Advancing systematic conservation planning for freshwater ecosystems
Januchowski-Hartley, Stephanie Renee (2011) Advancing systematic conservation planning for freshwater ecosystems. PhD thesis, James Cook University.
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Freshwater ecosystems and their associated biota are among the most endangered in the world. Key disturbances, such as water extraction, dams, and modifications to riparian and in-stream habitats, invasive species, and impacts on water quality have heavily altered these ecosystems. Escalating human pressure on, and disturbances to, water resources requires well-informed decision making and effective on-ground management to conserve and restore freshwater ecosystems. Systematic conservation planning offers the tools needed to address these issues, providing a strategic and scientifically defensible framework. Systematic conservation planning was pioneered in the terrestrial realm and has, with time, become the most commonly recommended approach to marine planning and management because it can ensure the selection of multiple protected areas that together achieve explicit objectives. However, in comparison to the terrestrial and marine realms, the adoption of systematic methods to inform decision making for the protection and/or restoration of freshwater ecosystems remains in its infancy. The principal focus of this thesis is on spatial conservation prioritisation applied to both protected area and off-reserve management decision making. It focuses on two areas in the field of freshwater systematic conservation planning that have been identified as research priorities: 1) assessing the sensitivity of conservation planning outcomes to different surrogates and objectives; and 2) enhancing applicability of systematic conservation planning to inform on-ground management decisions.
The aim of this thesis is to advance the scientific basis and application of systematic conservation planning for fresh waters. I address key questions in the field of systematic conservation planning in freshwater ecosystems, which are both novel contributions to the field and influential in informing conservation decisions both on and off-reserves, using the Wet Tropics of Queensland bioregion as a case study. My objectives were to 1) determine the occurrence of disturbances, and the incidental protection of fresh waters in terrestrial protected areas; 2) identify the effectiveness of using coarse-filter surrogates for representing freshwater fish diversity in systematic conservation planning; 3) develop methods to evaluate the effectiveness of invasive species management; and 4) integrate management costs into systematic conservation planning for invasive species.
There is a need for assessments that quantify the effectiveness of terrestrial protected areas for representing freshwater ecosystems and their dependent species, and that determine areas of vulnerability from human-induced disturbances. In Chapter 3, I used data on the spatial distribution of freshwater ecosystems and fish, human-induced disturbances, and the Wet Tropics protected area network to assess how well freshwater ecosystems and fish species are protected within this network. I identified human-induced disturbances likely to influence the effectiveness of freshwater protection measures and I evaluated the vulnerability of these ecosystems to human-induced disturbances within and outside protected areas. The representation of freshwater ecosystems and species in the protected areas of the Wet Tropics is poor: 83% of streams, 75% of wetland types, and 89% of fish species have less than 20% of their total lengths and areas in IUCN category II protected areas. Higher-order streams and their associated wetlands are influenced by the greatest number of human-induced disturbances and are also the least protected. My results indicate poor representation of freshwater ecosystems and fish species in protected areas, and high numbers of human-induced disturbances impacting on these systems both within and outside of protected areas despite the high level of protection of terrestrial areas in the Wet Tropics. My findings demonstrate the need for greater consideration of protection status and off-reserve management of freshwater systems.
Abiotic and biologically informed classifications are often used in conservation planning as coarse-filter surrogates for species. The relationship between these surrogates and the distribution of species is commonly assumed, but rarely assessed by planners. In Chapter 4, I derived four abiotic and eight biologically informed classifications of stream reaches to serve as surrogates for biodiversity patterns in the Wet Tropics. I used stream reaches as planning units and, as conservation targets for each surrogate, I used two percentages – 10% and 30% – of the total number of stream reaches occupied by each class. I then derived minimum sets of planning units to meet targets for each surrogate and tested the effectiveness of the surrogates by calculating the average achievement of the same targets for predicted distributions of 28 fish species. My results showed that neither abiotic nor biologically informed classifications were good at representing freshwater fish species; in fact none of the surrogates led to average representation of species better than randomly selected planning units. There were two main reasons for this poor performance. First, none of the surrogates had high classification strength or informativeness about compositional change in fish species within the study region. Second, frequency distributions of probabilities of occurrence for most fish species were strongly right-skewed, with few stream reaches having high probabilities. Combined, these results meant that selection of stream reaches to achieve surrogate targets were effectively random with respect to probabilities of fish species occurrence, leading to poor representation of fish species.
Often ecologists and natural resource managers can easily access data on invasive species occurrence across a region. Yet, collecting species abundance data over a large area is arguably more important for decision making, but inherently costly, so methods which can provide robust information at low-cost are particularly valuable. In Chapter 5, I tested the relationship of environmental suitability with local abundance of an aquatic invasive species, olive hymenachne (Hymenachne amplexicaulis) in the Wet Tropics. Least squares and quantile regressions revealed a positive relationship between environmental suitability and local abundance of olive hymenachne. I used the relationship between environmental suitability and local abundance to quantify the effectiveness of management (reduction in local abundance) under four different management investments. I showed that the upper limit of abundance can be used to evaluate management effectiveness based on varying investments, and that ongoing management is the most effective at reducing local abundance.
The successful management and eradication of invasive species is often constrained by insufficient or inconsistent funding. Consequently, managers are usually forced to select a subset of infested areas to manage. In Chapter 6, I present a spatially explicit decision method that can be used to identify actions to manage invasive species while minimizing costs and the likelihood of reinvasion. I apply the method to a real-world management scenario, aimed at managing an invasive aquatic macrophyte, olive hymenachne (Hymenachne amplexicaulis).
The approaches I developed in this thesis allowed me to overcome several challenges related to the conservation and management of fresh waters, advancing the field of freshwater systematic conservation planning by: 1) quantifying conservation gaps for fresh waters, 2) identifying the effectiveness of surrogate methods and invasive species management investments, and 3) advancing the application of systematic approaches to address resource allocation questions for invasive species management. I was able to achieve these outcomes by integrating systematic approaches and spatial models of native and invasive species distributions. The results of my work can be used to inform conservation decision makers about the limitations of 1) protection afforded to fresh waters and their dependent species and 2) surrogates for representing freshwater biodiversity in regional scale conservation plans. Further, using the method I developed for monitoring the effectiveness of invasive species management, and implementing actions at the sites that I identified as priorities for weed management, would provide more cost-effective solutions to managers in the region.
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