Are our urban streams on fire? Using studies on fire to learn about the Urban Stream Syndrome

The Urban Stream Syndrome is a term applied to describe the multiple impacts urbanisation has on aquatic ecosystems. Altered hydrology is considered to be the dominant stressor driving the syndrome. However, the current focus on hydrology may overshadow the importance of other stressors, such as poor water quality and a degraded riparian zone. Separating the effects of altered flow from other stressors is difficult in urban studies, because stressors typically change concomitantly. One novel way to learn is by comparing urban streams to streams affected by fire. Fire causes similar hydrologic symptoms to urbanisation, but can have reduced impacts if the riparian zone remains intact. Importantly, the effects of fire are independent of non-nutrient pollution. Thus fire can provide an insight into the role of hydrologic versus trophic and pollution disturbance in urban streams. Here we use the literature to compare and contrast the effects of urbanisation and fire on streams. We find marked similarities in symptoms between fire affected and urban streams, reinforcing the view that altered flow is the dominant stressor. However, we note some differences which suggest pollution and riparian vegetation exert some influence, even in flow-disturbed systems. We encourage researchers to explore novel ways to advance our understanding of the Urban Stream Syndrome.