Perhaps the most intriguing facet of agriculture as well as any ecosystem is waste management. From the bottom of any ocean to the middle of the Gobi Desert, there are cleanup crews from birds to microbial life that will help to continue the Carbon, Nitrogen, and Phosphorus cycles of their environments. Perhaps one of the better known amongst these natural janitors are Dung Beetles. These insects can be found on every continent, but Antarctica, and help to spread the contents of the feces of megafauna such as cattle into the soils of their environments. This feces contains not only necessary nutrients for plant growth, but also seeds.
This close relationship between megafauna, dung beetles, and plants is mutually beneficial and a major part of countless ecosystems worldwide. Likewise, dung beetles have proven quite helpful to humans in lowering carbon emissions as well as disease rates. Sadly, due to deforestation, veterinary drugs such as ivermectin used on livestock, as well as countless other issues tracing back to humans, dung beetles are dying off worldwide. This is not an acceptable outcome if humanity wishes to maintain many of Earth’s ecosystems, worldwide public health, prevent human starvation, and to fight climate change. Dung beetles must not be allowed to lose their place in our ecosystems or we will all feel the effects.
As previously stated, dung beetles share a very close and valuable relationship with plants and megafauna in their environment. Megafauna (such as cattle) consume plant matter which contains seeds that pass through the digestive tract without being digested in the process. The waste is excreted from the fauna as dung that is quickly found by dung beetles and burrowed into and stored underground for food or rolled into a ball to house the beetles’ eggs, depending on the species. The seeds from these dung piles are thus allowed to spread and penetrate the soil. The dung also acts as a nice fertilizer to keep the soil healthy. Finally, the seeds take root and the plants grow, mate, and the seeds are again eaten by hungry megafauna.
It’s easy to tell that any upset to this balance could quite possibly destroy an ecosystem. This has been seen in studies regarding overhunting for megafauna by humans. Namely, the activity on Barro Colorado Island in Panama lead to a significant decrease in the beetle population as well as genetic diversity among them. The subsequent lack of dung piles and beetles to bury them led to drastically lower Nitrogen mineralization into the soil, causing the soil to become less nutritious for plantlife. On top of this, the dung beetles were the only fauna who could successfully bury large seeds deeply into the soil. The drop in this activity meant less diversity among plants and decreased plant health.
Harm to plantlife obviously means less food for megafauna, but it can also directly harm the dung beetles. In instances of deforestation of tropical environments, the removal of plantlife for roads can lead to greater chances of fires, lower seed dispersal rates, and higher likelihood of human population and the introduction of invasive species. These kinds of changes, as seen in Borneo, can affect vegetation up to 34 meters from the roads, but likewise tunneling dung beetle populations up to 170 meters away. The beetles experience greater environmental risks even when vegetation is removed at a great distance.
All of these factors show that dung beetles are integral members of their habitats and when their numbers drop, wild animals as well as the flora itself and human livestock suffer greatly. However, human agriculture is affected beyond simply livestock; drops in dung beetle populations lead to increases in food borne illnesses as well as illnesses caused by pest flies. The most well-known food-borne pathogen today, Escherichia coli (E coli), is a form of bacteria that can be found in human feces as well as that of other animals and can wreak havoc on public health when it is improperly managed around crops. For example, a study found that deer scat left to decompose around blueberry bushes in Maine without being properly managed, can infect blueberry bushes with E coli. Contamination with the pathogen lasts for around 72 hours, in which time the berries are dangerous to consume. However, dung beetles in the area have been found to consume dung inoculated with E coli without experiencing harm or spreading the bacteria to the bushes. These beetles acted as a natural and effective buffer against the pathogen. If their role as buffers were to disappear, these blueberry bushes would be highly risky as human food resources without great measures needing to be taken to isolate them from the natural environment.
Furthermore, the beetles play yet another significant role in disease management worldwide with regards to pestiferous flies. These flies lay their eggs in dung so their larvae can live off of it until they reach adulthood. They can carry E coli and other pathogens and tend to land on larger animals, such as humans, and consume mucous or even feed on wounds. This kind of contact easily and rapidly spreads deadly diseases. Pestiferous flies can grow in population by around 3,000 in just two weeks off of just one dung pile. Dung beetles regulate this by breaking up the dung quickly and killing eggs and larvae in the process. To give an idea of how greatly disease rates among humans and other animals could increase without dung beetles, imagine a hot and humid Texan ranch with cows numbering around 30. Each cow produces around 12 piles per day. In one year, each cow will produce about 4380 piles. That’s a total of over 131,000 dung piles on just this one ranch. For each pile, 3,000 flies will reach adulthood. Therefore, without dung beetles to regulate pestiferous flies at this ranch, the flies will hatch about 393 million offspring from one Texan ranch (San Diego Zoo).
\[1\text{ cow}\times\frac{12\text{ piles}}{\text{ Day}}\times\frac{365\text{ days}}{\text{Year}}=4380\text{ piles/years}\]
\[30\text{ cows}\times\frac{12\text{ piles}}{\text{Day}}\times\frac{365\text{ days}}{\text{Year}}=131000\text{ piles/year}\]
\[131000\text{ piles}\times\frac{3000\text{ flies}}{\text{Pile}}=393000000\text{ flies/year}\]
That’s significantly larger than the population of the United States of America. This population spike could easily lead to extremely dense populations of flies that will then contaminate the wounds of animals as well as any food they can find in and around homes.
Dung beetles lower disease rates and help to maintain vital cycles in ecosystems, but they also serve valuable roles in pastures in lowering carbon emissions. Cows are some of the more prominent methane producers on the planet, methane being a dangerous greenhouse gas. Dung left alone, even with pestiferous fly activity, is unable to aerate on its own; the dung will quickly begin to condense over time, making an environment that is low in oxygen. Without the oxygen present, the hydrocarbons in dung produce methane and allow it to escape into the air. Research has shown that a diverse assemblage of beetles with varying practices in their usage of dung piles can reduce CO2 equivalent production from piles by 32%. This is highly useful in the effort to reduce climate change worldwide as cows have grown to a population of over 1 billion in 2019. As stated previously, cows produce around 4380 piles of dung in just one year. If a dung pile’s carbon emission can be reduced by 32%, that translates to a huge cut to GHG emission by cattle worldwide. Especially in tropical regions of the world, dung beetles can turn pastures into carbon sinks, thanks to the moist tropical climate.
Dung beetles cannot be overstated as vital denizens of this planet, given their massive contributions to practically every ecosystem above Antarctica, their massive implications on agriculture, the work they do to lower the risk of spreading harmful bacteria and other pathogens like E coli, and the amount of carbon they put back into the soil to prevent climate change. With the rising sea levels, vast dying-offs of thousands of species from the oceans to the deserts, and the promise of many future hardships thanks to climate change, natural bastions such as the noble dung beetle are vital in climate control and climate change research. They are just as vital in human efforts to provide clean food to the many people starving worldwide and the effort to lower disease rates. If we lose them, they’re taking thousands of other species and many of us with them. If we want to preserve a better future for the next generations, dung beetles need to be among humanity’s top priorities.
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