The Interior Least Tern, the pallid sturgeon and the fat pocketbook mussel will all benefit from recent changes in river engineering practices, which have been formalized in a landmark Conservation Management Plan (CMP) for the Lower Mississippi River signed at the end of August by the U.S. Army Corps of Engineers (USACE) and the U.S. Fish and Wildlife Service (FWS).
This CMP is believed to represent the first large-scale application of a powerful but seldom-used tool for proactive conservation in the Endangered Species Act (ESA): Section 7(a)(1). Under Section 7(a)(1), federal agencies work together and with partners to understand the effects of agency actions on endangered species and to formulate best management practices. This partner-building process is intended as a positive alternative to the often confrontational path of formal ESA consultation under Section 7(a)(2).
Section 7(a)(2) consultations can result in an atmosphere of compliance rather than collaboration. Because much of the breeding range of the Interior Least Tern is within USACE project areas, terms and conditions related to Section 7(a)(2) consultations have resulted in this species being ranked in the top five bird species for federal expenditures under ESA for the past decade. On the Lower Mississippi River, FWS and USACE chose a different path, taking notice of a 1994 MOU that was signed by many federal agencies expressing a desire to work more frequently within the framework of Section 7(a)(1).
The 1994 MOU was met with enthusiasm from the environmental community, and a 1995 article by Dr. J.B. Ruhl in the journal Environmental Law predicted that Section 7(a)(1), “because of its breadth and flexibility, may take its rightful place as the centerpiece of the nation’s species protection law.” Unfortunately, Ruhl confirmed recently, this MOU was followed by few significant agency actions prior to the signing of the Lower Mississippi River Conservation Management Plan.
The CMP describes the full range of federal engineering actions on the Lower Mississippi River, from levee construction to navigation channel dredging. For each of these actions, the plan analyzes the effects on endangered species and proposes best practices to avoid negative impacts and integrate habitat improvement into standard operating procedures.
One example of an engineering practice with benefits to wildlife is “dike notching.” In order to develop the Lower Mississippi River for barge navigation, the USACE built nearly 400 linear miles of hard rock dikes extending from the river bank into the main channel. Dike fields capture sediment along channel margins and work to maintain a deep navigation channel. Notching involves making a hole in the dike by simply removing enough rock to provide a path for river current between the dike and the shoreline. A properly designed notch restores depth and habitat complexity below the notch, providing substantial benefits to endangered species without any negative effect to the original engineering purpose of the dike.
Dike notching makes Least Tern nesting sandbars more difficult to access for mammalian predators that eat tern eggs and chicks; creates important side-channel habitat for pallid sturgeon larvae and juveniles; and increases the overall productivity of small fish species, which drive the river food chain. By 2013, about 30 percent of the nearly 1,000 dikes on the Lower Mississippi River had been notched, and new dikes are now being constructed with this design feature. Dike notching reverses some of the formerly negative impacts of river engineering (e.g., increased predation of ILT and fisheries habitat loss around dike fields) into a primary mechanism for habitat restoration and maintenance.
Dr. Mike Scott of the University of Idaho, one of the nation’s experts on the protection of conservation-reliant wildlife, praised the CMP, saying: “This agreement is an uncommonly creative use of section 7(a)(1). It formalizes practices that create favorable habitat conditions for several imperiled species over areas large enough to make a conservation difference. It is the kind of multi-agency partnership that is needed to manage species in human-dominated ecosystems that require management for the foreseeable future.”
Strong partnerships were necessary to develop and implement the CMP. For example, American Bird Conservancy (ABC) has been working with USACE and FWS for more than a decade to define the population ecology of the Interior Least Tern. The Lower Mississippi River Conservation Committee pulled state agencies together to develop a common vision of Lower Mississippi River management and works with USACE districts to identify, design, and implement local restoration projects throughout the river. Long-term implementation of the plan will continue to require strong collaboration between federal and state agencies, as well as nongovernmental partners.
“When the Interior Least Tern was first listed, it was widely believed that river engineering threatened the species’ continued existence. With this CMP, the FWS and USACE are successfully transforming ‘threats’ into conservation tools. Today, over 10,000 ILTs nest on the Lower Mississippi River, almost exclusively within dike fields, and more than 7,000 ILTs nest in hundreds of widely distributed colonies on a number of regulated rivers throughout the mid-continent,” said Casey Lott, ABC’s Coastal and Waterways Program Coordinator and the corresponding author of a recently published peer-reviewed paper on the ILT in the journal Ecology and Evolution.
“Many large rivers can be managed in ways that support ILT populations over the long-term and still meet the diverse needs of stakeholders,” George Fenwick, president of ABC said. “The Lower Mississippi River plan should be an inspiration for the development of similar plans in other regions with ILT and for other listed species in general.”