Abstract
PurposeThis paper aims to demonstrate the importance of taking into account precipitation and the vegetation response to it when trying to analyse changes of vegetation cover in drylands with high inter‐annual rainfall variability.Design/methodology/approachLinear regression models were used to determine trends in NDVI and precipitation and their interrelations for each pixel. Trends in NDVI that were entirely supported by precipitation trends were considered to impose climate‐induced vegetation change. Trends in NDVI that were not explained by trends in precipitation were considered to mark human‐induced vegetation change. Modelling results were validated by test of statistical significance and by comparison with the data from higher resolution satellites and fieldtrips to key test sites.FindingsMore than 26 percent of all vegetated area in Central Asia experienced significant changes during 1981‐2000. Rainfall has been proved to enforce most of these changes (21 percent of the entire vegetated area). The trends in vegetation activity driven by anthropogenic factor are much scarcer and occupy about 5.75 percent of the studied area.Practical implicationsPlanners, decision makers and other interest groups can use the findings of the study for assessment and monitoring land performance/land degradation over dry regions.Originality/valueThe study demonstrates the importance of taking into account precipitation and the vegetation response to it when trying to analyse changes of vegetation cover in drylands with high inter‐annual rainfall variability.
Highlights
Since in drylands Normalized Difference Vegetation Index (NDVI) is usually stronger affected by rainfall than any other factors including human activities, assessment of desertification may not be based on the use of NDVI time-series alone, it should take into account the rainfall
Our calculations revealed the borders of the precipitation-dependent areas in Central Asia and Kazakhstan
The monitoring system bases on the concept of synchrony/asynchrony in the trends of vegetation and climate, which has been presented and thoroughly described in this paper. This monitoring system used the temporal response of vegetation to precipitation as major indicator for degradation or improvement of the vegetation cover
Summary
Desertification is considered as result of a series of complex natural, mainly climatic, and anthropogenic processes that leads to gradual environmental degradation or loss of the lands biological and economical productivity. Drylands occupy about 40 percent of the land surface, contain about 30 percent of the world’s carbon and provide habitat to more than 1 billion humans. Their rangeland supports approximately 50 percent of the world’s livestock. Taking into account the importance of these territories for the survival of the mankind it is not surprising that the international community is making intensive efforts to combat desertification in drylands and to preserve them from further degradation
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