DURHAM, N.C. – Salt marshes, seagrass meadows and other coastal ecosystems are in rapid decline around the world. Restoring them is expensive and often unsuccessful. But an international team of researchers has discovered a way to sharply increase the odds of success by using biodegradable mats.
The team, which includes Duke University’s Brian Silliman, published their peer-reviewed findings July 22 in the journal Nature Communications.
“Using these mats allows us to mimic the buffering effects of having strong adult neighbors surround and protect baby plants from the erosive power of waves The result is a game-chasing leap forward in restoration growth rates that could likely double or triple our overall success rates,” said Silliman, Rachel Carson Distinguished Professor of Marine Conservation Biology at Duke’s Nicholas School of the Environment and director of Duke Restore.
The mats are made from interwoven plant-based materials that mimic the stabilizing effects of mature roots and stems. In field experiments in the Netherlands, Sweden, Bonaire and the United States they successfully shielded young plants from wave erosion long enough for the plants to establish interlocking root systems of their own to stabilize the restored marsh or seagrass meadow.
Temperate and tropical seagrasses grew best when the mats imitated their soil-stabilizing root network, while marsh grasses benefited most from mimicked stems.
“A real strength of this research is that we saw the results not just in a single species in a single region, but across different species and ecosystems in both tropical and temperate regions. This means that it’s a general principle for restoration ecology,” said Marjolijn Christianen, a researcher at Wageningen University who coordinated the international seagrass research.
Silliman and Christiansen coauthored the study with researchers from Radboud University, the Royal Netherlands Institute for Sea Research (NIOZ), Bureau Waardenburg and the University of Groningen.
Salt marshes and seagrass meadows help protect coastal communities from storm surges and flooding. They absorb and store carbon dioxide from Earth’s atmosphere; help filter out water pollution; and provide nursery and foraging habitat for many ecologically and economically important fish and shellfish species and other marine life.
Finding cost-effective ways to protect and restore these valuable ecosystems on a large scale has become increasingly urgent in recent years as more and more of them are disappearing due to the cumulative impacts of rising seas, intensifying storms, declining water quality, and other natural and human disturbances, including oil spills and coastal development.
The waves and currents in these systems make them hostile environments for lone wolf fauna and flora, so some species – including mussels, oysters, seagrasses and salt marsh grasses –give each other a helping hand by nudging up together. This causes them to display what's known as emergent traits, or properties that are found in the population level but do not exist when an individual is alone.
Emergent traits allow an entire seagrass meadow to withstand a storm that might sweep away a solitary plant, explained Ralph Temmink, a PhD candidate at Radboud University, who led the new study. Ecologists want to build that type of resilience into a restored marsh or seagrass bed, he said, but how can they achieve that if they are starting over nearly from scratch and those population-level properties have vanished?
“You can plant an entirely new meadow, but that means removing plants from somewhere else, which can be both damaging and expensive,” he said. A smarter approach is to use biodegradable mats.
Tjisse van der Heide, a researcher at NIOZ and professor of coastal ecology at the University of Groningen, said the study’s findings clearly show that “now we have a way of significantly improving (a restoration project’s) chances without needing much planting material.
“The next step is to refine our findings and apply them to restoration projects on a larger scale,” he said.
For Silliman, the study’s success also signifies that Duke Restore, the new Nicholas School initiative he leads, is on the right track.
“Our ambition is to make the school a global leader in ecosystem restoration and cultivation, so that this type of innovative conservation intervention can become a realistic recovery strategy for all ecosystems and economies in the face of intensifying global stress,” he said. “We need out-of-the-box thinking and cross-disciplinary collaboration to counter the massive habitat loss occurring worldwide.”
Silliman’s work on the new study was supported by the Lenfest Ocean Program.
CITATION: “Mimicry of Emergent Traits Amplifies Coastal Restoration Success,” R.J.M. Temmink, M.J.A. Christianen, G.S. Fivash, C. Angelini, C. Boström, K. Didderen, S.M. Engel, N. Esteban, J.L. Gaeckle, K. Gagnon, L.L. Govers, E. Infantes, M.M. van Katwijk, S. Kipson, L.P.M. Lamers, W. Lengkeek, B.R. Silliman, B.I. van Tussenbroek, R.K.F. Unsworth, S.M. Yaakub, T.J. Bouma, and T. van der Heide; July 22, 2020, Nature Communications. DOI: https://doi.org/10.1038/s41467-020-17438-4