|A prairie pothole landscape in South Dakota. Click for photo credit.|
Most of the wetlands in North Dakota are regionally called prairie potholes. The depressions that house the wetlands formed during the last ice age as glaciers pockmarked the landscape. The potholes range in size from very small depressions to extensive lakes. The EPA estimates that only about 40-50% of the depressions remain. The remainder were destroyed by farmers as the region's agriculture developed. Prairie potholes are not only found in North Dakota. They are also present in eastern Minnesota, northern Iowa, extreme northern Montana, southwestern Manitoba, southern Saskatchewan, and southeastern Alberta.
The potholes can be seasonally or permanently flooded depending on the groundwater regime in the region. During rainfall events or during snowmelt, the seasonally flooded ones can fill with water. As a result, the potholes are extremely important for migratory birds. It is estimated that half of the U.S. migratory wildfowl make their way through the area.
As one can imagine, the plant and animal life is highly diverse and highly dependent upon local hydrology. Often, the potholes have ringed zones of plant and animal communities that range from dry upland to extremely wet central areas sort of like cypress domes. The wetlands are linked to local surficial aquifer systems.
If you look at the photo in the linked article you will see that size of the wetland in which the oil spilled is rather small--about half an acre. Thus, while the amount of oil spilled is small compared to say the Deepwater Horizon Oil spill that took place in the Gulf of Mexico, it is locally devastating to a landscape that is already under threat.
Note that this pipeline is a different segment of the pipeline from the Keystone XL pipeline that was a focus of a previous On the Brink Series that you can see here.