Importance of using many taxa and having adequate controls for monitoring impacts of fire for arthropod conservation

Fire is a key natural and anthropogenic disturbance factor across many ecosystems, and also an important conservation management tool. However, little is known about arthropod responses to fire, particularly in Mediterranean-type ecosystems, including the biodiverse Cape Floristic Region (CFR). We investigate here the relative variety of responses by different arthropod taxa to fire, and ask whether single-taxon or multi-taxa approaches better suit post-fire biomonitoring for conservation management. Sampling involved multiple techniques and was conducted before fire, 1 year after fire, and 3 years after fire, with unburned areas as controls. Before-and-after statistics were used to identify changes in arthropod populations and assemblages as a result of fire, and between treatment and control sites. However, this was against a background of the annual effects having a major influence on the arthropods, irrespective of fire. Abundance was so variable, even in control plots, that we found it an unreliable indicator of the impact of fire. Overall, arthropods were remarkably resilient to fire, with most taxa recovering in species richness and assemblage composition within 3 years of the fire. Although all taxa showed resilience to fire, there was nevertheless little congruence in temporal recovery of the various taxa. Our results highlight the shortcomings of monitoring fire impacts using only a single-taxon without prior testing for complementarity or sensitivity to fire, while emphasizing the importance of sampling a wide range of taxa to represent overall responses of compositional biodiversity. From this, we recommend, at least for the CFR, that a cross-section of taxa, such as butterflies, ants, and scarab beetles, be used for monitoring arthropods in recovery/fire management conservation programmes. We also recommend that such monitoring be considered against the background of large annual variation seen in unburned areas.