Wade Lynton Hadwen

Recent advances in recreation ecology and the implications of different relationships between recreation use and ecological impacts.

Recreation ecology – the study of the environmental consequences of outdoor recreation/nature-based tourism activities and their effective management – is an emerging field of global importance. A primary research generalization in this field, the use–impact relationship, is commonly described as curvilinear, with proportionally more impact from initial recreation/tourism use. This finding has formed the basis of visitor management strategies in parks, wilderness, and protected areas in many parts of the world. In this paper, however, we argue that the current generalization may be an oversimplification derived from one ecological response: the response of vegetation cover in some plant communities to trampling. Use–response functions for other plant communities, wildlife, soils, and aquatic/marine systems, for example, can differ and require alternative management strategies for sustainable use. On the basis of the available literature, we propose several alternative response relationships.

Climate-change threats to native fish in degraded rivers and floodplains of the Murray–Darling Basin, Australia

Many aquatic ecosystems have been severely degraded by water-resource development affecting flow regimes and biological connectivity. Freshwater fish have been particularly affected by these changes and climate change will place further stress on them. The Murray–Darling Basin (MDB), Australia, represents a highly affected aquatic system with dramatically modified flow regimes. This has impaired the health of its rivers, and potentially limited the adaptive capacity of its biota to respond to a changing climate. Here, we present our predictions of the potential impacts of climate change on 18 native fish species across their distributional ranges against the back-drop of past and continuing water-resource development (WRD). Because most of these species are found across a wide range of geographical and hydrological settings, we classified the MDB into 10 regions to account for likely variation in climate-change effects, on the basis of latitude, elevation and WRD. Cold water-tolerant species will be under greater stress than are warm water-tolerant species. In some regions, the negative impacts on exotic fish such as trout are likely to improve current conditions for native species. Because the impacts of climate change on any given species are likely to vary from region to region, regional fish assemblages will also be differentially affected. The most affected region is likely to occur in the highly disturbed Lower Murray River region, whereas the dryland rivers that are less affected in the northern MDB are likely to remain largely unchanged. Although climate change is a current and future threat to the MDB fish fauna, the continued over-regulation of water resources will place as much, if not more, stress on the remnant fish species.

Human effects on ecological connectivity in aquatic ecosystems: Integrating scientific approaches to support management and mitigation

Understanding the drivers and implications of anthropogenic disturbance of ecological connectivity is a key concern for the conservation of biodiversity and ecosystem processes. Here, we review human activities that affect the movements and dispersal of aquatic organisms, including damming of rivers, river regulation, habitat loss and alteration, human-assisted dispersal of organisms and climate change. Using a series of case studies, we show that the insight needed to understand the nature and implications of connectivity, and to underpin conservation and management, is best achieved via data synthesis from multiple analytical approaches. We identify four key knowledge requirements for progressing our understanding of the effects of anthropogenic impacts on ecological connectivity: autecology; population structure; movement characteristics; and environmental tolerance/phenotypic plasticity. Structuring empirical research around these four broad data requirements, and using this information to parameterise appropriate models and develop management approaches, will allow for mitigation of the effects of anthropogenic disturbance on ecological connectivity in aquatic ecosystems.

Gut content-and stable isotope-derived diets of four commercially and recreationally important fish species in two intermittently open estuaries

Despite remaining closed for variable periods, intermittently open estuaries provide habitat for estuarine and marine fish species of commercial and recreational value. To better understand how these systems trophically support their fish assemblages, the diets of four valued fish species, namely Acanthopagrus australis, Platycephalus fuscus, Sillago ciliata and Mugil cephalus, were examined in two intermittently open estuaries in New South Wales, Australia. Fish diets were determined using both gut contents and stable isotope analyses because the different temporal resolutions afforded by these methods can provide insight into the flexibility of fish diets. Stable isotope signatures of prey and fish proved to be particularly useful in analyses of the diets of M. cephalus and P. fuscus, because these species consume large quantities of unidentifiable organic matter and have high incidences of empty guts respectively. Diet reconstructions across methods were generally consistent for A. australis, but differed substantially for S. ciliata, with fewer prey taxa identified in the guts than expected. This result suggests that individual S. ciliata switch between local resources on the basis of their fluctuating temporal availability. Trophic flexibility, coupled with broad physicochemical tolerances, enables these species to flourish in the challenging environment of intermittently open estuaries.

