To Plant or Not to Plant, That Is the Question: Reforestation vs. Natural Regeneration of Hurricane-Disturbed Mangrove Forests in Guanaja (Honduras)

Abstract

Background and Objectives: Mangrove forests offer many essential ecosystem services, including the protection of (sub)tropical coastlines, their inhabitants, and the infrastructure from severe storms and tsunamis. However, mangroves themselves suffer severely from such phenomena. After such events, reforestation efforts are widely undertaken to facilitate the recovery of the mangroves. Many of these laborious activities, however, fail for a number of reasons. Material and Methods: In October 1998, the Honduran Island of Guanaja was severely hit by Hurricane Mitch, and, after the storm, almost all of the mangrove forests (97%) were rated as dead. Seven years after Mitch, a longterm survey on the regeneration of the mangroves started. Field samplings in six variably disturbed mangrove zones was conducted in 2005, 2009, and 2016. Along permanent line-transects, all living plant species were recorded for statistical analyses and for quantifying progress. In this paper, the focus is on the three most severely hit areas. In two of them, planting efforts were carried out while the third one was left to regenerate naturally. This setting allowed a direct comparison between natural and human-assisted regeneration processes under otherwise similar conditions and equally severe previous disturbance. Results: Reforestation measures were characterized by high mortality rates of Rhizophora mangle L. propagules planted predominantly. Some, however, surely survived and might have contributed to regeneration after the disturbance. In 2016, roughly two decades after Hurricane Mitch, low-growing Rhizophora mangle forests, with high ground cover, were found. Surprisingly, the area without any planting also witnessed similar mangrove rejuvenation in the same period. Conclusion: Findings on the recovering mangroves in Guanaja confirm the lessons learned from other mangrove rehabilitation measures: planting mostly fails and commonly does not accelerate the revegetation of disturbed forests. In naturally regenerating forests, recolonization may occur after a certain time-lag only if few diaspore sources survived in the surrounding; as soon as established mangrove plants bear propagules, a quick return to viable forests takes place, proving the high resilience of these coastal ecosystems.

To Plant or Not to Plant: When can Planting Facilitate Mangrove Restoration?

“…This outcome has indeed been observed in various studies (e.g. Barnuevo et al, 2017;Fickert, 2020;Proisy et al, 2018), as well as behind the breakwater in Demak (Figure 9). It should be noted that in carbonate systems, Rhizophora species have been observed as pioneers of the coastal zone [e.g.…”

“…minerogenic versus organogenic soil (Worthington et al, 2020)], when selecting an appropriate pioneer species. The presence of a few fruiting pioneers can reportedly revegetate a site more efficiently than a planting effort with better surviving, but slower growing species (Fickert, 2020). Although we were not able to include formerly native pioneers such as Sonneratia alba and Aegialitis annulata (Balun, 2011;Ilman et al, 2016), our Q4 experiment indeed demonstrated that planting with pioneers can quickly lead to the presence of a few reproductive young trees.…”

Floristic composition and stand structure of mangrove forests with varying vegetation conditions in Sungai Apit, Siak, Riau, Indonesia

“…In many areas in the world, degraded mangrove forests are able to regenerate naturally. Comparison between natural mangrove regeneration and human-assisted regeneration after Hurricane Mitch in the Gulf of Honduras, Guanaja did not show a significant difference in the success of mangrove replanting (Fickert 2020). A total of 23 species of mangrove were recorded and they had good ability in terms of natural regeneration in several mangrove forests affected by the tsunami, including in the North Coast of Aceh, the East coast of Aceh, the West coast of Aceh and the coast of Peninsular Malaysia (Onrizal et al 2017).…”

Falling “fortresses”: Unlocking Governance Entanglements and Shifting Knowledge Paradigms to Counter Climate Change Threats in Biodiversity Conservation

“…Yet another radical re-imagination of ecosystem governance could involve allowing natural mangrove regeneration in the cyclone and flood affected regions as opposed to restorative mangrove plantation that constitutes a major part of institutional conservation governance across the Sundarbans. Natural regeneration is much more successful that plantations which are labour intensive and expensive, shows recent studies (Fickert 2020;Ellison et al 2020;Lee et al 2019, Kodikara et al 2017Iftekhar 2008;Primavera and Esteban 2008;Bosire et al 2008).…”