Detailed livestock models are crucial for effective land-use strategies, disaster response, and tackling food insecurity.
Researchers have utilized dung records to create detailed maps showcasing where herbivores are distributed globally. Their recent study, published in Nature Food, uncovers a significant correlation between the amount of dung found in a certain area and the level of grazing activity there, indicating that dung presence can provide insights into the population of herbivores in that location.
Many people view dung merely as the waste produced by horses and cattle at agricultural shows or an inconvenience when visiting farms. However, dung is a vital resource for millions of people across the globe.
Dung serves as a biological fingerprint, offering valuable information about the environment, including the species of animals grazing in specific areas and what these populations signify for environmental health.
In a groundbreaking effort, a team of scientists from Australia, Spain, China, and Saudi Arabia, led by Professor David Eldridge of UNSW Sydney, has conducted the first global evaluation of dung from both livestock and native grazing animals in drylands—regions that cover around 40% of the Earth’s land surface.
This research identifies key areas of dung production while also highlighting the fact that, as a general rule, livestock and wild herbivores don’t typically share the same habitats.
“Recognizing where herbivores are found is essential for a variety of reasons,” explains Prof. Eldridge. “It enhances our comprehension of the grazing industry, including the spread of diseases among cattle. A better grasp of animal distribution allows us to pinpoint where specific land management strategies may be necessary.”
Estimating livestock density
Existing methods for assessing livestock density rely on rough estimates of environmental factors like average annual rainfall and temperature, as well as some soil characteristics. These factors help indicate potential habitats for herbivores since more productive ecosystems generally have more grass, thus supporting larger herbivore populations.
Organizations such as the United Nations Food and Agriculture Organization (FAO) require knowledge about where livestock congregate and in what numbers. They generally employ relatively simplistic computer models for this purpose.
Improving these prediction methods for herbivore distribution is vital for various agricultural industries. Consequently, Prof. Eldridge and his team sought innovative solutions to these challenges using an unexpected resource.
Dung—an unavoidable byproduct of meat production, a source of nitrogen and phosphorus fertilizer, and a material used in construction and cooking by millions worldwide—could offer a method for refining coarse estimations of animal distribution, according to Prof. Eldridge.
Methods & findings
The research team compiled 50 global datasets that listed dung mass and grazing pressure from various herbivores, including antelopes, sheep, and kangaroos.
They found strong positive correlations between dung production and grazing pressure in nearly all datasets except one.
“This data demonstrates that increased dung production tends to correlate with greater animal grazing pressure,” observes Prof. Eldridge. “Recognizing how much dung exists enables predictions about animal distribution.”
The team also merged livestock and wild herbivore dung mass data collected from 760 sites in dryland regions worldwide, yielding detailed maps that reflect independent herbivory measurements.
“Interestingly, our models revealed some overlap between the ranges of native herbivores and livestock, but overall, there are many regions where they do not interact,” states Prof. Eldridge. “This could be due to competition for resources or wild herbivores avoiding areas where livestock might carry diseases and parasites.”
Notable hotspots for dung production included regions in central Africa, northern and eastern Australia, the Eurasian grasslands, central eastern India, and the western coast of the United States. Conversely, dung production was observed to be less prevalent in north-central Africa and west-central China.
Dung as a scientific tool
Globally evaluating livestock distribution is vital for efficient land-use planning, estimating methane emissions, forecasting global meat production, and identifying areas at risk for livestock diseases such as brucellosis.
This understanding also enhances organizations’ abilities to predict food production trends and assess how droughts or natural disasters could impact food security.
Counting dung can often be more straightforward and effective than counting the animals themselves, according to Prof. Eldridge.
“For instance, one study showed that estimating elephant populations through dung counts often provides more accurate density estimates than aerial surveys,” he explains. “Dung counts also prove to be efficient for examining the habitat preferences of elusive herbivores that are rare or hard to detect.”
On a local scale, dung assessments can inform farmers about the habitat choices of different herbivores and their interactions. This knowledge can assist farmers in optimally placing fences, water sources, and other infrastructure to enhance livestock production, notes Prof. Eldridge.
However, assessing dung is not without its challenges, as Prof. Eldridge elaborates. “In many regions, especially in Asia and Africa, farmers often collect dung, which can skew field assessments and lead to underestimates of dung production by animals.”
Additionally, certain animals, like deer, may conceal their dung, while in many tropical areas, dung beetles and termites can break down dung within days, complicating regional evaluations.
“These factors make it tough to achieve reliable assessments of animal densities,” Prof. Eldridge stated. “Nonetheless, even when adjusting for areas where dung collection occurs, a strong relationship with grazing pressure remains evident.”
Despite these obstacles, this research results in a pioneering and thorough global map of dung from both livestock and wild herbivores in drylands, setting the groundwork for organizations to integrate dung data into livestock mapping and modeling.
