Metrics for assessing the biodiversity values of farming systems and agricultural landscapes

Abstract

This paper reviews current approaches to assessing biodiversity values in agricultural landscapes in southern and eastern Australia and makes recommendations about their applicability to revegetation for commercial and non-commercial purposes. A typology based on the quantitative measurement of structural, functional and compositional attributes of biodiversity at multiple scales is used as the framework for the review. Metrics currently used to assess biodiversity primarily focus on conservation outcomes for natural systems rather than other cultural, social and economic values. They cover a range of scales (from local to global), landscape contexts (from intact to relictual) and levels of organization (from genes to ecosystems). Surrogate measures are commonly used to assess biodiversity, particularly vegetation type and condition. Recently developed metrics are beginning to attach weightings to different habitat attributes and incorporate "natural" benchmarks. While expert panels play an important role in developing and assessing biodiversity metrics, a number of untested assumptions underpin current approaches. Rigorous testing and validation is therefore required if the current set of metrics is to serve as a reliable indicator of biodiversity across agricultural landscapes in Australia. While it is encouraging that more explicit and repeatable measures are being developed, as well as metrics that score the biodiversity value of a broad range of land uses, clearer definitions and objectives are required. Metrics also need further development and testing for aquatic species and systems and their interface with terrestrial systems, non-woody terrestrial systems, revegetation and the persistence of species across the landscape. Importantly, there is a need for greater cross-fertilization between ecologists, agricultural, social and other scientists, and private land managers to identify specific and measurable attributes of biodiversity within a farming systems context. This will help ensure that the conservation and utilization of biodiversity becomes an integral part of natural resource management in rural landscapes.