Land degradation can be classified into physical, chemical, and biological types. These types do not necessarily occur individually; spiral feedbacks between processes are often present (Katyal and Vlek 2000). Physical land degradation refers to erosion; changes in the soil physical structure, such as compaction or crusting and waterlogging. Chemical degradation, on the other hand, includes leaching, salinization, acidification, nutrient imbalances, and fertility depletion, soil organic carbon loss. Biological degradation includes rangeland degradation, deforestation, and loss in biodiversity, involving loss of soil organic matter or of flora and fauna populations or species in the soil (Scherr 1999).
Causes of land degradation
are classified into proximate and underlying. Proximate causes of land degradation are those that have a direct effect on the terrestrial ecosystem. The proximate causes are further divided into biophysical proximate causes (natural) and unsustainable land management practices (anthropogenic). The underlying causes of land degradation are those that indirectly affect the proximate causes of land degradation (von Braun et al. 2013).
The negative processes related to development of land degradation have reached alarming proportions at the beginning of 2000s in the Russian Federation. More than 20 types of land
degradation processes can be identified, which lead to a deterioration in the quality of land, reversible and irreversible transfers of land from one category to another. In arable land, most degradation is caused by the development of processes of erosion and deflation, secondary salinization, reduction of humus, phosphorus and potassium content, and adverse values of pH. The reversible transfer of lands from one category to another is related to the covering with shrubs and woodland, the flooding of the floodplain meadows by water in reservoirs and clogging by the stones. Long-term and irreversible losses of arable land is due to factors such as the contamination by radioactive substances, the extraction of minerals, development of gully systems, subsidence effects associated with waterlogging of soil, and construction of residential and industrial buildings on lands suitable for farming (Kashtanov 2001; Dobrovolski 2002).
The Federal program “Preservation and restoration of soil fertility of agricultural lands and agricultural landscapes as a national treasure of Russia in 2006–2010 and for the period till 2013” established indicators for restoration and rehabilitation of agricultural lands for 2010. These target indicators were exceeded by 2010; however, the rate of rehabilitation of degraded agricultural land is insufficient in comparison to the scale of land degradation in Russia. The area protected from water erosion, inundation and flooding, wind erosion and desertification constituted approximately 0.4 % of lands of Russia. The decrease in the degree of acidity of the soil was approximately 0.6 %, which equates to 0.06 % of the amelioration of solonetzic soils of all agricultural lands (Ministry of Agriculture 2011).
According to estimates at the present time, the total expected yield of eroded and deflated arable land is about 25 % less than of areas not affected by erosion. It means that the loss is 400 kg per ha in the equivalent for grain, and for the entire country it is about 14 billion kg, even taking into account the actual low crop yields and low productivity of natural grasslands. The shortage of products from degraded grasslands is about 100 kg per ha of hay, which gives 1400 million kg loss for the total area of the country (Ministry of Natural Resources and Environment of the Russian Federation 2013).
Erosion is evident in areas with hilly terrain. About 20 % of agricultural lands in Russia are on slopes steeper than 20 %. Under these conditions, water flow, resulting from intensive snowmelt or precipitation of heavy rainfalls, lead to the development of gully erosion. The total area of the gullies is 2.4 million ha (0.14 % of the total land area of the Russian Federation). The main part of the gullies are located on agricultural lands (0.6 million ha), forest
(1.1 million ha) and protected environmental lands. Every year the area of ravines grows with devastating speed up to 180–200 thousand ha. The growth of gullies leads to the complete withdrawal of productive land or transforms it into other categories such as pasture or unused land. The land area affected by gully erosion is 2.5–3 times larger than the area of the gullies, because of the difficulties for operation of agricultural machinery. Due to production conditions they have low productivity and are eventually transformed into low productive grazing lands. The annual loss of production from these lands is estimated at 1200 million kg of grain (Ministry of Natural Resources and Environment of the Russian Federation 2013).
Soil compaction leads to the loss of tillage performance by up to 5–10 %. Costs
for fertilizer increase approximately by 1.5 times, as low-degraded lands require higher doses of fertilizers by 10 %, medium-degraded by 30 % and high-degraded 1.5–2 times (Gordeeva and Romanenko 2008). On heavily compacted soils yield reduction reaches 50 %. Low-compacted soils occupy 17 million ha; medium-compacted—69 million ha, and high-compacted—49 million ha of arable lands. Loss of fertility is 5–10, 20–30 and 50–60 %, respectively. Humus content is decreasing, the environmental condition of the soil is deteriorating, and more recently, the stability of the soils is decreasing. Humus storage in Chernozems is reduced annually by 0.62 t/ha over the last 15–25 years. Losses from the presence of acidic soils are 15–16 billion kg of agricultural products in terms of grain per year (Gordeeva and Romanenko 2008) (Table 18.7).
As it was mentioned above, it is more useful to take into analysis the macro-regions of Russia, such as the federal districts, because they are more homogenous in climatic conditions, economic development, and land-use practices. We have taken into consideration eight Federal districts—Central, North-Western, Southern, North Caucasian, Volga, Ural, Siberian, and Far Eastern.
Following Nkonya et al. (2011) we compare the changes in NDVI
between 1981 and 2006 and some key biophysical and socioeconomic variables, such as precipitation, population
density, government effectiveness, agricultural intensification, and Gross Domestic Product (GDP) (Figs. 18.2, 18.3, 18.4 and 18.5). Since such relationships could differ across the country, we disaggregate the analysis across the eight Federal districts of Russia. The analysis showed a positive correlation between changes in key biophysical and socioeconomic variables with NDVI in most of the Federal districts of Russia. The exceptions are the FD with large and more heterogeneous territory such as Siberian and Far Eastern FDs. The most positive results were in the Chernozem Agro-ecological zone—the southern part of Russia.
Le et al. (2014) used 7 broad land use/cover classes (see Fig. 18.6) aggregated from 23 classes of the Globcover 2005–2006 data (Bicheron et al. 2008). Figure 18.6 shows the main land-cover/land-use changes compared to long term NDVI
(1982–2006). The NDVI layer corrects for AF (atmospheric fertilization
), areas with a high positive correlation with RF (rainfall), and saturated areas of NDVI (see Chap. 5). The related statistics for Russia are shown in Table 18.8. Figure 18.6 shows that land degradation hotspots
in Russia are mainly on forested areas, croplands and areas with sparse vegetation. These are areas affected by forest fires (Sakha Republic, Krasnoyarskiy territory, etc.) and crop land degradation
(Saratov, Omsk, Tyumen, Kurgan regions, etc.), due to processes such as salinization, degradation of irrigated lands, and desertification. In the case study of the Rostov region, we can also see the manifestation of cropland
Table 18.8 shows that close to 20 % or more (except shrub-land) of each main land cover/use types were affected by degradation processes. Croplands, especially in the southern part of Russia, where the agricultural industry is more risky due to drought, wind erosion, and problems with moral obsolescence of the irrigation system, have the biggest percentage of degradation in Russia (27 %).