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Land area is dwindling due to degradation, both natural and anthropogenic, therefore, it is reasonable to save this important resource and put focus on achieving land degradation neutrality (LDN). An Investigation was taken to know the impact of erosion on soil physico-chemical and biological properties both in fertilized and unfertilized conditions in four phases of erosion viz., slightly eroded (0.5% slope), moderately eroded (2.5% slope), severely eroded (4.5% slope) and very severely eroded (9.5% slope). Productivity index (PI), vulnerability curve, soil loss tolerance limits (STL), soil quality index (SQI) and relative soil quality index (RSQI) were estimated for all phases of erosion. As the severity of erosion increases the soil quality and productivity index (PI) decreases. Very severely eroded soils have lower PI, SQI and RSQI as compared to slightly eroded soils. However, land use under fertilized condition have better soil quality with SQI value of 143.00 and 118.00 in slightly eroded and very severely eroded soils, respectively, compared to 126.00 and 106.00 in non-fertilized condition. Similarly, the productivity index ranged 0.748 in slightly eroded phase to 0.651 in severely eroded phase under fertilized condition. Compared to slightly eroded soil, severely and very severely eroded soils have lower microbial biomass carbon (MBC), CO2 evolution and dehydrogenase activities. Assessment of soil loss tolerance limit based on PI revealed that it ranged from 6.67 to 12.92 Mg ha−1 year−1 which implies that land degradation took place in the more eroded soils which needs higher priority in order to bringing these eroded land to degradation neutrality (LDN), and also requires suitable soil conservation interventions in different phases of erosion.

Land degradation and soil erosion are key environmental problems in Mediterranean mountains characterized by both a long history of human occupation, and strong seasonality of hydrological regimes. Experimental monitored catchments have identified main controlling factors on erosion dynamics, but because of the short time span of the instrumental measurements they do not integrate the complete temporal and spatial variability of these environments. To obtain some long-term series of Mediterranean landscape evolution we propose a novel strategy based on multi-proxy analyses of lake sediments aimed to quantify sediment delivery and erosion dynamics. Karstic lakes in the Iberian Range (Central Spain) provide an opportunity to reconstruct the depositional evolution of the watersheds and to evaluate the response to both, the variable anthropogenic impacts and climate forcings during the last 1000. years.The most significant periods of increased sediment delivery (26-483Tkm yr-1) in the Iberian Range sites took place during the 15th-16th and 18th-19th centuries as a result of large land use changes and land clearing. Positive synergies between increasing human population and more humid periods led to peaks in sediment deliver during some phases of the Little Ice Age. Recent changes associated with the rural exodus and land abandonment during mid-20th century are more clearly shown in larger watersheds by decreased sediment delivery to the lakes due to the re-vegetation of the landscape (6-200Tkm yr-1).This new integrated approach based on long-term lake sequences provides a longer perspective of erosion processes in Mediterranean watersheds and validates the main factors identified in monitoring surveys (land cover and surface formations erodibility). In both settings, lakes and experimental catchments, most sediment delivery occurs during flooding events. Measured and reconstructed values show comparable large ranges, underlying the punctuated nature of sediment dynamics in Mediterranean landscapes at decadal and centennial scales. © 2016 Elsevier B.V., This research was supported by the GLOBALKARST (CGL2009-08415) project funded by the Spanish Ministry of Economy and Competitiveness and by the I-LINK program (I-LINK0510) funded by the CSIC. F. Barreiro-Lostres acknowledges the ‘JAE-PreDoc’ predoctoral contract co-funded by C.S.I.C. and the European Social Fund.

