Glossary

Definitions of key terms and words used used by the CASCADE project and in this website.


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degraded systems

Systems resulting from reduced or loss of resilience in one or more aspects.

dehesa

Oak savanna in Spain, with cork oaks (Quercus suber) or holm oaks (Quercus rotundifolia) and cultivated fields or, most typically, grasslands.


desertification

1. Land degradation in arid, semi-arid and dry sub-humid areas resulting mainly from adverse human impact.

2. Land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variations and human activities (UNCCD 1994)

discounting

The procedure to arrive at the sum of either the costs or benefits over the lifetime of a project using a discount rate to scale down future benefits and costs. The effect of using a discount rate is to reduce the value of projected future costs and benefits to their value as seen from the present day (the main justification being individual time preference). It is often of an order of 6%.


dryland ecosystems

Ecosystems in arid, semi-arid and subhumid areas, characterised by water scarcity and harsh climatic conditions. Disturbances in these fragile ecosystems can easily result in widespread and severe land degradation and thus desertification. (from Schwilch 2012, Ph.D. Thesis, p.3)

drylands

1. Arid, semi-arid, and dry subhumid areas (UNCCD).

2.  All the terrestrial regions where water scarcity limits the production of crops, forage, wood and other ecosystem provisioning services, i.e. where the aridity index (AI), defined as the long-term ratio of mean annual precipitation to mean annual evaporation demand (expressed as potential evaporation), is less than 0.65 (Millenium Ecosystem Assessment). Formally, the definition encompasses all lands were the climate is classified as dry subhumid (0.5<AI<0.65), semiarid (0.2<AI<0.5), arid (0.05<AI<0.2) or hyper-arid (<0.05). Precipitations in drylands are characterised by their high variability and unpredictability. (from Kéfi 2008, Ph.D. Thesis, p.9)


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