Christopher J. O’Bryan, The University of Queensland; Eve McDonald-Madden, The University of Queensland; Jim Hone, University of Canberra; Matthew H. Holden, The University of Queensland, and Nicholas R Patton, University of Canterbury
Whether you call them feral pigs, boar, swine, hogs, or even razorbacks, wild pigs are one of the most damaging invasive species on Earth, and they’re notorious for damaging agriculture and native wildlife.
A big reason they’re so harmful is because they uproot soil at vast scales, like tractors ploughing a field. Our new research, published today, is the first to calculate the global extent of this and its implications for carbon emissions.
Our findings were staggering. We discovered the cumulative area of soil uprooted by wild pigs is likely the same area as Taiwan. This releases 4.9 million tonnes of carbon dioxide each year — the same as one million cars. The majority of these emissions occur in Oceania.
A huge portion of Earth’s carbon is stored in soil, so releasing even a small fraction of this into the atmosphere can have a huge impact on climate change.
The problem with pigs
Wild pigs (Sus scrofa) are native throughout much of Europe and Asia, but today they live on every continent except Antarctica, making them one of the most widespread invasive mammals on the planet. An estimated three million wild pigs live in Australia alone.
It’s estimated that wild pigs destroy more than A$100 million (US$74 million) worth of crops and pasture each year in Australia, and more than US$270 million (A$366 million) in just 12 states in the USA.
Wild pigs have also been found to directly threaten 672 vertebrate and plant species across 54 different countries. This includes imperilled Australian ground frogs, tree frogs and multiple orchid species, as pigs destroy their habitats and prey on them.
Their geographic range is expected to expand in the coming decades, suggesting their threats to food security and biodiversity will likely worsen. But here, let’s focus on their contribution to global emissions.
Their carbon hoofprint
Previous research has highlighted the potential contribution of wild pigs to greenhouse gas emissions, but only at local scales.
One such study was conducted for three years in hardwood forests of Switzerland. The researchers found wild pigs caused soil carbon emissions to increase by around 23% per year.
Similarly, a study in the Jigong Mountains National Nature Reserve in China found soil emissions increased by more than 70% per year in places disturbed by wild pigs.
To find out what the impact was on a global scale, we ran 10,000 simulations of wild pig population sizes in their non-native distribution, including in the Americas, Oceania, Africa and parts of Southeast Asia.
For each simulation, we determined the amount of soil they would disturb using another model from a different study. Lastly, we used local case studies to calculate the minimum and maximum amount of wild pig-driven carbon emissions.
And we estimate the soil wild pigs uproot worldwide each year is likely between 36,214 and 123,517 square kilometres — or between the sizes of Taiwan and England.
Most of this soil damage and associated emissions occur in Oceania due to the large distribution of wild pigs there, and the amount of carbon stored in the soil in this region.
Read more: Feral pigs harm wildlife and biodiversity as well as crops
So how exactly does disturbing soil release emissions?
Wild pigs use their tough snouts to excavate soil in search of plant parts such as roots, fungi and invertebrates. This “ploughing” behaviour commonly disturbs soil at a depth of about five to 15 centimetres, which is roughly the same depth as crop tilling by farmers.
Because wild pigs are highly social and often feed in large groups, they can completely destroy a small paddock in a short period. This makes them a formidable foe to the organic carbon stored in soil.
In general, soil organic carbon is the balance between organic matter input into the soil (such as fungi, animal waste, root growth and leaf litter) versus outputs (such as decomposition, respiration and erosion). This balance is an indicator of soil health.
When soils are disturbed, whether from ploughing a field or from an animal burrowing or uprooting, carbon is released into the atmosphere as a greenhouse gas.
This is because digging up soil exposes it to oxygen, and oxygen promotes the rapid growth of microbes. These newly invigorated microbes, in turn, break down the organic matter containing carbon.
Tough and cunning
Wild pig control is incredibly difficult and costly due to their cunning behaviour, rapid breeding rate, and overall tough nature.
For example, wild pigs have been known to avoid traps if they had been previously caught, and they are skilled at changing their behaviour to avoid hunters.
Read more: Dig this: a tiny echidna moves 8 trailer-loads of soil a year, helping tackle climate change
In Australia, management efforts include coordinated hunting events to slow the spread of wild pig populations. Other techniques include setting traps and installing fences to prevent wild pig expansion, or aerial control programs.
Some of these control methods can also cause substantial carbon emissions, such as using helicopters for aerial control and other vehicles for hunting. Still, the long-term benefits of wild pig reduction may far outweigh these costs.
Working towards reduced global emissions is no simple feat, and our study is another tool in the toolbox for assessing the threats of this widespread invasive species.
Christopher J. O’Bryan, Postdoctoral Research Fellow, School of Earth and Environmental Sciences, The University of Queensland; Eve McDonald-Madden, Associate professor, The University of Queensland; Jim Hone, Emeritus professor, University of Canberra; Matthew H. Holden, Lecturer, School of Mathematics and Physics, The University of Queensland, and Nicholas R Patton, Ph.D. Candidate, University of Canterbury
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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I have a rather tasty solution. It’s called cull the drove ( herd). Crisis resolved …and the kids go to bed with a full stomach.
In some way this article is funny if we read it and compare everything said with another species called Homo Sapiens. There are a lot of similarities.
