Abstract:
Over the past three decades, coastal marine ecosystems of Tanzania have experienced a notable decline in the state of their environment through loss of natural habitats and biodiversity. Much of this change is attributable to human activities. This study investigated changes that have occurred as a result of human activities and climate change/variability, for the period between 2001 and 2011. Two demographically different locations in Zanzibar, namely Kisakasaka and Bumbwini were selected for the study. Landsat ETM+ images were used to locate and quantify the changes for which the intensity analysis method was employed. The study revealed that between 2001 and 2011, the mangrove, cultivated land/shrubs and bare land covers declined by 127.4 ha (33.9%), 46.0 ha (7.4%) and 10.2 ha (22.6%) respectively while mixed trees, “Jangwa la bahari” and water covers increased by 147.2 ha (11.1%), 35.8 ha (119.7%) and 0.6 ha (0.02%) respectively for Kisakasaka location. During the same period, cultivated land/shrubs, mangrove and mixed trees covers declined by 262.2 ha (8.8%), 86.3 ha (12.6%) and 49.4 ha (1.3%) respectively while paddy, bare lands, “Jangwa la bahari” and water covers increased by 165.6 ha (37.6%), 109.7 ha (837.4%), 103.9 ha (151.5%) and 18.7 ha (0.8%) respectively for Bumbwini location. The study also revealed significant increases of population from 6 034 and 23 212 to 15 400 (155.2%) and 34 638 (49.2%) from 1988 to 2012 for Kisakasaka and Bumbwini locations respectively. Although long term rainfall data analysis for Zanzibar revealed no significant trend in amount, length of growing season and number of wet days indicated significant negative trends while both mean and minimum temperatures showed significant positive trends. It is concluded that changes in climate together with population pressure have mainly contributed significant changes in land cover observed over the respective study areas. Hence concerted actions are required to reverse the observed/perceived changes.
