Determined science reveals remarkable resilience of Pacific forests after cyclone

A remarkable and long-lived research program on Vanuatu has revealed the resilience of the island nation’s environment to severe tropical cyclones.

In March 2015, Tropical Cyclone (TC) Pam became the strongest storm on record in the South Pacific with maximum sustained winds of 278 kilometres/hour and maximum gusts up to 320 km/h.

It affected VanuatuTuvaluKiribati, and New Zealand. “Pam” produced high winds, coastal storm surges, heavy rains, and flooding in the affected countries and was classified for a time as a category 5 storm. Worst hit by far was Vanuatu, where the storm killed 16 people and caused widespread damage. About 166,000 people required immediate food aid.

But in the years prior to TC Pam, researchers on the island had established and surveyed 8 transects across three contrasting regions (leeward, windward, and north-central) on Tanna Island, one of the biggest islands in Vanuatu.

A transect is a straight line that cuts through a natural landscape so that standardised observations and measurements can be made.

The eye of the cyclone crossed over the leeward and north-central sites, but was just outside the windward site.

The authors of a paper outlining the damage monitored the transects post-TC Pam for nearly 5 years to observe the impact of Tanna’s forests to the wind-related effects of TC Pam and evaluate how resilient Vanuatu’s forests were.

Vanuatu tree regeneration
Team members monitor tree regeneration in study plots. (UH Manoa)

The team included researchers from University of Hawaii (UH) Mānoa, The New York Botanical Garden (NYBG), the University of the South Pacific, the Vanuatu Cultural Center and Vanuatu Department of Forestry.

They measured a total of 887 trees 5 cm tall or more across the 8 transects prior to TC Pam, representing 76 species in 63 genera. 

The results of the study published in the journal Science of the Total Environment documented what the authors describe as “the remarkable recovery” of Tanna’s forests.

“Compared to cyclones on other Pacific Islands, Pam caused relatively low levels of severe damage to Tanna’s trees,” says UH Mānoa School of Life Sciences Professor Tamara Ticktin, 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.”

Pacific climate mobility

The authors in a release to UH, conclude 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.

“This is because they promote a diversity of tree species, life histories and life stages; as well as a wide range of pathways for regeneration,” they write.

“Tanna stewards value a wide range of species useful for food, medicines and building materials,” says ethnobotanist 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 Center noted that after a cyclone, people weed around native tree species and even plant them.

“These actions can help ensure their regeneration while decreasing dominance of weedy understory species,” he says.

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,” says senior author Gregory Plunkett, who is NYBG’s Director.

Plunkett has been studying the plants of Vanuatu for two decades and had been carrying out research on Tanna, along with Balick and co-author Marika Tuiwawa of the University of the South Pacific, when Cyclone Pam hit.

They were on the island when the cyclone made landfall.

Aftermath getty
Damage from TC Pam, 2015. (Jeremy Piper/AFP via Getty Images)

“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,” says Plunkett.

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

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