Changing Climate and Overgrazing are Decimating Mongolian Steppes.
Liu, Y.Y., J.P. Evans, M.F. McCabe, R.A.M. de Jeu, A.I.J.M. van Dijk, A.J. Dolman and I. Saizen
PLOS ONE, 8(2), e57599, doi: 10.1371/journal.pone.0057599, 2013.
Satellite observations have identified the Mongolian steppes as a hotspot of
global biomass reduction, the extent of which is comparable with tropical
rainforest deforestation. To conserve or restore these grasslands, the relative
contributions of climate and human activities to degradation need to be
understood. Here we use a recently developed 21-year (1988-2008) record of
satellite based vegetation optical depth (VOD, a proxy for vegetation water
content and aboveground biomass), to show that nearly all steppe grasslands
in Mongolia experienced significant decreases in VOD. Approximately 60% of
the VOD declines can be directly explained by variations in rainfall and surface
temperature. After removing these climate induced influences, a significant
decreasing trend still persists in the VOD residuals across regions of Mongolia.
Correlation in spatial patterns and temporal trends indicate that a marked
increase in goat density, the associated grazing pressures, and wild fires are
the most likely non-climatic factors behind grassland degradation.
Figure 3. Trends in VOD residuals, changes in goat density and
fire hotspots. (A) Trends in VOD residuals after removing the influence
of climatic factors. Only statistically significant trends (p,0.05) are
shown. The analysis conducted on VOD was also applied on NDVI. No
significant trends were observed in NDVI residuals and thus they are not
shown here. (B) Differences in goat density (heads per square kilometer)
between 2008 and 1990. (C) Annual average number of recorded fires
for each 0.25u grid cell between 2001 and 2008, based on MODIS global
monthly fire location product.
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Last updated 31st January 2013