The climate impact of wild pigs around the world is equivalent to the greenhouse gas emissions of 1.1 million cars per year, according to a new study.
Modeling by an international team of researchers estimates that feral pigs release 4.9 million metric tonnes of carbon dioxide worldwide each year by uprooting soil.
Researcher Dr Christopher O’Bryan of the University of Queensland said feral pigs are one of the most common invasive vertebrate species on the planet.
“Pigs are native to Europe and parts of Asia, but they have been introduced to every continent except Antarctica,” he said.
“When we think of climate change, we tend to think of the classic fossil fuel problem. This is one of the additional threats to carbon, and potentially climate change, that has not really been explored in a global sense.
Wild pigs uproot the soil while foraging for food, in a process O’Bryan likens to “mini tractors plowing the soil.” This exposes the soil microbes to oxygen. Microbes “reproduce at a rapid rate and this can then produce carbon emissions. [in the form of] CO2. «
“Any form of land use change can have an effect on soil carbon emissions,” said O’Bryan. “The same thing happens when you put a tractor in a field or clear land. “
Researchers estimate that wild pigs uproot an area of over 36,000 km² (14,000 square miles) in areas where they are not native.
Oceania had the largest area of land disturbed by wild pigs – about 22,000 km² – followed by North America. Pigs in Oceania accounted for over 60% of the animal’s estimated annual emissions, emitting nearly 3 million metric tonnes of CO2, equivalent to approximately 643,000 cars.
The results of the study, published in the journal Global Change Biology, were taken from three models. A model predicted the density of feral pigs globally through 10,000 simulations, based on existing information on feral pig populations and locations.
A second model converted the density of pigs to an area of disturbed land, and a third estimated the amount of CO2 emitted when the ground is disturbed.
Nicholas Patton, a doctoral student at the University of Canterbury, said there was some uncertainty in the modeling due to the variability in carbon content in soils and the densities of feral pigs in different areas.
“Areas that are bogs or black soils… especially those that have a lot of moisture, they’re a carbon sink,” Patton said. “When the pigs come in there and take root, they have a lot more potential for that carbon to be released. [than from other soils]. «
In addition to their climatic impacts, the destructive impact of feral pigs has been well documented. O’Bryan said managing the animals was a challenge that would involve prioritizing whichever of their impacts deemed most important.
“If all we’re interested in is agriculture, then the cost and benefits of managing pigs will be different than if all we cared about was carbon emissions, than if all we cared about was biodiversity.
“At the end of the day, feral pigs are a human problem. We broadcast them all over the world. This is another human-made climate impact.