Potential effects of environmental change on landslide hazards in forest environments.

Abstract

The interactive roles of the natural factors that contribute to landslide initiation and potential climate changes are complex. Additional complexity is added when changing forest land uses are considered. Thus, while it is impossible to ascertain specific patterns of landslide response to possible climate change, certain generalizations can be made and scenarios can be discussed. Shallow, rapid landslides will only increase in scenarios of increasing rain event intensity, whereas, deep-seated mass movements will increase with seasonal increases in precipitation. Dry ravel may respond more directly to warming, increasing with sparse vegetation covers and increased frequency of fire. Climate change has the greatest impacts on landslide occurrence by modifying evapotranspiration and root strength of vegetation. Evapotranspiration affects soil water recharge and subsurface flow and thus influences slope stability. Climate change may alter canopy structure, soil runoff and evaporation, ground cover, and rooting depth; these in turn affect water storage and routing in unstable sites. Anthropogenic and climate-induced changes in vegetation cover particularly affect the potential for shallow landsliding due to modifications in root cohesion. While much attention has been placed on the impacts of forest harvesting practices on increased landslide erosion, the effects of permanent forest land conversion, particularly in the tropics, appear more problematic. Additionally, the increasing impacts of affluent recreation in the developing world need to be assessed. Agroforestry may offer some socioeconomic and natural resource advantages in selected cases, but cumulative off-site effects must be evaluated. Depending on the level of detail required and type of available data, landslide hazard can be assessed by several methods: (i) terrain stability classification; (ii) empirical landslide hazard assessment; and (iii) physically-based models. Including climatic change scenarios into landslide hazard models is a complex task because scenarios of climatic change are unclear even at regional levels. Also, most models only evaluate land use in a very general way. Thus, much progress is needed to predict these interactive climate-change and anthropogenic impacts on slope stability.