Since the IPCC Third Assessment Report (TAR), our understanding of the implications of climate change for coastal systems and low-lying areas (henceforth referred to as ‘coasts’) has increased substantially and six important policy-relevant messages have emerged. Coasts are experiencing the adverse consequences of hazards related to climate and sea level (very high confidence). Coasts are highly vulnerable to extreme events, such as storms, which impose substantial costs on coastal societies [6.2.1, 6.2.2, 6.5.2]. Annually, about 120 million people are exposed to tropical cyclone hazards, which killed 250,000 people from 1980 to 2000 [6.5.2]. Through the 20th century, global rise of sea level contributed to increased coastal inundation, erosion and ecosystem losses, but with considerable local and regional variation due to other factors [6.2.5, 6.4.1]. Late 20th century effects of rising temperature include loss of sea ice, thawing of permafrost and associated coastal retreat, and more frequent coral bleaching and mortality [6.2.5]. Coasts will be exposed to increasing risks, including coastal erosion, over coming decades due to climate change and sea-level rise (very high confidence). Anticipated climate-related changes include: an accelerated rise in sea level of up to 0.6 m or more by 2100; a further rise in sea surface temperatures by up to 3°C; an intensification of tropical and extratropical cyclones; larger extreme waves and storm surges; altered precipitation/run-off; and ocean acidification [6.3.2]. These phenomena will vary considerably at regional and local scales, but the impacts are virtually certain to be overwhelmingly negative [6.4, 6.5.3].

https://ro.uow.edu.au/cgi/viewcontent.cgi?article=1192&context=scipapers

Coastal systems and low-lying areas

Recognition of the escalating hydrological alteration of rivers on a global scale and resultant environmental degradation, has led to the establishment of the science of environmental flow assessment whereby the quantity and quality of water required for ecosystem conservation and resource protection are determined.

A global review of the present status of environmental flow methodologies revealed the existence of some 207 individual methodologies, recorded for 44 countries within six world regions. These could be differentiated into hydrological, hydraulic rating, habitat simulation and holistic methodologies, with a further two categories representing combination-type and other approaches.

Although historically, the United States has been at the forefront of the development and application of methodologies for prescribing environmental flows, using 37% of the global pool of techniques, parallel initiatives in other parts of the world have increasingly provided the impetus for significant advances in the field.

Application of methodologies is typically at two or more levels. (1) Reconnaissance-level initiatives relying on hydrological methodologies are the largest group (30% of the global total), applied in all world regions. Commonly, a modified Tennant method or arbitrary low flow indices is adopted, but efforts to enhance the ecological relevance and transferability of techniques across different regions and river types are underway. (2) At more comprehensive scales of assessment, two avenues of application of methodologies exist. In developed countries of the northern hemisphere, particularly, the instream flow incremental methodology (IFIM) or other similarly structured approaches are used. As a group, these methodologies are the second most widely applied worldwide, with emphasis on complex, hydrodynamic habitat modelling. The establishment of holistic methodologies as 8% of the global total within a decade, marks an alternative route by which environmental flow assessment has advanced. Such methodologies, several of which are scenario-based, address the flow requirements of the entire riverine ecosystem, based on explicit links between changes in flow regime and the consequences for the biophysical environment. Recent advancements include the consideration of ecosystem-dependent livelihoods and a benchmarking process suitable for evaluating alternative water resource developments at basin scale, in relatively poorly known systems. Although centred in Australia and South Africa, holistic methodologies have stimulated considerable interest elsewhere. They may be especially appropriate in developing world regions, where environmental flow research is in its infancy and water allocations for ecosystems must, for the time being at least, be based on scant data, best professional judgement and risk assessment. Copyright © 2003 John Wiley & Sons, Ltd.

http://www.swrcb.ca.gov/waterrights/water_issues/programs/bay_delta/deltaflow/docs/exhibits/swrcb/swrcb_tharme2003.pdf

A global perspective on environmental flow assessment: emerging trends in the development and application of environmental flow methodologies for rivers

Significant changes in physical and biological systems are occurring on all continents and in most oceans, with a concentration of available data in Europe and North America. Most of these changes are in the direction expected with warming temperature. Here we show that these changes in natural systems since at least 1970 are occurring in regions of observed temperature increases, and that these temperature increases at continental scales cannot be explained by natural climate variations alone. Given the conclusions from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report that most of the observed increase in global average temperatures since the mid-twentieth century is very likely to be due to the observed increase in anthropogenic greenhouse gas concentrations, and furthermore that it is likely that there has been significant anthropogenic warming over the past 50 years averaged over each continent except Antarctica, we conclude that anthropogenic climate change is having a significant impact on physical and biological systems globally and in some continents.

