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Missing the Middle: The Importance and Fragility of the Shrublands Habitat

When I chose the shrublands habitat to cover for this blog post, I thought a great way to start would be to interview my Master Naturalists who are extremely active and well-versed in local restoration work. They know the natural areas of Will County like the back of their hand. So, I was surprised when they said, what shrubland?

But then it occurred to me, shrublands are like trying to hold mercury—ever changing, difficult to hold, and require great attention to keep at hand. And realistically, with a limit of time and resources, restoration activities are usually consumed, even overwhelmed, with the basics—eliminating invasives that are choking out our prairie and forests. The shrubland habitat falls between the cracks. Many don’t even realize there IS a shrubland habitat—but to many of our Illinois species, the shrubland is an important part of their success as species.  

Shrublands are fluid and delicate habitats essential to many birds and other species. It is estimated that shrubland bird species have experienced a 70% decline in recent decades and much of that decline is attributed to habitat loss and fragmentation. Chicago Wilderness identified 13 shrubland bird species of highest conservation concern. Shrubland birds are not edge dwellers as often thought but prefer dense blocks of shrubs surrounded by grassy areas.  

The bad news is that shrublands are one of the most vulnerable, decimated habitat types in the Eastern US including Illinois. Historically, Illinois shrubland habitat was at its zenith when our forests were harvested for lumber. But now, according to the Illinois Department of Natural Resources there are only approximately 180 acres of shrubland prairie of good to fair quality remaining in Illinois.

Why are shrublands in such trouble? The answer lies in its very definition. Shrublands are considered an early succession habitat. Common species of shrublands include Hawthorn (Crataegus spp.), Dogwood (Cornus spp.), Crabapple (Malus spp.), and American Hazelnut (Corylus americana) surrounded by grassland areas. Shrublands are the result of some type of ecological disturbance. If left undisturbed, shrublands evolve into forests in a relatively short 20 to 30 years. When we add in the rate of growth of our most aggressive yet common invasive woody species, the life span of the shrubland habitat is dramatically reduced.

Disturbances that help to create and maintain shrubland habitats can be natural, such as fire, tornado, severe insect infestation, and beaver activity; or they can be manmade, as in the case of utility rights of way, abandoned fields, landscape and pastures.

Shrublands are also in trouble because most conservation management focuses on grasslands, leaving shrubland management often ignored and extremely underfunded.  Shrublands need intervention just to exist.

To the inexperienced eye, many of our natural areas appear to have large shrubland areas—but don’t be mistaken-those thickets of invasive buckthorn, honeysuckle, and autumn olive create ecological wastelands. Numerous studies show that these invasives offer little quality and richness for the many species that depend on shrublands.

But does the sad trifecta of being a fluid early succession habitat that attracts little funding for management and is under siege by invasive species, and even the natural growth of the forest spell disaster for the shrubland habitat?

Interestingly, a study by the Chicago Region of the Audubon in partnership with Illinois Natural History Survey and The Field Museum provides insight into a renewed hope for the shrubland habitat. This study investigated ways to turn degraded, invasive-laden sites into quality shrublands. By using simple mowing equipment and different size areas that were mowed, results indicated that the shrubland birds of concern demonstrated a slight preference for the shrubland habitats that received the densest mowing. Ref:

Perhaps these results that involve such a simple strategy can renew interest in development of shrubland habitats and improve the future of the species that depend on them.