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Healing the damage of Chernobyl: radiation-contaminated forests and their rehabilitation

V.A. Ipatyev

Victor A. Ipatyev is Director of the
Forest Institute of the National
Academy of Sciences of Belarus,
Gomel, Belarus.

Scientists are investigating means of decreasing the dangers of radiation-contaminated forest stands, but there is as yet no solution to the problem.

The explosion of a reactor at the Chernobyl Nuclear Power Plant on 26 April 1986 was responsible for the radioactive contamination of all of Belarus and 14 Ukrainian and 17 Russian administrative districts. As a result of the accident, more than 4 million hectares of forest in Europe were contaminated with radiation.

Measures taken immediately after the accident to minimize the exposure of the population to radioactive materials were primarily aimed at the agriculture sector. Forests were not given proper attention. Repeated appeals in scientific fora to focus attention on forests as a radiation source have had little effect, even in Belarus where radiation-contaminated forests cover about 10 percent of the territory. The potential spread of radioactivity from contaminated forests and the high levels of radionuclides in forest foods continue to represent health risks to people in the region.

The contamination of forests with radioactivity from Chernobyl has also had significant economic impacts. The damage suffered by forestry in Belarus alone is estimated to be more than US$8 billion (Ipatyev et al., 1999a). It will be at least 30 years before radioactivity will have declined enough for forest harvesting operations to be considered again. In the meantime, Belarus, Ukraine and the Russian Federation have all designated a category of radioactive forests in which forest management interventions are limited to fire prevention, forest protection and monitoring, and pest control. Radiation contamination limits for wood are established by laws implemented in the countries affected by the accident.

Researchers at the Forest Institute of the National Academy of Sciences of Belarus are investigating possible methods to accelerate the process of forest rehabilitation and to decrease the risk of exposure of the population to radioactivity from forest ecosystems. This article examines the current condition of forest ecosystems near Chernobyl and discusses potential methods for decreasing the dangers of radiation-contaminated forest stands.

The forest radiation testing area Bartolomeevka



Forest ecosystems have an important capacity to capture radioactivity and to prevent it from being spread to nearby areas. Forests act as physical barriers to moving air masses, and a large part of radioactive particles that enter the forest are deposited there. Forests captured more than 80 percent of the Chernobyl-derived radionuclides (of which the most long-lived are 137Cs, 239, 240, 241Pu and 90Sr). Forest ecosystems incorporate the radioactive material into their biological processes; thus it moves within the woody plants/forest litter and soil/woody plants system in stable annual cycles.

By incorporating this material, forests also act as biological barriers to the spread of radioactivity. However, there is a risk that pest infestations, diseases and forest fires can spread the radionuclides far from contaminated forest areas. In particular, contaminated forest ecosystems need to be constantly monitored and protected against the danger of fire to prevent the spread of radioactivity (see Box on p. 41).

Radioactivity continues to have negative effects on the forest ecosystems in the region. Radioactivity has weakened forest animals' physiological states and perhaps their immune systems, resulting in increased prevalence of such infectious diseases as tick-borne encephalitis and tularemia.

Moreover, contaminated woodlands are adversely affecting nearby populations in the most heavily contaminated regions. Contaminated forests pose a serious health risk to local people who depend on forests foods to supplement their diets.

Forests are a significant source of the annual dose of radiation ingested by the population. Because of the difficult economic situation in Belarus, people continue to harvest and consume forest foods in spite of government efforts to discourage this (Ipatyev et al., 1999a) According to data obtained by researchers at the Forest Institute of the National Academy of Sciences of Belarus and the Gomel Institute of Radiation Medicine, in many Belarus and Russian localities affected by the Chernobyl accident the radiation dose ingested through the consumption of forest-derived products is two to five times as high as that ingested through the consumption of milk and other agricultural foodstuffs. Moreover, the forest-derived contribution is growing steadily. For instance, forest products currently account for more than 40 percent of the radionuclides ingested by the inhabitants of Gomel Province, Belarus.

The contribution of contaminated forests to the radiation dose of the Belarus Polesye population is particularly high because of the specific soil cover and climatic conditions of this terrain. The contents of radiocesium (137Cs) in forest-derived products (berries, fungi and game meat) that are usual components of the diet of the village people are 20 to 50 times greater than those in agricultural produce (Table 1). These forest areas and their products should be placed under strict radiation control.

