Almost three decades after the Chernobyl nuclear power plant disaster, dead forests in the immediate radiation zone are still not decaying. Researchers say that this shows a disturbing facet of long-term radiation exposure that is little considered - how radiation impacts the process of decomposition.

According to a study published in the peer-reviewed journal Oecologia forest around  Chernobyl, particularly the infamous Red Forest - have shown little sign of decay since they first died nearly 30 years ago. This could be due to the fact that microbes and fungi have not recovered well from radiation contamination in the area.

The researchers involved in this latest study have been conducting analysis on environmental changes in the irradiated area since 1991, and have "noticed a significant accumulation of littler over time" - namely leaves and other dead brush that would normally decay in the course of a few years.

This observation prompted the researchers to launch a more extensive study of decomposition rates, especially in the Red Forest - a pine forest that tuned a reddish color and died almost immediately following the Chernobyl incident.

"Apart from a few ants, the dead tree trunks were largely unscathed when we first encountered them," lead author Timothy Mousseau said in a Smithsonian release. "It was striking, given that in the forests where I live, a fallen tree is mostly sawdust after a decade of lying on the ground." 

To fully measure decomposition rates in Chernobyl forests, the researchers made around 400 mesh bags containing leaves and other dead brush collected at an uncontaminated site. After making sure these bags did not contain insects and other small decomposers from the uncontaminated region, the researchers left the bags in various parts of Chernobyl where radiation levels varied.

The results spoke for themselves. After a year, 70 to 90 percent of the leaves had decomposed into nothing in areas with little-to-no radiation. In still irradiated areas however, 60 percent or more of the leaves remained.

According to the researchers, this is worrying. It shows that the radiation affected microbes and fungi severely, and is preventing natural decomposition, even after bush plants and other small trees have begun to grow once more in the region. The result is building dead brush over decades - the potential kindling for a catastrophic forest fire in the future if decomposition rates do not correct themselves.

The study was initially published in the May issue of Oecologia.