Soil erosion is a major worldwide threat to agro-ecosystem sustainability and land productivity. Fallout radionuclides and stable isotopes are used to measure magnitudes and sources of soil erosion, which can be controlled through efficient soil conservation practices.
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Soil erosion control
Land degradation currently affects 1.9 billion hectares globally or about 65 per cent of global soil resources. With 85 per cent, soil erosion is the main contributor. Approximately 1.5 billion people – a quarter of the world's population – depend directly on the food production from degraded lands. More than 36 billion tonnes of fertile soil is lost from world agricultural systems each year through soil erosion. The economic cost associated with on-farm and off-farm soil erosion is estimated at US$ 400 billion per year.
Jointly with the FAO, the IAEA helps Member States strengthen capacities in using nuclear and isotopic techniques to improve soil erosion management practices that support crop production and the preservation of natural resources.
Top soil loss threatens food security
Intensive agriculture and deforestation are major causes of land degradation involving soil erosion, leaving large areas vulnerable to the loss of fertile top soil. This, along with the losses of associated nutrients and chemicals to water bodies, is a serious threat to sustainable agricultural production, environmental protection and food security in many regions worldwide.
Adopting appropriate conservation practices such as intercropping, establishing water retention basins and building terraces can reduce soil erosion. However, these measures cannot be effective unless risk areas of soil erosion are identified. A quantitative approach is therefore required to better identify such risk areas for improving land management. Developing and refining methods for sediment budgeting and tracking is important to identify areas where soil erosion and sediment production are most critical.
The contribution of nuclear and isotopic techniques
Fallout radionuclides, such as caesium-137, lead-210 and beryllium-7, are used to assess medium- and short-term soil erosion and sedimentation processes, and often complement or even substitute traditional and more time-consuming techniques. These radionuclides are strongly fixed to fine soil particles and are not taken up by plants. During erosion and deposition processes they move with the soil particles and can be used to trace soil redistribution over large areas and extended periods of time.
The compound specific stable isotope technique, based on the measurement of carbon-13 signatures of specific soil organic compounds, such as fatty acids, is used to quantify the magnitude of soil erosion and to identify sources of land degradation. By linking fingerprints of land use to the sediment in deposition zones, this technique is useful in determining the sources of eroded soil and in identifying areas prone to soil degradation.
