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Use of land facets to design linkages for climate change



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Ecological Applications 22 1 2012 pp 87 103 2012 by the Ecological Society of America Use of land facets to design linkages for climate change BRIAN M BROST1 AND PAUL BEIER School of Forestry and Merriam Powell Center for Environmental Research Northern Arizona University Flagstaff Arizona 86011 5018 USA Abstract Least cost modeling for focal species is the most widely used method for designing conservation corridors and linkages However these linkages have been based on current species distributions and land cover both of which will change with large scale climate change One method to develop corridors that facilitate species shifting distributions is to incorporate climate models into their design But this approach is enormously complex and prone to error propagation It also produces outputs at a grain size km2 coarser than the grain at which conservation decisions are made One way to avoid these problems is to design linkages for the continuity and interspersion of land facets or recurring landscape units of relatively uniform topography and soils This coarse lter approach aims to conserve the arenas of biological activity rather than the temporary occupants of those arenas In this paper we demonstrate how land facets can be de ned in a rule based and adaptable way and how they can be used for linkage design in the face of climate change We used fuzzy c means cluster analysis to de ne land facets with respect to four topographic variables elevation slope angle solar insolation and topographic position and least cost analysis to design linkages that include one corridor per land facet To demonstrate the exibility of our procedures we designed linkages using land facets in three topographically diverse landscapes in Arizona USA Our procedures can use other variables including soil variables to de ne land facets We advocate using land facets to complement rather than replace existing focal species approaches to linkage design This approach can be used even in regions lacking land cover maps and is not affected by the bias and patchiness common in species occurrence data Key words adaptation climate change coarse lter approach connectivity conservation planning corridor ecological process land facets topography INTRODUCTION wildland blocks e g Walker and Craighead 1997 Singleton et al 2002 Beier et al 2006 2007 The objective of least cost modeling is to identify the swath of land that minimizes the ecological cost of movement through a landscape for a species Adriaensen et al 2003 Beier et al 2008 Each swath of land represents a corridor and corridors for multiple focal species are combined into a linkage design Like most other conservation plans these designs have been based on current species distributions and land cover However as climate changes it is likely that some species currently occupying a given area may no longer do so while other species may be new arrivals One approach to develop corridors that accommodate species shifting distributions is to incorporate climate models into their design We are aware of two efforts that use this approach both for the Cape Proteaceae of South Africa Williams et al 2005 identi ed dispersal chains for individual species through 2050 each chain consisting of temporally and spatially contiguous habitat intended to allow a species to shift its range in response to climate change Phillips et al 2008 used network ow models to optimize the identi cation of dispersal chains Both efforts relied on several linked components emissions scenarios general circulation models regional circulation models and models of climate envelopes each of which unfortunately con Shifts in species geographical distributions have been the most important mechanism through which plants and animals coped with previous large scale climate changes Graham and Grimm 1990 Huntley 2005 and have already begun in response to the current episode of climate change Grabherr et al 1994 Parmesan 1996 Thomas and Lennon 1999 Though some species may be capable of adapting to future climatic conditions Millar et al 2007 Skelly et al 2007 it is likely that many species will only persist if they are capable of colonizing newly suitable habitat Williams et al 2005 However habitat fragmentation can interfere with the ability of species to track shifting climatic conditions Consequently many advocate the need for conservation corridors and linkages between existing natural areas as a means to support movements necessary for species range shifts summarized by Mawdsley et al 2009 Least cost modeling for focal species is the most widely used method for designing corridors to connect Manuscript received 8 February 2011 revised 8 June 2011 accepted 20 June 2011 nal version received 27 July 2011 Corresponding Editor T G O Brien 1 Present address Great Lakes Indian Fish and Wildlife Commission P O Box 9 Odanah Wisconsin 54861 USA E mail bmbrost gmail com 87 88 Ecological Applications Vol 22 No 1 BRIAN M BROST AND PAUL BEIER tains some uncertainty For example emissions scenarios differ sixfold in predicted annual CO2 emissions by the year 2100 and climate projections differ vastly among the seven commonly used general circulation models Intergovernmental Panel on Climate Change 2001 Raper and Giorgi 2005 Divergence increases further among regional circulation models which project outputs from a general circulation model onto a scale more useful for modeling habitat change Climate envelope models require additional assumptions and necessarily exclude some important components e g species interactions and altered disturbance regimes that in uence species distributions Williams et al 2005 Furthermore species climate associations determined from climate envelope modeling performed no better than chance for predicting the current distributions of 68 of 100 European bird species Beale et al 2008 Because these models are linked errors propagate from each model to the next Additionally errors and uncertainties are compounded as models project further into the future Finally these models produce mapped corridors with a grain size km2 that is coarser than the scale at which conservation corridors are implemented To avoid these problems Hunter et al 1988 Anderson and Ferree 2010 and Beier and Brost 2010 suggested a coarse lter strategy to conserve biodiversity in the face of climate change Conventional coarse lter conservation strategies target biotic communities as the unit of conservation Noss 1987 but


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