|Giraffes in the African Savanna Image 123RF|
The five researchers report that "NDVI was more sensitive to herbaceous vegetation changes and short-term precipitation variations," while VOD "was more sensitive to changes in woody vegetation and longer-term precipitation variations." And, as a result, they remark that "co-trends between NDVI and VOD provide evidence of widespread woody vegetation encroachment at the expense of the herbaceous vegetation component in arid regions, and arid shrublands in particular." And as their ultimate conclusion about the matter, they concluded that the "spatial distribution of trends suggests that a global driver (e.g., CO2fertilization) is causing a change in relative performance of woody vegetation compared to herbaceous vegetation," while further noting that evidence for woody thickening and encroachment was also found for some semi-arid drylands.
In spite of the postulated growing negative impacts of man and climate alike, the greening of the earth continues - and in places where it's toughest of all to be green (arid lands) - with the proposed impetus for the phenomenon being the likely-enabling role of anthropogenic-induced atmospheric CO2 enrichment.