Tunnel erosion initiated by feral rabbits in gypsum, semi-arid New South Wales, Australia

Extensive gypsum deposits are widespread across semi-arid southern Australi a in winter rainfall areas. In western New South Wales, gypsum occurs in br oad shallow depressions in very gently undulating plains. A tunnel system h as developed on the margin of the Conoble Gypsum Mine. Feral rabbits dig bu rrows and warrens in the relatively soft gypsiferous soils. Infrequent heav y rain caused localised flooding that drained down rabbit burrows into the abandoned mine via tunnels. Burrows have expanded by collapse and erosion t o form holes up to 3 m diameter and 1.8 m deep. A network of expanded tunne ls up to 0.5 m diameter links these holes. A large tunnel 1.5 x 1.0 m runs some 20 m into the mine. Measurements of collapse holes from 1983 to 1996 s how low (and episodic) rates of expansion (erosion and collapse). The tunne ls are entirely localised to the edges of the mine and are an interesting g eomorphological curiosity illustrating interactions between substrate, clim ate, animals and mining.