3. Freshwater ecosystem services and their Vulnerability

General comments on Chapter 3

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3.     Freshwater ecosystem services and their vulnerability

This section of the report will identify key European freshwater ecosystem services and seek to explain why a thematic assessment of vulnerability is needed for Europe’s freshwater ecosystems and how this contributes to the process leading to the 'Blueprint to safeguard Europe's Water Resources'.

With freshwater ecosystem vulnerability we expand the concept of hazard and risk to humans, towards a more holistic view that incorporates ecosystem services and the susceptibility of a whole environment. It will illustrate why a move towards a risk-based management framework, incorporating fundamental concepts of resilience and vulnerability, could contribute towards safeguarding European waters through more effective freshwater ecosystem management and greater water security.

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This section will explore why some of the many definitions that exist for vulnerability, resilience and related terms, evolving over time and in different disciplines (e.g. climate change) can be applied in such a framework. This report will not, however, go into detail regarding the diversity of different concepts and applications that can exist across scientific and social science disciplines but will use the core concepts of vulnerability as a framework for outlining more sustainable water resource management in relation to ecosystem services.

The first part of this chapter is about freshwater ecosystem services, followed by a section on the vulnerability of water resources. The last section looks at relevant pressures for water resource management and how this affects the freshwater ecosystem services.

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3.1.    Freshwater ecosystems and the central role of water

Water plays a central role in the functioning of the biosphere and in supporting life. The freshwater ecosystems that exist are a result of the hydrological cycle, and these systems provide a unique and diverse array of services upon which human society depends upon. This section outlines the key ecosystem services that freshwater systems provide and how these are increasingly under threat.

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3.1.1.      What are freshwater ecosystem services?

Ecosystems provide valuable goods and services that have a significant, yet often undervalued, contribution towards continued human wellbeing, development, economic security that in many instances cannot be replaced. Attempts at valuing these services at a global level (Costanza et al. 1997) have provided economic valuations in excess of global gross national product. The principal freshwater provisioning, regulating and cultural services on which human development relies are listed below in Table 3.1. Aquatic and terrestrial ecosystems require adequate freshwater resources and flows to maintain the physiochemical processes and functions, species, and communities (Acreman and Ferguson 2010). Human regulation of the water environment and water resource development has affected the ability of many freshwater systems functioning and this pervasive alteration is contributing to significant biodiversity loss and degradation of the goods and services that these systems provide (N. LeRoy Poff et al. 2007). Protection and restoration of these irreplaceable ecosystems is increasingly being recognised as crucial in achieving sustainable development and often provide the most cost-effective options for securing food production and protection from natural hazards (UNEP, Nellemann, and Corcoran 2010).

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Table 3.1 Freshwater-related ecosystem services

Provisioning services                      Examples


Fish, agriculture,

Fuel and fibre

Wood for fuel and building, peat, fodder

Fresh water

Retention of water for domestic, industrial and agriculture


Medicine and materials from biota

Genetic material

Genes for resistance to plant pathogens

Regulating services

Hydrological flows

Groundwater recharge,

Natural hazards

Flood control, storm protection

Sediment transport

Distribution of nutrient rich sediments


Coastal delta maintenance,


Water purification and assimilation of waste

Cultural services


Religion, inspiration, health, aesthetic


Recreational activities, social events

Source: adapted from Millennium Ecosystem Assessment et al. (2005)

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The ecosystem provisioning, regulating and cultural services identified represent the flow of natural capital and stock of materials that humanity relies upon to drive economic growth (Costanza et al. 1997). Identifying and valuing such services represents a step towards what has been termed a ‘green economy’. This represents an economy based upon a realization that maintaining the natural systems that provide humanity with diverse and valuable services is central to sustainable development. The European Union view a green economy as generating growth, creating jobs, and eradicating poverty through investment and preservation of the natural capital upon which long-term sustainable development depends (EC 2011). Maintaining this flow of natural capital is only as sustainable as the ability of ecosystems to regenerate following the extraction of natural capital or recover following natural or anthropogenic disturbance. This ability to recover is the resilience of the system, and it is clear that many global ecosystems have been managed in such an unsustainable manner that once resilient systems are now facing collapse, with particular concern surrounding wild fisheries and freshwater systems (Millennium Ecosystem Assessment et al. 2005). As access to ecosystem services is overexploited there is a resulting degradation and loss of capacity to maintain that service in the future. This ultimately puts the ecosystem and the services it can provide at real threat to profound changes in its form and functioning. Improving the efficiency of resource use and maintaining the resilience of ecosystems are core challenges in moving towards a greener economy that values ecosystem services.

