Climate change, impacts and vulnerability in Europe ... - MemoFin.fr

Climate impacts on environmental systems3.5.5 Biomass production and recurrent negativeprecipitation anomaliesSoil degradation processes are global phenomenathat cause a reducing biophysical capacity in theland to sustainably produce ecosystems services andeconomic value. They are linked to complex patternsof land use and climatic variations. Observedchanges in primary productivity of ecosystemsare a strong indication of the onset or increasingvulnerability to soil degradation. As discussedin Section 3.5.2, organic matter is an importantdriver of several soil functions. A reduction in theproduction of biomass will have an impact on soilorganic matter levels and related nutrient cycles. Inparticular the parallel reduction in the vegetativecover and plant roots will increase the risk of bothwind and water erosion.Climatic conditions and intensive agriculture makethe Mediterranean region particularly vulnerableto soil degradation. Ever more demanding land useleads to water scarcity, limiting several ecosystemservices normally provided by soil. Amplifiedvariability of aridity limits the ability of intensivelyused human-environment systems to recover fromspecific pressures such as salinisation, droughtand fire (see Section 4.1). In turn, this leads to anincrease in soil degradation and, in extreme cases,desertification.Map 3.24 presents areas affected by three recurrentnegative precipitation anomalies over a period of10 years, and as such provides a first indicationof areas under risk of soil degradation. Many soiltypes in the Mediterranean region already showsymptoms of degradation (i.e. shallow depth,low soil organic carbon content, prone to erosion,low fertility, increased salinity and forest fires)which, together with the hot, dry climate of theregion, hampers the assessment of ongoing landdegradation.While the effects of reduced biomass productionmay be dramatic in the Mediterranean region,the consequences on soil resources may also beevident in more temperate or humid regions.Recent observations suggest that Mediterraneanecosystems are generally resilient and resistant todroughts. However, where human activity becomestoo intense, degradation is more pronouncedand can possibly become irreversible. Map 3.24illustrates that, even after recurrent droughts, theMediterranean environment recovers well, apartfrom areas that are under intense agriculturaluse and where the erosion risk is already high(see Map 3.21).Projections are very limited. Increases in therecurrence of extreme events, such as droughts,combined with risks, such as forest fires, and anexpansion of intensive land use will probably inducehigher levels of degradation, including soil erosionand, in turn, reduce the quality and availability ofnatural resources and ecosystems services.Key messages: 3.5.5 Biomass production and recurrent negative precipitation anomalies• Biomass production is a major soil function and its decline can be used as a proxy for soil degradation.• Recurrence of negative precipitation anomalies is leading to an increased risk of soil degradation dueto the reduction of biomass, which is the main source of soil organic matter and protects soils fromerosion.• Soil degradation processes are already intense in several parts of the Mediterranean and in some partsof central-eastern Europe.• In many cases, increased human pressure aggravated by climate change impacts can lead toirreversible soil degradation processes with adverse social, economic and environmental effects.• Increase in recurrence of extreme climate events, such as droughts, combined with specific hazards,such as fires and both natural and human-induced salinity, and/or an expansion of intensive land use orland-use change, will probably induce higher levels of land degradation.156 Climate change, impacts and vulnerability in Europe 2012