Do climatic or institutional factors drive seasonal patterns of tourism visitation to protected areas across diverse climate zones in eastern Australia

Abstract Seasonality in tourism is a regular and predictable cycle of visitation across a year. Although seasonality in visitation is extremely common and is known, in principle, often to be driven by temporal changes in a range of natural and institutional factors, the relative importance of different individual pressures has yet to be quantified for any large-scale geographical areas. To assess the relative importance of natural versus institutional factors in driving tourism seasonality, data on visitation patterns were collated from 23 protected areas across six Koppen climate zones in eastern Australia. Analyses sought to determine the degree to which climatic variables (such as mean monthly rainfall and minimum and maximum temperatures) explained visitation patterns, and to understand how these relationships could assist in the prediction of tourism futures. Climate was the principal force driving seasonal patterns of visitation in equatorial, tropical, desert, grassland and temperate zones, whereas visitation to alpine/sub-alpine areas was driven by a complex array of natural and institutional factors. Tourism seasonality was driven mostly by institutional factors only in the sub-tropical climate zone. These analyses suggest that seasonal characteristics of current visitation could be used to predict the degree to which changes in climate and/or institutional arrangements, such as school holiday periods, might influence tourism opportunities in protected areas in eastern Australia.

Within-lake detection of the effects of tourist activities in the littoral zone of oligotrophic dune lakes

Abstract Intensive recreational use of oligotrophic lakes can lead to increases in epilimnetic nutrient concentrations (through direct inputs from urine or re-suspension of sediments) and the development of undesirable algal blooms. Despite these adverse ecological responses to tourist activities, many lake monitoring programs do not address tourist nutrient inputs at appropriate spatial and temporal scales. This paper presents results of investigations aimed at detecting the effects of nutrient inputs to perched dune lakes on Fraser Island, principally through within-lake comparisons of nutrient and algal variables. Nutrient concentrations and algal biomass were measured in heavily visited (disturbed) and inaccessible (reference) sites within five perched dune lakes on Fraser Island, Australia, during the summer of 1999/2000. Whilst nutrient and phytoplankton chlorophyll a concentrations did not differ between sites, periphyton chlorophyll a concentrations were occasionally significantly higher in disturbed sites than in reference sites, particularly in the very popular clear lakes, suggesting that algal growth may be enhanced by tourist activities. Experimental manipulations of nitrogen and phosphorus concentrations in algal (phytoplankton and periphyton) bioassays were undertaken in each lake over the 2000/2001 summer, to assess algal responses to nutrient additions. The response of phytoplankton communities to nutrient additions varied greatly between lakes, with evidence of limitation or co-limitation by nitrogen and phosphorus in all systems. Periphyton biomass showed similar trends to phytoplankton in some lakes, but these were not significant. Nutrients added to lakes by tourists are likely to be rapidly assimilated by littoral zone periphyton communities in these oligotrophic lakes. As a result, impacts of tourism are not likely to be detected by traditional measurements of open water nutrient and phytoplankton chlorophyll a concentrations. Instead, measurement of periphyton growth and/or biomass (chlorophyll a) in the littoral zone might be the most spatially and temporally relevant indicator of tourist impacts in these lakes.

Tourists increase the contribution of autochthonous carbon to littoral zone food webs in oligotrophic dune lakes

Tourists can adversely influence the ecology of oligotrophic lakes by increasing algal production via direct nutrient inputs and/or re-suspension of sediments. To assess the influence of tourists on food web dynamics, we used the natural abundance of stable isotopes of carbon and nitrogen to calculate the relative importance of autochthonous and allochthonous carbon sources to littoral zone food webs across five variously visited perched dune lakes on Fraser Island, Australia. The relative importance of autochthonous (phytoplankton and periphyton) carbon to littoral zone consumers was highly variable across taxa and lakes. Despite the potential influence of algal biomass, ambient nutrient concentrations and tannin concentrations on the contribution of autochthonous carbon to littoral zone food webs, none of these variables correlated to the per cent contribution of autochthonous carbon to consumer diets. Instead, autochthonous sources of carbon contributed more to the diets of aquatic consumers in heavily visited lakes than in less visited lakes, suggesting that tourist activities might drive these systems towards an increased reliance on autochthonous carbon. The assessment of the contribution of autochthonous carbon to littoral zone food webs may represent a more robust indicator of the impact of tourists in oligotrophic lakes than standard measures of nutrient concentrations and/or algal biomass.

