UH researchers document ‘remarkable recovery’ of Pacific island forests in wake of powerful cyclone : Maui Now

In March 2015, Cyclone Pam touched down on the Pacific island of Tanna in Vanuatu, as the strongest Pacific island cyclone in history at the time. With sustained winds reaching 165 mph, Pam pounded the island for 18 hours.

Today, a new study in the journal, “Science of the Total Environment,” sought to explain the “remarkable” recovery of Tanna’s forests following Cyclone Pam.

The team, which included researchers from University of Hawaiʻi at Mānoa, The New York Botanical Garden, the University of the South Pacific, and the Vanuatu Cultural Centre and Vanuatu Department of Forestry, examined post-cyclone recovery across eight forested sites on Tanna over five years.

“Compared to cyclones on other Pacific Islands, Pam caused relatively low levels of severe damage to Tanna’s trees,” said UH Mānoa School of Life Sciences Professor Tamara Ticktin and lead author on the paper. “In addition, there was high resprouting, widespread recruitment of most tree species present and, basically no spread of invasive species.”

According to the UH author, the latter is especially surprising because invasive species often spread rapidly after Pacific island cyclones.

Cyclone history, stewardship practice, key to resilience

The authors of the study concluded that Tanna’s historical cyclone frequency likely fostered the abundance of resilient species, and that Tanna’s customary stewardship practices appear to augment the capacity for resilience. These practices include promoting a diversity of tree species, life histories and life stages; as well as a wide range of pathways for regeneration.

“Tanna stewards value a wide range of species useful for food, medicines and building materials,” said New York Botanical Garden Vice President for Botanical Science and Director and Senior Philecology Curator of the Institute for Economic Botany, and co-author Michael Balick. “And customary stewardship involves management practices that enhance the survival and reproduction of these species.”

Co-author Jean-Pascal Wahe of the Vanuatu Cultural Centre noted that after a cyclone, stewards weed around native tree species and even plant them. According to the report, these actions can help ensure their regeneration while decreasing dominance of weedy understory species.

UH Mānoa reports the study also showed that forests that had previously been subject to grazing by cattle and pigs were slower to recover and will likely be more vulnerable to future cyclones.

“This highlights the key role of forest management in building resilience to climate change,” said senior author Gregory M. Plunkett, New York Botanical Garden director and curator of the Cullman Program for Molecular Systematics, who has been studying the plants of Vanuatu for two decades.

Plunkett, along with Balick and co-author Marika Tuiwawa of the University of the South Pacific, had been carrying out research on Tanna when Cyclone Pam hit. They experienced the terror of the cyclone first-hand and were delighted to also witness forest recovery.

“As the world comes to grips with more frequent extreme weather events, our work suggests that the right kind of human interaction can play a significant role in the survival of forests,” said Plunkett.

This study is part of the wider Plants and People of Vanuatu program, led by Balick and Plunkett, and was supported by the National Science Foundation, the Critical Ecosystem Partnership Fund and the National Geographic Society.