An Assessment of the Status of Biodiversity in the ... - IUCN

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Identification of ecologically important areas (critical habitats)Areas of high ecological significance, which are critical habitats that needs priorityconservation action, were identified using the following ecological criteria:●●●●●Biodiversity - the variety or richness of habitats, communities and species (the latterwas assessed using species richness of woody plants and birds as surrogates ofbiodiversity).Naturalness - extent to which the area has been protected from, or has not beensubjected to, human-induced destruction, degradation or modification. (Assessed by thestatus of habitat degradation/deterioration)Representativeness - the degree to which the area represents a habitat type, ecologicalprocess, biological community or other natural characteristic, within the Madugangamangrove estuary. (Assessed by the number of representative habitat and vegetationtypes)Dependency/Uniqueness in terms of providing habitat for endemic and/or threatenedspecies of fauna and flora. (Assessed by number of endemic and/or threatened speciesin a strata)Integrity - the degree to which the area is an effective, self-sustaining ecological entity,in time and space, within Maduganga mangrove estuary. (Assessed by the overall statusof above criteria)The six major strata surveyed were assessed for each of the above ecological criteria, using aset of scores ranging from 1-5; the highest score being given to the higher significance of eachcriteria. The strata that received a cumulative score of above 20 were considered as areas ofhigh ecological significance in Maduganga.Assessment of threatsThe threats were categorised under habitat deterioration/degradation, direct exploitation ofspecies and spread of invasive alien species. The various threats to biodiversity under the abovecategories in each strata were assessed at three levels of significance; low, moderate and high,and the overall threat status of each strata was determined according to the frequency of threatsignificance levels.7
3. Flora of MadugangaFloristic composition and vegetation typesThe Maduganga wetland consists of 10 major wetland vegetation types (Table 3; Figure 3). Atotal of 302 species of plants belonging to 95 families (Appendix 1) were documented fromthese vegetation types. When considering the woody plants in the different vegetation types,121 species under 43 families were documented in the sampling plots. The total plant speciesinclude 19 endemics and 8 nationally threatened species (IUCN Sri Lanka, 2000), while 9 areinvasive alien species. Herbs represent the dominant plant life-form (59%) in Maduganga,while non-woody climbers forms the least common (1%) plant life-form (Figure 4). Based onthe extent of occurrence, mangroves and mangrove mixed swamps are the dominant wetlandvegetation type in Maduganga. The mangrove scrubs, mangrove mixed swamps, and bankscrubs represent different stages of degraded mangrove vegetation. The most abundantmangrove species is Rhizophora apiculata, while Lumnitzera littorea is the least foundmangrove species.In addition to these wetland vegetation types, three major terrestrial vegetation types are alsofound in the islands and the surrounding mainland area of the Maduganga estuary (Table 3).Perennial crops (Cinnamon, Coconut and Rubber) dominate the terrestrial vegetation types.The northern mainland of Maduganga is dominated by Cinnamon cultivations, while Coconutand Rubber plantations are more common in the southern mainland area. A small patch ofdegraded remnant lowland rainforest is located in the uppermost reaches of Maduganga. Atotal of 98 plant species, consisting of 41 woody species were recorded from the multi-specieshome gardens (Appendix 2).When considering the species richness of flora in different wetland vegetation types inMaduganga, mangroves harbour the highest number of species, closely followed by mangrovemixed swamps (Figure 5). A total of 14 species of true mangrove and mangrove associateplants were recorded from these two vegetation types. The tall shrub swamps, palm swamps,lentic macrophyte assemblages and tall sedge brackish marshes harbour a lower number ofplant species.Distribution patterns of mangrove and non-mangrove woody floraAnalysis of the distribution of mangrove plant species in sampling plots within Madugangashowed some interesting patterns. The sampling plots located within 3 km range from theestuary mouth were considered as proximal plots, and those located above 3 km wereconsidered as distal plots. Bruguiera sexangula occurred mostly in distal plots indicating theirpreference for low salinity. Similarly, relatively high abundance of Bruguiera gymnorrhiza andSonneratia caseolaria was observed in distal plots indicating their preference for low salinity.Conversely, Xylocarpus granatum and Lumnitzera littorea were found mainly in the proximal8
Page 1: Occasional Papers of IUCN Sri Lanka
Page 4 and 5: SummaryThe Maduganga estuary and ma
Page 6 and 7: Therefore, with a view to contribut
Page 8 and 9: 1.11.22.12.23.13.2Figure 2Sampling
Page 12 and 13: plots, while Excoecaria agallocha a
Page 14 and 15: 4. Fauna of MadugangaSpecies compos
Page 16 and 17: from these mammals, a few species o
Page 18 and 19: 6. Major Threats to Biodiversity in
Page 20 and 21: alien faunal species affect the nat
Page 22 and 23: 7. Recommendations for Conservation
Page 24 and 25: AcknowledgementsIUCN Sri Lanka wish
Page 26 and 27: No. Family Botanical name Status Li
Page 34 and 35: No. Family Botanical name Common na
Page 36 and 37: No. Family Botanical name Common na
Page 38 and 39: Family Species Status Abundance Hab
Page 40 and 41: Appendix 4List of Amphibians record
Page 42 and 43: Appendix 6List of Avifauna recorded
Page 44 and 45: Family Species Status RelativeAbund
Page 46 and 47: Appendix 7List of Mammals recorded
Page 48 and 49: Family Species Status AbundanceLemo
Page 50 and 51: Appendix 10List of terrestrial moll
Page 52 and 53: Pinto, M. L. (1986). Mangroves of S
Page 54 and 55: Notes51

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