An Ecological Resilience Index to Improve Conservation Action for Stream Fish Habitat

Stream fishes are increasingly threatened by consequences of climate change that will alter stream habitats. Conservation of stream ecosystems will be more effective if management actions retain or restore essential structures and functions that promote ecosystem resilience to disturbance. This study developed a method for assessing the resilience of stream fish habitat in Michigan, USA. Three sub-indices comprising different components of resilience were derived using information on natural landscape features, human impacts and habitat heterogeneity. These sub-indices were combined into a single overall index to broadly characterize resilience. Mapping sub-indices show that stream resilience based on natural features varies across Michigan, whereas resilience reduced by human impacts decreases from north to south, corresponding to patterns in human population density and land use. Higher stream resilience occurs in the Upper and Northern Lower Peninsulas of Michigan which have more natural features and fewer human impacts, although some resilient streams also occur in the Southern Lower Peninsula, suggesting that there are opportunities in every part of the state for protecting resilient streams. Resilience index scores combined with modelled distributions of a fish species of conservation importance show locations where specific conservation action would be most effective in protecting or improving habitat for this species. The assessment of Michigan stream resilience provides new information for supporting conservation strategies and action in relation to expected changes caused by climate change. It also offers an approach that can be applied in other regions.