Roughly 40 % of the US soybean crop, concentrated in farm belt states like Indiana, Wisconsin and Iowa, is exported to China. (cnbc.com)
New Groundwater Found Deep Under Central Valley: The Central Valley is home to California's productive farming belt, but the regions groundwater is so severely overdrafted in some places that the land has been sinking... (wineindustryadvisor.com)
It is mainly driven by US farm belt (read agribusiness) politics. (realclimate.org)