Odonata in the agricultural landscapes of the Maltese Islands : conservation and use as bioindicators of multiscale environmental variation

Abstract

Conservation of biodiversity has become an important matter in Mediterranean landscapes, such as in rural regions where landscapes have been modified for millennia, and where management practices have had a significant influence on native flora and fauna. Nevertheless, relatively little activity has targeted the conservation of insect species and their close relatives, which by far make up much of the planet's biodiversity. Given this premise, this study investigates the conservation status of Odonata species in the rural landscapes of the Maltese Islands through systematic observations of adult males near natural, semi-natural and man-made water bodies. These observations formed the basis of a study aimed at investigating the bioindicator properties of Maltese Odonata. Moreover, given the dominant role played by humans in the highly modified rural landscapes of the Maltese Islands, locals' knowledge of insect species, their diversity and conservation was investigated through a 'stakeholders' survey'. Standardised survey methodology for adult Odonata involved periodical counts over selective natural, semi-natural and man-made water bodies (valley systems, semi-natural ponds, constructed water reservoirs) within rural landscapes of the Maltese Islands. Given the pervasive role played by vegetation in the dragonfly lifecycle, this study investigates whether physiognomic characteristics and floristic composition of vegetation influence Odonata distributions. Moreover, the influence of the spatial patterns at the landscape scale on Odonata populations at breeding sites was also investigated. Results from this study suggest that Odonata populations are influenced by habitat characteristics at multiple scales, ranging from the physical properties and characteristic vegetation of the water body to landscape composition and diversity. Furthermore, Odonata abundance were found to be negatively correlated to that of invasive Great Reed (Arundo donax) stands presence within the water body. These observations have several management implications for the conservation of Odonata. The stakeholders' survey identified farmers' perceptions of insects and their abundance within agricultural landscapes. Persistent insect pest problems and the loss of 'beneficial' species, identified by farmers as the dominant trends in insect species dynamics within rural landscapes, were recognized to be a consequence of contemporary agriculutural management actions. Moreover, the likely impact of current practices in agriculture on Odonata conservation is documented within this study. Finally, the potential for sustainable agricultural management programmes through an iterative ecosystem-based management approach is discussed with reference to findings emerging from the current study.