Riparian ecosystems in the 21st century are likely to play a critical role in determining the vulnerability of natural and human systems to climate change, and in influencing the capacity of these ...systems to adapt. Some authors have suggested that riparian ecosystems are particularly vulnerable to climate change impacts due to their high levels of exposure and sensitivity to climatic stimuli, and their history of degradation. Others have highlighted the probable resilience of riparian ecosystems to climate change as a result of their evolution under high levels of climatic and environmental variability. We synthesize current knowledge of the vulnerability of riparian ecosystems to climate change by assessing the potential exposure, sensitivity, and adaptive capacity of their key components and processes, as well as ecosystem functions, goods and services, to projected global climatic changes. We review key pathways for ecological and human adaptation for the maintenance, restoration and enhancement of riparian ecosystem functions, goods and services and present emerging principles for planned adaptation. Our synthesis suggests that, in the absence of adaptation, riparian ecosystems are likely to be highly vulnerable to climate change impacts. However, given the critical role of riparian ecosystem functions in landscapes, as well as the strong links between riparian ecosystems and human well-being, considerable means, motives and opportunities for strategically planned adaptation to climate change also exist. The need for planned adaptation of and for riparian ecosystems is likely to be strengthened as the importance of many riparian ecosystem functions, goods and services will grow under a changing climate. Consequently, riparian ecosystems are likely to become adaptation 'hotspots' as the century unfolds.
Questions
What role do soil seed banks play in the resilience of coastal freshwater wetland vegetation communities? How might soil seed bank composition and similarity to standing vegetation drive ...changes in vegetation expression, particularly given projected changes in climate?
Location
Sixty wooded coastal freshwater wetlands in southeast Queensland, Australia.
Methods
We surveyed standing vegetation and investigated soil seed bank composition through an 8‐month‐long emergence experiment.
Results
Soil seed bank assemblages were dominated by forb and sedge species (23% exotic), but composition varied throughout the study region. Spatial (north–south) and land‐use (urban–rural) gradients explained some variation in soil seed bank composition. Soil moisture and groundwater dependence also influenced species distributions, particularly for freshwater wetland species. The similarity of soil seed banks to standing vegetation was low. Species present in both extant and soil seed bank assemblages were commonly native wetland taxa, including one salt marsh species (Juncus kraussii).
Conclusions
Projected climatic changes will likely drive changes in coastal freshwater wetland vegetation communities through increases in the frequency and intensity of disturbances (e.g., storm surge). Our results suggest that regeneration from soil seed banks could promote four potential scenarios: (1) expansion of weed communities, (2) expansion of salt marsh communities, (3) maintenance and expansion of wetland/terrestrial species, and (4) transformation to an unvegetated open water zone because of reduced regeneration success under changing conditions. These diverse vegetation futures highlight the vulnerability of wooded coastal freshwater wetlands and the need for research and management interventions to maintain their biodiversity and ecosystem services.
This study explores the diversity of soil seed banks in coastal freshwater wetlands of subtropical Australia and the role they have in supporting vegetation resilience under climate change. Seed banks, although diverse and highly varied, minimally reflected the standing vegetation, which suggests strong potential for transformation of this community with climate change for which we present four potential pathways.
Coastal wetlands are significant components of the coastal landscape with important roles in ecosystem service provision and mitigation of climate change. They are also likely to be the system most ...impacted by climate change, feeling the effects of sea levels rise, temperature increases and rainfall regime changes. Climate change impacts on estuarine coastal wetlands (mangroves, saltmarsh) have been thoroughly investigated; however, the impacts on coastal freshwater wetlands (CFWs) are relatively unknown. To explore the current knowledge of the impacts of climate change on CFWs globally, we undertook a systematic quantitative literature review of peer-reviewed published literature. We found surprisingly little research (110 papers of an initial 678), the majority of which was conducted in the USA, focusing on the effects of sea level rise (SLR) on CFW vegetation or sediment accretion processes. From this research, we know that SLR will lead to reduced productivity, reduced regeneration, and increased mortality in CFW vegetation but little is known regarding the effects of other climate change drivers. Sediment accretion is also not sufficient to keep pace with SLR in many CFWs and again the effects of other climate drivers have not been investigated. The combination of unhealthy vegetation communities and minimal gain in vertical elevation can result in a transition towards a vegetation community of salt-tolerant species but more research is required to understand this process.
