Biodiversity values of small headwater streams in contrasting land uses in the Auckland region

Abstract

The biodiversity values of 12 small headwater streams (catchments mostly <30 ha) were evaluated. Densities of aquatic macroinvertebrates were the same or higher in three headwater habitats (flowing water, isolated pools and wet mud) as in adjacent perennial streams. Alpha (per sample) richness of all aquatic macroinvertebrates and of Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa were as high in headwater flowing habitats and isolated pools as in perennial streams. Gamma (landscape-level) and beta (taxa turnover) richness appeared to be similar among isolated pools, mud habitats and perennial streams, but higher in headwater flowing habitats. Community composition was very similar among headwater flowing, isolated pool and perennial habitats. Some taxa in headwater habitats were headwater specialists, but none was identified as endemic to headwaters. Thus, macroinvertebrate evidence indicates that headwater streams should be given similar protection status to perennial reaches. Headwaters in pasture catchments had lower EPT richness than native forest headwaters. Riparian native woody vegetation appeared effective in maintaining EPT richness and community composition similar to the native forest condition.