Seeking details for the "historical rate" of arable land loss In doing research on the issue of desertification (aka land degradation) I keep running across the same basic sentence but no source or detail to support or clarify it:


  "Arable land loss is estimated to be at 30 to 35 times the 
  historical rate."


Can anyone help me find a source that specifies this "historical rate"? Over what length of time is history being measured? What is the geographic scope of this data?

Failing a specific source for this quote, can anyone provide a reliable source for the data subject the quote refers to (i.e. a long term track record of desertification)?
No context is given, but at face value this is a meaningless quotation. Globally there is a net increase in arable land from close to zero about 8000 years ago, to the current maximum of just over 40% of the gross biological productivity of the planet. 'Arable land loss' can refer to the land lost to urbanization, salinization or desertification. One might also make a distinction about agricultural land lost to hydrologic intervention, as in the decreasing flows of the Amu Darya, and Sur Darya in Central Asia. In addition, over the coming decades we will begin to see agricultural land lost to climate change impacts. No single assessment of the 'historical rate' of arable land loss is meaningful. One has to evaluate the various processes separately, and then aggregate them at regional level.