Internally displaced persons sit at a checkpoint as smoke rises from the burning oil wells in Qayyarah, about 31 miles south of Mosul, Iraq, (AP Photo/Marko Drobnjakovic)

The United Nations Environment Programme is highlighting the battle by Iraqi forces to reclaim Mosul from the Islamic State as the latest instance in the complex but very real linkage between military conflicts around the world and extreme environmental degradation.

Citing dangerous air conditions from 19 torched oil wells as Islamic State militants retreat from their positions, as well as toxic air pollution following the burning of the Mishraq Sulphate Factory, the group’s head Erik Solheim said in a statement, “This is sadly just the latest episode in what has been the wholesale destruction of Iraq’s environment over several decades – from the draining of the marshlands to the contamination of land and the collapse of environmental management systems.”

“This ongoing ecocide is a recipe for a prolonged disaster,” Solheim continued. “It makes living conditions dangerous and miserable, if not impossible. It will push countless people to join the unprecedented global refugee population. That’s why the environment needs to be placed at the centre of crisis response, conflict prevention and conflict resolution.”

In the case of the battle for Mosul, the link between conflict and the environment is relatively straightforward — Islamic State fighters are using environmental wreckage as part of their military strategy, through the torching of oilfields.

But as the Post’s Chelsea Harvey wrote earlier year, UNEP has increasingly highlighted how environmental issues can help lay the groundwork for the military conflicts and even sustain them, such as when illegal mining, timber, or wildlife trading provide income to militant forces.

In 2009, UNEP released a study finding that “over the last sixty years at least forty percent of all intrastate conflicts have a link to natural resources.”

And it’s not just how resources can cause or prolong conflicts — it’s also how conflicts destroy resources and the environment. Also in 2009, a study in the journal Conservation Biology found that “over 90% of the major armed conflicts between 1950 and 2000 occurred within countries containing biodiversity hotspots, and more than 80% took place directly within hotspot areas.”

Perhaps most pointedly, research has suggested that the ongoing conflict in Syria can be partly – if only partly — tied to climate change. “Water and climatic conditions have played a direct role in the deterioration of Syria’s economic conditions,” noted a 2014 study, which went on to describe how economic instability helped precipitate the Syrian civil war.

In general, there is a widespread fear that a changing climate will exacerbate existing vulnerabilities and tensions in societies, sometimes in such a way as to destabilize them — although again, researchers repeatedly emphasize that conflicts rarely have one single cause.

In its statement, UNEP cited a number of international resolutions devoted to preserving the environment even during military conflicts, and noted that next year, it will be hosting an “Environment and Emergencies Forum” at its headquarters in Nairobi.