Freedom to Roam – Wildlife Connectivity in Action from Data to Implementation and Assessment I

Symposium
ROOM: Room 215 – San Miguel
SESSION NUMBER: 68
 
As disturbance, urbanization, and land conversion increase globally, the need to maintain landscape connectivity that supports wildlife movements and population viability and sustains biotic diversity is critical. While climate change is not specifically addressed in this symposium, connectivity is often cited as a way to provide resilience to populations in the face of both land use and climate change. This symposium will provide wildlife professionals with information on techniques to model and assess connectivity and will cover an overview of best practices for ensuring that wildlife connectivity is maintained. Case studies of implemented connectivity projects around the country will be presented. Panel discussions after each half will allow audience members to ask questions of the experts as well.

1:10PM Foundational Principles of Managing Landscapes for Wildlife Movement and Habitat Connectivity: The State of the Practice of Modeling Wildlife Connectivity
  Sam Cushman
Connectivity has emerged as an issue of immense importance in conservation and management. There has been a surge of recent research in developing and evaluating a wide range of methods of estimating landscape resistance and predicting patterns of connectivity across resistant landscapes. This talk will review several major issues and approaches for integrating rigorous data and analysis into estimations of landscape resistance and predictions of landscape connectivity. Several methods to produce robust resistance layers include landscape genetics and path-selection modeling. Application of scale-dependent synoptic connectivity modeling approaches, such as resistant kernels and factorial least cost paths, provide a powerful basis of producing useful and defensible connectivity predictions.
1:30PM Inference About Landscape Connectivity Using Spatial Occupancy Models
  Chris Sutherland
Occupancy studies that track the occurrence and or abundance of a species at a collection of locations provide rich spatiotemporal point process data that have typically been employed to understand colonization-extinction dynamics and (meta)population persistence. Until recently, dispersal has been implicitly assumed in occupancy models despite being the fundamental driver of spatiotemporal dynamics in spatially structured populations. Spatial occupancy models explicitly incorporates a dispersal-based connectivity component and offers a formal link between patch occupancy dynamics and landscape connectivity. Here I will demonstrate the value of integrating well-established ideas from metapopulation theory with modern repeat-measure occupancy models to make formal inference about dispersal and the emergent property landscape connectivity.
1:50PM Density-Weighted Connectivity for Landscape Management and Connectivity Conservation
  Angela K. Fuller; Jeffrey A. Royle; Dana J. Morin; Yexiang Xue; Bistra Dilkina; Amrita Gupta; Chris Sutherland; Carla Gomes
The intended purpose of corridors is to provide regions of the landscape that facilitate movement of individuals. Specific objectives include increasing gene flow, reducing isolation and inbreeding, increasing fitness and survival of species, and allowing species to move and adapt to changes in the landscape. Corridor conservation typically focuses on either 1) conserving areas that support high abundance of species to reduce the risk of demographic stochasticity or 2) conserving areas that allow individuals to move between reserve areas to maintain gene flow. Most corridor design applications focus on patterns of habitat and landscape structure (structural connectivity). However, the impetus of corridor design is the process of animal movement (functional connectivity). Functional connectivity considers the degree to which the landscape facilitates or impedes the movement of organisms and is the product of landscape structure and the response of organisms to this structure. We suggest that maintenance of spatially structured populations requires considerations of both species abundance as well as functional landscape connectivity. We present a model for corridor design in the Chocó-Andean region of Ecuador, home to the endangered Andean bear (Tremarctos ornatus) and numerous endemic and threatened birds. We describe a novel metric related to biodiversity conservation and corridor design. The density-weighted connectivity metric is derived from encounter history data commonly collected in capture-recapture studies. Such data allow for simultaneous inference about population density and landscape resistance to movement using spatial capture-recapture models. We demonstrate how density-weighted connectivity models two ecological processes on the outcome of density – movement and resource selection. We highlight how this metric can be used in spatial optimization objective functions applied to landscape management and connectivity conservation decision making.
2:10PM Genetic Data to Estimate Connectivity for US-Mexico Border Species
  Melanie Culver
