Towards a Process Domain‐Sensitive Substrate Habitat Model for Sea Lampreys in Michigan Rivers

Habitat mapping is a common and often useful tool in the ecological management of rivers. The complex nature of fluvial processes, however, makes it difficult to predict the reach‐scale distribution of substrate habitat from landscape‐scale covariates. An option is to identify and partition a data set on boundaries of geomorphic process domains, within which the globally complex relationships between landscape, climate, and instream habitat may potentially be approximated by a simpler model. In this study, we used regression trees as a machine learning method for partitioning and identifying useful strata in a geographically extensive substrate habitat model for larvae of the sea lamprey Petromyzon marinus, an invasive and economically harmful species in the Laurentian Great Lakes. We used field survey data from over 5,000 substrate habitat transects collected in 43 watersheds of the Lower Peninsula of Michigan, and we created a geographic database of geographical information systems‐derived covariates that represent the principal geomorphic influences on substrate habitat. We created three trees in which tree splits delineated (1) spatially contiguous units, (2) noncontiguous units defined by values of the covariates, and (3) both contiguous and noncontiguous units. The adjusted R2 values of the three trees were 0.30, 0.30, and 0.32, respectively, and all three trees outperformed a single model fitted to the entire data set and a set of models fitted to each watershed individually. The trees identified useful stratifications of Michigan’s Lower Peninsula, important geomorphic influences on substrate habitat, and variation in the influence of geomorphic processes on substrate habitat across our study region. Conservation and management applications of our model predictions and tree‐based stratifications include sea lamprey population modeling, habitat survey design, and evaluation of dam removal.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141668/1/tafs0313.pd

Conservation planning in an uncertain climate: Identifying projects that remain valuable and feasible across future scenarios

Conservation actors face the challenge of allocating limited resources despite uncertainty about future climate conditions. In many cases, the potential value and feasibility of proposed projects vary across climate scenarios. A key goal is to identify areas where conservation outcomes can balance both environmental and human needs. We developed a conservation prioritization framework that jointly considers the value and feasibility of candidate projects across future climate scenarios. We then applied this framework to the challenge of meeting environmental flow targets across the Red River basin of the south-central United States. To estimate the conservation feasibility of meeting environmental flow goals in a river reach in each climate scenario, we used a basin-wide hydrologic planning tool to quantify the reduction in societal water usage needed to meet environmental flow targets. To estimate the biodiversity value of each river reach in each climate scenario, we used climate-driven species distribution models and species’ conservation status. We found that river reaches in the east-central portion of the basin may be good candidates for conservation investments, because they had high biodiversity value and high sociopolitical feasibility in all future climate scenarios. In contrast, sites in the arid western reaches of the basin had high biodiversity value, but low feasibility of achieving environmental flow goals. Our framework should have broad applicability given that the value and feasibility of conservation projects vary across climate scenarios in ecosystems around the world. It may serve as a coarse filter to identify sites for more detailed analyses and could be integrated with complementarity-based approaches to conservation planning to balance species’ representation across projects. A free Plain Language Summary can be found within the Supporting Information of this article

Prioritizing ecological restoration among sites in multi‐stressor landscapes

Most ecosystems are impacted by multiple local and long‐distance stressors, many of which interact in complex ways. We present a framework for prioritizing ecological restoration efforts among sites in multi‐stressor landscapes. Using a simple model, we show that both the economic and sociopolitical costs of restoration will typically be lower at sites with a relatively small number of severe problems than at sites with numerous lesser problems. Based on these results, we propose using cumulative stress and evenness of stressor impact as complementary indices that together reflect key challenges of restoring a site to improved condition. To illustrate this approach, we analyze stressor evenness across the world’s rivers and the Laurentian Great Lakes. This exploration reveals that evenness and cumulative stress are decoupled, enabling selection of sites where remediating a modest number of high‐intensity stressors could substantially reduce cumulative stress. Just as species richness and species evenness are fundamental axes of biological diversity, we argue that cumulative stress and stressor evenness constitute fundamental axes for identifying restoration opportunities in multi‐stressor landscapes. Our results highlight opportunities to boost restoration efficiency through strategic use of multi‐stressor datasets to identify sites that maximize ecological response per stressor remediated. This prioritization framework can also be expanded to account for the feasibility of remediation and the expected societal benefits of restoration projects.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134184/1/eap1346_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134184/2/eap1346.pd

