Chernobyl's legacy recorded in trees

Exposure to
radiation from the
1986 Chernobyl
accident had a
lasting negative
legacy on the
area's trees, a
study has
suggested.
Researchers said the
worst effects were
recorded in the
"first few years" but
surviving trees were
left vulnerable to
environmental
stress, such as drought.
They added that young trees appeared to be
particularly affected.
Writing in the journal Trees, the team said it
was the first study to look at the impact at
a landscape scale.
"Our field results were consistent with
previous findings that were based on much
smaller sample sizes," explained co-author Tim
Mousseau from the University of South
Carolina, US.
"They are also consistent with the many
reports of genetic impacts to these trees," he
told BBC News.
"Many of the trees show highly abnormal
growth forms reflecting the effects of
mutations and cell death resulting from
radiation exposure."
Prof Mousseau, who has been carrying out
field studies since 1999 within the 30km (19-
mile) exclusion zone around the site of the
1986 explosion, said it was the first time that
a study of this scale - involving more than 100
Scots pines ( Pinus sylvestris) at 12 sites - had
been conducted.
"There was one similar study conducted before
but it only looked at a total of nine trees and
was mainly interested in wood structure, not
growth," he said.
"Another study was performed in the 1950s
but it was for a different tree in the US and it
used a single external gamma source
suspended above the ground to show growth
effects for a very limited number of trees."
For this study, the team took core samples
from Scots pine trees for a number of reasons,
such as the species is found across Europe and
well dispersed within the Chernobyl region.
"They are also a favourite for silviculture and
have enormous economic value," Prof
Mousseau added.
"Also, based on past
work and our own
observations, they
appeared to be a
good target for
radioecology as they
showed signs of
being impacted by
the fallout.
"In fact, one of the
first ecological
observations at
Chernobyl was the
death of the so-
called red forest: a
stand of these pines
which very quickly
died and turned red following the disaster."
Scots pines' tree rings were also easier to read
than other species, such as birch, found in the
study area, he explained.
Prof Mousseau and his team hope to follow up
this study by carrying out similar work in the
Fukushima region in Japan, where logging also
had considerable economic importance and
pine trees were widely dispersed.
"Based on our limited field observations in the
most contaminated regions of Fukushima
prefecture, there did not appear to be a major
die off as seen in Chernobyl for Scots pines,"
he said.
"However, anecdotally, we have noticed
significant die off of growing tips and branches
in some areas that suggests that there could be
impacts on growth.
"This is worth further investigation."