Wild Pigs Release as Much CO2 as More Than 1 Million Cars

Feral pigs have the same climate impact as 1.1 million cars, according to recent research.

Using modeling and mapping techniques, an international team of scientists predict that wild pigs are releasing 4.9 million metric tonnes of carbon dioxide each year around the world when they uproot soil.

One of the study’s authors, Christopher O'Bryan, is a postdoctoral research fellow of the University of Queensland. He tells Treehugger that feral pigs are prolific globally.

“Wild pigs (Sus scrofa) are found on every continent except Antarctica but are native throughout most of Europe, Asia, and parts of northern Africa,” he says. “As such, they have been spread around the world by humans and are invasive species in Oceania, parts of Southeast Asia, parts of southern Africa, and North and South America.”

For the study, which was published in the journal Global Change Biology, researchers only looked at areas where wild pigs are invasive and not native.

How C02 Is Released

Feral hogs release CO2 when they go rummaging through soil, hunting for food.

“Wild pigs are like tractors plowing a field, using their tough snouts to turn up soil in search of fungi, plant-parts, and invertebrates. When they uproot the soil, they expose the organic material in the soil to oxygen, which promotes the rapid development of microbes that break down organic material containing carbon,” O’Bryan explains.

“This rapid breakdown results in the release of carbon in the form of carbon dioxide or CO2.”

He points out that the same thing happens when humans disturb habitat by changing land in nearly any way, such as deforestation or tilling crops for agriculture.

“This is important because soil is one of the largest carbon pools on the planet,” he says.

A Massive Impact

The researchers used computer simulations utilizing real-world data to make predictions about wild pig population density, soil disturbance, and CO2 emissions. They came up with a range of outcomes.

Their 10,000 simulated results showed median CO2 emissions of 4.9 million metric tonnes, which is equivalent to the emissions of 1.1 million cars per year globally where wild pigs are not native.

“However, our results showed a wide range of uncertainty because of variability in wild pig populations and soil dynamics,” O’Bryan says. “In North America, our models showed that the CO2 emissions are 1 million metric tonnes, equivalent to the emissions from all the registered cars in Vermont (200,000 cars per year).”

The researchers estimate that wild pigs are uprooting an area of around 36,000 to 124,000 square kilometers (13,900 to 47,900 square miles) in areas where they're not native.

“This is an enormous amount of land, and this not only affects soil health and carbon emissions, but it also threatens biodiversity and food security that are crucial for sustainable development,” O’Bryan says.

Because wild pigs are so abundant and cause so much damage, they are difficult and expensive to manage, says co-author Nicholas Patton, a PhD candidate at the University of Canterbury.

“Invasive species are a human-caused problem, so we need to acknowledge and take responsibility for their environmental and ecological implications,” Patton said in a statement.

“If invasive pigs are allowed to expand into areas with abundant soil carbon, there may be an even greater risk of greenhouse gas emissions in the future.”