Abstract
Mounds of the harvester termite Coarctotermes clepsydra (Sjöstedt) (Isoptera: Termitidae, Nasutitermitinae) are a typical feature of savanna woodlands in Madagascar. With densities of up to 300 termitaria ha−1, this species provides key ecosystem services and is an important food source for wildlife. Following large-scale aerial blanket and barrier treatments with the insecticide fipronil to control an outbreak of migratory locust in the late 1990s, evidence emerged that C. clepsydra and related food webs were adversely affected. However, neither the scale nor the duration of the effects were known. The present ex post study investigated the recovery of C. clepsydra populations subjected to multiple barrier treatments against hopper bands in 1998 and 1999 at estimated cumulative dose rates of 1.7–3.4 g fipronil ha−1. At the time of the survey in 2007, both the density of occupied termitaria (30.2 versus 106.8 mounds ha−1) and mound occupancy (24.3% versus 70.0%) were significantly lower in repeatedly sprayed so-called hotspots than in unsprayed areas. The overall adverse effect (mortality in sprayed areas corrected for mortality in unsprayed areas) was E = 64.4%. The main outcome of this study is a strikingly low resilience of C. clepsydra populations, which did not recover in hotspots within eight years, with likely repercussions on food webs. This study shows that the environmental benefits of barrier treatments are forfeited if the same areas are treated repeatedly during the same campaign. Recommendations are given for the mitigation of these risks.
Highlights
Madagascar is a global biodiversity hotspot and has a high level of endemism in most taxonomic groups
Original shape files of the Geographical Information System were lost after the campaign, but hard copies of the monthly spray maps and copies of the original spray protocols for 33 barrier treatments were retrieved by the author at the Delegation of the European Union (EU) in Madagascar in 2005
≤3 inhabited termitaria ha−1, 4 out of 9 barrier treatment sites were virtually void of live harvester termite colonies though remnants of termitaria were frequently found
Summary
Madagascar is a global biodiversity hotspot and has a high level of endemism in most taxonomic groups. The grasslands and savanna woodlands in the semi-arid southwestern part of the island are home to just one mound-building species: the grass-feeding harvester termite Coarctotermes clepsydra (Sjöstedt) (Isoptera: Termitidae, Nasutitermitinae), whose conspicuous conical-shaped termitaria can reach densities of 100–300 mounds ha−1 [2,3]. Coarctotermes is one of three grass-feeding genera in the Nasutitermitinae and the only one in Madagascar [4]. Given their high biomass and exposed lifestyle during nocturnal grass-harvesting bouts, harvester termites are an important food source for both invertebrates [5] and vertebrates [6].
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