We investigated the genesis and local response of soils in mountain sites of the Sila Massif (Calabria, southern Italy), reforested ca. 60 years ago, and their relationships with geomorphic dynamics and forest stand structure. A multidisciplinary approach is proposed, focused on an often neglected soil profile scale and horizon-wise sampling strategy, and including pedological field observations, physical, chemical, mineralogical analyses, isotope geochemistry including fallout radionuclides (137Cs and 210Pbex), geomorphology, historical documentation of anthropogenic land cover changes, forestry and dendrometric measurements. Reforestation was carried out following extreme land degradation, which took place after forest clearance and field cultivation. Different tree species and soil preparation techniques were used according to site conditions. We focused on the main properties of selected soil profiles and the distribution of some radionuclides, in order to understand the effects of forest stands on hampering soil erosion and promoting novel soil formation, and to evaluate the potential hazard of natural gamma radiation. A comparison with soil profiles developed under naturally regenerated forest and field crops was achieved. The soil profiles in reforested sites showed a poor degree of development and a complex history of reworking processes alternated with soil-formation processes, in line with modern to historical radiocarbon dates increasing downprofile, the presence of buried horizons and 137Cs in the topsoils. Inventory changes obtained for 210Pbex and 137Cs highlight a process of soil stabilization occurred after reforestation, with more efficient effects under Calabrian pine than oak forest, whereas major geomorphic dynamics (erosion and accumulation) were triggered by forest coppicing, thinning and agricultural practices. Our data remark a positive response of the soil ecosystem to reforestation against erosion, trapping mobile material, stabilizing buried soils, promoting humus accumulation leading to new shallow topsoils, and the protective role of forests against anthropogenic and climatic-induced threats. Average values of the annual outdoor effective dose equivalents of gamma-emitting radionuclides calculated for all the soil horizons showed lower values than the population-weighted world’s average, with the exception of the soil profiles under forest stands developed on granite, exceeding this threshold. A deeper comprehension of soil genesis, geomorphic processes, land use and vegetation dynamics in vulnerable ecosystems such as mountain environments represents a fundamental basis for sustainable land management policies.

Slope deposits in North Pare provide evidence of two millennia of anthropogenically driven land clearance, soil erosion and land degradation. Drawing on deposit stratigraphy, soil magnetic parameters, stable carbon isotope composition and radiocarbon dating, three phases of soil erosion are distinguished characterized by distinct surface processes and increasing levels of agricultural land use. Onset of slope deposit formation in Pare since about 300 BC documents soil erosion as an immediate consequence of new land use practices associated with the spread of agriculture and iron working across northern Tanzania. By AD 500, slope deposits extended into valley bottoms and to middle slopes suggesting catchment-wide land clearance and soil erosion. In the 15th century AD, progressive anthropogenic soil erosion had exhausted the topsoil resource and material changes of the slope deposits reflect widespread subsoil erosion. The exposure of subsoils represents an ecological tipping point and triggered the transition to a new morphodynamic framework dominated by runoff-based erosion processes that are recorded as sand lenses and sand layers. The most recent deposits show ongoing accelerated erosion and severe land degradation whilst cessation of sand lens preservation indicates pre-colonial intensification of agricultural land use. Land use changes and socioeconomic transitions associated with the establishment of the Ugweno chiefdom and the 19th-century caravan trade are discussed as possible responses to imperceptible long-term land degradation in Pare. The study demonstrates that anthropogenic soil erosion and not external climatic drivers shaped landscape development in Pare and shows that the identification of environmental thresholds is essential for the assessment of resilience in human-dominated ecosystems.

The strongly incised mountain landscape of northern Thailand has changed dramatically during the last few decades due to increased population pressure, agricultural commercialization, limitation to use old fallows and reforestation of upper catchments. The traditional shifting cultivation with fallow periods of 7 years and longer was gradually replaced by 1 to 4 year fallow periods. As a result, in high population areas the landscape became dominated by fields planted to rainfed upland crops, wetland rice terraces, fallow vegetation, and patches of secondary forest. This new land-use system seems to have triggered new land degradation processes that are easy to observe when travelling through this landscape. The objective of this research was to assess the multiple effects of land-use intensification in a tropical steepland environment on land degradation processes. A case study was conducted at Pakha village (located in Thailand's northern most Chiang Rai province), which is dominated by steepland with average slope gradients ranging from 30 to 70%. Soil erosion processes were monitored in a selected catchment for 2 years, and informal interviews were conducted to elucidate farmers' perceptions regarding land degradation processes. The rapid land-use changes at the Dze Donglo catchment (164 ha) resulted in severe and accelerated land degradation, including tillage erosion (386 ton/year), inter-rill and rill erosion (502 ton/year), gully erosion (423 ton/year), and landslides (7572 ton during 1994). Water erosion is most common in intensively farmed areas. The combination of runoff-generating areas, runoff-concentrating features and connectivity led to extensive gully erosion. Landslides were most common in steep fallows and in wetland terraces along incising streams. Many of these steepland degradation processes interacted with each other (i.e. rills with gully erosion, tillage erosion with water erosion, gullies with landslides). The observed land degradation processes matched very well with farmers' perceptions. This study enabled to identify potential land degradation hotspots and indicates the necessity to analyze steepland degradation processes in a holistic way. (Resume d'auteur)

