Decomposers such as microbes, fungi and some types of insects inhabiting the exclusion zones around Chernobyl and Fukushima have suffered from contamination. These organisms are responsible for an essential component of any ecosystem: recycling organic matter back into the soil and issues at this basic level could have compounding effects for the entire ecosystem. Chernobyl, in particular, is also at risk of fire, 27 years’ worth of leaf litter, scientists think, would likely make a good fuel source for such a forest fire, which could redistribute radioactive contaminants to places outside of the exclusion zone.
https://www.smithsonianmag.com/science-nature/forests-around-chernobyl-arent-decaying-properly-180950075/