Applications of Bayesian belief networks in water resource management

Bayesian belief networks (BBNs) are probabilistic graphical models that can capture and integrate both quantitative and qualitative data, thus accommodating data-limited conditions. This paper systematically reviews applications of BBNs with respect to spatial factors, water domains, and the consideration of climate change impacts. The methods used for constructing and validating BBN models, and their applications in different forms of decision-making support are examined. Most reviewed publications originate from developed countries (70%), in temperate climate zones (42%), and focus mainly on water quality (42%). In 60% of the reviewed applications model validation was based on the expert or stakeholder evaluation and sensitivity analysis, and whilst in 27% model performance was not discussed. Most reviewed articles applied BBNs in strategic decision-making contexts (52%). Integrated modelling tools for addressing challenges of dynamically complex systems were also reviewed by analysing the strengths and weaknesses of BBNs, and integration of BBNs with other modelling tools. The application of BBNs to water resource management was rarely applied in developing countries and in tropical regions.Only 8% reviewed papers explored potential impacts of climate change on water resources.Only 11% and 6% of reviewed articles applied influence diagrams and Object-Oriented Bayesian Networks respectively.Most reviewed articles applied BBNs in strategic decision-making contexts (52%) for water resource management.Results from BBN models were rarely compared or tested against other modelling approaches to validate their performance.

Flow events drive patterns of phytoplankton distribution along a river-estuary-bay continuum

Freshwater flow events drive phytoplankton productivity in subtropical coastal river systems. However, few studies have the necessary temporal and spatial resolution to fully characterise the effect of events on the distribution of phytoplankton across the full river-estuary-bay continuum. The present study characterised the response of phytoplank- ton to high-flow events in an Australian subtropical system; and identified the primary drivers of this response. During high-flow events, the concentration of phytoplankton chlorophyll a (Chl a) initially declined in the estuary, a response primarily driven by the shortened water-residence time.In the bay, phytoplanktongrowth in the near-shore zone was light limited;however,nutrientsstimulatedphytoplanktongrowthontheseawardedgeoftheriverplume.Duringthepost-high- flow phase, the concentration of Chl a in the freshwater reaches peaked downstream, where catchment-derived nutrients accumulated. In the estuary, elevated nutrient loads stimulated phytoplankton growth upstream and downstream of the light-limited zone. In the bay, nitrogen availability declined, and Chl a declined with an increasing distance offshore. The phytoplankton response to events documented in the present study can be used to identify when and where phytoplankton in subtropical systems may be strongly influenced by changes in the magnitude of nutrient, sediment and freshwater loads associated with high-flow events which result from anthropogenic pressures within the catchment.

Linking Visitor Impact Research to Visitor Impact Monitoring in Protected Areas

Growing demand for natural area recreation and tourism has seen a rise in visitor numbers to protected areas. In response, there has been an increase in research into visitor impacts. There has also been increased interest in establishing and maintaining visitor impacts monitoring programmes. Here, we evaluate the relationship between recreation ecology research and visitor impact monitoring and discuss how the aims and scope of these two activities often differ. We highlight that recreation ecologists design observational and experimental treatments to test causal relationships between a particular load or stress and environmental indicator(s) of interest. Some of these studies identify thresholds of concern, with the intention that managers can use thresholds of indicator response in their monitoring programmes. However, agencies interested in monitoring visitor impacts often do not need to establish causality, but rather detect change in the indicator of interest. Therefore, simplified protocols which can be easily conducted by agency staff in the field at regular and operationally appropriate time intervals can be used. We present a visitor assessment flow chart that demonstrates how research and monitoring objectives can interact and contribute to the cost-effective management of heavily visited sites within protected areas.