Impact of surface water extraction on water quality and ecological integrity in Arusha National Park, Tanzania

Abstract

Surface water has been extracted from Arusha National Park (ANP) to meet human demand for over 30 years; however, there has been no evaluation of the impact of extraction on surface water quality, budget or ecological integrity. A reduction in water availability and flow is likely to also have impacts on the distribution and space use of large mammals. To assess the surface water quality and budget, 30 water sources were measured for three months over the dry and wet seasons. Nearly 70% of water is extracted, with the complete extraction of surface water common during the dry and early wet seasons. However, extraction did not lead to a decrease in downstream water quality, but wetland plant diversity was highest in areas with no surface water extraction. Extraction also influences large mammal space use: abundance along seven transects was typically higher upstream of extraction sites, especially in the case of large herbivores. Impacts of extraction therefore include the disconnection of streams, changes in space use of large mammals, decreases in plant diversity and changes in species composition of the riparian wetlands. We therefore recommend that monitoring and evaluation of extraction as well as sustainable water use practices be introduced as a matter of urgency.

Summary comments on assessment methods of ecosystem integrity for national parks

“…)。 建立国家公园能够促进生态环境和生物多样 性的保护, 对于维护典型生态系统的完整性具有重 要意义 (Timko & Satterfield, 2008;Timko & Innes, 2009; 唐芳林, 2017)。 然 而 , 许多国家公园在运行和 管理的过程中面临诸多问题和挑战, 如管理有效性 缺失、保护目标难以实现、生物多样性和生态系统 完整性(ecosystem integrity)下降以及生态可持续性 发展遭受质疑等 (Scott et al, 2001;Salafsky et al, 2002;Rodrigues et al, 2004;Abebe & Bekele, 2018)。 为了发挥国家公园作用、体现国家公园建立的初衷 并消除公众的质疑, 对其地位、功能以及效益进行 全面评价是非常必要的 (Hockings et al, 2000;Stolton, 2004;Troy & Yolanda, 2017), 国家公园生态系 统完整性评价的概念正是在这一背景下提出的 (Dudley et al, 1999;Parrish et al, 2003;Stolton, 2004)。近年 来, 以美国和加拿大为代表的国家已经 开展了许多相关的研究工作 (Timko & Innes, 2009;Ladin et al, 2016;Elisa et al, 2016;Schroeder et al, 2017), 如加拿大设立国家公园时特别强调"典型 性"和"生态系统完整性", 为保护和展示自然景观 一个重要概念 (Harwell et al, 1999), 这一概念最早 由Leopold (1949)在一篇关于土地伦理学的文章中 提出。生态系统完整性评价是指评价一个生态系统 的结构、功能以及过程的完整性 (Karr & Dudley, 1981;Karr, 1981;Young & Sanzone, 2002;Parrish et al, 2003) Ecosystem integrity is the capability of supporting and maintaining a balanced, integrated, adaptive community of organisms having a species composition and functional organization comparable to that of the natural habitat of the region. Karr & Dudley, 1981;Karr, 1981 优势种 Dominant species 当原生物种成为优势种并主宰整个生物群落时, 生态系统将表现出相对稳定和健康, 即为生态 系统完整性。 When native species become dominant species and dominate the entire community, the ecosystem exhibits relative stability and health, namely ecosystem integrity.…”