Migration, like other ecological functions and processes, depends on connected landscapes. Alaska’s vast forests, river valleys, and mountain ranges provide wildlife with diverse habitats and the ability to move between them as conditions require. In this article, we review why landscape connectivity is important and how to plan for connectivity given climate change. We describe “Bridging the Boreal” as a collaborative, multi-jurisdictional strat-egy to maintain landscape connectivity between protected areas in the Northwest Boreal Region with implementation examples from ongoing planning projects.
Ecologically, Alaska is relatively intact, but the region is changing quickly (Chapin, III et al. 2004, Saura et al. 2017). The climate associated with current biomes is changing and we can no longer expect them to be stable into the future (Murphy et al. 2010). Spruce forests are in the process of converting to hardwood, while glacier retreat is rerouting entire rivers in boreal Canada (Shugar et al. 2017). In addition to climate change, land development fragments and degrades habitats (Forman 2014). Alaska has a vast network of federally managed conservation lands. As development occurs, these protected areas could become isolated islands surrounded by other, perhaps incompatible, land uses. By applying landscape connectivity practices, land managers can support the flow of individuals and genes across the landscape to maintain healthy populations (Belote et al. 2016). In the future, as investment in infrastructure increases, there will be fewer options to provide for landscape connectivity between conservation lands. Once lost, it’s politically and financially difficult to restore and reconnect isolated islands of habitat (Morrison and Boyce 2009).
Alaska’s decision makers have an opportunity to proactively design landscape linkages to ensure that connectivity between protected areas is maintained into the future (Chapin, III et al. 2004). Many management strategies can be used to maintain landscape connectivity, from road-crossing structures to greenways that facilitate the movement of people and other species to compensating landowners to manage their lands for wildlife movement.
Landscape Connectivity Matters
Landscape ecologists have empirically described a robust pattern of land-use conversion and habitat fragmentation that coincides with western economic development and increasing human population size (Forman 2014). In less than thirty years, from 1973 to 2000, developed areas in the contiguous United States increased by 33% and the conversion rate is accelerating (Sleeter et al. 2013). Alaska’s protected areas are currently in connected landscapes, but Alaskans should anticipate an increasing anthro-pogenic footprint as global economies and increasing human populations shape northern regions (Chapin, III et al. 2004, Saura et al. 2017).
Species diversity is higher in landscapes that have historically been connected (Lindborg and Eriksson 2004). A connected network of conservation lands increases the likelihood that animal populations will persist because immigration between sub-populations allows for recolonization and decreases inbreeding and other problems associated with small, isolated populations. Large carnivores, such as brown bears (Ursus arctos), wolves (Canis lupus), and wolverine (Gulo gulo), have been extirpated from portions of their range due to land-use conversion and the resulting habitat loss, degradation, and fragmentation (Ceballos and Ehrlich 2002, Yackulic et al. 2011). Roads and other linear, anthropogenic features can also isolate animal populations. For example, sub-populations of desert bighorn sheep (Ovis canadensis nelsoni) in California became genetically isolated and lost genetic diversity after a highway bisected adjacent habitat areas (Epps et al. 2005). Highways and infrastructure in Anchorage, Alaska correspond with genetic subdivision in moose (Alces alces) that is likely due to reduced gene flow (Wilson et al. 2015). Many animals depend on annual migrations across large regions to survive (Newton et al. 2017). Moreover, connected lands allow for populations to migrate to new areas as climate change alters current habitats and makes novel habitats more suitable for individual species (Schneider 2002). Connectivity is crucial for a natural change in species distributions (as opposed to more intensive active relocations) and thus, increases the resilience and adaptive capacity of the landscape substantially.
To deal with the problem of conservation lands becoming isolated from anthropogenic land-use change, landscape ecologists and restoration ecologists began planning for landscape connectivity. In this paper, we present a strategy to plan for landscape linkages between established protected areas.
