In Borneo's Mahakam Delta, vast underground fires smolder for years, releasing more carbon than millions of cars and creating a haze that can darken skies across Southeast Asia.
Earth Science and Remote Sensing Unit, Lyndon B. Johnson Space Center, Public domain
The Million-Year Carbon Bomb
Deep beneath the swampy forests of Borneo's Mahakam Delta lies a massive deposit of carbon, stored in the form of peat. This dark, soil-like material is the result of thousands of years of partially decayed vegetation accumulating in waterlogged conditions. Some peat layers in Indonesia reach depths of up to 20 meters. In their natural, flooded state, these peatlands are fire-resistant sponges. Decades of drainage for agriculture—primarily for oil palm and pulpwood plantations—have dried out the upper layers, transforming this enormous carbon sink into a highly flammable fuel source.
When this drained peat ignites, it doesn't burn with open flames; it undergoes smoldering combustion, a slow, low-temperature, flameless process that can creep along underground at speeds of about one centimeter per hour. These fires are notoriously difficult to detect and even harder to extinguish. They can burrow deep into the peat, surviving for months or even years, earning them the name "zombie fires." A smoldering fire can withstand rainy seasons only to re-emerge when conditions become dry again.
A Haze Across Nations
The environmental consequences of these fires are extensive. Indonesia’s peatlands store an estimated 55 to 61 gigatons of carbon. When they burn, this ancient carbon is released into the atmosphere as carbon dioxide and other greenhouse gases. During the severe fire season of 2015, daily emissions from Indonesia's fires frequently surpassed the average daily emissions from the entire U.S. economy. The 2015 fires generated economic losses estimated at $28 billion.
The smoke from these fires creates a thick, toxic haze that blankets the region, causing severe air pollution. This haze contains high concentrations of fine particulate matter (PM2.5), which poses significant health risks. Major fire events, such as those in 1997 and 2015, have caused diplomatic tensions as the smoke cloud spread to neighboring countries like Malaysia and Singapore, affecting the health of millions.
As the peat burns away, the ground level drops, a process known as subsidence. In the first five years after drainage, the land can sink by as much as 1.5 meters. This ongoing collapse of the land surface increases the risk of flooding, a critical issue in a low-lying delta region, and damages infrastructure.
💡Fun Facts
Peat fires are often called "zombie fires" because they can smolder underground for months or even years, surviving wet seasons to re-emerge later.
During the peak of the 2015 fire crisis, the daily greenhouse gas emissions from Indonesian fires were greater than the daily emissions of the entire United States economy.
Extinguishing deep peat fires is extremely difficult; firefighters often have to flood entire areas or inject water deep into the ground with long pipes because surface water is ineffective.
Indonesia hosts the largest area of tropical peatlands in the world, holding an estimated 57 gigatons of carbon, which is more than the carbon stored in all the world's forests combined.
This is a broad environmental region, not a formal attraction. Access is unrestricted but depends on local conditions and safety advisories, particularly during the dry season (typically June-October) when fire risk is highest.
Admission
Free
Accessibility
The terrain consists of drained peatlands, canals, rivers, and plantations. It is not developed for tourism and access is generally difficult, often requiring private boat transport along the delta's waterways from cities like Samarinda.