The US-Mexico border wall represents a potential barrier to gene flow for wildlife species occurring the Sonoran Desert region of Arizona and Mexico. Natural gene flow among population is necessary to maintain genetic connectivity and prevents population isolation and bottlenecks caused by fragmentation and barriers. Particularly for species with a small part of their range on one side of the fence (either in the US or Mexico). The objective if this study is to examine connectivity of mammal, reptile, bird, and invertebrate species and populations across the international border using genetic methods. A second objective is to re-examine connectivity after wall/fence construction occurs at the international border. Thirteen species have been sampled between 1995-2015 across the border region of Arizona-Mexico, and were examined for levels of genetic diversity and gene flow/connectivity using genetic methods involving mtDNA sequencing and microsatellite DNA analyses. Species include eight mammals (black bear, jaguar, puma, ocelot, bobcat, Sonoran pronghorn, black-tailed prairie dog, lesser long-nosed bat), two reptiles (desert tortoise, flat-tailed horned lizard), one amphibian (Chiricahua leopard frog), one bird (yellow-billed cuckoo), and one invertebrate (California mussel). Results presented indicate that all thirteen species/populations exhibited connectivity across the international border region for this comprehensive range of border species prior to construction of the current border fence. Genetic results will also be presented on a subset of these species following the installation of the current border fence; including a discussion of the impact to these species resulting from the current semi-permeable fence, versus the potential impact of a new impermeable fence.
2:30PM From Swamp Tigers to Desert Lions: Wild Cats as Flagship Species for Landscape Conservation
  Ashwin Naidu
The persistent demand for land and infrastructure to increase supplies and connectivity for humans has compromised natural landscapes and habitat connectivity for wildlife. In today’s world, many wild animals are restricted to fragmented “islands” surrounded by “seas” of anthropogenic developments. The need to improve conservation strategies to enhance wildlife habitat connectivity has led to the application of novel research in landscape ecology and large landscape conservation designs. However, are landscape designs quite effective by themselves, or can they become more effective when a species, like a ‘flagship or an umbrella species’ is used in conjunction as a major reason to protect a large landscape? Based on a collection of field experiences in three unique landscapes and my research work in the past on tigers (Panthera tigris), leopards (Panthera pardus), mountain lions (Puma concolor), and fishing cats (Prionailurus viverrinus), I find considerable potential in marketing these wild cats as ‘flagship species’ to achieve results in landscape-level conservation. To substantiate my statement, I present key results from a presence-absence survey of tigers, leopards, and dholes (Cuon alpinus) in south-central India, a landscape genetic analysis of mountain lions in the southwestern United States and northwestern Mexico, and a community-managed study on fishing cats in coastal South India’s last remaining mangrove forests. However, much remains to be learned on the effectiveness of flagship species-based conservation designs and the extent to which such approaches serve the objectives of large landscape conservation. Hence, in conclusion, I seek expert opinion on how we can hone the use of flagship species for landscape-level conservation.
2:50PM Refreshment Break
3:20PM Estimating Connectivity in a Metapopulation System
  Paige Howell; Blake Hossack; Erin Muths; Brent Sigafus; Richard Chandler
The fields of metapopulation and landscape ecology aim to understand how spatial structure influences ecological processes, yet the two disciplines address the problem using fundamentally different approaches. Whereas most metapopulation models ignore environmental heterogeneity between habitat patches, models used in landscape ecology include detailed descriptions of landscape structure and its effects on movement. The simplistic view of landscape structure used in metapopulation models has been defended as necessary to maintain connections to classical theories of population dynamics. We present a framework for unifying these disciplines by incorporating landscape structure into spatially explicit metapopulation models that allow for inference on landscape resistance to movement. We demonstrate the approach by fitting models to seven years of data from a study of Lithobates chiricahuensis (Chiricahua leopard frog) metapopulation dynamics. Results suggest colonization and extinction dynamics are determined primarily by the hydroperiod and spatial distribution of patches, with landscape topography playing a relatively minor role. However, the relative importance of patch and landscape variables in governing ecological processes may be species- and system-specific, which emphasizes the need for statistical models such as ours that are based on theory and generalizable to multiple systems.
3:40PM Graph-Theoretic Approaches to Connectivity and Dynamic Spatial Processes
  Joseph Drake; Xavier Lambin; Chris Sutherland