Summary
Riparian ecosystems are hotspots for ecological restoration globally because of the disproportionately high value and diversity of the ecological functions and services which they support and ...their high level of vulnerability to anthropogenic pressures, including climate change. Degraded riparian ecosystems are associated with many serious anthropogenic problems including increased river bank erosion, water quality decline, increased flood risk and biodiversity loss. Conventional approaches to riparian restoration, however, are frequently too narrow in focus – spatially, temporally, ecologically and socially – to adequately or equitably address the goals to which they aspire. Climate change, along with the intensification of other human pressures, means that static, historically oriented restoration objectives focused solely on prior ecological composition and structure are unlikely to be defensible, achievable or appropriate in the Anthropocene. Conversely, open‐ended restoration strategies lacking clear objectives and targets entail substantial risks such as significant biodiversity losses, especially of native species. A functional approach to planning and prioritising riparian restoration interventions offers an intermediate alternative that is still framed by measurable targets but allows for greater consideration of broader temporal, spatial and cultural influences. Here, we provide an overview of major riparian functions across multiple scales and identify key drivers of, and threats to, these. We also discuss practical approaches to restoring and promoting riparian functions and highlight some key concerns for the development of policy and management of robust riparian restoration in the Anthropocene.
The concepts of ecosystem regime shifts, thresholds and alternative or multiple stable states are used extensively in the ecological and environmental management literature. When applied to aquatic ...ecosystems, these terms are used inconsistently reflecting differing levels of supporting evidence among ecosystem types. Although many aquatic ecosystems around the world have become degraded, the magnitude and causes of changes, relative to the range of historical variability, are poorly known. A working group supported by the Australian Centre for Ecological Analysis and Synthesis (ACEAS) reviewed 135 papers on freshwater ecosystems to assess the evidence for pressure-induced non-linear changes in freshwater ecosystems; these papers used terms indicating sudden and non-linear change in their titles and key words, and so was a positively biased sample. We scrutinized papers for study context and methods, ecosystem characteristics and focus, types of pressures and ecological responses considered, and the type of change reported (i.e., gradual, non-linear, hysteretic or irreversible change). There was little empirical evidence for regime shifts and changes between multiple or alternative stable states in these studies although some shifts between turbid phytoplankton-dominated states and clear-water, macrophyte-dominated states were reported in shallow lakes in temperate climates. We found limited understanding of the subtleties of the relevant theoretical concepts and encountered few mechanistic studies that investigated or identified cause-and-effect relationships between ecological responses and nominal pressures. Our results mirror those of reviews for estuarine, nearshore and marine aquatic ecosystems, demonstrating that although the concepts of regime shifts and alternative stable states have become prominent in the scientific and management literature, their empirical underpinning is weak outside of a specific environmental setting. The application of these concepts in future research and management applications should include evidence on the mechanistic links between pressures and consequent ecological change. Explicit consideration should also be given to whether observed temporal dynamics represent variation along a continuum rather than categorically different states.
•We assessed evidence for multiple stables states in freshwater ecosystems.•Evidence was mainly limited to studies of shallow temperate lakes.•Most studies using such terms lacked convincing evidence or appropriate data.•There were few reports of freshwater ecosystem recovery from alleviated pressures.•Inconsistent terminology and vague links with theory lead to its inappropriate use.
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.
