Tana Delta Irrigation Project, Kenya: An Environmental Assessment

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Rehabilitation of the Tana Delta Irrigation Project, Kenya: An Environmental Assessment. Even for colobus, an obligatory arboreal species, riverine forest, isolated trees and small forest patches may provide adequate tree cover to allow for dispersal between larger forest patches explaining the changes of pattern of troop locations through time, with due consideration to census error. Possible seasonal changes of movement must also be taken into account. On the other hand, mangabeys previously appeared throughout the census area in all but seven (31.8%) of the forests. As recorded in this census, their range has expanded into forests that previously did not report mangabeys (forest #46 and #69). Nine forests (40.9%) with previous records of mangabey did not have mangabeys noted in 2005. Interestingly, three troops are missing from the forests on the west side of the river (#54, 59, 62) in the vicinity of forest #58 while forest #58 has three troops more than previously reported in the 2001 census. Inter-forest movement of groups may account for this. Comparing the forest area of the current census to the map of forest areas generated by Karere et al. (2004), this survey did not census the northern portion of forest #56 or 63b, 67b. Interestingly, two troops of colobus accounted for in the 2001 study (one each in forest #63 and #67) that were not counted in this census, come from these forests. It is possible, that these uncounted troops were previously observed in these uncensused forest patches. Complete loss of both species of primate has occurred in five of the 22 areas censused (22.7%) however only Wema West 2 (#54), had both species missing. This forest was noted in 1994 for having “moderate human activity”. The other forests which had complete loss of groups, either colobus or mangabey had varying levels of human activity as noted in Table 3. Please note that the activity level noted in Table 5 may well have changed from 1994 description as it has been stated that forest clearing has escalated since then (Wieczkowski et al., 2002). There may not be a direct relationship between forest disturbance and primate group density but that disturbance may lead to reduced group sizes rather than a reduction in troops (Muoria et al., 2003). Table 16. Levels of disturbance in forests that have lost colobus and mangabeys in this census. Colobus Mangabey Forest # Human Reference Forest # Human Reference Activity Activity 47 Light Butynski and Mwangi 1994 49 light Butynski and Mwangi 1994 48 Heavy Butynski and Mwangi 1994 54 moderate Butynski and Mwangi 1994 54 Moderate Butynski and Mwangi 1994 56 cleared Muoria et al., 2003 areas 63 Moderate Muoria et al., 2003 57 heavy Muoria et al., 2003 68 cleared areas Muoria et al., 2003 59 cleared areas Muoria et al., 2003 93
Rehabilitation of the Tana Delta Irrigation Project, Kenya: An Environmental Assessment. Table 17. Red colobus census data 1972 – 2005. Adapted from Appendix A Butynski & Mwangi 1994. Forest # Forest 1972/74 1975 1985 1986 1987 1989 1990 1992 1994 2000 2001 2005 Est. ind. 46 Sailoni 1 0 1 NC 0 0 0 47 Sailoni 2 0 0 NC 1 0 0 48a Kulesa East 1 0 1 0 0 NC 2 0 0 48b Kulesa East 2 0 0 NC 0 NC NC 49 Kulesa West 1 0 0 NC 1 1 8 50 Kulesa West 2 0 NC 0 0 0 53 Wema West 1 0 0 1 NC 0 0 0 54 Wema West 2 0 1 NC 2 0 0 55 Wema West 3 some 1S 0 0 1 8 56 Wema East 1 0 1 0 1 0 2 1 0 0 0 0 0 0 57 Wema East 2 0 0 0 0 0 0 0 58 Hewani West 1 some 1 0 0 1 1 1 3 6 5 7 67 59 Hewani East 1 some 0 0 1 1S 1 1 1 1 1 7 60 Hewani East 2 some 1 1 1 2 1 1 1 1 2 11 61 Hewani East 3 1 1 0 1 1 1 1 0 0 0 0 62 Hewani West 2 some 1 0 1 1 1 0 0 0 63 Hewani South 1 0 0 0 0 0 3 1 0 0 64 Hewani South 2 8 5 0 1-2 2 3 10-13 1S NC 4 1 9 65 Bvumbwe North 0 0 0 NC 0 0 0 66 Bvumbwe South 0 NC 0 0 0 67 Lango La Simba 2 0 2 (2) NC 1 1S 1 68 Wema East 4 0 0 0 1 0 0 69 Mitapani 1 0 1S 0 0 0 0 70 Mitapani 2 2 3 0 0 NC NC Unknown forest 1 16 Total: 20 14+1S 127 S - solitary individual 94
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REHABILITATION OF THE TANA DELTA IR
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Rehabilitation of the Tana Delta Ir
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INSTITUTIONAL LINKAGES Primary link
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