Rene N. Rollon

Growth performance of planted mangroves in the Philippines: revisiting forest management strategies.

Abstract The effort toward restoring lost mangroves in the Philippines has been commendably immense, specifically during the past two decades. In light of such, it is important to evaluate outcomes and, where appropriate, apply the lessons learned to the current strategies in mangrove forest management. This article synthesizes the results from several research projects assessing the performance of planted mangroves across the country. Overall, there is a widespread tendency to plant mangroves in areas that are not the natural habitat of mangroves, converting mudflats, sandflats, and seagrass meadows into often monospecific Rhizophora mangrove forests. In these nonmangrove areas, the Rhizophora seedlings experienced high mortality. Of the few that survived (often through persistent and redundant replanting), the young Rhizophora individuals planted in these nonmangrove and often low intertidal zones had dismally stunted growth relative to the corresponding growth performance of individuals thriving at the high intertidal position and natural mangrove sites. From this evidence, this article argues that a more rational focus of the restoration effort should be the replanting of mangroves in the brackish-water aquaculture pond environments, the original habitat of mangroves. For such, a number of management options can be explored, the implementation of which will ultimately depend on the political will of local and national governments.

Contrasting Recolonization Strategies in Multi-Species Seagrass Meadows

Abstract This study shows that in a multi-species seagrass meadow in a shallow and clear-water site, all the former seagrass species were able to recolonize in the artificially created gaps of 0.25 m 2 in size within ca. 2 yr. Extrapolation of the recolonization curves of the different species predicted a full recovery within 10 yr post-disturbance. Fitted curves for the dominant species Enhalus acoroides and Thalassia hemprichii showed contrasting strategies, the latter having a comparatively high intrinsic rate, achieving full recovery within ca. 2 yr post-disturbance. E. acoroides was the latest species to establish and the projected full-recovery time was among the longest (ca. 10 yr). The effect of timing of gap creation was generally not significant (except for Syringodium isoetifolium ) neither was the temporal variation in density of most species outside the gaps. As recolonization by sexual propagules was found to be low, increasing the gap size would most probably require a much longer recovery period. A crude estimate for E. acoroides would be >10 yr for 1 m 2 of gap. Further, since the densities of most seagrass species vary significantly between sites, and colonization rates depend on adjacent seagrass densities, the recovery curves would also be different across sites.

The Pressing Challenges of Mangrove Rehabilitation: Pond Reversion and Coastal Protection

The 2004 Indonesia tsunami as well as the increasing storm frequency and intensity associated with climate change–sea-level rise have highlighted the coastal protection function, among the many goods and services that mangrove forests provide. This wider awareness of mangroves has increased national and international rehabilitation efforts, given only 15 million ha remaining and yearly rates of 1–3% loss. Rehabilitation programs employ two strategies: seafront planting and pond reversion. Seafront planting is necessary because coastal populations will not move to safer ground by choice, or cannot move due to poverty, and is also preferred because the sites are open access with no tenurial conflicts. However, former sites of fringing mangroves are difficult to rehabilitate as their lower intertidal–subtidal levels are not optimal for mangroves (due to frequent inundation and wave action). Planting in tidal flats and seagrass beds is also ecologically misguided. This chapter evaluates the relevant mainstream and gray literature (on site and species selection, propagule sources, nursery protocols, outplanting techniques, biophysical/anthropogenic threats, and novel interventions, e.g., integrated approaches using barriers) to improve the low survival rates of seafront planting. However, this strategy should not preclude the long-term relocation of coastal communities to safer ground and the politically difficult option of pond reversion. Given thousands of hectares of underutilized and abandoned brackish water ponds in Southeast Asia, this option holds greater potential for rehabilitation of wide areas of mangroves and greater species diversity. It is ecologically easier as it merely requires restoring hydrology (by breaking pond dikes); mangrove recruitment and succession naturally follow (if propagule sources are present) in these ponds located at mid-upper intertidal levels where mangroves naturally occur. The Philippines, with its long history of mangrove–pond conversion and problematic enforcement of laws that mandate mangrove reversion of idle ponds, is examined as a case study. The chapter assesses the Fishpond Lease Agreement (FLA) system by which vast expanses of mangroves were transferred from the public domain (government-leased ponds) to private ownership and recommends ways to improve the FLA system.