The dynamics of mature and emerging freshwater conservation programs

Conservation programs range from small, place-based initiatives to large, bureaucracy-heavy systems. The dynamics of these programs vary greatly. New initiatives may experience exponential growth, but participation and spending in mature programs may rise and fall in response to a number of factors. Here, we analyze historical patterns of participation and spending across five freshwater conservation programs in the United States. Our analysis highlights fundamental differences between emerging programs, which may experience exponential or logistic growth, and mature programs with slower growth, in which changes in participation may be driven by a number of internal and exogenous factors. We propose that changes in the number and spatial distribution of conservation projects are associated with four key factors: changes in legislation that open new funding streams; shifting priorities of actors; changes in the policies or management of a program that align it with new funding opportunities; and increases in individuals’ willingness to participate in a program as it grows. These programmatic shifts represent windows of opportunity for strategically reorienting conservation programs to leverage newly-available resources. Given that large, mature conservation programs support biodiversity and ecosystem services worldwide, comparison of their dynamics with those of emerging programs may reveal key opportunities for maximizing the benefits of investments in these programs.SW was supported by a Nancy L. Mergler Dissertation Completion Fellowship at OU. Financial support was provided by the University of Oklahoma Libraries’ Open Access Fund.Ye

Prioritizing native migratory fish passage restoration while limiting the spread of invasive species: A case study in the Upper Mississippi River

Despite increasing efforts globally to remove dams and construct fish passage structures, broad-scale analyses balancing tradeoffs between cost and habitat gains from these mitigations infrequently consider invasive species. We present an optimization-based approach for prioritizing dam mitigations to restore habitat connectivity for native fish species, while limiting invasive species spread. Our methodology is tested with a case study involving 240 dams in the Upper Mississippi River, USA. We integrate six native migratory fish species distribution models, distributions of two invasive fishes, and estimated costs for dam removal and construction of fish passes. Varying budgets and post-mitigation fish passage rates are analyzed for two scenarios: ‘no invasives’ where non-selective mitigations (e.g., dam removal) are used irrespective of potential invasive species habitat gains and ‘invasives’ where a mixture of selective (e.g., lift-and-sort fish passage) and non-selective mitigations are deployed to limit invasive species range expansion. To achieve the same overall habitat connectivity gains, we find that prioritizations accounting for invasive species are 3 to 6 times more costly than those that do not. Habitat gains among native fish species were highly variable based on potential habitat overlap with invasive species and post-mitigation passabilities, ranging from 0.4–58.9% (‘invasives’) and 7.9–95.6% (‘no invasives’) for a $50M USD budget. Despite challenges associated with ongoing nonnative fish invasions, opportunities still exist to restore connectivity for native species as indicated by individual dams being frequently selected in both scenarios across varying passabilities and budgets, however increased restoration costs associated with invasive species control indicates the importance of limiting their further spread within the basin. Given tradeoffs in managing for native vs. invasive species in river systems worldwide, our approach demonstrates strategies for identifying a portfolio of candidate barriers that can be investigated further for their potential to enhance native fish habitat connectivity while concurrently limiting invasive species dispersal

Spatial planning for water sustainability projects under climate uncertainty: balancing human and environmental water needs

Societies worldwide make large investments in the sustainability of integrated human-freshwater systems, but uncertainty about water supplies under climate change poses a major challenge. Investments in infrastructure, water regulation, or payments for ecosystem services may boost water availability, but may also yield poor returns on investment if directed to locations where water supply unexpectedly fluctuates due to shifting climate. How should investments in water sustainability be allocated across space and among different types of projects? Given the high costs of investments in water sustainability, decision-makers are typically risk-intolerant, and considerable uncertainty about future climate conditions can lead to decision paralysis. Here, we use mathematical optimization models to find Pareto-optimal satisfaction of human and environmental water needs across a large drought-prone river basin for a range of downscaled climate projections. We show how water scarcity and future uncertainty vary independently by location, and that joint consideration of both factors can provide guidance on how to allocate water sustainability investments. Locations with high water scarcity and low uncertainty are good candidates for high-cost, high-reward investments; locations with high scarcity but also high uncertainty may benefit most from low regret investments that minimize the potential for stranded assets if water supply increases. Given uncertainty in climate projections in many regions worldwide, our analysis illustrates how explicit consideration of uncertainty may help to identify the most effective strategies for investments in the long-term sustainability of integrated human-freshwater systems.The project described in this publication was supported by the Science Applications division of the Southwest Region of the US Fish and Wildlife Service, and by Grant No. G17AP00120, Balancing Water Usage and Ecosystem Outcomes Under Drought and Climate Change: Enhancing an Optimization Model for the Red River, from the United States Geological Survey. Open Access fees paid for in whole or in part by the University of Oklahoma Libraries.Ye

