Land degradation is the result of a number of largely human-induced factors, such as poor soil and water management practices, deforestation, overgrazing, improper crop rotation and unsustainable land use. In turn, these can significantly affect soil fertility, resulting in diminished crop yields and food insecurity. Traditional methods of modelling and monitoring soil erosion usually require a large number of parameters and many years of taking measurements. However, over the past decade, nuclear technologies and isotopic techniques have been introduced, which can effectively assess the soil and water status of an area, as well as identifying hot spots of land degradation. But how does it work?
The use of past radioactive fallout radionuclides (FRN’s) can measure soil erosion rates and reveal erosion processes, because their concentration in undisturbed soil differs, depending on its distance to the surface. For example, much of the work so far has focussed on Caesium-137 (as well as Beryllium-7 and Lead-210), which is rapidly absorbed by the surface soil and subsequently redistributed by erosion processes. These radionuclides can therefore be used to trace the origin of the soil over a large area within a short period of time. This valuable information is then used to develop effective soil conservation techniques.
Nuclear technologies such as this can play another important role other than merely assessing soil erosion. The International Atomic Energy Agency (IAEA) uses nuclear techniques to help countries develop crops that are drought resilient, improving agricultural productivity by calculating the precise amount of fertiliser and water required to optimise yields.
Another technique involves the use of Compound Specific Stable Isotope techniques (CSSI), based on the measurements of carbon-13 stable isotopes from organic compounds in the soil which are used as tracers, to identify exactly where the eroded soil originated from. According to the IAEA, CSSI’s are specific to different plants and so by analysing the CSSI make-up of the eroded soil, scientists are able to trace it back to its origins, therefore enabling them to design and apply appropriate conservation measures. Isotopic techniques are also used to study fertiliser use and uptake as well as determining transpiration and evaporation rates. Results can then be used to apply management practices such as mulching, minimum tillage and a drip/spray irrigation system to reduce soil evaporation.
The IAEA and the Food and Agriculture Organization (FAO) are helping to promote climate smart agricultural practices such as these across a number of different countries. According to the IAEA/FAO, the use of FRN’s to measure soil erosion rates have successfully been used within 65 IAEA Member States. For example, CSSI have been used as tracers to identify exactly where eroded soil originated as well as determining evaporation and transpiration rates in a number of countries. This information has then been used to implement a number of targeted conservation measures that have enabled Indonesia, Pakistan, Vietnam and China to reduce land degradation in targeted areas by almost 50 percent.
Use of these techniques however, is an expensive undertaking. Due to the sophistication of the process involved, it requires trained personnel as well as suitable laboratory facilities to analyse fallout radionuclides and erosion rates. But this would appear to be a necessary expense when considering the economic cost of global land degradation. Last year, a report by the Economics of Land Degradation Initiative estimated that land degradation is costing the world an estimated $10.6tn each year, equivalent to 17% of global GDP, largely due to the loss of ecosystem services such as water filtration, erosion prevention and nutrient cycling. A CABI blog post written last year provides further insight on the report.
Following the 2012 United Nations Convention to Combat Desertification, a policy brief was published, calling for world leaders to agree a goal on land: zero net land degradation by 2030. In order to achieve this goal it outlined how the degradation of productive land should be avoided and already degraded land should be restored.
More recently, on September 25th 2015, world leaders formally adopted a set of new sustainable development goals to “protect the planet, end poverty and ensure prosperity for all”. Many argue that ensuring sustainable land management is relevant to achieving half of these goals, such as food security, poverty reduction and water resource management. Goal 15 specifically addresses land degradation and under target 15.3, it states: “By 2030, combat desertification, restore degraded land and soil, including land affected by desertification, drought and floods, and strive to achieve a land degradation-neutral world”.
Soil has many roles, as a medium for plant growth and the production of food, as well as supplying clean water and resilience to flooding and droughts. As the largest store of terrestrial carbon, its conservation contributes to the adaptation and mitigation of climate change, therefore the importance of its preservation and restoration should not be ignored.
Further information on the use of techniques to assess land degradation is available to subscribers of the CABI Environmental Impact database.
Further reading and resources