Mangrove Revegetation Potentials of Brackish-Water Pond Areas in the Philippines

The Philippines is one of the countries with the most number of true – mangrove species (about 42 species, 18 families, Table 1) (Primavera, 2004; Spalding et al 2010; Polidoro et al 2010). However Philippine mangrove forests suffered greatly from anthropogenic activities, i.e. cutting for firewood and charcoal, siltation caused by upland deforestation, and conversion of mangrove areas to shrimp ponds, fishponds and salt ponds (Primavera 1991, 1995, 2000; Field, 1998; FAO, 2003, 2007). From 1918 (~450,000) to 1998 (112,400), mangrove cover declined by more than 75% (Figure 1). In 2007, the remaining mangrove areas in the Philippines was estimated at 289,350 hectares (DENR-NAMRIA 2007), a value which is 61% (176,950) higher than 1998 estimate. However, most of these are estimates based on satellite images that need to be validated on field.

Preliminary assessment of post-Haiyan mangrove damage and short-term recovery in Eastern Samar, central Philippines.

Strong winds and storm surges from Typhoon Haiyan caused damage of US

Estimating Biomass from the Cover of Gelidiella acerosa along the Coasts of Eastern Philippines

12-15billion and >10,000 human casualties in central Philippines in November 2013. To validate a proposed government US

Propagule dispersal of the SE Asian seagrasses Enhalus acoroides and Thalassia hemprichii

22million mangrove replanting program, mangrove damage and short-term recovery were surveyed in seven natural and planted mangrove sites in Eastern Samar province at 2.5month and 4.5month post-Haiyan. The preliminary assessment showed that natural mangroves (except for those directly hit by the storm) were recovering by means of tree sprouts and surviving seedlings and saplings compared to the devastated plantation. Likewise, tree mortality was higher in the plantation and natural forests hit by the storm surge, compared to more undamaged and partially damaged trees in natural mangroves. Hence the main recommendations to government are (1) to protect recovering mangroves by not releasing rehabilitation funds (that will inadvertently pay for clearing of live trees and for removal of seedlings), (2) to only plant in totally damaged sites (e.g., plantations), and (3) to only plant naturally dominant species, e.g., Sonneratia alba and Avicennia marina (instead of the popular Rhizophora apiculata, R. mucronata and R. stylosa).

Meadow fragmentation and reproductive output of the SE Asian seagrass Enhalus acoroides

Abstract In three Gelidiella acerosa beds on the poorly-studied eastern coasts of the Philippines, cover and biomass of this commercially important agar-producing red alga were measured. The three selected G. acerosa beds represented low (mean cover < 5%), medium (approximately 10%) and high cover (> 20%) vegetation. In each of the sites, we estimated the cover of G. acerosa fronds within 10 x 10 cm grids (n ranged from 33–36) in various strata. All G. acerosa fronds within each grid were harvested, cleaned of attached epiphytes and sediments, and subsequently, oven-dried at 60 °C to constant weight. We applied regression analysis to establish empirical relationships between cover and biomass. All linear regression lines were highly significant (p < 0.001, R2 > 0.6) indicating that biomass could be confidently estimated from cover estimates: low cover (y = 0.0171x + 0.310;R2 = 0.67, p < 0.0001), medium cover (y = 0.0363x + 0.118, R2 = 0.83, p < 0.0001) and high cover (y = 0.0304x + 0.481, R2 = 0.80, p < 0.0001). Evidently though, sites with higher overall mean cover (also longer thalli) had significantly steeper regression slopes, which was most pronounced when comparing sites with the lowest (< 5%) and highest (> 20%) mean cover. Nevertheless, we subsequently projected a minimum annual yield from the known 51 ha along the eastern coasts amounting to, at a minimum, 23 t dw y−1. Such yield may translate to approximately 68.8 million pesos (US

Vegetative dynamics and sexual reproduction of monospecific Thalassia hemprichii meadows in the Kalayaan Island Group

1.38 million) in gross sales of agar.