‘Destructive’ wild pigs may help cultivate biodiverse rainforests, study suggests

Pigs’ contribution to forests despite their reputation for damaging woodlands highlights the complexity of the relationships between flora and fauna, writes Harry Cockburn

It may look like a mess, but wild boars’ rootling can have unexpected benefits for forests, research suggests (University of Queensland)

Wild pigs may appear to leave a trail of devastation in their wake, but it turns out these animals may have considerable positive benefits for the landscapes they inhabit.

A new study by Australian scientists have found wild pigs can cultivate biodiverse rainforests in their native habitats.

Dr Matthew Luskin, who has been researching the effect of native pigs in Malaysian rainforests, said the pigs’ nests may be a “critical” contribution in maintaining diverse and balanced tree communities.

“We’ve shown that wild pigs can support higher diversity ecosystems and are not just nuisances and pests, thanks to a beneficial effect of their nesting practices,” Dr Luskin said.

“Prior to giving birth, pigs build birthing nests made up of hundreds of tree seedlings, usually on flat, dry sites in the forest.

“As they build their nests, the pigs kill many of the dominant seedlings and inadvertently reduce the abundance of locally dominant tree species, but usually not rarer local species, supporting tree diversity.”

Dr Luskin said wild pigs, also known as boar, (Sus scrofa) descended from the same species of domestic pigs and both have generally been considered pests by farmers, land managers and conservationists.

“Their negative impacts on natural and cultivated ecosystems have been well documented - ranging from soil disturbances to attacking newborn livestock,” he said.

The researchers said the study was the first to link animals to this key mechanism for maintaining “hyper-diverse rainforests”.

In order to assess the impacts the pigs were having, the team tagged more than 30,000 tree seedlings in a Malaysian rainforest.

This allowed them to examine how tree diversity changed in the areas where pigs nested after recovering more than 1,800 of those tree tags from inside more than 200 pig birthing nests.

“You could consider pigs ‘accidental forest gardeners’ that prune common seedlings and inadvertently maintain diversity,” Dr Luskin said.

“In many regions, there’s a focus on managing overabundant pig populations to limit their negative environmental impacts.

“But our results suggest there may be some positives to maintaining pigs in the ecosystem.”

Dr Luskin said that as the fieldwork was conducted in Malaysia where pigs are native - the impacts of invasive pigs in Australia may not create similar effects.

“We’re currently in the process of designing new research to study the same pig processes here in Queensland,” he said.

“And we’ll also be comparing our initial Malaysian results with conditions in a nearby Malaysian forest that is heavily hunted and where many native pigs have been killed.

“It’s an intriguing insight, as pigs have become the most widespread large animal on earth, so documenting any new ecological impacts has massive repercussions globally.”

In the UK, the return of wild boar to areas such as the Forest of Dean, where the animals’ natural predators have also been wiped out has resulted in a growing population of the animals, despite annual culls.

According to Forestry England, “boar at low densities are probably good for the natural environment as the rooting and wallowing behaviours break-up static eco-systems and allow an increased range of plant species and insect fauna to grow.

“However, as the density of boar rises the negative issues of boar, such as continually disturbing the same area of ground so that all is left is bare mud, and eating insects and other plant material could be damaging to specific species in the long run.”

The research is published in the Proceedings of the Royal Society B.