Browsing by Author "Ginsburg, Aimee"

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    Planning for biodiversity and cereal production in the Gariep Basin : a conservation perspective
    (Stellenbosch : Stellenbosch University, 2006-04) Ginsburg, Aimee; Van Jaarsveld, Albert. S.; Reyers, Belinda; Stellenbosch University. Faculty of Science . Dept. of Botany and Zoology.
    ENGLISH ABSTRACT: Biodiversity feature richness and cereal production potential increase west to east across South Africa's Gariep basin, the regional focus area in the Southern African Millennium Ecosystem Assessment. lrreplaceability, developed for measuring biodiversity value, provides a unit free, spatially explicit measure that can be used to measure an area's importance in terms of cereal production. It provides a common currency to measure competing land-uses. This study models cereal production potential for four cereal types (maize, millet, sorghum, wheat) and sets three cereal production targets, based on minimum nutritional cereal demands and models of actual consumption rates. Chapter 2 uses C-Plan to determine irreplaceability and compares the irreplaceability values for cereal production potential and biodiversity. Higher cereal production targets increase the irreplaceability of sites for cereal production and increase the number of sites with high irreplaceability for both biodiversity and cereal production. These sites thus have high potential for conflict between these land-uses. Areas of conflict occur primarily across the central eastern region, largely in the grassland biome. The biodiversity features and cereal production potential of these sites are known, thus making potential trade-offs involved in the conservation of these sites explicit. Sites with conflict potential can be avoided using area selection algorithms that maximise conservation target achievement while minimising the cost to cereal production. CPlan' s simple iterative heuristic approach to minimising costs succeeds in avoiding some areas of conflict potential but more complex algorithms provide better solutions. The simulated annealing algorithm available in another conservation planning software platform, MARXAN, offers a more complex consideration of penalties and costs associated with meeting conservation targets and minimising cereal production costs. Chapter 3 finds that the balance between the penalties for not achieving all biodiversity targets and those for exceeding the cereal cost thresholds in MARXAN are critical, impacting the achievement of certain biodiversity feature targets. Important penalties include the conservation feature penalty factor, the cost threshold, and the cost threshold control parameter. MARX.AN generates numerous solutions for a single problem, providing a measure of a site's selection frequency over a number of runs. The central eastern region has highest variability in selection frequency where both cereal production and biodiversity irreplaceability are high. As cereal production targets increase, sites in this region become more difficult to avoid and trade-offs are unavoidable. Comparing the software, chapter 4 concludes that the relationships between the inputs and planning parameters on outputs are crucial for effective conservation decision making. CPlan' s sensitivities are restricted to the combination size and site selection rules. MAR.XAN requires numerous input parameters that collectively provide more variable outputs. Further documentation on best and current practices in MARXAN, sensitivities of conservation outputs to input parameters, and awareness of these sensitivity in capacity building exercises are required to guide decision makers. Irreplaceability allows the comparison of two different objectives and the potential trade-offs that might exist. Explicit inclusion of cereal production potential into systematic conservation planning frameworks generates more cost effective and socially acceptable reserve solutions that strengthen the partnership between conservation and civil society. Key Words: conservation planning, biodiversity, cereal production, irreplaceability, tradeojfs, opportunity costs, MARXAN, C-Plan.