In southern Lower Michigan, the populated landscapes of farms, homes, and towns create predictable, right-angle patterns of human settlement when viewed from above. But winding across and through those straight-line grids, meandering corridors trace the paths of streams and rivers.
These corridors often harbor something really important, a dynamic natural community known as a floodplain forest. Floodplain forests are a vital part of Michigan’s natural heritage. Periodic flooding, scouring, erosion and sediment deposition follow the rise and fall of water levels creating diverse microhabitats that are used by a variety of wildlife.
Land meets water in a floodplain forest. When that stream or river tops its banks, it reshapes the bottom lands with tree falls, migrating river channels, new sediment deposits or erosional scour. These actions create fluvial landforms such as natural levees, backswamps, oxbow ponds, and terraces – all associated with a particular type of vegetation.
The flowing waters help the soils thaw earlier in the spring, meaning these are often the places where the first wildflowers bloom. Insects, invertebrates, reptiles, and amphibians appear almost simultaneously to take advantage of the food sources provided by these wildflowers. “These forests are often very important stopover or even nesting sites for declining neotropical migratory birds as well.” “Often they are the last forested strongholds in a lot of agriculturally-dominated landscapes and are therefore valuable for a variety of plants and animals.”
Threats to these impressive habitats are an all too familiar list – invasive plants and animals, hydrological modifications (levees, impoundments, channelization, dams), including those brought by climate change, habitat loss due to industrial, residential and agricultural fragmentation, and incompatible timber management. For those reasons, floodplain forests are both globally and state-ranked as vulnerable.
For sometimes being no more than a narrow, green edge along a river, the magnitude of floodplain forest benefits outweigh their seemingly limited size. Besides important habitat, they play a critical function in Michigan’s fight against climate change. When water flows across the land to a river, the floodplain forest serves as a buffer, absorbing both the quantity and the energy of that flow while filtering pollutants. Floodplain forests therefore help to protect the water quality in many of Michigan’s watersheds.