Wild pigs are releasing nearly five million tonnes of trapped soil carbon dioxide annually – about the same as that produced by a million cars – which may contribute to climate change, according to a new study published in Global Change Biology.
A team of researchers, led by Christopher O’Bryan of the University of Queensland, used predictive population models and advanced mapping techniques to estimate the global climate damage of wild pigs across five continents.
They determined that, in digging up soil, the pigs helped release 4.9 million tonnes of trapped carbon dioxide, making the animals a significant contributor to climate change.
“Wild pigs are just like tractors ploughing through fields, turning over soil to find food,” says O’Bryan.
“When soils are disturbed from humans ploughing a field or, in this case, from wild animals uprooting [soil], carbon is released into the atmosphere.
“Since soil contains nearly three times as much carbon than the atmosphere, even a small fraction of carbon emitted from soil has the potential to accelerate climate change.
“Our models show a wide range of outcomes, but they indicate that wild pigs are most likely currently uprooting an area of around 36,000 to 124,000 square kilometres, in environments 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.”
Building on existing maps of wild pig distribution, the team simulated another 10,000 maps to estimate total global pig density.
They then modelled how much carbon would be trapped – and subsequently released – in the entire area of soil that would be disturbed by pigs. This included areas that had different types of vegetation and elevations, such as lowland grassland and subalpine woodland.
“Invasive species are a human-caused problem, so we need to acknowledge and take responsibility for their environmental and ecological implications,” says co-author Nicholas Patton of the University of Canterbury.
“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.
“Because wild pigs are prolific and cause widespread damage, they’re both costly and challenging to manage.
“Wild-pig control will definitely require cooperation and collaboration across multiple jurisdictions, and our work is but one piece of the puzzle, helping managers better understand their impacts.
“It’s clear that more work still needs to be done, but in the interim, we should continue to protect and monitor ecosystems and their soil, which are susceptible to invasive species via loss of carbon.”