Born from a group project in a Marine Ecology course, a recent publication in Sustainability reveals trends in coastal habitat restoration research and suggests how this research field can move improve for more effective conservation.

Lead author Stacy Zhang, a PhD candidate in Marine Science and Conservation, says the paper’s topic was spurred by a question of what the scientific literature recommends for coastal habitat restoration versus what types of restoration efforts are actually implemented or feasible. The study examined hundreds of publications and discovered large gaps in geographic coverage of coastal restoration research, a lack of inclusion of species interactions in restoration considerations, as well as scarcity of collaborations across all three sectors of academia, NGOs and government.

Restoring coastal habitat provides numerous advantages. In addition to thwarting environmental degradation, restoration benefits anyone who visits or lives near the coast. Oyster reefs and salt marsh grasses protect shoreline properties from erosion and provide habitat for fisheries. Oysters clean recreational waters by filter-feeding, and the edges of marshes and seagrasses are some of the best places to fish.

To achieve these benefits globally with limited resources and personnel, it’s necessary to evaluate restoration research to determine how to make it more effective.

A Global Synthesis

Zhang and her co-authors compiled a staggering digital pile of 1,203 publications by searching for studies related to habitat restoration for oyster reefs, salt marshes, and seagrasses. After cutting that pile in half due to logistical constraints, the team meticulously combed through about 600 randomly-picked studies to determine which were actually relevant (301 were). They collected information from relevant studies to create a database, recording details about the who, what, where and when of each study.

Academics dominate coastal habitat restoration research

The team found that over half of the relevant coastal restoration papers had authors from a single sector—either academia, government organizations or non-government organizations (NGOs). Out of these single-sector publications, most came from academia. Less than one in 10 of the publications had authors from all three sectors, an ideal scenario of collaboration.

Due to the different strengths and resources of different sectors, effective restoration requires long-term collaboration between all of them, and the study suggests further efforts should be taken to foster these research collaborations. After all, Zhang comments, “all restoration projects are experiments.”

Zhang mentions a few ways these collaborations could develop. Scientists in government or academia could collaborate with NGOs by collecting pre- and post-restoration data. Most of restoration research funding in these studies came from government and NGOs, so academics could also make sure to communicate often with their funding organizations to foster collaborations. Publishing open-access and making data publicly available are also necessary to increase the flow of knowledge, since NGOs often don’t have access to subscription journals. Less than one out of 10 of the studies included in their database were open-access.

Restoration research focuses mostly on physical variables

Zhang and her team noted what each study measured and considered important for restoration. Most of the top factors considered were physical, such as salinity, sediment type or water depth. For seagrasses, the factor mentioned most often as influential for restoration success was human interactions/disturbance; for salt marshes, it was water depth or tidal elevation; and for oyster reefs, it was recruitment. In the context of oysters, recruitment refers to oyster larvae (‘baby’ oysters) settling down and permanently attaching to hard surfaces. Of all the factors directly measured in the studies, salinity, water depth/elevation, and nutrients were most often significant for restoration success.

“We certainly need to get the physical template right first,” says Zhang about choosing restoration sites, but also points out that we need to fully consider how interactions between living things will affect restoration success. However, only four of the studies in their database tested how positive species interactions or grazing and predation affected restoration success.

Exploring the role of species interactions and how species could mutually benefit from one another should therefore take a larger role in coastal restoration research, the publication explains, especially since marine restoration proves to behave differently than the more historical tenets of terrestrial restoration. For example, Zhang commented on failed coastal restoration projects where negative species interactions weren’t accounted for, in which worms or birds ripped out the roots of newly planted grass habitat.

Larges areas of the globe may be left out of coastal restoration research

Most restoration studies included in the team’s database occurred in North America or Europe. None occurred in South American or Africa. This finding may be partially due to the exclusion of non-English publications and non-peer-reviewed publications, however still highlights an overall lack of knowledge about coastal restoration effectiveness in South America and Africa. Distance of researchers to a field site, and local investment, are some reasons that could explain the rather uneven distribution of restoration studies across the global coasts.

These geographical results of the study were most surprising to Zhang, and indicates the need to re-prioritize where to focus research efforts. Even in the United States, the Pacific coast lacked restoration studies. However, Zhang mentions this could be from a publishing lag since she’s aware of oyster restoration research in those areas.

Looking to the future

The coastal restoration database revealed an increase in publications within the last 15 years. Zhang confirms that this trend matches the recent increase in research interest that she’s witnessed, but may also be related to an increase in number of academics and pressures to publish.

This momentum in coastal habitat restoration science could benefit from heeding the suggestions that Zhang and her co-authors propose. Long-term collaborations between academics, NGOs, and government could improve flows of knowledge and restoration management efforts. Expanding research efforts to understudied areas is necessary to determine the applicability of restoration practices to different environments. Lastly, including species interactions in those studies is necessary to understand the full spectrum of ecological processes that affect restoration success.

In addition to Zhang, other Duke Marine Lab affiliates including William Cioffi, Rebecca Cope, Eleanor Heywood, Carmen Hoyt, and Brian Silliman co-authored this study. Carter Smith of UNC Institute for Marine Sciences and Pedro Daleo, a collaborator from Argentina, are also co-authors.