Attributing physical and biological impacts to anthropogenic climate change

Understanding the ecological impacts of climate change is a crucial challenge of the twenty-first century. There is a clear lack of general rules regarding the impacts of global warming on biota. Here, we present a metaanalysis of the effect of climate change on body size of ectothermic aquatic organisms (bacteria, phyto- and zooplankton, and fish) from the community to the individual level. Using long-term surveys, experimental data and published results, we show a significant increase in the proportion of small-sized species and young age classes and a decrease in size-at-age. These results are in accordance with the ecological rules dealing with the temperature–size relationships (i.e., Bergmann's rule, James' rule and Temperature–Size Rule). Our study provides evidence that reduced body size is the third universal ecological response to global warming in aquatic systems besides the shift of species ranges toward higher altitudes and latitudes and the seasonal shifts in life cycle events.

/pdf/global-warming-benefits-the-small-in-aquatic-ecosystems-g9kqvuk94x.pdf

Global warming benefits the small in aquatic ecosystems

▪ Abstract Aquatic insects and other benthic invertebrates are the most widely used organisms in freshwater biomonitoring of human impact. Because of the high monetary investment in freshwater management, decisions are often based on biomonitoring results, and a critical and comparative review of different approaches is required. We used 12 criteria that should be fulfilled by an “ideal” biomonitoring tool, addressing the rationale, implementation, and performance of a method. After illustrating how the century-old but still widely used Saprobian system does not meet these criteria, we apply them to nine recent approaches that range from the suborganismal to the ecosystem level. Although significant progress has been made in the field, no recent approach meets all 12 criteria. Given that the use of biomonitoring information has important financial consequences, we suggest that societies and governments prioritize how these criteria should be ranked.

DEVELOPMENTS IN AQUATIC INSECT BIOMONITORING: A Comparative Analysis of Recent Approaches

There is increasing evidence that the global climate change is already having measurable biological impacts. However, no study (based on actual data) has assessed the influence of the global warming on communities in rivers. We analyzed long-term series of fish (1979–1999) and invertebrate (1980–1999) data from the Upper Rhone River at Bugey to test the influence of climatic warming on both communities. Between the periods of 1979–1981 and 1997–1999, the average water temperature of the Upper Rhone River at Bugey has increased by about 1.5°C due to atmospheric warming. In the same period, several dams have been built from 12.5 to 85 km upstream of our study segment and a nuclear power plant has been built on it. Changes in the community structure were summarized using multivariate analysis. The variability of fish abundance was correlated with discharge and temperature during the reproduction period (April–June): low flows and high temperatures coincided with high fish abundance. Beyond abundance patterns, southern, thermophilic fish species (e.g. chub, and barbel) as well as downstream, thermophilic invertebrate taxa (e.g. Athricops, Potamopyrgus) progressively replaced northern, cold-water fish species (e.g. dace) and upstream, cold-water invertebrate taxa (e.g. Chloroperla, Protoneumura). These patterns were significantly correlated with thermal variables, suggesting that shifts were the consequences of climatic warming. All analyses were carried out using statistics appropriate for autocorrelated time series. Our results were consistent with previous studies dealing with relationships between fish or invertebrates and water temperature, and with predictions of the impact of climatic change on freshwater communities. The potential confounding factors (i.e. dams and the nuclear power plant) did not seem to influence the observed trends.

Long-term changes within the invertebrate and fish communities of the Upper Rhone River: effects of climatic factors

1. Relationships between fish and their habitat over whole geographic regions, which are evident from studies of many streams and species, can improve understanding of lotic communities and provide reliable management tools. Nevertheless, most habitat preference studies have been based on single sites, and confined to small streams and to game species.



