The Minnesota Natural Heritage Program estimates that oak savanna in Minnesota, at the time of settlement, covered 10 percent of the state, approximately, eighty seven hundred square miles. Most of these were on sandy, rocky or drought-like substrates. Most of the oak savanna disappeared within 20 to 40 years of settlement due to the cessation of fire and the land use of the settlers and today, only .02 percent of high quality oak savanna remains in the entire Midwest. W hile there is no single definition of a Midwestern oak savanna, the community is generally described as one that is dominated with large oak trees growing as individuals or in groups having 10 and 80 percent canopy with or without a shrub layer and with open spaces. It is a fire-maintained community.
Frequent fires prevent fuel buildup and control woody shrub and tree invasion.
No species are considered endemic to the oak savanna. W hile only a few high quality remnants of oak savanna remain, it is estimated that there are thousands of degraded and potentially recoverable remnants of oak savanna. There is an urgent need to take action to preserve and restore this ecosystem lest we lose more bio diversity. Prompted by its mission to preserve and protect the lower Minnesota River Valley and its watershed, Minnesota Valley National Wildlife Refuge is committed to the challenge of restoring the oak savanna at Louisville Swamp through prescribed burns and mechanical control of woody species. I t is estimated that there are approximately 200 acres of oak savanna at Lousiville with Burr oak being the dominate tree species.