Waterfall Glen: Hine's Emerald Dragonfly Habitat Restoration
Federally endangered Hine’s emerald dragonflies have very specific habitat requirements. They rely on groundwater-fed, calcium-rich streamlet systems that are lined with shallow dolomite and limestone and support vegetative structures from cattail stands to high-quality wet prairies and sedge meadows.
The insects have a long life cycle, as much as four to five years from egg to adult. Hine’s emerald dragonfly larvae spend much of their time hiding in crayfish burrows though it is not fully understood how they coexist with crayfish in the burrows. With such specific needs, a small disturbance in habitat can dramatically harm a population of the dragonflies.
As a condition of the Army Corps of Engineers permit to build the Interstate 355 extension, the Illinois State Toll Highway Authority (ISTHA) had to mitigate for possible damages to existing Hine’s habitat as a result of building the bridge over the Des Plaines River. The U.S. Fish and Wildlife Service wrote a “Biological Opinion” as part of the formal consultation between the federal agencies and ISTHA. This document states that ISTHA must pay for specific mitigation strategies including habitat restoration at adjacent Hine’s emerald sites, habitat creation, develop a Hine's Emerald Dragonfly Work Group of local stakeholders and scientists to guide the project, and contribute to scientific research on the population biology and genetic structure of Hine’s emerald dragonflies in Illinois.
The Work Group – of which the District is a member – identified conservation measures to be carried out before, during and after construction, including habitat restoration and maintenance, genetics research, and captive rearing for introduction into restored habitat. The Group also worked to create breeding habitat—a recovery task never attempted before.
In DuPage County, the restoration is being carried out at Waterfall Glen Forest Preserve in Darien, where work focuses on removing invasive plants and improving existing groundwater flow. Dense thickets of invasive shrubs were cleared from adjacent uplands and replanted to create open woodland. Dr. Daniel Soluk of the University of South Dakota and his graduate students regulated groundwater flow from existing artesian wells to create streamlets. Rock basins were installed to catch outfall from the wells, allowing the water to warm. Water is slowly released from these basins to form small streamlets that flow through planted wet prairie and then into existing marsh.
Caged dragonfly larvae, reared in captivity, were placed in rivulets within the created systems to compare growth rates to larvae in natural systems. Data collected on the captive larvae and created systems have been used to adapt management of the created systems. Adult Hine's emerald dragonflies have been documented throughout the newly created habitats, and eventually, captive-reared larvae may be released at the project site.
The project is funded by the Illinois State Toll Highway. The District also contributes time and materials to the project.
Permanent temperature regulation ponds constructed in May, 2009.