In this post Angela Strecker discusses a Review paper she recently handled by Robin Hale and colleagues ‘Identifying, preventing and mitigating ecological traps to improve the management of urban aquatic ecosystems’.

Urbanization greatly alters ecosystems, yet management attempts to mitigate these effects can be confounded by incomplete information on the potential outcomes of management activities. In particular, the responses of organisms to management efforts to provide or restore quality structural and functional habitats are notoriously variable – in other words, organisms do not always respond in a predictable way. Ecological traps may compromise species ability to survive and reproduce in these altered habitats.

Great Copper butterfly Lycaena xanthoides. Creative Commons license, Jeffrey Oliver.
Great Copper butterfly Lycaena xanthoides. Creative Commons license, Jeffrey Oliver.

Ecological traps occur when organisms select low quality habitats, reducing their overall fitness. These traps are associated with human-induced rapid environmental change – the environment changes so quickly that what was once a cue of good habitat is no longer a reliable indicator. An example of these ecological traps was illustrated with the Great Copper butterfly in restored wetlands in western Oregon, USA. The rare butterflies oviposited on their only larval host plant, which was planted in a seasonally flooded restored wetland. The flooding greatly reduced larval survival, resulting in an ecological trap. Their larval host plant became a cue of poor habitat within the context of the restored wetland – it was no longer a useful cue in the wetlands that did not flood because other invasive grasses masked it.

In their recent paper in the Journal of Applied Ecology, Hale et al. (2015) propose a framework to evaluate how management activities could cause ecological traps in urban aquatic ecosystems. The authors illustrate how the framework can be used with stormwater wetlands in Melbourne, Australia, focusing on mitigating ecological traps for frogs. Their case study demonstrates that management actions in wetland habitats could entail changes in: 1) water and sediment quality; 2) hydrology; 3) wetland form or area; 4) vegetation; and 5) invasive species. Each of these factors could alter the fitness of the focal organisms.

Sweetwater Marsh at San Diego Bay National Wildlife Refuge. Creative Commons license, Lisa Cox (US Fish and Wildlife Service).
Sweetwater Marsh at San Diego Bay National Wildlife Refuge. Creative Commons license, Lisa Cox (US Fish and Wildlife Service).

The decision framework uses simple classifications of likelihood of change and consequences for the species to estimate the risk of an ecological trap (risk = likelihood x consequences). For instance, the probability of invasive species, such as mosquitofish, becoming established is likely, and the consequences of their introduction would be quite severe for frogs, generating a very high risk of an ecological trap. Importantly, Hale et al. also link specific management activities to traps and discuss how traps could be prevented or mitigated by managers. The novelty of this research is that most studies thus far have focused on the ecological and evolutionary outcomes of these traps – Hale et al. have extended the theory to apply to specific management activities. This blend of theory and application provides managers with practical guidelines and a decision framework to evaluate the risk of ecological traps in urban aquatic ecosystems.

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