With forest fires burning across Indonesia, officials decided to close Mount Merapi National Park.

Fires are now burning on the slopes of the stratovolcano, officials confirmed on Tuesday, and suffocating haze has blanketed much of the island nation.

"We had to ask 250 hikers to go down from the mountain during the fire on Sunday and so we have closed the tracks, for safety," Tri Atmojo, a park administrator, told reporters.

Many of the fires, of which there are thousands, have been burning for several weeks. They are mostly illegal man-made fires, started by big and small timber and agricultural operations to clear land and settle land disputes. The climatological effects of El Nino have fanned the flames and worsened the deadly haze.

The fog of particulates that hangs across the archipelago has forced school and business closures. Thousands have been evacuated from their homes. The toxic haze contains methane, carbon monoxide, ozone and myriad other poisonous gases. More than 500,000 people have been treated for respiratory illnesses and 19 have died of suffocation.

Less apparent are the ecological costs. Conservationists suggest the fires and haze are forcing endangered species from their homes, potentially snuffing out entire populations of orangutans, clouded leopards, Sumatran tiger, sun bears and gibbons. And these are the species researchers know about.

Hundreds of new species are discovered and classified every year. A disproportionate number are found in the nooks and crannies of Indonesia's forests -- forests environmentalists say are quickly disappearing.

"Species are going up in smoke at an untold rate," political activist George Monbiot wrote in an op-ed, published in The Guardian last week. "It is almost certainly the greatest environmental disaster of the 21st century -- so far."

Though weather conditions have exacerbated the calamity, Monbiot and others have argued the disaster is the result of decades of reckless development -- forests fragmented by logging and rubber and palm oil plantations.

Much of the fire and smoke is fueled by peat moss, a thick layer of vegetation which would normally be water-logged, quite resistant to fire. But peat forests have been gutted by canals and drained for agriculture.

"Dry peat ignites very easily and can burn for days or weeks, even smouldering underground and re-emerging away from the initial source," Susan Page, a geographer at the University of Leicester, told The Express last month. "This makes them incredibly difficult to extinguish. Smouldering fires produce high levels of harmful gases and particulates."

These peat swamps, which have accumulated peat and stored carbon over thousands of years, are disappearing overnight -- their carbon along with them. On some days, researchers estimate the fires are releasing more daily CO2 than the entire U.S. economy.

Recent rains have helped dampen the flames and scatter the haze, but the catastrophe isn't over yet. Crews continue to battle fires on the ground as planes disperse cloud-seeding chemicals to incite more rain.

"Efforts to stop the fires are being stepped up, but are currently insufficient to cope with the scale of the problem" said conservationist Mark Harrison, managing director of the Orangutan Tropical Peatland Project. "Stopping the fires requires both urgent on-the-ground fire-fighting during drought periods and, in the longer term, damming of canals in drained peatlands to prevent future fires. Any further canal construction and peatland drainage should be avoided."