Shifting Baseline Syndrome as a Barrier to Ecological Restoration in the American Southwest

More than a century of human encroachment on an industrial scale has eroded the resilience of forests across the southwestern United States, resulting in ecosystems that depart profoundly from historical conditions (e.g., Murphy et al. 2007). Regional ponderosa pine (Pinus ponderosa) forests, since at least the mid-20th century, now experience high-severity crown fires that are inimical to both ecological health and the socioeconomic security of local communities (Table 1). The situation is exacerbated by climate change, which has increased the intensity of and area burned by fires (Westerling et al. 2006). This has galvanized an expansion of ecological restoration treatments—mechanical thinning and prescribed burning aimed at reducing forest density and ground litter. These measures significantly decrease the intensity of wildfires and help re-create the structure, composition, and functions of a healthy forest system (Fulé 2008). However, despite demonstrated successes and cogent scientific reasoning, a barrier to effective landscape-level implementation exists (Hjerpe et al. 2009).

Table 1.

Shifted ecological conditions between the mid-1800s and now in ponderosa pine forests in the American Southwest. Historical conditions also reflect typical restoration targets; current conditions are before restoration treatment.

We believe that many of the factors contributing to this barrier are consistent with shifting baseline syndrome (SBS), where a discrepancy between social perceptions and ecological realities contributes to ineffective management as human communities fail to recognize change, considering recent ecological conditions to be normal and thus perceiving them as baseline (Papworth et al. 2009). Despite broadening application of the SBS concept, the implications for restoration are scarcely noted in the existing literature; when SBS is mentioned in the context of restoration, the references we have found explore the association accurately but fleetingly (e.g., Pauly 1995). The analysis presented in this paper is, to the best of our awareness, the first study to examine the likely occurrence of SBS in a restoration scenario.

A common obstacle in diagnosing SBS is the lack of empirical data on altered ecological conditions (Papworth et al. 2009). In this case, the ecological history of southwestern ponderosa pine forests is well understood, and abundant research indicates that the ponderosa pine ecosystems of today are vastly different from those of earlier generations. Additionally, a key tenet of SBS is that it is a social phenomenon (Papworth et al. 2009), and the weight of current scientific and policy-relevant research suggests that existing discrepancies between social perceptions and ecological conditions are due to a failure of the former to keep pace with changes in the latter (e.g., Ostergren et al. 2008).

We believe “generational amnesia” is the form of SBS that describes the socioecological dynamics of forest restoration in southwestern ponderosa pine forests. Generational amnesia refers to a loss of or change in ecological knowledge when earlier generations fail to pass on their experiences to later generations, thus altering perceptions of ecological conditions and interpretations of past anthropogenic modifications (Pauly 1995, Papworth et al. 2009). As a result, the baseline used to interpret current ecological conditions is closer to a single human lifetime than to longer, multigenerational time frames. From an extensive survey-based study of social attitudes toward forest restoration in north-central Arizona, Ostergren and others (2008) found that rural residents—those living closer to forests—were less likely to support restoration treatments such as tree removal. The authors infer that this is because rural residents “are accustomed to relatively dense forest stands and thus may have difficulty perceiving a heavily thinned forest as a ‘healthy’ forest” (Ostergren et al. 2008, 57). The contemporary misunderstandings of the meaning and values of forest restoration are, in many ways, to be expected (Hjerpe et al. 2009). The aim of restoring regional forests to resemble an ecosystem that hasn’t existed for decades, if not hundreds of years, is to make a difficult perceptual demand on residents who don’t benefit from any continuity of local ecological knowledge.

When the forest ecosystem more closely resembled the target conditions of contemporary restoration efforts...