Earlier this year I wrote about a lichen that was named after President Barack Obama in which I included a brief introduction to lichens. They are fascinating organisms that are actually two organisms in one – a fungus and an algae or cyanobacteria. They are not plants, but are often appreciated by plant enthusiasts, probably due to their plant-like appearances and behaviors and because they commonly associate with plants. Lichens have great ecological importance and are regularly used by a variety of animals for food and shelter. Their sensitivity to air pollution and acid rain is well documented, which brings me to a more tragic story about lichens.
As Heloise Rheault puts it in the book, Nature All Around Us, “Lichens live essentially from the light and water they obtain directly from their environment. Because they have no way to regulate or filter these resources, they directly absorb all particles suspended in the air and in rain, including all pollutants.” Absorbing enough pollutants over time can lead to the death of lichens, which is why researchers can use the presence or absence of lichens to map polluted areas. Lichens that have absorbed high levels of pollutants might also be eaten by animals, which moves these toxic substances up the food chain.
On April 26, 1986, the world’s worst nuclear disaster occurred at the Chernobyl Nuclear Power Plant in what at the time was the Ukrainian Soviet Socialist Republic. An explosion and fire completely destroyed one of the reactors and sent massive amounts of radioactive particles into the atmosphere. The radioactive fallout quickly spread across western USSR and Europe. Areas in close proximity obviously suffered the most dramatic effects of the explosion, but effects were also felt hundreds of miles away.
One distant area where effects were felt was Lapland, a region in northern Finland where the Sami people have lived for thousands of years. Lapland is about 2300 kilometers (1430 miles) north of Chernobyl, yet the fallout was detected shortly after the blast. Due to atmospheric nuclear weapons testing, regular monitoring of radiation levels in Lapland and the surrounding areas had been taking place long before the Chernobyl disaster. In Lapland, studies were focused on radiocesium concentrations in lichens and reindeer. Lichens are the main food source for reindeer during the winter when little else is available, and reindeer are regularly consumed by the Sami people. Threatened by fallout from Chernobyl, monitoring intensified in the area.
Reindeer in Lapland, Finland (photo credit: wikimedia commons)
A report published in Rangifer in 1990 summarized results of sampling that was carried out in Lapland in 1986 – 1987. Hundreds of samples were taken from three species of lichens in the genus Cladonia (C. stellaris, C. mitis, and C. rangiferina). These species were selected because they are “the most important ground lichen species used as winter fodder by the reindeer.” Thousands of samples were also taken from the meat of slaughtered reindeer during this period. Researchers found that higher radiocesium concentrations in lichens within the sampling area correlated with higher radiocesium concentrations in reindeer within the same area. The test results were used to determine “whether the meat could be delivered for consumption or not.”
The researchers also found that contamination of the reindeer meat varied depending on when the reindeer were slaughtered. They determined that “lichens contain higher amounts of [radiation] activity than other forage,” so in the fall after the reindeer had spent the summer eating tree leaves and other plant material, “the activity concentration in the meat decreases rapidly.” Harvesting the reindeer from December through March, after they had spent the winter eating mostly lichens, resulted in meat with higher radiocesium concentrations.
Star reindeer lichen (Cladonia stellaris) – Researchers found that the concentration of radioactivity in this species of lichen was unevenly distributed, in that “the top layer of the lichen was twice the concentration of the middle layer.” (photo credit: www.eol.org)
An article published in the New York Times in September 1986 told a similar story. Laplanders in Sweden lamented that 97% of the first 1000 reindeer slaughtered so far that fall “measured in excess of permissible radiation levels and [were] declared unfit for human consumption.” The reindeer had spent the summer browsing “vegetation watered by the nuclear rains,” including “rain-sopped renlav lichen savored by the deer.” This was the first year of many in which contaminated meat would have to be disposed off. The article reports on the concerns of the Sami people that “their way of life is slipping into an irradiated limbo,” especially considering that the worst of the contamination has a half-life of 30 years and “the affected lichen will linger for a decade.” A paper published in the Journal of Environmental Radioactivity in 2005 reported that high levels of radioactivity were still being detected in this region’s “soil – plant/lichen – reindeer food chain” in the late 1990’s.
This is, of course, only one of many tragic and horrendous results of the Chernobyl disaster. Even now, 30 years after the event, effects are still being felt and clean up is ongoing.
awkward botany 