آب و هواهای نوین: گذارهای تغییر اقلیم در آنسوی مرزهای سیستم مدیریت دانش جنگل های بریتیش کلمبیا Novel climates: Trajectories of climate change beyond the boundaries of British Columbia’s forest management knowledge system

1. Introduction 1.1. Emerging challenges to the “local is best” ethic in forest management The necessity to adopt non-local practices in response to climate change is a major new dimension in forest management. Historically, forest managers have developed specialized management regimes for their local ecosystems (Puettmann et al., 2009). The complex interactions of productivity, competition, stress, and disturbance are often idiosyncratic to individual places, leading forest managers towards a “local is best” ethic with respect to silvicultural systems, stand-tending practices, and species and provenance selection (Seymour et al., 2002; Ying and Yanchuk, 2006). These local idiosyncrasies are strongly driven by climate (Pojar et al., 1987), but the climates of the 20th century were sufficiently stable for forest managers to understand climate as a stationary quality of place. The non-stationary climates of the 21st century are a fundamental challenge to this place-based understanding of climate and ecosystem function (Millar et al., 2007). Forest managers have entered an era in which the “local is best” ethic is no longer reliable, and are looking to other locations for species, provenances, and management regimes that may be better suited to the anticipated future climates of their jurisdictions (Potter and Hargrove, 2012; Williams and Dumroese, 2013). This use of non-local climate analogs is an emerging cornerstone of 21st century forestry management, and underlies assisted migration through remote provenance selection (Aitken and Whitlock, 2013), assisted range expansion (Rehfeldt and Jaquish, 2010), and in situ tree species conservation (Hamann and Aitken, 2013). Moreover, climate analogs are essential to maintaining the relevance of accumulated practitioner knowledge in a changing climate. As climate zones shift across the landscape, so must the ecological knowledge with which they are associated. Where analogs for anticipated future climates are available within local jurisdictional boundaries—e.g., from downhill locations—forest managers are able to draw on their familiar local knowledge systems. However, the projected magnitude of climate change over forest management timescales is compelling forest managers to look for climate analogs in the relatively unfamiliar climates of other jurisdictions (Potter and Hargrove, 2012). While some locally unfamiliar climates may have historical analogs in nearby jurisdictions, previous research suggests the potential for novel climates that have no historical analogs at continental (Rehfeldt et al., 2012; Mahony et al., 2017) and even global (Williams et al., 2007; García-López and Allué, 2013) scales. These truly novel climates represent conditions for which little knowledge is available from observational experience (Williams and Jackson, 2007), and therefore for which ecological predictions are unreliable (Fitzpatrick and Hargrove, 2009). Forest management in a changing climate will inevitably involve some extrapolation of accumulated knowledge into novel, unfamiliar conditions. Nevertheless, the risk of management failures will likely increase with the degree of extrapolation (Peterson et al., 2011, pp. 126–8). Measurement of novelty in projections of climate change indicates the degree of confidence that can be placed in climate analogs for forest management guidance.