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The Framework for Ecosystem Service Provision (FESP) assesses environmental change driver impacts on ecosystem services and to subsequently identify the most relevant mitigation or adaptation strategies (see figure 3.1). The approach is based upon the DPSIR (Drivers-Pressures-States-Impacts-Response) framework (Stanners et al. 2007) and incorporates the concept of the social-ecological system, whereby human society and natural systems are directly linked. Population and associated economic growth act as driving forces for pressure upon the environment, and society can monitor and evaluate intervention measures. The resulting states and impacts upon the environment have direct implications for human health, development and well-being. Yet providing robust assessments of such potential environmental states and impacts is, however, not a simple process due to the complexity of the interactions in between ecosystem (natural capital), economy (produced capital) and human well-being (social and human capital). The intrinsically link in between these 3 types of capital are central in most interpretations of what Green Economy is and at the core of these links is a dual challenge of (EEA 2012d):

  • ensuring ecosystem resilience of the natural systems that sustain us (and limiting pressure on natural systems so that their ability to function is not lessened);
  • improving resource efficiency (and reducing the environmental impacts of our actions).

Figure 3.1 Framework for Ecosystem Service Provision (FESP)

Source: Harrison and Rubicode Consortium 2012

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Several of the reports EEA in 2012 will deal with the resilience of freshwater dependent ecosystems. While water quality aspects and hydro-morphology are the main aspects defining the status of water bodies as defined by the water framework directive (EEA (report under preparation) 2012a) this report focusses on the quantitative volumes available for the environment. In detail the more extreme situations in terms of water quantity – water scarcity and drought and floods – are assessed in current situation and in relation to the climate change and land use pressures. More about improving water resource efficiency can be found in other EEA reports (most recent: EEA 2012a).

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3.1.2.      Freshwater as the lifeblood of natural and human systems

Freshwater can be considered the bloodstream of the biosphere, providing pathways for physical, chemical and biological processes that maintain ecosystems (Falkenmark 2003), Humans are reliant on the biological systems and processes this biosphere and associated ecosystems provide, which are essentially life-support systems that provide the bulk of renewable resources and regulating services upon which the continued development of human society is based. In this regard, the water resource flow acts as a global conveyor of physical and chemical services between the atmosphere, terrestrial and aquatic environment, as illustrated in Figure 3.2. These systems are both dynamic and interacting but there are the increasing impacts of human development (see section 3.1.3) on the quantity and quality of freshwater available. The fluxes cannot be maintained and are changing in volume and quality which is increasingly having negative impacts upon the natural environment and the ecosystem services society depends upon (N. LeRoy Poff et al. 2007).

Figure 3.2 Schematic illustration of water as the bloodstream of the biosphere

Source: Falkenmark 2003

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3.1.3.      Human development and freshwater ecosystem services

Water has always been essential to human development and remains central as the link between food, energy, climate, and economic growth – a nexus of issues that is increasingly being identified as a threat to human security due to over exploitation and poor management of freshwater resources. Water resources as natural capital and providing ecosystem services is influenced by and influences environment policy priority areas like climate change, nature and biodiversity, natural resources and waste and health and quality of life (EEA 2010b; EEA 2010d). The international nature of trade places particular vulnerability on the areas that suffer low water availability or extreme hydrological variability yet exploit a high proportion of their water resources for production of agricultural and industrial products.  This in turn increases the vulnerability of economies that depend upon resources from these water stressed regions. Economic, social, political, technological and environmental trends on a global scale (EEA 2010b; EEA 2010d) are driving forces with effect on climate, land use, and demographic changes; identified as key pressures on water availability and hydrological variability.  The recently published European Environmental Indicator Report (EEA 2012d) outlines that while progress in ensuring greater resource efficiency is clear the evidence for improvements to ecosystem resilience is lacking. The report identifies that human demand directly competes with ecological systems’ demands.

