It's not the rural areas that are shedding population; its St. Louis and Kansas City.
St. Louis lost population, Kansas city gained, amongst rural areas some gained and some lost.
In fact looking at this map:
http://2010.census.gov/news/img/cb11cn49_mo_perchange_2010map.jpg
you can see that both Obama's best county (St. Louis city) and Mccain's best county (rural Barton) lost population.
Jackson County gained, but Kansas City didn't, at least not much. Cleaver's 5th district is 114k short on population, and other than the 2 St. Louis districts, its the smallest in the state.