in Sri Lanka - Ministry of Environment

Nearly 80% of the known crab species of Sri Lanka are restricted to the wet zone where 95%of the forest cover has been converted for human use during the last century. The remainingforests are also severely fragmented with three fragments (Knuckles, Sinharaja and PeakWilderness) accounting for half of the remaining forest cover and the balance are contained in> 100 fragments of varying size. Studies done in Brazil (Bierregaard et al., 2001; Ferraz et al.,2003) have shown that extreme rainforest fragmentation could lead to catastrophic declinesand extinction of species within a short period of time. Therefore, the long-term security of SriLanka’s biodiversity will depend on minimizing fragmentation impacts through effective landuseplanning and restoration initiatives while maximizing habitat connectivity between forestsites. Such goals can be met only through a policy framework built on sound scientific data,implemented through sustained, long-term financing mechanisms.Given the fact that conservation of freshwater crabs hinges almost entirely on preservingpatches of natural forest large enough to maintain good water quality, it is of concern that waterquality is deteriorating even in key natural habitats (Gunawardena et al., 1998). Many freshwatercrabs are extremely sensitive to polluted or silted waters and will not survive when exposed tothese factors. In Singapore for example, the small patch of primary forest of Bukit Timah Hill(~70 ha) has been sufficient to maintain a thriving population of the endemic potamid Johorasingaporensis (Ng, 1988; 1989; 1990). The same is also true for Parathelphusa reticulata,which is known to occur in only a small remnant patch of peat-swamp forest patch of less thanfive hectares (Ng, 1989; 1990). Decade-long monitoring of these populations demonstratesthat crab species will persist even in small habitat fragments if these are managed well, thoughexposed to extirpation by stochastic events (Brook et al., 2003).Recommended conservation actionsThe fact that exploration carried out during the last two decades alone has resulted in thedescription of 43 new species, provide strong support for the necessity of a national freshwatercrab survey, leading to a gap analysis and the identification of key habitats for conservationattention. It is also necessary to closely monitor at least the Critically Endangered species,especially to detect actions that could alter habitat, so that these could be treated before theyimpact on the population involved. Further, as discussed above, the long term conservation offreshwater crabs depends heavily on maintaining water quality of their habitat. Since one ofthe key drivers of freshwater habitat change is pesticides, it should become mandatory for allpesticides be assessed for impact on non-target organisms and the environment in general, andthe labeling of such products should include information on environmental safeguards beforebeing approved for use within Sri Lanka. Many of the freshwater crabs occur outside the protectedarea network in private lands (e.g. Perbrinckia armata, Perbrinckia callista and Clinothelphusakakoota). Therefore, introducing legal and institutional reforms necessary to engage localcommunities in the in situ conservation of point-endemic freshwater crabs is an important step. Atthe same time it is necessary to establish an ex situ management programme to maintain captivepopulations of at least the Critically Endangered species. Finally, lack of information on many ofthe freshwater crab species signifies the need for promoting further research and awarenesson this unique taxonomic group. Therefore, developing a user-friendly guide for identificationof freshwater crabs and conducting education and awareness programmes for school children,university students, policy makers and the civil society are also identified as key elements of asuccessful campaign to conserve the freshwater crabs of Sri Lanka.60