Wednesday, January 27, 2010

To intervene or not to intervene: this is a real question

Should land managers actively manipulate the structure and function of ecosystems within protected areas? Is intervention appropriate to protect or maintain native biodiversity and natural processes in areas such as national parks and wilderness areas? These are the questions that stem from a new paper by Richard Hobbs and others in Frontiers in Ecology and the Environment. US national parks and wilderness areas have legislative mandates to maintain ‘naturalness’, but what does this mean in the context of dynamic ecosystems with current and future changes including invasions by nonnative organisms and climate change?

Hobbs and his colleagues challenge concepts of naturalness and propose several ‘guiding principles’ for stewards of national parks and wilderness. They suggest that more useful concepts for managing protected areas relate to ecological integrity and resilience. Concepts of ecological integrity have been adopted by Parks Canada and relate to maintaining ecosystem components. Resilience concepts focus on the ability of a system to “absorb change and persist” without undergoing a “fundamental loss of character”. While maintaining ecological integrity in the face of global changes may - by definition - require protection of species, maintaining ecological resilience tends to focus more attention on ecosystem function “over preserving specific species in situ”.

Rather than protecting an area to maintain naturalness, focusing on ecological integrity and resilience acknowledges that a diversity of approaches - from non-intervention to actively managing systems - may be required. The flexibility in this view, demands that conservation planning span gradients of land uses across landscapes. Management objectives and success need to be re-evaluated in an adaptive and experimental framework, which requires careful and robust monitoring.

At The Wilderness Society and specifically here in Montana, these very questions are being wrestled with in terms of forest restoration, fire management, and climate change. Current forest conditions have been shaped by historic logging practices and fire suppression leading to altered structure and function – including increasing the severity of fires. Through active management, including removing small diameter trees and lighting prescribed fires, managers hope to restore forests and fire intensities to conditions more closely resembling those that historically occurred. Much of the research on restoration was conducted in dry forests in the American Southwest where low-severity fires occurred across large areas. However, in the Northern Rockies, many forests were shaped by a ‘mixed severity’ fire regime, where fires crept along the forest floor in some areas and torched trees in others. In many cases, these forests have not been fundamentally altered and need only the return of fire to restore their resilience. In other cases, forests are recovering from past logging practices and may benefit from thinning to restore a fire-resilient structure.

To return to the paper at hand: what is the appropriate level of intervention to maintain ecological integrity and resilience given past forest management and future climate change? If the current forest lacks integrity (novel stand structure) and resilience under a predicted climate of warmer, drier conditions, what is the appropriate level of management? While The Wilderness Society continues to work with diverse partners to answer these questions, one thing is clear: whatever actions take place, they need to be conducted with humility in an experimental framework that includes sufficient ecological monitoring. For the ‘experiment’ to be most helpful, we should maintain adequate hands-off “controls” along with the “treatments” to allow us to gauge the effects of intervention.

Richard J Hobbs, David N Cole, Laurie Yung, Erika S Zavaleta, Gregory H Aplet, F Stuart Chapin III, Peter B Landres, David J Parsons, Nathan L Stephenson, Peter S White, David M Graber, Eric S Higgs, Constance I Millar, John M Randall, Kathy A Tonnessen, Stephen Woodley (2009) Guiding concepts for park and wilderness stewardship in an era of global environmental change. Frontiers in Ecology and the Environment e-View.
doi: 10.1890/090089