Background
According to the authors of this intriguing research report, the dry northern and northwestern regions of China, including the Inner Mongolia Autonomous Region (IMAR), have been thought by many to have experienced declining vegetative productivity over the past few decades due to "increasing livestock numbers, expansion of cultivated land on erosive soils and the gathering of fuel wood and herb digging," which practices are believed to have been driven by "rising living standards, which, in combination with a continued growing population, [are] assumed to have increased the pressure on [these] marginal lands."  In the case of increasing grazing pressure, for example, Brogaard et al. note that the total number of livestock in the IMAR increased from approximately 46 million head in 1980 to about 71 million in 1997.

What was done
To better assess the seriousness of this "ongoing land degradation process," as they describe it, the researchers adapted a "satellite-driven parametric model, originally developed for Sahelian conditions, to the central Asian steppe region of IMAR by including additional stress factors and growth efficiency computations."  The applied model, in their words, "uses satellite sensor-acquired reflectance in combination with climate data to generate monthly estimates of GPP [gross primary production]."

What was learned
"Despite a rapid increase in grazing animals on the steppes of the IMAR for the 1982-1999 period," Brogaard et al. report that their model estimates "do not indicate declining biological production."

What it means
Clearly, some strong positive influence compensated for the increased human and animal pressures on the lands of the IMAR over the period of Brogaard et al.'s study.  In this regard, they mention the possibility of increasing productivity on the agricultural lands of the IMAR, but they note that crops are grown on "only a small proportion of the total land area."  Other potential contributing factors they mention are "an increase in precipitation, as well as afforestation projects."  Two things that are not mentioned are the aerial fertilization effect and the transpiration-reducing effect of the increase in the air's CO2 concentration that was experienced over the study period.  Applied together, the sum of these several positive influences (and possibly others) was demonstrably sufficient to keep plant productivity from declining in the face of greatly increasing animal and human pressures on the lands of the IMAR from 1982 to 1999, which outcome must have been somewhat of a surprise to Brogaard et al., as they originally thought they were studying an "ongoing land degradation process."