Illuminating the dawn of pastoralism: Evaluating the record of European explorers to inform landscape change

The rapid spread of pastoralism across Australian and North American rangelands and the lack of reference sites mean that recurring arguments about the cause and magnitude of landscape change are frustrated by the rarity of records that predate the critical watershed of European settlement. The journals of European explorers from the 1840s are the first written descriptions of inland Australia. Prevailing paradigms based on a synthesis of published material relating to five key themes of environmental change are presented: vegetation structure, fire regimes, waterhole permanence, macropod abundance and medium-sized mammal assemblages. Six hypotheses relating to these themes were tested against the explorer record for inland eastern Australia. Nearly 4500 observations from fourteen journals spanning twelve expeditions between 1844 and 1919 were geo-referenced, using landscape features, distances, bearings and latitudes, combined with topographic maps and high-resolution satellite imagery. Careful evaluation of the record suggests little change in broad vegetation structure or waterhole permanence, running counter to prevailing paradigms. The sparse observations of fire suggest burning was infrequent and mostly restricted to creek-lines and higher-rainfall grasslands in the east and north of the study area and spinifex-dominated vegetation. Kangaroos were apparently uncommon in semi-arid areas where they are abundant today. The journals contain important observations of medium-sized mammals that are now extinct or rare. Our results highlight the importance of accurate geo-referencing compiled from entire journals of multiple explorers and contrasting the record with contemporary observation. Systematic evaluation of the explorer record for a region can provide ecological insights that are difficult to obtain by other means, and can be used to test prevailing assumptions common to arid systems that have been subject to abrupt management upheaval.

► Explorer journals provide rare observations that predate pastoral settlement in inland Australia. ► 4500 Observations from 12 expeditions were geo-referenced and used to test six hypotheses about landscape change. ► Fire was rare and we detected little change in vegetation structure or waterhole permanence. ► Medium-sized mammals have declined but large macropods are more abundant in semi-arid areas. ► Geo-referencing of multiple journals and comparison with contemporary observation enhances the power of ecological insights.