Impact of Haiyan on Philippine mangroves: Implications to the fate of the widespread monospecific Rhizophora plantations against strong typhoons

• Main Authors: Villamayor, Betty May R., Rollon, Rene N., Samson, Maricar S., Albano, Giannina Marie G., Primavera, Jurgenne H.
• Format: text
• Published: Animo Repository 2016
• Subjects: Mangrove forests > Philippines; Mangrove restoration > Philippines; Mangrove conservation > Philippines; Rhizophoraceae > Philippines; Rhizophora > Philippines; Biology
• Online Access: https://animorepository.dlsu.edu.ph/faculty_research/4211
• Institution: De La Salle University

In the aftermath of super typhoon Haiyan, which devastated central Philippines on 08 November 2013, mangroves gained renewed national interest. Other than claiming thousands of lives and displacing millions of people, Haiyan wrought massive damage to infrastructure, crops, and coastal systems including mangroves. In this paper, the impact of Haiyan on mangroves across the entire impact corridor (i.e., Samar-Palawan stretch; broad-scale survey) was assessed, with particular focus on the planted Rhizophora cohorts (various forest age; detailed assessment) in Bantayan Island, typical of the massive planting programs in the country. Of the 21 mangrove species recorded within the impact corridor encompassing some 28,000 ha of heavily defoliated forests, the large-sized (older) Rhizophora spp. individuals were generally unable to produce epicormic sprouts resulting in mass mortality, in contrast to the other dominant mangrove taxa with high epicormic resprouting potential (e.g., Sonneratia, Avicennia, and Aegiceras). Focusing on the Bantayan cohorts, this paper found that, overall, 45% of the existing 20-ha, multi-aged Rhizophora plantations was severely damaged by typhoon Haiyan, but with mortality gradient being clearly directly related with stand age, i.e., for those >32 yr old, mortality was massive (>95%), while those < 8 yr old, although similarly totally defoliated, full recovery was attained < 2 years after Haiyan. Within old plantations, this paper also found significant differences in the mortality of trees in the core and in the periphery. These findings (1) offer a number of insights on the general age-frequency distribution and the growth architecture of Rhizophora spp. vis-a-vis other mangrove species within typhoon belts in the Philippines and in other countries with similar circumstances, and (2) demonstrate the high vulnerability of Rhizophora plantations against super typhoons, eventually suffering mass mortality upon attaining certain age threshold (>32 yr). Thus, the post-Haiyan mangrove enhancement practices which still insist to prefer Rhizophora as the main taxa for planting, must be seriously reconsidered to avoid similar fate, taking into account the wind exposure - growth and forest architecture dynamics, as Haiyan uniquely demonstrated in this paper. © 2016 Elsevier Ltd