Landslide erosion risk to New Zealand pastoral steeplands productivity
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Authors: P. G. Luckman, R. D. Gibson, and R. C. Derose
Date: 1999
Journal: Land Degradation & Development
Volume: 10
Number: 1
Pages: 49-65
Summary of Methods: A simple model was developed to evaluate the impacts of long-term soil erosion on pasture productivity caused by storm-induced landslides steep (>25°) hill slopes. The study area is located on the North Island of New Zealand (38° 24' S; 175° 43' E) where the risk of landslides can increase following initial forest or scrub clearance, ultimately leading to a decrease in pasture productivity caused by increased soil erosion. The basic modeling unit of measurement used was the terrain mapping unit (TMU) which is described as a relatively homogenous parcel of land covering several hectares up to several thousand hectares. Several variables were included in this model (surface and subsurface soil properties within the TMU, landslide occurrences, intensity of rainfall events, natural terrain controls and productivity).
Article Summary / Main Points: Stabilization of steep slopes was not economically beneficial for today’s farmers, as the returns would likely be seen by future generations. The rate of pasture recovery following a landslide was found not to be a significant factor in determining overall productivity. In all landslide simulations examined, pasture productivity had stabilized well before 100 years, although the areas affected by landslides continued to grow. The results of the model show declines in productivity caused by soil erosion are unlikely in areas that have been under pastoral land use for 50-100 years, regardless of landslide risk. This model did not take into account lateral surface soil movement which is an important component of soil recovery, thus reducing the efficacy of the results as actual landslides continue to occur.
Vegetation Types: Intermountain Grasslands (includes Palouse Prairie and Canyon Grasslands)
MLRA Ecoregions: Not Applicable
Agrovoc Control Words: Pasture management Landslides Erosion
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: erosion, landslides, mass movement, land stability, pasture productivity, risk analysis, sustainability, simulation model, monte carlo
Annotation: The scientific strength of the model has been validated by several previous studies focused on modeling landslide risk and ecological impacts. However, important variables such as lateral soil surface movement and direct measurements of hillslope-scale productivity were excluded, thus potentially compromising the effectiveness of this model. Notably, this study points out the strong need to adopt sustainable land management practices when utilizing steep slope ecosystems as grazing lands. Further long-term field studies in conjunction with model simulations need to be undertaken to improve land management decisions and landslide risk analysis.
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