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University of Pretoria (2021)

Land-use mosaic effects on insect abundance, bat activity and macadamia production, South Africa

Swartz, Emma

Titre : Land-use mosaic effects on insect abundance, bat activity and macadamia production, South Africa

Auteur : Swartz, Emma

Université de soutenance : University of Pretoria

Grade : MSc (Wildlife Management) 2021

Résumé partiel
Rapid increases in the global human population have led to agricultural intensification worldwide, highlighting the need for conserving the remaining fragmented natural areas and incorporating more sustainable farming techniques. South Africa is currently the largest producer of macadamia nuts in the world and macadamia plantings are increasing rapidly, resulting in the loss of natural vegetation. The study area, Hazyview in Mpumalanga, is an agricultural mosaic, with fragments of natural vegetation patches in between. These natural vegetation patches are key to retaining important ecosystem services for the agricultural industry such as pollination and pest-control. This study evaluated how a land-use mosaic, represented by an agricultural landscape with natural vegetation retained around the farms, is related with macadamia nut yield and quality, the activity of insectivorous bat species, and nocturnal insect abundance, with a specific focus on five different macadamia farms. The role and contribution of bats and insects in agro-ecosystems are becoming more apparent, and their importance as indicator species which can reflect environmental changes in plant and insect communities is of key value. With this information, I could gain a better understanding of the relationships between the surrounding biodiversity and the commercial macadamia nut production industry, as well as the potential impact that agriculture-induced landscape fragmentation has on the biodiversity in the region. Firstly, on-farm characteristics (e.g. tree age, density, height) for five farms were used, aswell as their yield and quality measures and land-use types surrounding each farm to determine potential relationships between macadamia nut yield and/or quality and proximity to surrounding natural vegetation. Farm characteristics such as the height and density of the macadamia trees planted had a significant association with yield and quality of the nuts which both decreased with increasing tree height and density. Additionally, a characteristic of land-use type (in this case, extent of waterbodies such as rivers/ dams and wetlands surrounding the farms) was found to have an association with yield. The surrounding natural areas likely act as a reservoir for both insects and their predators, which could be beneficial for the neighbouring agricultural lands by improving pollination, yield and nut quality through biological pest-control.

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