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

Abstract

Global change processes such as sea level rise and the increasing frequency of severe storms threaten many coastlines around the world and trigger the need for interventions to make these often densely-populated areas safer. Mangroves could be implemented in Nature-Based Flood Defense, provided that we know how to conserve and restore these ecosystems at those locations where they are most needed. In this study, we investigate how best to restore mangroves along an aquaculture coast that is subject to land-subsidence, comparing two common mangrove restoration methods: 1) mangrove restoration by planting and 2) Ecological Mangrove Restoration (EMR); the assistance of natural mangrove regeneration through mangrove habitat restoration. Satellite data revealed that historically, landward mangrove expansion into the active pond zone has mainly occurred through mangrove planting on pond bunds. However, there is potential to create greenbelts along waterways by means of EMR measures, as propagule trap data from the field revealed that propagules of pioneer species were up to 21 times more abundant in creeks of the pond zone than near their source in the coastal zone. This was especially true during the prevailing onshore winds of the wet-season, suggesting that smart seasonal sluice gate management could help to efficiently trap seeds in target ponds. In the coastal zone, field experiments showed that permeable brushwood dams, aimed at expanding mangrove habitat, could not sufficiently overcome subsidence rates to increase natural mangrove expansion in the seaward direction, but did significantly increase the survival of already established (planted) seedlings compared to more wave-exposed sites. The survival and growth rate of EMR-supported plantings greatly varied between species. Out of the four planted species, Rhizophora mucronata had the highest survival (67%) but the lowest growth rate. Whereas the pioneer species Avicennia alba and Avicennia marina had lower survival rates (resp. 35 and 21%), but significantly higher growth rates, even resulting in fruiting young trees within a 16-month timeframe. Overall, we conclude that 1) EMR has potential in the pond zone, given that propagules were observed to reach well into the backwaters; and 2) that mangrove recovery in the coastal zone may be facilitated even at very challenging coastal sites by combining EMR with the planting of pioneer species.

Assessment and Perceived Impact of Coastal Resource Management (CRM) Programs in the Southern Part of Masbate Island, Philippines

“…This is the preferred species because this is a fast-growing specie with a 67% survival rate but a lower growth rate. Compared to Avicennia, with a significantly higher growth rate but lower survival rates depending on the location (Bijsterveldt et al, 2022). The activity was supervised by a…”

Monitoring of Coastal Areas by Remote Sensing and Engineering Approaches

“…Coastal wetlands such as mangroves and salt marshes have gained interest as important ecosystems for reducing the vulnerability of coastal communities. Mangrove restoration is considered a broadly applicable strategy to improve coastal security [64]. Soft engineering is less expensive to implement and maintain and can give more sustainable long-term solutions than hard engineering projects.…”

“…The approach requests planting mangrove trees along the shore By using mangrove trees, their roots keep soil in place preventing erosion and helping dissipate wave energy During the process, non-native mangroves can become invasive to an area's natural plants [63,64]…”

Rehabilitasi Kawasan Pesisir untuk Mitigasi Perubahan Iklim: Peranan mangrove dan penurunan emisi tingkat sub-nasional

“…Hal ini dapat dilakukan dengan menelusuri distribusi mangrove dari peta menggunaan teknologi penginderaan jauh dan Geographical Information System (GIS). Selain pemilihan lokasi yang sesuai, metode restorasi mangrove juga perlu dikembangkan dari yang selama ini didominasi oleh kegiatan penanaman mangrove saja, menjadi restorasi mangrove secara ekologi yaitu dengan lebih berfokus kepada restorasi habitat mangrove itu sendiri yang nantinya akan memfasilitasi pertumbuhan mangrove secara alami, dan dengan metode kombinasi restorasi habitat mangrove dan penanaman (van Bijsterveldt et al, 2022). Tentunya pemilihan metode restorasi ini disesuaikan dengan kondisi lokasi rehabilitasi/restorasi.…”