Status and potential role of rangeland insect pollinators for pastoralist livelihood diversification in northern Tanzania

Abstract

Pollinators provide ecosystem services that support other living organisms. However, they are currently threatened by land use changes including habitat fragmentation. In Tanzania, Maasai rangelands are under pressure from population increase, habitat fragmentation and decline in grazing areas that cause overgrazing. Little is known about local Maasai knowledge on pollinator communities and how they are affected by grazing management in semi-arid rangelands in Tanzania. Semi structured questionnaires, key informant interviews and focus group discussions were used during the survey in order to understand local knowledge of insect pollinators. Findings revealed varied pollinator identification skills, with males having higher skills (χ 2 = 6.319, P = 0.042) compared with females. Honey bee, Apis mellifera was the most important pollinator as reported by 93% of males and 78% of females. Beekeeping contributed to livelihood diversification for 61% of respondents, with women participating more frequently in this activitiy than men (χ 2 = 46.96, P = 0.0001). Ultraviolet (UV) white, yellow and blue pan traps were used to trap insects in four different grazing management, namely private and communal enclosures, wet and dry season grazing areas. Pan trapping was further supplemented by a standardized sweep netting method. Findings showed that environmental factors and grazing management affected insect pollinators. Insect abundance, diversity and richness varied with seasonality, whereby the mean number of insect abundance was significantly higher (χ² = 136.77, P < 0.0001) during the wet (148 ± 70.57) compared with the dry season (17 ± 7.14). Moreover, flower abundance (χ² = 3.5, P = 0.05) and percentage herbaceous cover (χ² = 5.99, P = 0.015) influenced pollinators. Private enclosure management category contained significantly more pollinators (χ² = 27.63, P < 0.001) compared with the communal dry grazing area. The study also investigated pollinator-plant interactions to understand the foraging preference of bees and other pollinators. Aspilia mossambiensis and Justicia debile were the most preferred plants. The most common visitors were honey bees and butterflies. Pollinator networks showed that enclosures contained larger networks compared with open rangelands. The study concludes that the Maasai community have limited knowledge of pollinator ecosystems services. In addition, traditional range management especially the use of enclosures is an important tool towards the conservation of insect pollinators in semi arid rangelands threatened by overgrazing and degradation