· · · Repository Hydraulic Engineering Reports

Textbook on the ecology of mangroves, detailed description of mangroves and their environment.

Mangroves are productive ecosystems, that sustain important fisheries, provide a variety of forest products and harbour millions of resident and migratory birds as well as endangered mammals and reptiles. Reclamation for aquaculture and agriculture is currently considered the main way to achieve development of mangrove areas. These types of reclamation are costly, often unsustainable, and have adverse environmental effects. They mainly benefit outsiders, and to a lesser extent local communities, to the prejudice of those traditionally engaged in fisheries and the gathering of forest products. Partial reclamation may be beneficial and cause limited environmental damage provided that activities are properly designed, judiciously located (Le. largely outside the mangroves, and on suitable soils), implemented on a small scale and controlled by the local population. However, reclamation is certainly not the only option available and priority should be given to the development of mangrove-related activities such as fisheries, forestry, open water aquaculture and nature-orientated tourism. These activities require less investments, are easily taken over by local communities and offer more opportunities for conservation. However, most of them may induce environmental risks and need proper management and control. Integrating sustainable development of mangrove coasts with conservation may take place along three different lines: optimising mangrove-related activities, while maintaining the integrity of mangrove ecosystems as wildlife habitat and naturally functioning ecosystems, optimising reclamation activities while maintaining the integrity of adjacent mangrove ecosystems, integrating conservation into coastal development.

A description of Mangrove ecosystems. Especially the hydrological processes in these ecosystems are described. The rapport can be used as manual for studies in these Mangrove ecosystems as the rapport gives several points of attention for these studies. Furthermore the rapport gives several hints on how to analyze the data. Next to these hints and tips the rapport covers a case study of the Klong Ngao near Ranong, Thailand.

Field investigation by Vuong Van Quynh on the dissipation of wave energy in a mangrove field off the coast of southern Vietnam. Based on regression analysis a formula has been developed to determine the wave height decrease as function of the tree density and the tree sizes.

This monograph represents a shortened selective version of Dr. Spenceley's PhD thesis. Following a brief introductory survey of current views on the distribution and characteristics of mangrove associations. There is a summary of the relevant conditions of the natural enviroment of the Townsville area. The specific local features of the investigation sites on Magnetic Island and at Saunders Beach, including detailed tabulations of the characteristics of soil texture, are presented. In addition for each of these areas vegetation transects from low water inland are described. The author then outlines the field, laboratory and statistical analytical methods he employed. Appendix 1 indicates the details of the techniques of the chemical analysis undertaken. The results of the analysis of the field data which cover both the differences between the individual mangrove zones and those over the different months of the year is extensively summarised in the Appendices 2 and 3. The data provided on the variation in the various soil nutrients offer a valuable foundation for comparative investigations by other workers in mangrove environments elsewhere. The results of a factor analysis at three levels (surface, 100 mm and 300 mm depths) of the soil variables are tabulated and graphical representations of means and strandard deviations for each site are included to illustrate the range of the soil nutrients studied. The discussion is then directed to a consideration of a number of questions that arise from the general problems of trying to relate mangrove distributions to the multivariate soil profiles. The outcome of the study demonstrates the complexity of the ecology of mangroves. No one vegation group correlatd with a particular set of soil nutrients. Local site factors cleary played a significant role. These included the vegatation cover and the organic matter in the soil derived from it, the sediment texture, the rainfall seasonality and the related inflow of fresh water and localized sources of nutrients within the root zone of the mangroves. The monograph will provide additional quantitative data which will in turn contribute to continuing research into mangroves. The specific data are there for comparative studies of mangroves elsewhere in Australia or in other low latitude regions. The monograph follows in the pattern of tropical enviromental research.