Often, efforts to increase connectivity are based on identifying corridors using current habitat use information from a single species. In many cases, corridor design focuses on restoring movement between isolated habitat patches in urbanizing regions. In more-intact regions, designing and implementing corridors for many species independently is not practical. Landscape connectivity can be more generally assessed using measures of ecological intactness (Belote et al. 2016). Another approach is to base planning for connectivity on underlying landscape characteristics that will not change, these are called enduring features (Reid et al. 2017). Enduring features are less dynamic than species composition or land cover that change over the course of years or decades. Protecting the diversity of enduring features, or geodiversity, has also been suggested as a strategy for conserving biodiversity.
Connectivity and Climate Change
Wildlife are already moving in response to climate change and will continue to do so (Parmesan 2006). For example, moose in Alaska are moving further north and west into the Arctic following the expansion of riparian shrub habitat (Tape et al. 2016). Climate change will only increase the need for connected landscapes so that species can move to access needed habitat (Heller and Zavaleta 2009, Galatowitsch et al. 2009). Species are expected to respond individually and not together as a cohesive ecosystem. Therefore, we can expect new ecological communities to form as species redistribute with changing climate conditions (Hobbs et al. 2013, Williams and Jackson 2007).
Landscape planning efforts need to incorporate changing habitat conditions into planning and management approaches (Stein et al. 2014). In other words, corridors based on current habitat conditions may not be well suited for future conditions. Modelling can be used to understand where species may move as the climate changes, but these forecasts are highly uncertain (Brost and Beier 2012). Furthermore, habitat suitability may not represent dispersal and migration pathways well (Keeley et al. 2017). Enduring features provide a climate-resilient solution to designing landscape linkages since as the climate changes, the current habitats and how species will use them over the course of their lifecycles will not be stable (Beever et al. 2015). Topographic features, such as elevation, slope, and aspect, influence ecological processes and therefore, structure habitat conditions (Beier and Brost 2010). The idea is that similar enduring features with similar topography (for example, places that are steep, high-elevation, with sunny slopes) can host similar species and community assemblages. As the climate changes, the composition of species and ecosystem type on a given enduring feature will change, but we expect that similar enduring features will have the capacity to host similar species assemblages. Using these enduring features and providing connectivity for all geodiversity types should allow all species to reshuffle where they occur on the landscape given the new climate conditions. In other words, connecting geodiversity will allow species to adapt and find new habitat. However, it is difficult to determine the long-term ecological results of using enduring features for connectivity in Alaska where landscapes are currently largely intact. We will not have empirical evidence of how well linkages perform until future land-use changes landscape permeability. Maintaining connectivity is a key strategy for maintaining biodiversity in the future (Lawler et al. 2015).
Bridging the Boreal with Proactive Planning: An Opportunity in the North
With the Alaska Native Lands Conservation Act (ANILCA; PL 96-487), Congress established a vast network of protected areas that provides essential habitat for boreal species like caribou (Rangifer tarandus), lynx (Lynx canadensis), and moose. Fifteen National Park System and 12 National Wildlife Refuge System units were identified resulting in 120 million acres of core protected lands managed by the National Park Service and U.S. Fish and Wildlife Service. The lands between protected areas (another 100 million acres) are multijurisdictional including other federal agencies such as the Bureau of Land Management (BLM), Department of Defense, and U.S. Forest Service with mandates for multiple use; Alaska Native Corporations; and the state of Alaska.
There is an opportunity to proactively maintain landscape connectivity between the ANILCA conservation system units before development occurs to avoid the high economic costs of retroactively restoring connectivity once it is lost. The idea is not to add more lands to Alaska’s vast protected areas network, but to find creative solutions to maintain connectivity between them. In this way, we are leveraging the federal conservation estate to allow for development and other uses while keeping the lifestyle enjoyed by Alaskans. Linking these large protected areas is a cost-effective strategy because these investments maintain animal populations and therefore do not carry the large costs associated with avoiding extinction after a species has declined (Drechsler et al. 2011). Currently, the land between the ANILCA protected lands is permeable, so animal movement is not constrained (Saura et al. 2017). It may seem strange to overlay linkages on an intact landscape, but the key is to consider the future value of these planned linkages when land-use change is more of an issue. Proactive conservation, or conservation action that plans for future changes, rather than reacts to historic or current impacts, is the opportunity of the north (Schmiegelow et al. 2014). Anticipating future changes and getting ahead of them is more cost effective and arguably more ecologically effective to maintain natural systems and processes. Landscape-scale connectivity clearly requires deliberate collaboration in land-use and natural resource planning as no one landowner or agency has the jurisdiction or responsibility for lands outside its own boundaries.
