For Honduran soldiers fanning out in the pine forest the enemy is like no other: numbering in the thousands, invading a sizeable chunk of their country and causing incalculable environmental damage.

Their tenacious adversary? A tree-munching bug called Dentroctomus frontalis, more commonly known in North and Central America as the southern pine beetle.

It has always been present in Honduras, in smaller numbers. But this year has seen a sudden explosion that some experts blame on global warming.

A new report released this week during a UN climate change conference in Paris warned that Honduras, along with Myanmar and Haiti, is top of a new list of nations hardest hit by threats from increased global temperatures.

The 2016 Global Climate Risk Index, produced by the advocacy group Germanwatch, said the warming has unleashed storms, floods and landslides over the past two decades that were especially costly to Honduras.

For Honduran soldiers from the First Artillery Battalion confronting the pine tree bugs in Zambrano province just north of the capital with chainsaws, much of that climate chatter is just theory and abstraction.

But battle is one thing they know -- just as they know their current combat against this tiny southern pine beetle is one they are losing.

The tenacious critter has already destroyed 400,000 hectares (one million acres) of pine forest -- nearly a quarter of the country's primary forest cover. And its appetite shows no sign of abating.

The devastation in such a biodiverse country, a third of which is covered with trees, is being called an unprecedented "ecological catastrophe" by experts.

- Insect 'plague' -

"This plague will leave us with just half the pine trees in Honduras -- if we're lucky," said a military adviser, Lucky Medina, supervising the soldiers as they cut down trees.

Commanders of the battalion of 350 men admit feeling impotent against the beetle, and have called in the country's Forest Conservation Institute (ICF) and the military's Forest Commando unit to help cut down infected trees, and healthy ones nearby.

"It's a shame to see this," one commando officer, Colonel Bernardo Avila, told AFP.

Angela Sevilla, an ICF expert watching the operation, added sadly that it took "40 to 50 years to have a forest like this."

"But we need to cut the tree to save the forest," responded Medina.

He noted that a prolonged drought caused by the El Nino weather phenomenon in the Pacific Ocean this year boosted insect numbers six-fold. From September to November, it is estimated that the area they had spread to tripled.

- 'Climate change' blamed -

"The increased insect population is the product of climate change, due to the elevation in temperatures," Medina asserted.

El Nino wreaks havoc on world weather patterns every two to seven years, causing floods and droughts.

Although there is no global scientific consensus that El Nino is itself a sign of climate change, researchers have noted it is occurring with greater frequency.

The US Department of Agriculture calls the bug "one of the most destructive pests of pines." It says sudden outbreaks have been recorded in the United States every few years for "unknown" reasons.

In the group watching the Honduran soldiers is Sergio Quinonez, an expert sent by the Mexican government to help Honduras tackle its bug infestation.

He used a knife to cut into one of the trees, then tweezers to lift out beetles no bigger than a grain of rice. He put them in a plastic container for later study.

Quinonez said the long drought had "stressed" the trees, making their bark more vulnerable to the encroaching insects.

Thousands of the beetle eggs are under the bark of a stricken tree, with each female able to lay 50 eggs at a time, prompting Quinonez to urge the soldiers to burn the bark and harvest the wood to help finance the fight against the bugs.

Medina pointed out a tall tree about 50 years old that was streaming with resin.

"When a tree is infected by the larvae it secretes the resin as a defense mechanism, to protect itself. But the discharge it receives from the insects is so great that it ends up succumbing," he said.

"It's like cancer in humans."