[photochemsyn]

The Red Forest is highly contaminated, such that surface level microroentgens per hour are at least 10X than what's considered maximum safe level for humans, and likely a good deal higher in the soil.

There are other tests that could have been done, such as measuring the ability of soil suspensions taken from the Red Forest to breakdown cellulose in a test tube (studies that would probably require a lot of care in a radiation-safe lab), but the kind of study described in the article (leaving bags of leaves around to see what happens to them) seems to be enough to prove the point; fungal/insect breakdown of plant matter is inhibited in the most severely contaminated areas of the exclusion zone.

Looking around, here's a study on the contamination of fish in surrounding lakes (still an issue). Some fish are more genetically sensitive to it than others, but you probably wouldn't want to eat any of them:

"Impact of Environmental Radiation on the Health and Reproductive Status of Fish from Chernobyl" (2018)

https://pubs.acs.org/doi/10.1021/acs.est.8b02378

[aeternum]

I wonder if any studies have looked at potential positives. For example the Red Forest is applying a selection pressure towards radiation-hardened Fungi, insects, and even potentially wildlife. This seems pretty important given the ongoing risk of nuclear war.