Trees and shrubs improve the aesthetic quality of urban areas. It is the aesthetic and recreational value of trees, forests and parks that is most directly identified by most urban dwellers, in developed and developing countries alike. Trees fulfill certain psychological, social and cultural needs of the urban dweller (Dwyer, et al., 1991). They play a very important social role in easing tensions and improving psychological health; people simply feel better living around trees. One study has demonstrated that hospital patients placed in rooms with windows facing trees heal faster and require shorter hospital stays (Ulrich, 1990). When appropriately selected and placed, trees are effective in screening out undesirable views and ensuring privacy while permitting free visual access to the rest of the landscape. Parks provide easily accessible recreational opportunities for people. Health Parks and green areas provide opportunities for healthy physical activity (Kuchelmeister, 1991). Enjoyment of green areas may help people to relax or may give them fresh energy. In addition, the passive benefit to physical and mental health of an urban landscape with trees has been documented in industrialized countries (Clarke et al. 2000).
2.5. Microclimate, air quality improvement and carbon dioxide reduction
Trees, shrubs and other vegetation help to control temperature extremes in built up environments by modifying solar radiation. The shade of one large tree may reduce the temperature of a given building to the same extent as would 15 air conditioners at 4000 British thermal units (BTU), i.e. 4220 kJ, in a similar but unshaded building. In addition, energy saving through tree-planting around houses ranges from 10 to 50 percent for cooling and from 4 to 22 percent for heating (NAA/ISA, 1991).Trees of coastal forest help to improve the air quality by cooling and cleaning the air. Landscaping involving strategic tree planting can conserve energy and maintain comfort without air conditioning (Kuchelmeister & Braatz, 1993). Coastal forests are utilized as an effective approach for reducing air pollution. Trees mitigate pollution by reducing energy use, carbon dioxide emissions and ground-level ozone. Some urban forestry projects, in several cities in the United States for example, have been financed by carbon sequestration projects (Akbari et al., 1992; McPherson and Rowntree, 1993)
2.6 Species diversity in coastal forests
The flora and fauna of the coastal forests are recognized as being of global importance due to high levels of biodiversity and endemism found within the small, fragmented and highly threatened patches of forests. The closed canopy coastal forests retain high numbers of endemic plant and animal species (Luoga, 2000). It has been explained that these forests constitute 554 plants, 43 birds, 3 mammals, 24 reptiles, five amphibians, 86 molluscs and 75 insects. The mosaic of habitats within the Hotspot, including forest, woodland and thickets, contain a greater total number of endemic species inlcuding 1,750 plants, 11 birds, 11 mammals, 53 reptiles, six amphibians and 32 freshwater fishes. Out of these, include 333 globally threatened (IUCN Red list) species, with 105 species being represented in Kenya and 307 in Tanzania (Michael, 1984; Mittermeier et al., 1998).
Mafia is a district of the Coast Province, which is one of the provinces of mainland Tanzania Clarke, 2000).
Source: Tanzania Natural Resource Information Centre (TANRIC)
Figure 1: A map showing Mafia Island Forest Reserves
3.1.1. Geographical location
The Mafia Archipelago is scattered over the Indian Ocean 21 km off the Rufiji River Delta in central Tanzania. The largest of a score of islands, atolls and tidal sandbars, Mafia itself is approximately 50 km long by 15km across, and is located between Latitude 7.850S and Longitude 39.7830 E surrounded by a barrier reef teeming with marine life (Clarke, 2000).
Temperatures are mild, even when we speak of the “hot” season, as the temperature in Mafia rarely exceeds 30°C. Mafia has a relatively dry tropical climate with approximately 1,800 mm of rain each year divided into two seasons of “long” rains in late March-May and “short” rains in November-early December. Mafia Island lies across the trade winds and experiences the north-east and south-east seasons (Clarke, 2000).
3.1.3 Population and Economic Activities
The population of Mafia Island is around 40, 801 people living in 24 villages scattered throughout the main island, Jibondo, Juani and Chole islands. According to 2002 poulation census the population was found to be 40,816 (URT, 2002). The peoples’ livelihood mainly depends on rustic fishing and farming. The main farming activities are mainly coconut plantation, and very few cases maize, cassava and banana. However previous studies indicated that due to extended land clearance, succeeding years will be accompanied by great expansion of agriculture, fishing activities, apart from these activities there is also livestock keeping (Clarke, 1999).
Natural vegetation on Mafia ranges from tidal mangrove thickets and scrubby coastal moorlands to palm-wooden grassland and lowland rainforest. Magnificent baobabs are prominent along with the native Albizia. Patches of coastal high forest remain in localities all over Mafia; one of the most picturesque, the Chunguruma Forest, is a dense tree canopy interlaced with palms, lianes and epiphytes and has an abundant floor covering of ferns (Clarke, 2000).
The closed canopy coastal forests retain high numbers of endemic plant and animal species (Luoga, 2000). It has been explained that these forests constitute, 43 birds, 3 mammals, 24 reptiles, five amphibians, 86 molluscs and 75 insects (Clarke, 2000).