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Mapping of mangrove forest land cover change along the Kenya coastline using Landsat imagery

Kirui, Bernard K Y; Kairo, James G; Bosire, J O; Viergever, Karin M; Rudra, S; Huxham, Mark; Briers, Robert A

Authors

Bernard K Y Kirui

James G Kairo

J O Bosire

Karin M Viergever

S Rudra



Abstract

Mangroves in Kenya provide a wide range of valuable services to coastal communities despite their relatively small total area. Studies at single sites show reductions in extent and quality caused by extraction for fuel wood and timber and clearance for alternative land use including saltpans, aquaculture, and tourism. Such studies suggest that Kenyan mangroves are likely to conform to the general global trend of declining area but there are no reliable recent estimates of either total mangrove extent or trends in coverage for the country. The total extent of Kenyan mangroves was estimated at four points in time (1985, 1992, 2000 and 2010) using Landsat satellite imagery. Due to its medium resolution, Landsat may underestimate mangrove areas in Kenya where relatively small, linear, coastal features occur. There is also a high frequency of clouds in the coastal areas which can cause data gaps during analysis. However comparison with aerial photographs taken in 1992 showed satisfactory levels of accuracy (87.5%) and Cohen’s Kappa (0.54) validating its use in this context. These 1992 data provided an independently validated baseline from which to detect changes (fore- and hind-casted) in other periods after removing cloud coverage. We estimated total mangrove coverage in 2010 at 45,590 ha representing a loss of 18% (0.7% yr−1) in the 25 years between 1985 and 2010. Rates of mangrove loss for Kenya varied both spatially and temporally with variations possibly due to legislative inadequacies and differences in habitat alteration patterns. Hence freely available Landsat images proved adequate to detect changes in mangroves and revealed that Kenya shows rates of decline similar to (although slower than) global estimates.

Journal Article Type Article
Publication Date 2013-10
Deposit Date Sep 24, 2013
Print ISSN 0964-5691
Electronic ISSN 1873-524X
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 83
Pages 19-24
DOI https://doi.org/10.1016/j.ocecoaman.2011.12.004
Keywords Mangroves; Kenya; Landsat imagery; deforestation; coastal erosion;
Public URL http://researchrepository.napier.ac.uk/id/eprint/6423
Publisher URL http://dx.doi.org/10.1016/j.ocecoaman.2011.12.004