TABLE 1. Radionuclide contents in principal foodstuffs


Radionuclide contents

Belarus Polesye

Gomel Province








2 000-10 000


Wild berries

1 000-2 500


Flesh of wild animals

2 000-50 000

2 000-80 000

The author (left) with research team; the sign at the barrier announces "radiation-contaminated forest"


Although forest ecosystems are capable of retaining, accumulating and redistributing radionuclides, they cannot neutralize the radioactivity absorbed. Studies on long-term radionuclide behaviour in forest ecosystems (A. Dvornik, personal communication) indicate that the radionuclide concentration in forests is now approaching its maximum. The decline in radioactivity to tolerable levels will take some 30 to 50 years depending on contamination levels, species composition of the stand, stand age and ecological conditions (Ipatyev et al., 1999b). In the meantime, efforts are being made to develop means to limit the uptake of radioactivity by forest foods and trees, which represents risks to human health and economic activities.

In agriculture, the usual way to decrease the radionuclide contents in produce to within acceptable limits has been through chemical and cultural practices, for example mineral fertilizer application and deep ploughing. Application of these techniques to forest soils is not easy owing to, for example, the lack of ploughing in forests and the prolonged intervals required for growing mature wood.

A radiation-contaminated woodland affected by fire

Researchers at the Forest Institute, located 120 km from the Chernobyl plant where the explosion took place, are working to devise a system of silvicultural, chemical and biochemical methods for decreasing the rate of soil-to-woody plant uptake of radionuclides. Experiments suggest that different soil moisture and nutritive regimes can decrease the rate of uptake of radionuclides by the above-ground parts of woody plants (Ipatyev, Dvornik and Bulko, 1995, 1997, 1998; Ipatyev, Bulko and Mitin, 1996). Thus organic matter from annual leaf and needle fall has lower radionuclide contents, forming cleaner forest litter and upper soil horizons and consequently a cleaner root layer.

In this way radioactivity is redistributed throughout the parts of the forest ecosystem (plants, litter, soil and fauna) in a "dissolution" process. Radioactive material migrates downwards from vegetation and down through the soil profile. Thus the amount in annual biological cycles gradually becomes smaller (Ipatyev, 2001).

For the first few years after the accident a greater fraction of the radioactive material was concentrated in the above-ground layer. Today, about 90 percent of the radioactivity has moved downwards to the forest litter and upper soil layers. Therefore the herbaceous layer, forest litter and uppermost soil layers together form the most intense "dose fields" (Krivolutsky, 1994) or "dose sheets" (Ipatyev, 2001). The gradual cleaning of radiation from a "dose sheet" is the essence of the function of the biological barrier.

Manipulation of the uptake of radionuclides, particularly through changes in the moisture regime, can thus be used to influence the accumulation of radioactivity in forest products (woody plants, herbs, fungi, wild berries, soil organisms, soil, wild animals) (Ipatyev et al., 1999a). Table 2 presents data on the 137Cs accumulation in wild berries and fungi harvested in 2000 from the experimental site under specific moisture regimes. This work suggests that it is possible to control the uptake of radiocesium by forest vegetation.

TABLE 2. Impact of different moisture regimes (average vegetative groundwater level [GWL]) on 137Cs accumulation in forest-derived products harvested from the eutrophic-mesotrophic bog in 2000

Forest product

137Cs accumulation (kBq/m2)


GWL 27 cm

GWL 56 cm













Cowberry plants

6 724



Paxillus fungi

29 680

10 640


Russula fungi

7 509

3 683



The distribution of the Chernobyl derived radionuclides over a vast area, and the effect that this has had on human populations, ecological systems and economic activities, points to the need for a concerted research effort. Investigations to determine not only the social and ecological but also the economic potentials of contaminated ecosystems should hold a central position in research agendas.

Two factors should govern appropriation of financial and human resources for the solution of the problem:

Methods to reduce the uptake of radionuclides by forest vegetation can have a positive impact on human health by reducing the amount of radioactivity entering the food chain through harvesting of forest foods. The costs of using the proposed methods for decreasing radioactivity in the above-ground parts of plants and soil can be recouped many times if these methods can shorten the stand rehabilitation period by eight to ten (or even more) years.

The measures taken to decrease both external and internal doses, the efficacy of forest protection measures and the benefits of a decrease in the amount of radioactivity captured in woody plants and forest foods are difficult to evaluate. Not only forest experts and economists but also specialists in radiation medicine should be involved in evaluating these.

So far the cost of rehabilitation of radiation-contaminated agricultural lands, to say nothing of forest ecosystems, has not been estimated. It is not inconceivable that a part of agricultural lands could be used for forest cultivation in the future, but the appropriateness of doing so would first have to be economically and ecologically substantiated. It is also necessary to determine the cost of restricting human activities in radiation-contaminated forests or wood enterprises. Unquestionably, the socio-economic effects of decreasing radionuclide accumulation in different components of the forest ecosystem go far beyond the forest sector. The ultimate goal is to protect the health of the community.

Research on radioactivity in the forests of Belarus will be relevant not only to accident-affected woodlands but also to protective forest belts around present and future nuclear power plant stations. More than 150 nuclear accidents in 14 countries are evidence for the necessity of this research. 


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