Plagues and Players: an Environmental and Scientific History of Australia's Southern Locusts

Abstract

This thesis traces the changing course of locust and grasshopper outbreaks in southern Australia and relates them to environmental changes. It also examines the creation and use of scientific knowledge about locusts over more than a century of research. Together, these historical investigations show how the insects’ responses to environmental change influenced the course of ecological and agricultural science. Digitised newspaper records of locust occurrence allow a more complete reconstruction of historic plagues and a new interpretation of the species involved and the environmental correlates of their changing incidence. They also provide a different view of the scientific players who investigated locusts in Australia. These sources are complemented by the writings of many entomologists about locust outbreaks and ecologies from the 1840s to the 1970s. The popular and scientific sources reveal the complexity of ecological ideas, technologies and institutional settings, framed by the common material context of environmental change. This is a history of entomological, ecological and public agricultural science as well as an analysis of the environments in which the outbreaks developed. European settlers encountered grasshoppers and locusts soon after establishing pastoral and agricultural land use. Swarming populations developed patterns of occurrence that were observed by farmers and naturalists, and there is evidence that their incidence increased during the nineteenth century. Two species, Austroicetes cruciata and Chortoicetes terminifera, developed frequent outbreak populations on the southern grasslands, making them significant agricultural pests, but they responded differently to changes of climate, landscape and land use. The former swarmed almost annually soon after livestock altered grassland ecosystems within its range, but it declined during the twentieth century. The latter first swarmed across the southern grasslands in the 1870s, but has since maintained irregular outbreak populations through migratory exchanges. They are taxonomically related native locusts with a similar appearance but distinct ecologies. Untangling their identities was historically marked by scientific confusion. However, the two species can sometimes be distinguished in newspaper reports by diagnostic morphological features, and can often be separated by differences in their seasonal occurrence, abundance, phenology and behaviour. This thesis argues that the fundamental changes to grassy ecosystems resulting from the rapid expansion of the pastoral industry favoured the development of swarming populations of both Australian species. Evidence comes from early Aboriginal comments, thousands of newspaper and official reports, climatic sequences and the nature of landscape changes, as well as the subsequent contraction in outbreak extent and frequency when land use and land cover stabilised in the second half of the twentieth century. The writings of many investigators reveal overlapping trends in ecological and technological investigations, and place each player within their scientific era. These are examined in the context of international developments and the broader public discourse about locusts and the importance and relevance of science. In this long relationship of feedbacks, the materiality of the insects allowed scientists to discern their ecologies. Science directed government policy on how to respond and governments sponsored more science in managing the politics of successive agricultural crises. Show more