water cycles [5; 6; 7; 8]. To sum up, the term 'degradation', referring to the condition of natural grasslands and pastures, is widely used in different circumstances by different stakeholders, from researchers and rural extension agents to policy makers, without a commonly agreed definition. The causes of rangeland degradation are generally attributed to a combination of overgrazing, unscientific livestock management, historical-cultural barriers to adopting modern livestock management concepts, global climate change, and soil damage by small mammals [9]. From the perspective of farmers, pasture and meadow degradation reduces the economic performance and sustainability of livestock production, which may result in a reduction in the body weight and wool yield of sheep [10], forage quality [11], cattle production [12], milk production [13], etc. Another important aspect is the criterion used for assessing the degradation of pastures and grasslands. The United Nations has proposed the changes in the land cover, productivity, and carbon reserves as sub-indicators for monitoring land degradation processes [14]. Other monitoring indicators that are often used are vegetation cover, vegetation height, aboveground biomass, grass yield, and net primary productivity, especially in remote-sensing scenarios [15]. Nevertheless, scientists classify the degradation of pasture/meadow/grassland into different categories, using different assessment criteria. In [16], the pastures in the state of Minas Gerais, Brazil, were categorized into only two classes, based on their chemical and physical characteristics: healthy pasture and degraded pasture. In another Brazilian study [17], three degradation levels of pastures are used, and the chosen criterion is the share of exposed soil. Level 1, no or low degradation (\(\leq\)20% exposed soil); Level 2, medium degradation (20-45% exposed soil); and Level 3, high degradation (>45% soil exposed). Another study for Brazil assessed the degradation of humid tropic pastures in four classes, based on the erosion of the soil [18]: no visible degradation; light degradation (pastures with sheet erosion or shallow cattle tracks); moderate degradation (some vertical erosion is visible, such as gullies); and strong degradation (pastures that are partly interrupted and vertically broken with cattle tracks as well as large gullies). In a study dealing with Kazakhstan pastures [19], the vegetation cover was the main criterion for assessing their degradation. Furthermore, it applied the Drude scale [20], where the following classes are defined:  
1. Soc. : plants grow close to each other, joining with their aboveground parts (90-100%);
2. Cop. 3: plants occur in very large numbers (75-90%);
3. Cop. 2: plants occur in large numbers (50-75%);
4. Cop. 1: plants occur in considerable numbers (25-50%);
5. Cop. 1-Sp. : the species are relatively abundant (15-25%);
6. Sp. : the species are abundant, but do not form a continuous cover (5-15%);
7. Sol.-Sp. : low abundance (1-5%);
8. Sol. : the species grow sparsely (<1%);
9. Un. : the species occur in single instances. In [21], the grassland degradation was assessed in Northern Tibet. The suggested classification was based on the grassland degradation index (GDI):  
\[GDI=\frac{\left(\sum_{i=1}^{5}D_{i}\times A_{i}\right)}{A}, \tag{1}\]  
where \(D_{i}\) is the grading score of grassland degradation, \(A_{i}\) is the distribution area of grade \(i\), and \(A\) is the total area of the investigated grassland. The degradation was then categorized into five classes: undegraded (GDI \(\leq\) 1); light degradation (GDI \(\leq\) 2); moderate degradation (GDI \(\leq\) 3); serious degradation (GDI \(\leq\) 4); and extremely serious degradation (GDI \(>\) 4). Another approach is the classification of degradation, based on the coverage of a certain plant or the canopy coverage. In [22], the grassland degradation in China was assessed based on the coverage of Stellera chamejasme (SC).