ABSTRACT

Estuaries are complicated systems to manage effectively, requiring the monitoring of robust environmental indicators to assess health and detect changes. Routine estuarine monitoring programmes in New Zealand have only existed for 30 years at most, but estuaries have been significantly affected by anthropogenic pressures for at least 100 years. We reconstructed long term changes in indicators of estuarine health using historical information from sediment cores and aerial photographs, and combined this information with recent monitoring data. This study is focused on four estuaries in the Waikato region of New Zealand, but the findings are likely applicable elsewhere. Sediment accumulation rates increased by orders of magnitude c. 100 years ago, but mangrove forests only started to rapidly expand c. 50 years ago, which coincided with the intensification of agriculture and urban development, and resultant declines in freshwater quality. Over the past 20 years, state of the environment monitoring shows declines in benthic health at most monitoring sites, as well as continuing sediment accumulation and mangrove expansion in some places. This adds to the weight of evidence that environmental management has not been sufficient to safeguard estuarine health and demonstrates the magnitude of change in these systems over the past 100 years.

摘要

河口是有效管理的复杂系统，需要监测强大的环境指标以评估健康状况和检测变化。新西兰的常规河口监测计划最多仅存在 30 年，但河口受到人为压力的显着影响至少 100 年。我们使用来自沉积物岩心和航空照片的历史信息重建了河口健康指标的长期变化，并将这些信息与最近的监测数据相结合。这项研究的重点是新西兰怀卡托地区的四个河口，但研究结果可能适用于其他地方。沉积物积累率增加了几个数量级 c。100 年前，红树林才开始迅速扩张 c. 50年前，这恰逢农业和城市发展的集约化，导致淡水质量下降。在过去的 20 年中，环境状况监测显示，大多数监测点的底栖生物健康状况有所下降，以及一些地方的沉积物不断积累和红树林扩张。这增加了环境管理不足以保护河口健康的证据的重要性，并证明了这些系统在过去 100 年中的变化幅度。