Human land use of the Tigray landscape (north Ethiopia) can be traced back for at least 3000 years and is recognizably very complex, but in the past half-century there have been multiple narratives on environmental change in the Northern Ethiopian Highlands in which statements such as “the forest and soil resources in Tigray are dwindling at unprecedented rates” are common. In an attempt to provide an objective assessment, we made a semi-quantitative analysis of observed changes in the environment of the central Tigray plateau, between 1975 and 2006, and its impact on soil erosion. The first part of this period saw strong degradation, caused by a combination of drought, impoverishment, poor land husbandry and war; but over the whole period intense rehabilitation activities have been high on the agenda. To study these changes, two sets of 51 landscape photographs have been used. The older photo-set was taken in 1975 by R.N. Munro during the Tigrai Rural Development Study; locations were revisited in 2006 by J. Nyssen and colleagues, when a new set of photographs was made at the same locations and with the same aspect. Based on longstanding experience in soil erosion and landscape analysis worldwide and in Ethiopia, the time-lapsed photographs were rated for visible erosion, land cover and protective measures. We present a quantitative evaluation of the change of soil loss by sheet and rill erosion, involving the Universal Soil Loss Equation (USLE) and particularly the changes in the C (cover) and the P (management) factors. This allowed assessing soil loss in 2006 as a percentage of the 1975 situation. Both the landscape and land unit analysis show that the situation for natural resources has improved (and locally strongly improved) since 1974. The rehabilitation is due both to improved vegetation cover and to physical conservation structures. The USLE application indicates that in terms of a whole landscape the current average soil loss would be at around 68% of its 1975 rate. Exceptionally, degradation is still ongoing around Desa'a forest and some other remnant forests, and conservation should be strongly implemented too in these forests. On average, gullies have expanded slightly since 1975, but these incisions appear to have originated in the drought years of the 1980s. This photo-monitoring analysis invalidates hypotheses on (a) irreversibility of land degradation in Tigray; and (b) futility of Soil and Water Conservation (SWC) programmes. The study demonstrates that (a) land management has become an inherent part of the farming system in Tigray, and (b) that the authorities and NGOs are on the right track when promoting SWC.

Historical land use changes may have significant impact on erosion and agricultural soil properties, including soil degradation by acidification, nutrient leaching and organic matter depletion. The Kali Basin study area, a small catchment of high landscape value located in a national park at Lake Balaton, Hungary, with its historical agricultural records, together with the available unique historical land use data for the last 200 years, provides an opportunity to study and model impacts of historical land use changes on erosion and agricultural soil properties. Comparison of long-term land uses with present soil degradation indicator parameters showed that permanent arable land use has led to degradation of both the physical and chemical properties of soils in the Kali Basin. Application of the SEDEM/WATEM distributed erosion and sediment transport model showed that, despite the low overall sediment export from the catchment, land use changes introduced by property ownership and agricultural changes have decreased average soil erosion in the catchment but increased relative sediment export to Lake Balaton. This is due to changes in the land cover pattern that allow more sediment transported to the river system. The overall conclusion of this study is that besides the size and area proportion of land use types, land use pattern seems to be equally important in soil erosion and degradation processes, thus land use pattern is a key factor for landscape planning and development in the Kali Basin. A relationship between the sociological and agro-ecological reasons for the recorded land use changes is also shown in this study.

