South African National Parks, PO Box 37 Steenberg, Cape Town, 7947, South Africa; Department of Conservation Ecology and Entomology, Stellenbosch University, Private Bag X1, Matieland, 7602, Stellenbosch, South Africa.
Department of Conservation Ecology and Entomology, Stellenbosch University, Private Bag X1, Matieland, 7602, Stellenbosch, South Africa; Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland, 7602, Stellenbosch, South Africa.
J Environ Manage. 2019 May 15;238:274-282. doi: 10.1016/j.jenvman.2019.02.112. Epub 2019 Mar 7.
In many protected areas in South Africa, invasive Australian Acacia species pose on-going management challenges, perpetuating high long-term management costs. Due to limited availability of resources, conservation actions need to be prioritised within and across Protected Areas (PA). We draw on comprehensive datasets spanning over 20 years from the Table Mountain National Park to model long-term outcomes of clearing Acacia species at different levels of management clearing efficacy. We test a 50 year outlook based on current and 38 incremental levels of management efficacy, ranging from 5 to 100%, to assess under which scenarios a management goal of reducing Acacia density to below 1 plant per hectare for the 22,671 ha protected area is achieved. With the current clearing resources and maximum clearing efficacy (100% control), it would take between 32 and 42 years to attain the management goal. The modelling revealed two main drivers of Acacia persistence. Firstly, germination of seeds added to the seedbank from standing plants made a significantly larger contribution to future clearing requirements than fire stimulated seed germination or the existing (pre-management) seedbank. Secondly the relationship between the number of hectares and management units that could be treated and the efficacy of the treatment was non-linear. When clearing efficacy was decreased from 100% to the current project minimum target of 80% efficacy, the goal was not achieved in all areas, but the area that reached a density of <1 plant per hectare was significantly reduced to 53% of the PA for the simulated 50 years. Results emphasize the need to differentiate between increasing financial resources and increasing efficacy. While increasing financial resources allows for increased effort, this is of little value for Acacia management in the absence of an increase in clearing efficacy, as low quality implementation perpetuates the need for large budgets over time. Conversely, improving efficacy allows for decreased budget requirements over time, allowing fund re-direction to additional areas of alien species management such as the early detection and rapid control of newly introduced species.
在南非的许多保护区中，入侵的澳大利亚金合欢物种构成了持续的管理挑战，长期管理成本居高不下。由于资源有限，需要在保护区内和跨保护区内确定保护行动的优先次序。我们利用图尔布山国家公园 20 多年的综合数据集，模拟在不同管理清除效果水平下清除金合欢物种的长期结果。我们根据当前和 38 个增量管理效果水平（从 5%到 100%）测试了一个 50 年的展望，以评估在哪些情况下可以实现将 22671 公顷保护区内的金合欢密度降低到每公顷 1 株以下的管理目标。在当前的清除资源和最大的清除效果（100%的控制）下，需要 32 到 42 年才能达到管理目标。建模结果揭示了金合欢持续存在的两个主要驱动因素。首先，从站立植物添加到种子库中的种子萌发对未来清除需求的贡献明显大于火灾刺激的种子萌发或现有的（管理前）种子库。其次，可处理的公顷和管理单位的数量与处理效果之间的关系是非线性的。当清除效果从 100%降低到当前项目的最小目标 80%的效果时，并不是所有地区都能达到目标，但达到密度<1 株/公顷的区域显著减少到模拟 50 年内保护区的 53%。结果强调需要区分增加财政资源和提高效率。虽然增加财政资源可以增加努力，但在缺乏清除效果提高的情况下，这对金合欢管理几乎没有价值，因为低质量的实施会随着时间的推移持续需要大量预算。相反，提高效率可以随着时间的推移降低预算需求，允许将资金重新分配到外来物种管理的其他领域，例如新引入物种的早期发现和快速控制。