My dream girl: http://www.thesportinglifeshow.com/wp-content/uploads/2014/06/Kellie-Nightlinger-Boar.jpg
In early America, and probably elsewhere, laws fined pig-owners who failed to ring their swine. The nose-rings made it too painful or awkward for hogs to root and disturb farm fields.
A phrase that used to be in common use, to needle lazybones, was “root, hog, or die.” That could be revised in a way to encourage pushback against hogs’ invasion: “root, hog, and die.”
In Texas there is or was talk of establishing state-run processing stations / butchering plants to which hunters could bring in their kills. Feral deer could also be brought in, I suggest.
I don’t know about state run but there are places in Texas open 24-7 where you can drop off your hogs to be processed for dog meat. You have to gut and weigh them and then take a picture of the scale then put them in the refrigerated area.
Myself and plenty others here in Louisiana have bought thermal weapon sights just to hunt hogs at night. And even more so in Texas.
I guess I missed something here. Echidnas are good for soil and the ecosystem, but feral pigs are bad?
I’m sure that pigs increase the fertility of the soil from their droppings while foraging. Also, the disturbed soil is more permeable, potentially decreasing runoff.
Help me out here. What’s the difference? Size?
Prejudice, apparently. I saw that too. The Conversation can’t even manage their own fact checking.
Didn’t they once call B.S. journalism muckraking?
The only good thing about them is they taste good.
Do climate models have a formula for pig forcing? If not, why not?
Men are from Mars, women are from Venus? Babies are delivered by Stork.
Oh, vegans. Or is it Vogons?
For all the problems invasive species like pigs cause, the one I couldn’t care less about is their C02 emissions.
Well we can always use more blood and bone fertilizer but first, did they measure how much carbon they are putting back into the soil as they overturn the grass?
Quote…”On average 23.1% more CO2 was released from these plots, which we associated with potential alterations in CO2 diffusion rates, incorporation of litter into the mineral soil and higher fine root/microbial biomass.”
1/ I’m sceptical about increased diffusion. Any soil soft enough to turn over like that will have high diffusion rates at 5-10cm and I doubt turning would increase the rate much.
2/ Incorporation into the soil of organic matter (by turning sods upside down) returns what they help release.
3/ What does higher root/microbial mass have to do with it other than increasing soil carbon which would normally be released as it decomposes on the surface.
All in all I would not be surprised if the net carbon flux would be close to zero.
How many do I need to barbecue and eat to offset the CO2 from my clapped out old SUV?
Very good point.
Instead of planting trees for carbon credits, can we just shoot and eat a few of these big guys.
We could even set a non-profit and sell the credits to John Kerry so he can keep up his guilt free flying around.
(maybe I should have used hypocrite that has the capacity to feel guilt….)
Wild boar were eliminated from the island of Britain and the removal of this key forest species from the process of natural woodland development here was catastrophic.
In the yard of my Surrey home there are 4 oak trees (2 giant Durmast and 2 English). When I took ownership of the property 16 years ago the ground below the durmasts was covered in thick multi-year layers of ground smothering iv that took me 4 years to eradicate. Now twelve years later, and after 2 good mast years (which typically occur every 5 years), the ivy has gone and the density of the oakling regeneration below the canopy is astonishing.
Wild boar were discovered some years ago by a conservationist in Staffordshire to be the absolutely fundamental animal that allows for natural regeneration of oak woodlands. What is seen as damage is in fact the removal of the shade tolerant climax species, such as ivy that throttles (there is no other word for it) the regrowth of the woodland flora.
That other natural vectors such as Jays and Grey Squirrels – itself an oak woodland species, unlike the Red Squirrel which is a pine woodland species and is red for camouflage reasons when seen in the branches of the Red Pine (Scots Pine), these animals like the boar are ignored as critical agents in woodland ecology which seems to me to be another example of environmental hubris.
Next there will be a ban on all tillage of soil.
What did Pig Ebola do to the wild pig population in the last couple years?
Thus ploughed fields doe crops produce far more CO2 than beef and dairy, which is just a cow, in a field.
Not to mention the tractor, machinery, steel industry, fertiliser, pesticide, iron ore, coke mining, and oil drilling and refining, all this machinery depends on, to plough a field.
Yet again, the suggestion bread produces less GH gas than beef is shown to be ridiculous.
‘…fields for crops…’
A huge portion of Earth’s carbon is stored in soil, so releasing even a small fraction of this into the atmosphere can have a huge impact on climate change.
Not satisfied with undoing the industrial revolution, now our overlords want to cancel the agricultural revolution.
We can’t burn stuff any more, and now we cant plough the land either.
Or even bury the dead – or cremate them.
If the goal is return to hunter-gathering lifestyle with no technology why don’t they just say it?
G7 governments have announced funding initiatives for technologies to assist in the right-on green goal of removing the element carbon from the whole universe. And from any other universes. With the element already cancelled on social media the job is already half done according to experts at London’s Imperial College.
Tenders are invited to hoover up organic compound containing the bad element from nebulae and interstellar dust clouds. And technologies are sought for solving the problem at source – intervening in supernovas to stop fusion from settling at the island of atomic stability of Z=6, but instead moving on to heavier elements.
In a longer term approach favoured by astrophysicists including Roger Penrose invoking conformal cyclic cosmology, the distribution of energy in the expanding universe can be altered in such a way to influence the next Big Bang following the diffusive loss of all matter to energy, such that the next recursive Big Bang will be prevented from allowing the element carbon to form.