Practitioners of environmental water management (EWM) operate within complex social-ecological systems. We sought to better understand this complexity by investigating the management of environmental ...water for vegetation outcomes. We conducted an online survey to determine practitioners' perspectives on EWM for non-woody vegetation (NWV) in the Murray-Darling Basin, Australia with regards to: i) desirable outcomes and benefits; ii) influencing factors and risks; iii) challenges of monitoring and evaluation, and iv) improving outcomes. Survey participants indicated that EWM aims to achieve outcomes by improving or maintaining vegetation attributes and the functions and values these provide. Our study reveals that EWM practitioners perceive NWV management in a holistic and highly interconnected way. Numerous influencing factors as well as risks and challenges to achieving outcomes were identified by participants, including many unrelated to water. Survey responses highlighted six areas to improve EWM for NWV outcomes: (1) flow regimes, (2) vegetation attributes, (3) non-flow drivers, (4) management-governance considerations, (5) functions and values, and (6) monitoring, evaluation and research. These suggest a need for more than 'just water' when it comes to the restoration and management of NWV. Our findings indicate more integrated land-water governance and management is urgently required to address the impacts of non-flow drivers such as pest species, land-use change and climate change. The results also indicate that inherent complexity in EWM for ecological outcomes has been poorly addressed, with a need to tackle social-ecological constraints to improve EWM outcomes.
How people value rivers, wetlands and floodplains influences their attitudes, beliefs and behaviours towards these ecosystems, and can shape policy and management interventions. Better understanding ...why people value rivers, wetlands and floodplains and their key ecosystem components, such as vegetation, helps to determine what factors underpin the social legitimacy required for effective management of these systems. This study sought to ascertain perspectives on the value of non-woody vegetation in river-floodplain systems via an online survey. The survey found that participants valued non-woody vegetation for their provision of a range of ecosystem functions and services, with strong emphasis on ecological aspects such as regulation functions, habitat provision and biodiversity. However, the inclusion of a question framed to focus on stories or narratives resulted in a different emphasis. Responses indicated that non-woody vegetation, and rivers, wetlands and floodplains were valued for the way they made people feel through lived experiences such as recreational activities, personal interactions with nature, educational and research experiences. This highlights the important role of storytelling in navigating complex natural resource management challenges and ascertaining a deeper understanding of values that moves beyond provision of function to feeling. Improved understanding of the diverse ways people value and interact with river-floodplain systems will help develop narratives and forms of engagement that foster shared understanding, empathy and collaboration. Appreciation of plural values such as the provision of functions and services along with the role of emotional connections and lived experience will likely increase lasting engagement of the general public with management to protect and restore river-floodplain systems.
Intensification of the use of natural resources is a world-wide trend driven by the increasing demand for water, food, fibre, minerals and energy. These demands are the result of a rising world ...population, increasing wealth and greater global focus on economic growth. Land use intensification, together with climate change, is also driving intensification of the global hydrological cycle. Both processes will have major socio-economic and ecological implications for global water availability. In this paper we focus on the implications of land use intensification for the conservation and management of freshwater ecosystems using Australia as an example. We consider this in the light of intensification of the hydrologic cycle due to climate change, and associated hydrological scenarios that include the occurrence of more intense hydrological events (extreme storms, larger floods and longer droughts). We highlight the importance of managing water quality, the value of providing environmental flows within a watershed framework and the critical role that innovative science and adaptive management must play in developing proactive and robust responses to intensification. We also suggest research priorities to support improved systemic governance, including adaptation planning and management to maximise freshwater biodiversity outcomes while supporting the socio-economic objectives driving land use intensification. Further research priorities include: i) determining the relative contributions of surface water and groundwater in supporting freshwater ecosystems; ii) identifying and protecting freshwater biodiversity hotspots and refugia; iii) improving our capacity to model hydro-ecological relationships and predict ecological outcomes from land use intensification and climate change; iv) developing an understanding of long term ecosystem behaviour; and v) exploring systemic approaches to enhancing governance systems, including planning and management systems affecting freshwater outcomes. A major policy challenge will be the integration of land and water management, which increasingly are being considered within different policy frameworks.
•This paper considers the impacts of land use and hydrological intensification on inland waters•Global issues are considered through the lens of Australian examples•Likely scenarios include wet regions becoming wetter, dry regions drier and storms more intense•The legacies of past land use change will need to be addressed•Proactive governance based on innovative science and adaptive management will be critical
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