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Water has increasingly become an international concern, as shocks such as droughts and floods in one country can have international repercussions. Such dependency and potential disruption will increase with growing population and resource requirements and is predicted to be further exacerbated by climate change (Vörösmarty et al. 2000). These shocks will cause more indirect impacts upon the natural services and capital lost through disturbance to ecosystems. This could result in a potential chain-reaction of events across globalized systems of trade, driving increased vulnerability for those dependent on affected services. As the true value of ecosystem services has only recently been recognised it may yet be a long time before they are properly accounted for in more sustainable management decisions and incorporated into international trade within ecosystem services. Various accounting tools and methodologies have been proposed that can assist our understanding of how to value water in an international trading environment, such as the Water Footprint concept (Hoekstra and Chapagain 2006; Hoekstra and Mekonnen 2012), which is essentially a conceptual way to communicate water use. While this approach provides a useful tool with which to raise awareness of how water is utilized and traded at the international level it should not provide any indication of how water footprints affect water supply or requirements of ecosystems (EEA 2010a). Freshwater and the ecosystem services it provides are therefore an international concern, for agricultural and energy sectors as well as domestic consumption, and this global dimension and nexus of issues surrounding water vulnerability will increasingly need to be considered in any policy trade-offs.

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3.2.    Vulnerability, Resilience and adaptive capacity – managing for variability

The preceding section has introduced the concept that anthropogenic disturbance of natural ecosystems can significantly affect the ability and vulnerability of such systems to sustain their functioning and to recover following disturbance. This section seeks to ‘un-package’ what these terms imply for the management of freshwater ecosystems, particularly considering the high level of natural hydrological variability that can occur. Freshwater ecosystems and the services they provide society are constantly affected by natural changes in the environment such as seasonal changes in flow or extreme hydrological events such as floods and droughts. This variability in quantity, timing and quality is a central part of what drives the unique ecosystems that can exist (N. Poff 2009), renewing and sustaining higher ecological functioning. These systems are also increasingly under threat from anthropogenic disturbance of such natural variability, particularly where more static environmental conditions are created in order to maintain more dependable water supplies (e.g. abstraction for agriculture, reservoirs) or provide flow regulation (e.g. dams, weirs). While such intervention might serve to reduce the vulnerability of human populations to extreme hydrological events, the vulnerability of the natural environment to such shocks can be increased - with repercussive impacts upon parts of society that depend on the services these affected ecosystems provide. The aim of this section is to outline the fundamental concepts relating to ecological and social vulnerability and how these relate to the growing awareness that managing for hydrological variability is a central part of sustainable water management.

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A variety of definitions exist for Vulnerability according to the specific context. The United Nations International Strategy for Disaster Reduction (UNISDR 2009), for example, defines vulnerability as the characteristics and circumstances of a community, system or asset that make it susceptible to the damaging effects of a hazard. The Intergovernmental Panel on Climate Change defines vulnerability to climate change as the degree to which a system is susceptible to, and unable to cope with, adverse effects of climate change, including climate variability and extremes. Vulnerability is a function of the character, magnitude, and rate of climate change and variation to which a system is exposed, its sensitivity, and its adaptive capacity (IPCC, Bernstein, et al. 2008). While being aware of the different definitions and concepts of vulnerability, we do not use a specific definition or concept stringently in this report but rather use the term in a more generic way (EEA 2012c; EEA (report under preparation) 2012b) (see also Figure 3.3).

Figure 3.3 Conceptual schemes of the components of vulnerability in relation to water scarcity and floods

Source: adapted from Füssel and Klein 2006; Metzger et al. 2006; Uyttendaele et al. 2011

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In the same way, Resilience - in a more generic way - is described as the ability of a social or ecological system to absorb disturbances while retaining the same basic structure and ways of functioning, the capacity for self-organisation and the capacity to adapt to stress and change (EEA 2012c).

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3.2.1.      Social vulnerability and resilience

The transformation of natural systems in order to improve socio-economic development often results in a wide range of detrimental impacts upon natural systems (Rapport and Singh 2006). Efforts to reduce these negative impacts require conceptual frameworks that acknowledge coupled human-environment systems and the complex linkages that exist between them (Turner et al. 2003). The social-ecological system, is the proposed analytical unit that comprises societal (human) and ecological subsystems in recursive feedback (Gallopín 2006; Alessa et al. 2008). Fundamentally the social-ecological system acknowledges that ecological and social vulnerability are inextricably inter-dependant, and building resilience in either system requires management that accounts for both components.

