased flame height and rate of fire spread. https://doi.org/10.1111/acv.12269.

In 2022, California’s Black-tail deer and Mule deer populations combined totaled 475,000, a sharp decline from about two million back in 1960. The loss of 1.5 million animals has contributed significantly to an accumulation of flammable vegetation since deer consume about seven pounds (3.1 kilograms) per day, or about 2,555 pounds (1158 kilograms) annually per animal. https://www.deerfriendly.com/deer/california


However, regardless of these diverse effects herbivores have on wildfires, both past and present, most researchers, conservationists, and media stories have typically focused on how such disasters are devastating some species and their habitats (media images of emaciated-looking koala bears escaping an Australian bush inferno in 2019 broke countless hearts). But these animals are not merely helpless victims but are also part of the solution in any ecological restoration strategy (i.e. rewilding and pastoralism) to avert or limit these massive blazes.

The consequences of megafires are devastating, widespread, and enduring. They not only endanger human lives, but they have caused fatalities in the tens of thousands around the world. In fact, one study has shown that annual exposure to toxic smoke from wildfires caused the deaths of an estimated 30,000 + individuals in 43 countries http://doi: 10.1016/S2542-5196(21)00200-X. In addition, these infernos add significantly to CO2 emissions to the Earth’s atmosphere annually among other consequences, a vicious cycle of environmental destruction.


The economic impacts from wildfires are great, as homes and businesses are destroyed. Other activities such as tourism and recreation are decimated. In 2020, wildfires in the US are said to have caused $21.9billion dollars in property damage https://www.nfpa.org/News-and-Research/Data-research-and-tools/US-Fire-Problem/Fire-loss-in-the-United-States.


Wildfire is not always an enemy though; like rainfall, fire nourishes nature. Low-intensity fire in many ecosystems can be a positive force in improving forest health and biodiversity (wildfires can help rid an environment of invasive species that have not adapted to regular wildfires).


But what makes megafires unique is that even when they appear to have been extinguished above ground, the sheer high surface temperatures create below-ground infernos called “zombie fires” that continue to smolder throughout the winter and can re-ignite with warmer weather. https://doi.org/10.5194/essd-9-697-2017.


Reintroducing large herbivores into fire-prone environments needs careful planning and management in order to effectively reduce fuel loads. For starters, any reintroduction of wild/semi-wild or domestic herbivores (i.e. livestock herding) should be based on science and should involve extensive or targeted intensive grazing, which is the application of a specific kind of livestock at a determined season, duration, and intensity to accomplish defined vegetation or landscape goals.


According to experts, the most effective management strategy generally is to combine both grazing and browsing herbivores in sufficient numbers in any rewilding effort (browsers feed primarily on leaves, soft shoots, or fruits of high-growing, woody plants such as shrubs, while grazers eat grass and other herbaceous plants). In addition, herbivore food preferences also need to match the local vegetation (certain types of goats have been found to have more of an impact in reducing fuel biomass than cows given that the former feeds on more diverse vegetation types than the latter which mainly eats grass). It has also been suggested that a combination of mixed-feeding herbivores and other management strategies, such as mechanical clearing, is necessary to reduce wildfire damage.

Successful land management strategies have been found to be all-inclusive and involve a variety of groups and individuals who have a vested interest in such schemes including livestock ranchers, NGOs, fisherfolk, hunters, indigenous peoples, private landowners, recreationists, and so forth.






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