This scale of collaborative conservation often requires a bridging organization to provide a neutral platform, build trust among agencies and landowners, and orchestrate key alignments in planning and decision making. Landscape Conservation Cooperatives (LCCs) can fill that role. LCCs are “an international conservation network of organizational entities that facilitate adaptive co-governance by offering a much needed structure and process for analytic deliberation; refinement of perspective based on exposure to new information and social learning; coordination of information generation, conservation planning, and delivery; and leveraging of resources to improve conservation at a landscape scales” (Jacobson and Robertson 2012: 335). Each organization, agency, and landowner has different mandates, responsibilities, and management authorities. The Northwest Boreal LCC is comprised of over 30 federal and state/provincial agencies, non-governmental organizations, Tribes and First Nations, and research institutions in the boreal zones of Alaska and Northwest Canada. Maintaining landscape connectivity has emerged as one of three central goals for the partnership and it is working on aligning strategies among these organizations to achieve measurable outcomes. These landscape linkages can also provide for human movement and support the subsistence lifestyle that is highlighted in ANILCA and valued by Alaskans.
Implementing Bridging the Boreal
The BLM is considering management decisions in their planning alternatives that would leverage the acreage of these conservation lands to increase the conservation value of the entire planning area via connectivity while providing for other landscape uses and values. Because the Northwest Boreal LCC stakeholders determined that a strategy of maintaining connectivity between protected areas is important, we were able to offer this problem framing and supporting analysis to regional planning efforts. The BLM’s Resource Management Plan (RMP) process provides an example of where the Bridging the Boreal strategy is being considered in a planning process for implementation.
The BLM is currently engaged in two planning processes in Alaska. The BLM’s Central Yukon (CY) Planning Region is 59 million acres with 13.1 million acres of BLM-managed public lands and the Bering Sea Western Interior (BSWI) planning area is over 62 million acres with 13.2 million acres of BLM-managed public lands. Both planning areas are multijurisdictional landscapes with multiple values and uses. Approximately 74 million acres of lands in the conservation estate occur within or directly adjacent to the planning area. This includes Gates of the Arctic and Denali national parks and preserves managed by the National Park Service and eight national wildlife refuges managed by the U.S. Fish and Wildlife Service. In addition, Noatak National Preserve and Kobuk Valley National Park are contiguous and therefore, provide another 8 million acres that would benefit from landscape connectivity in the planning areas. We modelled landscape linkages between protected areas based on a least-cost path between enduring features (Brost and Beier 2012, Magness et al. 2018; Figure 1). The least-cost pathway is the pathway with the lowest resistance and shortest distance between geodiversity termini (Magness et al. 2018). There are stunning opportunities to connect protected areas. For example, managing as little as 87,025 acres would ensure connectivity for approximately 50 million acres of conservation lands; essentially maintaining connectivity for the majority of the Brooks Range. In the CY RMP, linkages constituting as little as one percent of the study area could connect over 64 million acres of existing conservation lands.
Planning for landscape connectivity at this scale requires extensive collaboration as Northwest Boreal LCC partners put in place the management structures, decisions, and policies that are necessary to maintain connectivity in this region. While future habitat and climate are difficult to project, connecting large protected areas through linkages based on geodiversity can allow species to adapt to a changing landscape. It is a clear and quantifiable case study for the effectiveness of LCCs, or bridging organizations in general, in aligning management goals and objectives for multiple agencies, organizations, and landowners at a very large scale.
The authors wish to thank the Northwest Boreal LCC steering committee partners from Alaska and Canada. BLM staff, in particular Tim Hammond and Jorjena Barringer, were helpful in writing this article.
The findings and conclusions in this article are those of the author(s) and do not necessarily represent the views of the U.S. Fish and Wildlife Service.
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