December 9, 2020

Managing Ecosystem Restoration: What Does Success Look Like?

Systems ecology-based methods to advance effective large-scale restoration

Picture of water fowl inside a body of water

Interconnected networks of wetland restoration projects benefit many species, such as these wetland wading birds in the Florida Everglades.

(Photo by Paul Stodola | U.S. Army Corps of Engineers)

Restoration projects are getting larger and more complex due to population growth, climate change, and disaster response. In the last decade alone, billions of dollars were spent to mitigate the effects of crises like Hurricane Sandy and restore habitats lost over centuries.

As projects grow in size and complexity, so do the restoration costs. This underscores the need for a strategic approach to maximize both ecological and economic benefits.

A national team of researchers, led by Pacific Northwest National Laboratory (PNNL), evaluated large-scale restoration efforts across the country and developed criteria, techniques, and tools to determine outcomes and ultimately, maximize benefits. This work was the focus of a study published in Frontiers in Ecology and the Environment.

Measuring the outcomes of expensive ecosystem restoration efforts

In the Florida Everglades, improved stormwater management since the 1990s has facilitated restoration efforts for wetland habitat, benefitting species such as alligators (adult and juvenile pictured). (Photo by Paul Stodola | U.S. Army Corps of Engineers)

Anyone flying over San Francisco Bay will see a colorful kaleidoscope of large ponds jig-sawed together along the shoreline. These current and former salt ponds are a turn-of-the-century remnant of one of the region’s historical industries. They also are a reminder of the wetlands that once spanned the region. Over two-thirds of the ponds are now combined into one of the largest restoration projects on the West Coast, exemplifying challenges with restoration of fragmented habitats.

Vast restoration projects like these are taking place across the country—along with efforts related to climate change mitigation, water quality improvement, and saving species—prompt bigger-picture questions about how to maximize benefits of large-scale regional efforts.

“Decision makers, project sponsors, and the public rightly demand a defensible method and accounting of the results of expensive projects,” said Ron Thom, an emeritus scientist at PNNL and co-author on the study.

Currently, there are few requirements for restoration practitioners to add up the cumulative benefits, so evaluating the effectiveness of restored ecosystem function is often overlooked. Historically, restoration started off as a small endeavor, and only recently is it practiced at large, regional, or landscape scales. At these scales, the complexity of ecosystems means that a simple additive approach does not adequately capture change.

While the idea of maximizing operational efficiency isn’t new—it’s a core tenet of business—what is new is the application to restoration projects across large regional areas. How do you maximize benefits and sidestep common challenges practitioners face, such as fragmented funding, conflicting goals, geographic overlap, ecological complexity, and efforts siloed by jurisdictional boundaries?

That’s the shift in thinking researchers hope to spark at the national level.

Cumulative Effects
To aid future restoration planning, the research team evaluated some of the country’s major restoration programs in recent decades and defined eight major effects to consider in future planning (Illustration by Nathan Johnson and Heida Diefenderfer | Pacific Northwest National Laboratory)

Linking together small projects for bigger ecosystem restoration benefits

The team, led by PNNL’s Heida Diefenderfer, identified synergistic effects of restoration outcomes and synthesized an ecosystem-management framework supported by techniques and a toolbox for resource managers. 

This framework encourages practitioners to look beyond boundaries, across landscapes, and over time, while considering the cumulative effects of projects. For example, migratory birds nesting on the shore of the lower Missouri River can be impacted by upstream river management decisions, such as flow. This is a type of a cross boundary effect—both the migratory birds and the Missouri River span lines on a map. So, if populations were managed for only a specific portion of the river, the approach could miss the forest for the trees. 

“The intent is to give environmental planners, scientists, and engineers the conceptual and decision frameworks needed to plan large-scale restoration in a way that maximizes benefits, as well as monitoring tools suitable for evaluating those benefits,” said Diefenderfer.

Another example: suppose a natural resource manager is faced with restoring salmon populations in the lower Columbia River and estuary to provide habitat for threatened and endangered salmon populations? They might be confronted with a large number of management questions, such as:

  • How big of an area should be restored?
  • Should it be only marshes, or should it include small rivers?
  • Will other species benefit?
  • How do geographic boundaries influence methods?

The research team evaluated some of the country’s major restoration programs over the past several decades seeking similarities. They also sought ways to leverage positive feedback and avoid unintended consequences, such as adverse changes to water quality during restoration.

The culmination of ecosystem restoration efforts

From the Florida Everglades, to the Columbia River, to the Northeastern coastal states, the research team noticed some common effects and defined eight types of ecological responses operating in large-scale restoration, collectively referred to as “cumulative effects.” These effects help planners and scientists plan and evaluate environmental change across landscapes, time periods, and ecological systems, like food webs.

“The ideas collected here set the stage for a new era of restoration coordinated at a larger scale, recognizing synergistic and additive effects and providing broader ecological and social benefits,” said David Burdick, director of the University of New Hampshire’s Jackson Estuarine Laboratory and coauthor on the study.

In light of the upcoming United Nations Decade of Restoration (2021-2030), with efforts such as large-scale tree planting being proposed globally to mitigate climate change, the authors reasoned that the next step scientifically is to broaden the lens. Looking across landscapes will help guide strategies to leverage cumulative effects and maximize the development of ecological and habitat functions.

Evaluating restoration outcomes with cumulative effects is the focus of “Applying Cumulative Effects to Strategically Advance Large-Scale Ecosystem Restoration,” a paper published online October 29, 2020, in Frontiers in Ecology and the Environment, a journal of the Ecological Society of America, DOI: 10.1002/fee.2274.

The research team includes PNNL’s Heida Diefenderfer, Kate Buenau, Gary Johnson (retired), and Ronald Thom (emeritus), along with Gregory Steyer, Hilary Neckles, and Neil Ganju (U.S. Geological Survey), Matthew Harwell (U.S. Environmental Protection Agency), Andrew LoSchiavo (U.S. Army Corps of Engineers), David Burdick (University of New Hampshire), Elene Trujillo (Puget Sound Partnership), John Callaway (University of San Francisco), and Robert Twilley (Louisiana State University).


About PNNL

Pacific Northwest National Laboratory draws on its distinguishing strengths in chemistry, Earth sciences, biology and data science to advance scientific knowledge and address challenges in sustainable energy and national security. Founded in 1965, PNNL is operated by Battelle for the Department of Energy’s Office of Science, which is the single largest supporter of basic research in the physical sciences in the United States. DOE’s Office of Science is working to address some of the most pressing challenges of our time. For more information, visit For more information on PNNL, visit PNNL's News Center. Follow us on Twitter, Facebook, LinkedIn and Instagram.