2. Regional habitat preference models, based on local velocity, depth and roughness, were developed for twenty-four species and their size classes commonly found in large European streams. Fish surveys were conducted in six large streams in southern France over an 8-year period. To limit the influences of habitat variables other than those studied, we estimated fish preferences within each survey and averaged this information across surveys. Preferences were fitted with confidence intervals and their sensitivity to field uncertainty was evaluated.



3. Most species and size classes had significant preferences for local habitat conditions which were consistent across the region. Habitat preferences predominant in the region overall were not always observed at any one site, but habitat conditions preferred on average in the region were never actually avoided locally. These results support the use of regional preference models for fish and the development of similar models for other lotic groups whose sensitivity to local habitat conditions has been reported elsewhere.

Fish habitat preferences in large streams of southern France

Hydrological and biotic forces constrain brown trout (Salmo trutta) population dynamics, but tests of their role across numerous streams are uncommon. In 30 French stream reaches, using 58 samples...

The influence of hydrological and biotic processes on brown trout (Salmo trutta) population dynamics

1. Bottom-up approaches based on individual behaviour can help to identify key variables influencing populations at larger scales. Instream habitat models have been developed to predict the consequences, for populations in stream reaches, of fish preferences for particular hydraulic conditions observed at the scale of individuals. Conventional instream habitat models (e.g. PHABSIM) predict habitat values for species or life stages in reaches, and their changes with discharge. Despite their worldwide use, they have been subject to continuing criticism and have been mainly limited to site-specific case studies.



2. We ran conventional instream habitat models in 58 French stream reaches dominated by brown trout. Using non-linear mixed effect models, we demonstrated that the outputs of instream habitat models (habitat values for three trout life stages and five other species) are predictable from average characteristics of reaches (discharge, depth, width and bed particle size).



3. Our models closely reflect variations in habitat values within-reaches (with discharge) and between-reaches. Within-reach changes are linked to the Reynolds number of reaches, while between-reach changes depend mainly on the Froude number at median daily discharge. These two dimensionless variables combine discharge, mean depth and mean width of reaches. Independent model validations showed robust model predictions that are consistent with studies of habitat values for brown trout made in larger streams from western North America.



4. Our results contribute to identifying the main hydraulic variables governing estimates of fish habitat values. They should facilitate habitat studies in multiple streams, at the basin or larger scales, while reducing their cost. They should enhance the biological validation of habitat model predictions, which remains critical.

Simple predictions of instream habitat model outputs for target fish populations

Quantitative estimates of habitat suitability in a stream reach generally result from coupling a hydraulic habitat model with a biological model of habitat use. The choice of each of these models has led to much controversy and discussion. Nevertheless, most habitat studies of lotic fish use a deterministic hydraulic model and univariate suitability curves. The objective of this contribution is to present a new, alternative method, which relates statistical hydraulic models to multivariate habitat use models.



Our statistical hydraulic models predict the frequency distributions of hydraulic variables such as velocity or water depth within stream reaches. Their main advantage is the simplicity of their input variables (mainly discharge and average characteristics of the reach). Our multivariate formulation of habitat use models takes into account the local variability of fish habitat, predicting habitat suitability as a function of the frequency distribution of hydraulic variables within the local fish habitat.



We demonstrate how these two model types can be linked to estimate habitat suitability in a stream reach as a function of discharge, focusing on two fish species (barbel, chub) in a regulated reach of the French Rhone River. The main limitations of this new method are a result of mathematical constraints associated with the linkage of the two modelling approaches and to uncertainties in transferring biological models from one stream to another because of insufficient data. Despite these limitations, the method provides solutions to several critical problems facing existing approaches and the simplicity of its input variables can accelerate the validation process of habitat models. Therefore, our first simulations strongly encourage: (i) the use of statistical approaches to describe hydraulic variables; and (ii) the study of multivariate habitat use models that apply to a large variety of streams. © 1998 John Wiley & Sons, Ltd.

Hervé Capra

Papers

Long-term changes within the invertebrate and fish communities of the Upper Rhone River: effects of climatic factors

Fish habitat preferences in large streams of southern France

The influence of hydrological and biotic processes on brown trout (Salmo trutta) population dynamics

Simple predictions of instream habitat model outputs for target fish populations

Predicting habitat suitability for lotic fish: linking statistical hydraulic models with multivariate habitat use models