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The concepts of social vulnerability and resilience have evolved from integrated considerations of ecological resilience and human vulnerability to natural hazards and climate change. Social vulnerability can be defined as focusing on the demographic and socio-economic factors that act to mitigate or augment the impacts of natural hazards (Uyttendaele et al. 2011). Thus, social vulnerability represents the susceptibility of community to harm from exposure to hazard, and is a function of the sensitivity and adaptive capacity of society. It implies that while such interlinked social-environmental systems are characterised by non-linear relationships, thresholds and uncertainty, the resilience of a group is the ability to respond to, and recover from, hazards and represents an opportunity for innovation and development (Folke 2006). Therefore, considerations of social vulnerability imply a move away from control of stable systems, towards managing the capacity of social-ecological system to adapt to and even shape change (Walker et al. 2004).

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Based on the work of Adger (2000) the variable components that define the resilience concept are illustrated in figure 3.4. Early definitions employed the measure of resistance to denote the degree of disruption the system can tolerate before a significant change past a threshold takes place. The inclusion of the social-ecological interactions incorporates societies potential response when exposed to a hazard - recovery indicates the preservation and restoration of fundamental structures and functions, while creativity is the ability of resilient communities to improve their capacity for response. A resilient system can also return to a state of higher functioning that is less vulnerable, and this is a function of the creativity or adaptive capacity of the system.

Figure 3.4 The components of resilience

Source: FREEMAN project / Uyttendaele et al. 2011; CRUE, Thieken, and Beurton 2012

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3.2.2.      Introducing ecological resilience and vulnerability

It has long been understood that ecological systems are not stable assemblages of species in a static environment; rather they are dynamic systems able to withstand stress and shocks yet still maintain function and remain within a general state. Ecological resilience denotes the capacity of an ecosystem to withstand disturbance without changing self-organized processes (Gunderson 2000). The terms resilience, vulnerability and adaptive capacity of ecological systems to both natural and anthropogenic stressors were introduced into the ecological literature by Holling (1973) to explain how a natural system functions and changes over time in response to such disturbance and naturally fluctuating environmental processes.

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A fundamental concept in considering ecological resilience is that while stability is defined as a system near to an equilibrium state that we might consider the reference condition, resilience is most often thought of as the amount of disturbance a system can be subjected to before a change in state occurs (Gunderson 2000). A certain amount of caution should be exercised in not interpreting this equilibrium state as good ecological status (GES), as the environment could already have been significantly affected and thus already be in an altered stability domain. Folke (2003) illustrates in figure 3.5 how humans can drive a decrease in resilience that ultimately leads the ecosystem into a different state, termed ‘stability domain’. As phosphorus accumulates in the soil and mud of the lake system the stability domain is reduced and the subsequent pressure of flooding or over exploitation of predators causes the system to shift into a turbid eutrophied water state.

Figure 3.5 Shifts between states in lakes from human-induced reduction of resilience

1 – free flowing river   2 – regulation, over-exploi-      3 – decreased variability         4 – regulated water-
                                     tation of flow, pollution            increased episodes of low,       course with low
                                                                                 flow, drought and flooding       genetic diversity

Source: ETC/ICM, Based on Folke 2003
Note: The figure is an illustration using the ball and cup view of stability. Valleys are stability domains and balls the system, with arrows indicating disturbance. Engineering resilience is defined by the slopes, while ecological resilience is the width of the stability domain (Gunderson 2000).

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In terms of how the concept of resilience applies to a European freshwater river, we can consider the different stages and states that exist as a free flowing and naturally variable system gradually becomes a more regulated and exploited river - and the associated impacts due to such anthropogenic regulation. As the freshwater system becomes over exploited and regulated to meet anthropogenic demands the natural variability is removed, flow is reduced, and pollution events become more regular and less diluted. Such changes erode the systems resilience to further disturbance and ecological research has shown that faced with a sudden event, such as a flood or prolonged drought, a threshold can be reached causing the system to slide into a reduced state of functioning (Scheffer et al. 2001) – reflected in reduced species diversity and loss of habitat.

