Several theories have emerged that explain the impact of population on the use of natural resources.1 Local population growth may directly affect use of resources and influence the rate of habitat change. Although the relationship between population size and growth and biodiversity loss is complicated, the use of a variety of indicators make it possible to explain the effect of population growth on natural resources. For example, it is evident that countries with high population densities have converted relatively more land to agricultural use.
It is tempting to follow this line of argument to explain biodiversity loss in the deltas. However, due to the paucity of data on population trends, one must be careful with the conclusions. Data collected from the study area suggests different population dynamics for Rufiji and Bagamoyo Districts: rapid growth for Bagamoyo and slower growth for Rufiji. The population of Bagamoyo increased from 136,059 in 1978 to 173,918 in 1988, an annual growth rate of 2.4 percent (United Republic of Tanzania, 1997a). Similarly, the population of Rufiji District grew from 135,334 in 1978 to 152,316 in 1988, an annual growth rate of 1.3 percent (United Republic of Tanzania, 1997a). In 1988, the population in the delta area alone was 33,000 (Semesi, 1994; Fottland and Sorensen, 1996; Rufiji Environmental Management Project, 1998). In-migration is likely to cause an increase of Rufiji’s population in future if the Rufiji prawn-farm project takes off. The project proposes to employ about 7,750 people when fully operational (National Environmental Management Council, 1997).2 However, a careful analysis of events in the study area shows that local population may have fallen over the last few decades. Many elder villagers in Rufiji Delta remember that, between the 1950s and 1970s, the Delta bustled with people who flocked there to trade in mangrove poles, logs, and bark, fish, cashew nuts, prawns, cotton, rice, and coconut. Rufiji was one of the major outlets to Arab and Far East countries for mangrove products and timber. This market was central in linking the delta islands, including Mafia Island, and the other parts of the coastal area. Coconut and other products from Mafia passed through this market. The Delta’s history of interaction with various traders included Arabs, Portuguese, Germans, English, and Indians who visited the East African coast. Arabs did most of the trade with the local people. Over 62 dhows (boats) were “docking at various ports” in the Delta each season to buy mangrove products for export when trade was strong. This situation began to change in 1974 when traders stopped coming from the Arab countries. Several factors contributed to the decline in trade, but the local people attribute it to political interference.3On the basis of this history, there is little evidence to suggest that current population pressure has been a direct cause of the loss of biodiversity in the Rufiji Delta.
Rather, what emerges is that poor management has contributed to increased depletion of mangroves. In Rufiji, the mangrove forest has passed under public, private, and cooperative management. In the 1940s, the Rufiji mangrove was under the management of two foreign businessmen. The forests were leased to private dealers for harvesting and management. Harvested areas were replanted and the mangrove forests flourished during that time, despite the great demand, due to good management, monitoring, and control.
The system continued until 1965 when these businessmen closed the operation. From 1965 to 1987, the Department of Forestry managed the forests but various local cooperative unions and individuals harvested them haphazardly. Because management was so weak, unsustainable harvesting was common. In 1987, the government instituted a ban on mangrove harvesting that lasted until 1991 when a management plan was put in place. Therefore, it was not population pressure, but rather a management vacuum created by the departure of the two businessmen that led to over-harvesting.
The mangrove forests in Ruvu and Wami were not put under such an arrangement. Because the physical characteristics of these deltas render them uninhabitable, human settlement in the Wami and Ruvu Deltas is almost non-existent. However, access to the area is an important variable for understanding the process of biodiversity loss. Although isolated by distance and the poor quality of the roads, Ruvu and Wami Deltas have been suffering pressure from the town of Bagamoyo and beyond. As noted above, the population of Bagamoyo increased at a rate of 2.4 percent annually between 1978 and 1988. This increase is reflected in household sizes. Households in Bagamoyo average more than six people who depend on the head of household for their survival.4Because families are big, they exert great pressure on natural resources in providing for basic needs.