The local farmers markets starting losing their oystermen even before Hurricanes Katrina and Rita. The ecological consequences of being at the mouth of the river that drains 2/3 of the Continental US should have been seen as a crisis by every level of government long ago. Instead, the beds became increasingly polluted with runoff and then without proper levees in place Empire La (the home of oyster harvesting down here) was toppled and little money or energy was offered to rebuild it.
The good news is that there are smart scientists and fishers working on solutions, such as making new beds away from the river and pollution and introducing new types of shellfish, such as triploids quahogs. (Some information on these mollusks here. )
How do I know all of this? Why, because I go to the farmers market where it is discussed and shared regularly. Another way to measure the need for farmers markets is to add up all of the conversations that flow from the market square back to the habitats of the wildlife we want to save.