Aging infrastructure creates opportunities for cost-efficient restoration of aquatic ecosystem connectivity

A hallmark of industrialization is the construction of dams for water management and roads for transportation, leading to fragmentation of aquatic ecosystems. Many nations are striving to address both maintenance backlogs and mitigation of environmental impacts as their infrastructure ages. Here, we test whether accounting for road repair needs could offer opportunities to boost conservation efficiency by piggybacking connectivity restoration projects on infrastructure maintenance. Using optimization models to align fish passage restoration sites with likely road repair priorities, we find potential increases in conservation return-on-investment ranging from 17% to 25%. Importantly, these gains occur without compromising infrastructure or conservation priorities; simply communicating openly about objectives and candidate sites enables greater accomplishment at current funding levels. Society embraces both reliable roads and thriving fisheries, so overcoming this coordination challenge should be feasible. Given deferred maintenance crises for many types of infrastructure, there could be widespread opportunities to enhance the cost-effectiveness of conservation investments by coordinating with infrastructure renewal efforts

River ecosystem conceptual models and non‐perennial rivers: A critical review

Conceptual models underpin river ecosystem research. However, current models focus on continuously flowing rivers and few explicitly address characteristics such as flow cessation and drying. The applicability of existing conceptual models to nonperennial rivers that cease to flow (intermittent rivers and ephemeral streams, IRES) has not been evaluated. We reviewed 18 models, finding that they collectively describe main drivers of biogeochemical and ecological patterns and processes longitudinally (upstream-downstream), laterally (channel-riparian-floodplain), vertically (surface water-groundwater), and temporally across local and landscape scales. However, perennial rivers are longitudinally continuous while IRES are longitudinally discontinuous. Whereas perennial rivers have bidirectional lateral connections between aquatic and terrestrial ecosystems, in IRES, this connection is unidirectional for much of the time, from terrestrial-to-aquatic only. Vertical connectivity between surface and subsurface water occurs bidirectionally and is temporally consistent in perennial rivers. However, in IRES, this exchange is temporally variable, and can become unidirectional during drying or rewetting phases. Finally, drying adds another dimension of flow variation to be considered across temporal and spatial scales in IRES, much as flooding is considered as a temporally and spatially dynamic process in perennial rivers. Here, we focus on ways in which existing models could be modified to accommodate drying as a fundamental process that can alter these patterns and processes across spatial and temporal dimensions in streams. This perspective is needed to support river science and management in our era of rapid global change, including increasing duration, frequency, and occurrence of drying.info:eu-repo/semantics/publishedVersio

Pet Project or Best Project? Online Decision Support Tools for Prioritizing Barrier Removals in the Great Lakes and Beyond

Structures that block movement of fish through river networks are built to serve a variety of societal needs, including transportation, hydroelectric power, and exclusion of exotic species. Due to their abundance, road crossings and dams reduce the amount of habitat available to fish that migrate from the sea or lakes into rivers to breed. The benefits to fish of removing any particular barrier depends on its location within the river network, its passability to fish, and the relative position of other barriers within the network. Balancing the trade-offs between ecological and societal values makes choosing among potential removal projects difficult. To facilitate prioritization of barrier removals, we developed an online decision support tool (DST) with three functions: (1) view existing barriers at various spatial scales; (2) modify information about barriers, including removal costs; and (3) run optimization models to identify portfolios of removals that provide the greatest amount of habitat access for a given budget. A survey of available DSTs addressing barrier removal prioritization indicates that barrier visualization is becoming widespread but few tools allow dynamic calculation of connectivity metrics, scenario analysis, or optimization. Having these additional functions, our DST enables organizations to develop barrier removal priorities based on cost-effectiveness in restoring aquatic connectivity

Large-scale river connectivity restoration requires planning for the presence of unrecorded barriers

Conservation decisions are invariably made with incomplete data on species’ distributions, habitats, and threats, but frameworks for allocating conservation investments rarely account for missing data. Here, we demonstrate how explicit consideration of missing data can boost return on investment in ecosystem restoration. We focus on the challenge of restoring aquatic ecosystem connectivity by removing dams and road crossings from rivers, a global conservation challenge. In Maine, USA, we find that failing to account for unmapped barriers leads to habitat gains nearly 50% lower than predicted. Explicitly acknowledging missing data during project selection, however, can boost habitat gains by 20-273% on average, depending on the true number of unmapped barriers. Importantly, these gains occur without additional data – simply acknowledging that some barriers are unmapped, regardless of their precise number and location, improves conservation outcomes. Given incomplete data in ecosystems worldwide, our analysis demonstrates the value of accounting for data shortcomings during project selection