Erosion in Mediterranean landscapes: Changes and future challenges

Abstract

Intense erosion processes are widespread in the Mediterranean region, and include sheet wash erosion, rilling, gullying, shallow landsliding, and the development of large and active badlands in both subhumid and semi-arid areas. This review analyses the main environmental and human features related to soil erosion processes, and the main factors that explain the extreme variability of factors influencing soil erosion, particularly recent land use changes. The importance of erosion in the Mediterranean is related to the long history of human activity in a region characterized by low levels of annual precipitation, the occurrence of intense rainstorms and long-lasting droughts, high evapotranspiration, the presence of steep slopes and the occurrence of recent tectonic activity, together with the recurrent use of fire, overgrazing and farming. These factors have resulted in a complex landscape in which intensification and abandonment, wealth and poverty can co-exist. The changing conditions of national and international markets and the evolution of population pressure are now the main drivers explaining land use changes, including farmland abandonment in mountain areas, the expansion of some subsidized crops to marginal lands, and the development of new terraces affected by landslides and intense soil erosion during extreme rainstorm events. The occurrence of human-related forest fires affecting thousands of hectares each year is an increasing problem in both the northern and southern areas of the Mediterranean basin. Here, we highlight the rise of new scientific challenges in controlling the negative consequences of soil erosion in the Mediterranean region: (i) to reduce the effects and extent of forest fires, and restructure the spatial organization of abandoned landscapes; (ii) to provide guidance for making EU agricultural policy more adapted to the complexity and fragility of Mediterranean environments; (iii) to develop field methods and models to improve the identification of runoff and sediment contributing areas; (iv) to contribute to the conservation of landscapes (i.e. bench-terraced fields) having high cultural and productivity values; (v) to improve knowledge of the hydrological and geomorphological functioning of badlands, with the aim of reducing sediment yield and accessibility; (vi) to better understand the effect of climate change on soil erosion in the Mediterranean region; and (vii) to improve quantitative information on long-term soil erosion. COVER LETTER

Effects of permanent grass versus tillage on aggregation and organic matter dynamics in a poorly developed vineyard soil

“…The topsoil of the studied vineyard was rather vulnerable to aggregate breakdown in both 264 treatments (Figure 3), as often observed in hilly areas of the Mediterranean, where OC contents as 265 low as 20 g kg -1 are not unusual (Jones et al 2005) due to erosion (García-Ruiz et al 2013;Novara 266 et al 2015) and poor soil development (Novara et al 2015). Moreover, deep tillage before vine 267 planting could have also contributed to reducing OC contents due to the combined effects of (i) 268 mixing of deep horizons with the topsoil, as often happens after severe disturbances (e.g., Stanchi et 269 al.…”

Coupling distributed stormwater collection and managed aquifer recharge: Field application and implications

“…In WY14, far less accumulated, 8.3 Â 10 4 kg, but the runoff sediment load was 2 g/L, similar to WY15. Although runoff sediment loads were modest, the annual sediment yield of the drainage area, 120e735 Mg/km 2 , is in the middle range of values from other agriculturally developed regions (Koluvek et al, 1993;de Vente and Poesen, 2005;Ficklin et al, 2010;García-Ruiz et al, 2013). Grain size analyses showed that accumulating sediment had a different texture from both upland soil available for transport and subsurface soil in the infiltration basin.…”

Impact of Soil Depth and Topography on the Effectiveness of Conservation Practices on Discharge and Soil Loss in the Ethiopian Highlands

“…It causes the loss of agricultural productivity and a decline of water quality [2][3][4]. It is estimated that about 10 million ha of cropland is lost in the world due to soil erosion every year [5] and is often a common occurrence in the Mediterranean and China [6,7]. Erosion rates vary throughout the world: In the hilly areas of the northern Mediterranean region, along the Atlantic coastline and stretching from France to Greece, the annual sediment losses are in the order of 1.5 Mg ha −1 y −1 [8].…”