Optimizing dispersal corridors for the Cape Proteaceae using network flow.

AT&T Labs-Research, 180 Park Avenue, Florham Park, New Jersey 07932, USA.
Ecological Applications (Impact Factor: 4.13). 08/2008; 18(5):1200-11. DOI: 10.1890/07-0507.1
Source: PubMed

ABSTRACT We introduce a new way of measuring and optimizing connectivity in conservation landscapes through time, accounting for both the biological needs of multiple species and the social and financial constraint of minimizing land area requiring additional protection. Our method is based on the concept of network flow; we demonstrate its use by optimizing protected areas in the Western Cape of South Africa to facilitate autogenic species shifts in geographic range under climate change for a family of endemic plants, the Cape Proteaceae. In 2005, P. Williams and colleagues introduced a novel framework for this protected area design task. To ensure population viability, they assumed each species should have a range size of at least 100 km2 of predicted suitable conditions contained in protected areas at all times between 2000 and 2050. The goal was to design multiple dispersal corridors for each species, connecting suitable conditions between time periods, subject to each species' limited dispersal ability, and minimizing the total area requiring additional protection. We show that both minimum range size and limited dispersal abilities can be naturally modeled using the concept of network flow. This allows us to apply well-established tools from operations research and computer science for solving network flow problems. Using the same data and this novel modeling approach, we reduce the area requiring additional protection by a third compared to previous methods, from 4593 km2 to 3062 km , while still achieving the same conservation planning goals. We prove that this is the best solution mathematically possible: the given planning goals cannot be achieved with a smaller area, given our modeling assumptions and data. Our method allows for flexibility and refinement of the underlying climate-change, species-habitat-suitability, and dispersal models. In particular, we propose an alternate formalization of a minimum range size moving through time and use network flow to achieve the revised goals, again with the smallest possible newly protected area (2850 km2). We show how to relate total dispersal distance to probability of successful dispersal, and compute a trade-off curve between this quantity and the total amount of extra land that must be protected.

Download full-text


Available from: Guy F Midgley, Jul 28, 2015
  • Source
    • "Several authors have noted (e.g. Fábrega-Álvarez and Parcero- Oubiña 2007, Gietl et al. 2008, Herzog 2010, Howey 2011, McRae et al. 2008, Neutens et al. 2010, Phillips et al. 2008, Zakšek et al. 2008) that the outputs of least-cost path models are more sensitive to used algorithms and input values than least-cost corridor analyses theoretically based on the time-geographical potential path area modelling. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Published chapter available as a pdf on request (due to publisher's restrictions), here a final draft.
    Past mobilities. Archaeological Approaches to Movement and Mobility, Edited by J. Leary, 05/2014: chapter 5: pages 79-112; Ashgate Publishing.
  • Source
    • "Other studies have explored this additional complexity. Phillips et al. (2008) used graph theory to calculate network flow to inform corridor locations under climate change. Carroll et al. (2010) used species distribution forecasts with zonation analysis to inform reserve locations under future climate conditions. "
    [Show abstract] [Hide abstract]
    ABSTRACT: AimHabitat fragmentation threatens species’ persistence by increasing subpopulation isolation and vulnerability to stochastic events, and its impacts are expected to worsen under climate change. By reconnecting isolated fragments, habitat corridors should dampen the synergistic impacts of habitat and climate change on population viability. Choosing which fragments to reconnect is typically informed by past and current environmental conditions. However, habitat and climate are dynamic and change over time. Habitat suitability projections could inform fragment selection using current and future conditions, ensuring that corridors connect persistent fragments. We compare the efficacy of using current-day and future forecasts of breeding habitat to inform corridor placement under land cover and climate-change mitigation and no mitigation scenarios by evaluating their influence on subpopulation abundance, and connectivity and long-term metapopulation abundance. Our case study is the threatened orangutan metapopulation in Sabah.LocationSabah, Malaysian Borneo.Methods Using coupled niche–population models that capture a metapopulation distribution and its major processes, we forecast the effect of current-day and future-informed habitat corridor implementations under two scenarios where (1) land cover and climate change continue unabated (no mitigation) and (2) local and international cooperation mitigates their synergistic impact (mitigation).ResultsWe show that Future-informed corridor placement maximizes long-term metapopulation abundance when human-driven land cover and climate change alter the spatio-temporal composition of suitable habitat. By contrast, there is no apparent benefit in using future forecasts of breeding habitat to inform corridor placement if conditions remain comparatively stable. For the Sabah orangutan under unabated land cover and climate change, habitat corridors should connect current-day populated eastern habitat fragments with vacant fragments in the state's west.Main conclusionsThe efficacy of habitat corridors can be improved by using habitat-suitability model projections to inform corridor placement in rapidly changing environments, even for long-lived, low-fecundity, philopatric species such as orangutan.
    Diversity and Distributions 04/2014; 20(9). DOI:10.1111/ddi.12208 · 5.47 Impact Factor
  • Source
    • "The strategy assumes long term conservation efforts can be maintained , and risks future loss of resources. In temporary conservation , increased conservation now is potentially paid for by reduced conservation in the future, which could be justified when temporary measures are only needed to help a population through a temporary bottleneck (Phillips et al., 2008; Vos et al., 2008; van Teeffelen et al., 2012). Rayfield et al. (2008) found that the effectiveness of dynamic reserves compared to permanent ones was limited by a regional limit on the density of mature forest stages. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a novel framework for the structured analysis of conservation strategies, concentrating on their conceptual, causal, logical and qualitative aspects. The analysis both increases our understanding of conservation strategies and provides a tool for supporting their use in decision making. It facilitates answering such questions as: What are the basic characteristics of the strategy? What are its biological targets? What are its aims, paths of influence and expected benefits? Where should the strategy best be applied and by whom? How should the strategy be applied over time? What are the data needs? What major assumptions underlie the strategy? Which are the major costs, constraints, and uncertainties that might influence its feasibility and application? How does the strategy relate to other conservation strategies? Are there viable alternatives? We also examine the emergent properties of the strategy, asking what the world would be like if the strategy was applied extensively. We examine the usefulness of structured analysis by applying it to the strategy of temporary conservation, which incorporates dynamic reserves and temporary conservation contracts, either to maintain a regional distribution of successional habitats or to facilitate climate-change induced range shifts of species. This application showed that these strategies have appeared under various names, that they require extensive data, that implementation involves significant uncertainties, and that associated uncertainties increase through time. Applying the proposed framework to a range of conservation strategies would improve our ability to identify most appropriate paths of conservation when many alternatives exist.
    Biological Conservation 02/2014; 170:188–197. DOI:10.1016/j.biocon.2014.01.001 · 4.04 Impact Factor
Show more