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Box 3.1: Change in ecological state - eutrophication of rivers

The increases in the primary production (eutrophication) of water bodies, such as algae and rooted plants, due to significant nutrient inputs is a serious consequence of increased pollution loads in many water bodies. Eutrophication can have significant economic impacts on society and communities that depends on freshwater from affected sources. From the current understanding of lake systems the pre-dominant cause of shift from a macrophyte to phytoplankton dominated system has been identified as the development of algal growths on macrophytes which effectively reduce the available light. There are, however, multiple stable states that can exist between these two extremes, representing interaction between phytoplankton biomass, turbidity, light availability, grazing macroinvertebtates and the feedback effects that exist.

A conceptual model of how eutrophic conditions develop in short-retention-time river systems has been developed by Hilton et al. (2006), based upon the literature available. While there is agreement that nutrient increases are required to develop eutrophic conditions to develop, there is in fact a lack of evidence in short-retention-time rivers and that in fact the interaction of hydraulic drag with light limitation is the most significant factor. The impacts of this interaction and the types of macrophytes that exist through these changing states are shown below in figure 3.6, from a clear flowing river containing tall submerged plants (A) towards dominance of floating leaved plants (B) and emergent plants (C) and finally a river with high nutrient loading dominated by filamentous algae (D). Thus while the lower reaches of long slow flowing or impounded rivers tend towards phytoplankton domination under nutrient-enriched conditions, these short-retention-time rivers should tend towards a dominance of benthic algae driven primarily by the development of epiphytic algal communities reducing light availability. What is also clear from this research is that there are multiple interacting processes involved in the gradual eutrophication of short-retention-time rivers, highlighting the complexity of the system and the difficulty in pinpointing how exactly such a system will respond to anthropogenic disturbance and what essentially constitutes a loss of resilience.

Figure 3.6 Changing states in a river system

Source: Hilton et al. 2006 (text and photos) 

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3.2.3.      Environmental flows and natural variability

Ecologists now better understand how flow regime and natural variability, especially the extremes in form of floods and droughts, can be important determinants for ecosystem structure and resilience. A more holistic understanding of ecosystem health has led to a paradigm shift in ecosystem management that considers whole ecosystems containing diverse species with variable flow preferences, sustained by a dynamic flow regime (N. Poff 2009). The variation in flows can act to rejuvenate and maintain aquatic habitats, and changes to the timing of flows can have some of the most significant impacts on freshwater ecosystems (N. Leroy Poff and Zimmerman 2010). Extreme events can exert a selective pressure on ecological populations, renewing biodiversity and building resilience in the system. A shift in thinking is required that moves management interventions away from hard-engineered control in all situations, to accepting change is inevitable (Folke 2003), and to accept that variability can be beneficial. This variability must however be balanced against the requirements for society to be protected against the most extreme events, something that will not always be possible through more ‘soft’ interventions. Reducing human vulnerability to floods through ‘hard-engineering’ options like dams, dikes or channelization could, for example, lead to a reduction of ecosystem functioning (e.g. flow regulation, loss of floodplain connectivity). More examples can be found in chapter 5.2 on flood risk management.

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Maintaining the environmental flows that provide freshwater ecosystem services is an essential element in preserving the biodiversity and ensuring resilience to uncertain futures and system shocks. The term environmental flows emerged to emphasise that a share of the water moving through an environment should be allocated to natures requirements if the goal of integrated water resource management is to be realized (Bernhardt et al. 2006). Such requirements are central to the Water Framework Directive (WFD) goal of Good Ecological Status, despite not explicitly using the term (EC 2000). A key issue however in actually achieving such ecologically acceptable flows depends on how they are defined and implemented. Incorporating elements of natural variability and resilience provides a more realistic and perhaps achievable way of assessing how vulnerable freshwater ecosystems are and what would be the most appropriate improvement interventions.