Landscape fragmentation and the resulting loss of connectivity among wildlife populations is a longstanding conservation concern. Within the emerging research area of spatial ecology, many methodological advances have been made in modeling and quantifying landscape connectivity, including with the promising application of graph theory. Initially used to measure structural connectivity between habitat patches, this method has quickly developed to incorporate species and location specific information, such as dispersal, into a wider connectivity modeling framework. Compared to least-cost paths and other connectivity frameworks, graph theory applications are less data intense, allowing for the pragmatic analyses of real landscapes and alternative management scenarios. Graph theory has promise in diverse applications, such as predicting invasive species spread and directing habitat conservation, yet it is still unclear how these graph-theoretic metrics compare against established connectivity measures when used to model spatial dynamics. Here we present a brief overview of graph connectivity modeling and then demonstrate the value of graph theoretic approaches for inferences in a spatially structured population of water voles (Arvicola amphibious) in the Scottish Highlands. Specifically, we compare the use of biologically motivated graph-theoretic metrics to more traditional distance-based connectivity metrics in their applicability to patch occupancy models. This application explores the use of graph theory to do more than show pattern, but help expand knowledge of processes such as long-term colonization-extinction in metapopulation dynamics.
4:00PM Circuitscape Connectivity Modeling with gflow
  Paul Leonard; Rob Baldwin
Connectivity analyses have been constrained by scale – grain size and extent – as a result of computational limits. The larger the area under analysis and the finer the grain, the more computational “workarounds” have been employed. While adjustments are made to minimize the biases imposed, for example, spatial bias due to boundary effects, computational solutions that can execute wall to wall analyses at the continent scale, using locally meaningful grain sizes, and do so in a manageable time frame (hours instead of weeks) would allow more comprehensive, and accurate assessments. We report the development of a new piece of circuit theory software, gflow. gflow massively parallelizes the computation of circuit theory-based connectivity. The software is developed for high-performance computing, but scales to consumer-grade desktop computers running modern Linux or Mac OS X operating systems. We report high computational efficiency representing a 173× speedup over existing software using high-performance computing and a 8·4× speedup using a desktop computer while drastically reducing memory requirements. gflow allows large-extent and high-resolution connectivity problems to be calculated over many iterations and at multiple scales. We envision gflow being immediately useful for large-landscape efforts, including climate-driven animal range shifts, multitaxa connectivity, and for the many developing use-cases of circuit theory-based connectivity.
4:20PM Focal Species and Landscape Naturalness Approaches to Modeling Habitat Connectivity
  Meade Krosby
As habitat fragmentation and climate change increase in pace and magnitude, connectivity conservation has emerged as a key strategy for biodiversity conservation. In response, a diverse suite of approaches has been developed for modeling habitat connectivity networks to guide conservation investments. Traditionally, such networks have been modeled using a limited number of focal species intended to serve as surrogates for a region’s broader biota. However, a focal species approach can be time consuming and expensive, especially at large landscape scales, where many focal species are needed to represent diverse habitats. In response to these limitations, there has been growing interest in the application of coarse-filter approaches to connectivity planning, particularly those that model connectivity based on the degree of landscape ‘‘naturalness’’ or ‘‘ecological integrity.’’ This approach assumes that species will find it more difficult to move through areas heavily modified by human activities, and identifies corridor networks connecting areas with low levels of modification. The Washington Connected Landscapes Project completed both focal species and landscape-naturalness based approaches for greater Washington State, USA. To inform use of the two approaches, we assessed complementarity between their resulting networks by examining the spatial overlap of predicted corridors, and regressing organism traits against the amount of modeled corridor overlap. We found that a single naturalness-based corridor network represented connectivity for a large (>10) number of focal species as effectively as a group of between 3 and 4 randomly selected focal species. The naturalness-based approach showed only moderate spatial agreement with composite corridor networks based on large numbers of focal species, and better agreed with corridor networks of large-bodied, far-dispersing species in the larger scale analysis. Naturalness-based corridor models may thus offer an efficient proxy for focal species models, but a multi-focal species approach may better represent the movement needs of diverse taxa.
4:40PM Panel Discussion
 

 
Organizers: Melissa Merrick, University of Arizona, Tucson, AZ; Julie Mikolajczyk, Arizona Game and Fish Department, Phoenix, AZ
 
Supported by: TWS Southwest Section Geospatial Advisory Group, TWS Southwest Section, TWS Biometrics Working Group

Symposium
Location: Albuquerque Convention Center Date: September 26, 2017 Time: 1:10 pm - 5:00 pm