nikhilsoman
Degradation of soil - or specifically - the ability of topsoil to retain enough nutrients to support agriculture - is not the primary problem we are facing today.
The key issues are -
#1 Reclamation of fertile land for housing the burgeoning population is the largest reason for declining food production - which in turn leads to the increasing use of chemical fertilizers for enhanced yield from the same or reduced available land.
#2 The % of population engaged in agriculture as compared to pure consumers of agricultural produce. This is perhaps what msandford meant. The net number of agricultural workers 'producers' is rapidly declining due to higher yield 'jobs' off farm. This impacts output/acre significantly.
However the ceiling for human resource in farming is pretty low. Perhaps we need to look at a metric like Man month/unit of produce.
The need of the hour is to change the basic value chain. Consumers have no stake in (and dont care about) the production or the land itself.
Farmers are being marginalized by increasing land prices/roi on selling farmland for other purposes.
Landowners/Bulk Consumers are driven by volumes - not necessarily by sustainability. This is like strip mining.
Perhaps a new platform is required to realign the value chain. The above is particularly true for India - which will also be one of the hardest hit - earliest.