Hydrological Classification, a Practical Tool for Mangrove Restoration

PLoS One. 2016 Mar 23;11(3):e0150302. doi: 10.1371/journal.pone.0150302. eCollection 2016.

Abstract

Mangrove restoration projects, aimed at restoring important values of mangrove forests after degradation, often fail because hydrological conditions are disregarded. We present a simple, but robust methodology to determine hydrological suitability for mangrove species, which can guide restoration practice. In 15 natural and 8 disturbed sites (i.e. disused shrimp ponds) in three case study regions in south-east Asia, water levels were measured and vegetation species composition was determined. Using an existing hydrological classification for mangroves, sites were classified into hydrological classes, based on duration of inundation, and vegetation classes, based on occurrence of mangrove species. For the natural sites hydrological and vegetation classes were similar, showing clear distribution of mangrove species from wet to dry sites. Application of the classification to disturbed sites showed that in some locations hydrological conditions had been restored enough for mangrove vegetation to establish, in some locations hydrological conditions were suitable for various mangrove species but vegetation had not established naturally, and in some locations hydrological conditions were too wet for any mangrove species (natural or planted) to grow. We quantified the effect that removal of obstructions such as dams would have on the hydrology and found that failure of planting at one site could have been prevented. The hydrological classification needs relatively little data, i.e. water levels for a period of only one lunar tidal cycle without additional measurements, and uncertainties in the measurements and analysis are relatively small. For the study locations, the application of the hydrological classification gave important information about how to restore the hydrology to suitable conditions to improve natural regeneration or to plant mangrove species, which could not have been obtained by estimating elevation only. Based on this research a number of recommendations are given to improve the effectiveness of mangrove restoration projects.

MeSH terms

  • Asia, Southeastern
  • Avicennia*
  • Conservation of Natural Resources
  • Hydrology*
  • Wetlands*

Grants and funding

BtB is employed by a commercial company. This funder provided support in the form of salaries for author BtB during the final phase of preparation of the manuscript, but did not have any role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. Research design and data collection, as well as a major part of the data analysis and manuscript preparation have been carried out prior to the employment of BtB by the funder. The specific roles of this author are articulated in the “author contributions” section.