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3.2.4.      The role of vulnerability assessments

In considering climate change and its impacts on society and the environment it became clear in the climate change debate that the severity of impacts depended not only on the event extremity but also on the exposure and sensitivity of the affected systems (see also figure 3.3). Vulnerability was thus raised as a central concept in climate change policy through article 4.4 of the United Nations Framework Convention on Climate Change (UNFCCC) and adaptation for vulnerable countries (UN 1992), and became a central theme in the ‘Climate Change 2007 – Impacts, Adaptation and Vulnerability report’ (IPCC 2007). These documents evaluate key vulnerabilities to climate change and highlight the role of stresses. Vulnerability assessments and the indicators they provide are widely perceived as providing the preferred bridge between academic work and policy need - synthesising complex data into a single index that can be applied by policy makers and managers (Hinkel 2011). The recent IPCC special report on managing the risks of extreme events and disasters (IPCC 2012) exemplifies the standardised use of vulnerability assessments to a particular topic of risk, namely climate change. It moves beyond merely considering the direct risk to society from increased hazards towards considering how such events can affect vulnerability to future extremes by modifying the resilience and adaptive capacity of affected societal or ecological systems.

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There is considerable scope for developing vulnerability assessments to assess policy trade-offs and particular need to represent the interactions between society and ecological systems. A range of vulnerability assessment models exist, with the requirement that such assessments be enlarged and revised to include the capacity to consider coupled human-environment systems. A revised assessment architecture is proposed, that incorporates: i) links with broad human and biophysical conditions; ii) perturbations and stressors that emerge from these processes and condition; and iii) the coupled system in which vulnerability rests (Turner et al. 2003). Although comprehensive, such a methodology clearly illustrates is the complexity of managing water in a coupled human-environment system, and the need for freshwater policy to consider vulnerability if sustainable management and informed policy trade-offs are to be achieved.

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3.3.    Environmental pressures and environmental change

3.3.1.      Natural variability, pressures and perturbations

The natural environment is highly variable in time and space, and can change slowly over time as a result of a continuously increasing pressure (stressor) or during major events (perturbation) outside the normal range in which the system exists (Turner et al. 2003). While perturbations such as major floods and droughts clearly exist outside of the local social-economic-ecological system, these events could be considered internal phenomena for the global level (Gallopín 2006). These perturbations represent direct hazards to human settlements and typically require engineering solutions to reduce the sensitivity and exposure of population and infrastructure; such is their potential for human and economic loss. More gradual changes, such as decreased groundwater availability, are typically a function of how the social-economic-ecological system operates and represent over-exploitation and mismanagement of natural resources.

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Large scale changes in ecosystem service supply are expected across Europe as a result of changes in climate and land use, leading in most cases to increased vulnerability to reduced services provided (Metzger et al. 2006), especially in the Mediterranean region (Schröter et al. 2005). A multitude of human activities denoted direct drivers by Postel and Richter (2003), can have adverse impact on the freshwater environment and the resulting ecosystem services (see table 3.2). These activities generally represent the replacement of naturally functioning systems characterised by high levels of variability and resilience with more regulated systems engineered solely for human requirements (Millennium Ecosystem Assessment et al. 2005). Such regulations reduce the amount of freshwater available for ecosystems and the remaining water is subject to a highly unnatural regime. These activities reduce the resilience of naturally functioning systems to perturbation events, and in some cases this causes greater vulnerability to the society that depends upon those services that would act to mitigate and attenuate such events.

Table 3.2 Summary of direct drivers

Source: Postel and Richter 2003

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Box 3.2: Long-term studies of Lake Windermere, Cumbria, United Kingdom

Lakes provide essential ecosystem goods and services on which humans depend, and are integral to many global biogeochemical cycles, yet are sensitive to environmental perturbation operating at global, regional and local scales, many resulting from human influence. Such pressures from human activity and long-term background changes can degrade ecological status, a loss that arisen in part due to the underestimation of ecosystem goods and services that are not fully accounted for. The complex web of external pressures and internal interactions that control the biological structure and ecological function of lakes requires a ‘systems approach’, where different trophic levels are studied and different approaches including long-term monitoring are taken (Maberly and Elliott 2012). This complexity can result in dramatic shifts in the functioning and structure of such systems. Long term monitoring is key to understanding and developing insights into how systems react to change in the environment and external stressors.

