Assessing biodiversity integrity for the conservation of grazed and burnt grassland systems: avian field metabolic rates as a rapid assessment tool

Abstract

The South African grassland system is home to over 3,300 plant species, 15 of the country’s 34 endemic mammal species, 12 of the 40 endemic bird species (four of which are globally threatened) and five RAMSAR wetland sites. To assess and address the ecological integrity of farmed grasslands we used process-oriented techniques, including nesting success and field metabolic rates (FMR) of birds, and an adaptation of the multi-taxon biodiversity intactness index (BII) using plant, arthropod and bird diversity data which is a comprehensive tool for assessing ecological integrity using multiple taxonomic groups. Current pastoral management practices have a significant detrimental effect on avian abundance, species richness, nest density and fledgling output. Overall energy turnover and BII values confirm the importance of conserved areas for birds in moist highland grassland systems and support the need for further conservation efforts in grassland systems by both private landowners and reserve managers. Findings based on both avian FMRs and the BII in this study were found to be comparable, lending support to the use of FMR as a rapid assessment technique for assessing ecosystem integrity for future studies of this nature. Scenarios of potential biodiversity improvement with changes in fire management regimes are also presented.