Population Density and Diversity of Trees on Farmlands in Three Districts of the Upper East Region of Ghana: Implications for Food Security and Ecosystem Sustainability

Ghanaian farmers have been practicing farming since time immemorial and trees are a natural
component of farmlands. However, the choice of particular tree species and their population on the
farms is greatly influenced by the farmers’ preferences and therefore, the utility value placed on
particular tree species. This study was conducted to determine the number of trees per unit area of
farmland, the diversity of the tree species, and the factors that influence farmers’ decision to leave
trees on their farms in three districts of the Upper East region of Ghana. It also seeks to determine
any relationship between tree density and the yields of commonly cultivated crops in the study area.
The area falls within the Guinea and Sudan savanna zones, characterized by a short unimodal rainfall
regime (about 5 months) and a rather long dry season. Twelve communities (4 per district) were
randomly selected and farmers were interviewed on their reasons for allowing trees on their farmlands
as well as the yields of major crops cultivated. Ten farms in each community were also randomly
selected and inventories of trees were conducted, where trees were identified, and enumerated. Farm
sizes were also measured. Mean tree population densities on farms were 18.5, 18.4 and 25.9 trees
per hectare in the Garu-Tempane, Bawku West and Kassena Nankana West districts respectively. A
Shannon Weiner diversity index of 1.563, 1.195 and 1.551 were calculated for Garu-Tempane, Bawku
West and Kassena Nankana West districts respectively. Forty-two (42) different tree species
belonging to 23 families were encountered in Garu-Tempane district, 28 species from 18 families
were encountered in the Bawku West district and 37 species belonging to 21 families in the Kassena
Nankana West district. Azadirachta indica, Combretum molle, Diospyros mespiliformis were the
commonest on all farms. Factors that influenced farmers’ decision to allow trees on their farms were
shade (22%), fuelwood (18%), food (15%), medicine (13%), housing (13%), soil improvement (10%),
erosion control (7%), fodder (1%) and others (1%). Crop yields were generally high in the Bawku
West district and there was no significant relationship between tree population density and the yields
of crops.