Research Summaries

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Palmer, M.A., et al.
2006. “Standards for ecologically successful river restoration.” 2005. Journal of Applied Ecology. 42:208-217.

Increasingly, river managers are turning from hard engineering solutions to ecologically based restoration activities in order to improve degraded waterways. River restoration projects aim to maintain or increase ecosystem goods and services while protecting downstream and coastal ecosystems. There is growing interest in applying river restoration techniques to solve environmental problems, yet little agreement exists on what constitutes a successful river restoration effort. We propose five criteria for measuring success, with emphasis on an ecological perspective. First, the design of an ecological river restoration project should be based on a specified guiding image of a more dynamic, healthy river that could exist at the site. Secondly, the river’s ecological condition must be measurably improved. Thirdly, the river system must be more self-sustaining and resilient to external perturbations so that only minimal follow-up maintenance is needed. Fourthly, during the construction phase, no lasting harm should be inflicted on the ecosystem. Fifthly, both pre- and post-assessment must be completed and data made publicly available. Determining if these five criteria have been met for a particular project requires development of an assessment protocol. We suggest standards of evaluation for each of the five criteria and provide examples of suitable indicators.

Billions of dollars are currently spent restoring streams and rivers, yet to date there are no agreed upon standards for what constitutes ecologically beneficial stream and river restoration. We propose five criteria that must be met for a river restoration project to be considered ecologically successful. It is critical that the broad restoration community, including funding agencies, practitioners and citizen restoration groups, adopt criteria for defining and assessing ecological success in restoration. Standards are needed because progress in the science and practice of river restoration has been hampered by the lack of agreed upon criteria for judging ecological success. Without well-accepted criteria that are ultimately supported by funding and implementing agencies, there is little incentive for practitioners to assess and report restoration outcomes. Improving methods and weighing the ecological benefits of various restoration approaches require organized national-level reporting systems.

Hughes, F. M. R., A. Colston, and J. O Mountford.
2006. “Restoring ecosystems: the challenge of accommodating variability and designing restoration trajectories.” Ecology and Society 10:12 (on line).

Flood disturbance processes play a key role in the functioning of riparian ecosystems and in the maintenance of biodiversity along river corridors. As a result, riparian ecosystems can be described as mobile habitat mosaics characterized by variability and unpredictability. Any river restoration initiative should aim to mimic these attributes. This paper suggests that there needs to be an increased institutional capacity to accept some levels of both variability and unpredictability in the ecological outcomes of river restoration projects.

Restoration projects have frequently used some form ofhistorical or contemporary reference system to define objectives and to help in the evaluation process. Using these reference systems can give a false sense of the predictability of ecological outcomes. We suggest that reference systems need to be used with caution for six reasons: (1) there are often no appropriate reference systems to use, (2) many catchment parameters have changed since the times of chosen historic reference systems, (3) climate change has been continuous throughout the Holocene, (4) projected climate change is of uncertain magnitude, (5) alien species cannot be avoided, and (6) landscape context changes through time.

As well as defining short-term objectives, we suggest that river restoration projects should also formulate longer-term (decadal) restoration trajectories that are less predictable but more representative of real system attributes. Restoration trajectories could be defined using a range of ecological outcomes to accommodate inter-annual variability. The challenges of defining what levels of variability are important for restoring European floodplain forests are used to demonstrate the difficulties of broadening approaches and creating trajectories. In particular, the changing significance of variability at different spatial and temporal scales is discussed. An account is given of a restoration project at Wicken Fen in the United Kingdom in which nondeterministic approaches to goal setting have been initiated.