Land degradation versus fire: A spiral process?

摘要

Originally associated to arid regions, vulnerability to land degradation (LD) has rapidly spread in temperate areas, such as the Mediterranean basin. In this region LD increased in the last years due to worsening climate conditions, land-cover changes, soil erosion and anthropogenic pressures. Increasing land vulnerability is mutually linked with an increasing risk of disturbance propagation: the spatio-temporal distribution of areas with different degrees of LD determines different dynamic patterns of the disturbance; in turn, LD is strongly affected by the disturbance occurrence regime, which alters the status quality of a given territory. These considerations invite a comparison between vulnerability to LD and fire occurrence, since historically, in the Mediterranean areas, fire represents one of the main disturbance sources, which is mostly human-induced and with a strong seasonality pattern. Under certain conditions, LD may create conducive conditions for fire to thrive that in turn if repeated may alter the quality status of a landscape, setting the interested area into a LD-fire feedback dynamic. The aim of this paper is to analyse the relationship between fire incidence and LD and their potential feedbacks in Sardinia during two reference periods, 1990 and 2000. Results indicated that in areas already affected by high LD vulnerability there is a sort of LD-fire spiralling connection that can be seen as a 'mutual early-warning system' with strong implications on fire prevention strategies and landscape quality status monitoring.