The isolated Easter Island (Rapa Nui) is an outstanding example of land degradation caused by land use in a sensitive ecosystem. The focus of the investigation was placed on Poike peninsula, the most eastern part of Rapa Nui. While Poike peninsula was once supplied with fertile soils, in large areas desertification takes place today. Detailed analysis of soil profiles allowed the reconstruction of the history and of causes and effects of soil erosion and gullying in the context of land use history and cultural evolution. The results of the stratigraphic analysis prove that from the beginning of human settlement around AD 300/600 until AD 1280 the agriculture on Poike peninsula was characterised by sustainable land use and a traditional type of agro-forestry. Soil erosion was not significant. At around AD 1280 the woodland on Poike, dominated by the endemic palm Jubaea sp., was cleared by slashing and burning. Intensive farming on the upper slopes of the volcanic peninsula resulted in sheet erosion lasting until the 20th century. Settlements and ceremonial places which were built around AD 1300 on downslope areas were buried soon by sediments. Agriculture ceased around AD 1400 on downslope areas as the fertile soils were completely eroded. From AD 1400 until the late 19th century sheet erosion and the accumulation of fine-layered sediments migrated upslope. On average 8.6 Mg of soil per hectare and per year were reworked by erosion (eroded and accumulated within the catchment). Gullying began on Rapa Nui with the sudden increase in the number of sheep during the early 20th century. Gullies are still developing on the island and their ongoing enlargement created extended badlands on Poike which pose a significant problem for ecological and archaeological conservation strategies. Gullying rates exceed 190 Mg ha− 1 y− 1.

This article describes some of the results of a land evaluation within the framework of a research project carried out in a small catchment on the Loess Plateau in northern China, which has long been exposed to land degradation from erosion. The project aimed to identify an approach for land use planning, combining participatory (land users) planning, land evaluation and soil erosion modelling. The results from this study were intended to provide the biophysical properties of importance to be used together with results from participatory approach (PA) studies and soil erosion modelling to construct scenarios for a more sustainable use of land. Land properties, which were restricting for agricultural cropping, were defined and values of each property were matched with the requirements for cropping. By defining the spatial distribution of critical properties, they could be combined to achieve compound suitability classes in each land unit for the chosen land use. Information was gathered from measurements and data searches as well as from farmers, using PA methods. Properties for which data and other information were available and which were considered to be relevant for the study included climate, soil water content, slope aspect, soil water storage capacity, rooting environment, tillage constraints, slope gradient, infiltration capacity, soil nutrients and flooding hazard. Each of the properties were discussed in relation to their influence on land suitability, primarily for agricultural crops. Whatever management changes were carried out to improve the productivity and sustainability in the project catchment, restrictions for agricultural production were large. The major constraints were water availability, nutrient availability and erosion hazard. The properties chosen for further use in suitability evaluation and scenario analyses were those having a significant spatial variability in the catchment: soil type, slope gradient and slope aspect. The results from this study are applied in other articles this issue.

This study demonstrates the use of a Geographic Information System (GIS) for monitoring land use change, land degradation and erosion risk in the Albudeite catchment, S.E. Spain. A land use classification of the area was obtained by Air-photo Interpretation (API). Two sets of air-photos (1957 and 1986) were interpreted enabling land use changes over the 29 year period to be assessed. Gullied areas were also mapped from 1986 photographs and used to compute gully density. A Digital Elevation Model (DEM) derived from elevation contours was used to calculate terrain parameters, such as slope and aspect. The land use data were analysed together with DEM, slope, and aspect using a GIS to study the distribution of land use and land degradation features, and to monitor land use changes. An erosion risk map of the area was also produced by combining land use, gully density and slope data using the GIS. It was found that nearly 50% of the total area is susceptible to erosion risks, ranging from moderate to very severe, and that 56% of the cultivated land is threatened by these risks. Slopes of between 2–8° were found to be critical as both land use changes and erosion risks were greatest at these gradients.