Figure 3.7 Views over the Windermere lake system and catchment

Copyright photos: CEH

Long term monitoring of Windermere since 1945 has revealed that eutrophication of the lake started before monitoring and was driven by nutrient enrichment from population increases, sewage disposal and agricultural intensification. Since then nutrient enrichment has enhanced the lake response to meteorological change (McGowan et al. 2012). Climate change impacts have been picked up in Blelham Tarn (Foley et al. 2012) showing that over 40 years the duration of stratification had increased by nearly 40 days, as had the hypolimnetic anoxia period. Another study of Daphnia galeata (Thackeray et al. 2012) data collected over 80 years indicated change in nine of ten phonological metrics, primarily driven by phytoplankton phenology and spring water temperature, both linked to climate change.

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3.3.2.      Tipping point or gradual change?

Ecosystems can change gradually over time or may have a tipping point that can be triggered by an extreme event or meeting a certain threshold value for an important system component. The external drivers discussed in section 3.3.1 can change gradually over time (e.g. habitat fragmentation, overharvesting) or represent a catastrophic change to the system (e.g. dam installation, significant pollution event). Natural perturbations’ such as floods and droughts can cause a significant shift in the timing, quantity and quality of flows in river systems. However change is caused or manifests it will to differing degrees upset the functioning state of the ecosystem in some way and cause a reduction in resilience. Ecological research has shown that with reduced resilience from human alteration of the freshwater system a sudden event may trigger a critical threshold to be reached from which the system will move into a less desirable state with reduced ecosystem service provision (Scheffer et al. 2001). Much of this can be explained by considering the pathways in which the system is able to return to a previous state and how particular species can re-colonize. Any disturbance in a natural system will act like a selective force, moulding traits so that species can persist. This can be expressed in traits such as resistance to high flow and capacity to recover following a flood, or resistance to high temperatures and low oxygen during droughts (Lake 2007). Also important are the availability of refugia that bolster resilience after disturbance by providing sources for decolonization after the disturbance. Any reduction in the natural flow regime will thus render a less adaptive set of species to flood events or low flow conditions. Also by un-coupling the river form the floodplain in order to provide flood defence structures there is a reduction in the availability of refugia and re-colonization pathways for biota following either a gradual change or extreme event.

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3.3.3.      Climate change

Any change in climate will lead to changes in regional weather and have range of associated impacts upon society and the environment. There is considerable evidence that the world’s climate and weather are continually changing as a result of naturally fluctuating climatic systems and due to the anthropogenic emission of carbon dioxide driving a global trend in temperature increases. The complexity of what drives these changes leads to significant uncertainty when attempting to predict future patterns of change. This uncertainty is amplified when considering the impacts upon the hydrological cycle and the associated impacts upon society and freshwater ecosystems. The IPCC Fourth Assessment Report on impacts, adaptation and vulnerability (IPCC 2007) chapter on Freshwater resources and their management identified vulnerabilities of freshwater to climate variability from changing precipitation patterns and greater year-to-year hydrological variability. While this is most apparent in semi-arid and low-income countries, the fact that water infrastructure is generally designed for stationary conditions means there exists a high degree of sensitivity and vulnerability to uncertain non-stationary future conditions driven by climate change. Changes to hydrology identified include (IPCC 2007):

i.   Changes in volume, intensity, type and timing of precipitation will alter river flows and resultant wetland and lake levels;

ii.  Temperature, radiation, humidity and wind speed changes will affect the hydrological cycle and further exaggerate impacts of decreased precipitation;

iii.  Groundwater is less directly affected but can become more strongly relied upon to provide secure access to freshwater;

iv.  Increased variability and intensity of precipitation is projected to increase flood risk and drought;

v.   Water quality will be significantly affected by multiple stressors such as higher temperatures, increased low flows, more intense rainfall all exacerbating many forms of water pollution.

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Significant progress has been made since the release of the IPCC fourth assessment reports (AR4) (IPCC, Bernstein, et al. 2008) that outlined the physical basis and the impacts, adaptation and vulnerability in ascribing confidence to the direction of change and associated impacts. Both the data sets and climate models have progressed, as has the terminology used to ascribe confidence in the available evidence. A recent IPCC document (Mastrandrea et al. 2010) provides guidance for the treatment of uncertainties for the AR5 authors, whereby the evidence type, quality and consistency are combined with an assessment of agreement between evidence. There are also more rigorous statements to indicate the likelihood of a potential outcome using probability criteria. While the AR5 is still in development a special report on the risks of extreme events and disaster (IPCC 2012) updates the global assessment, with more rigorous terminology and consideration of the role of vulnerability and exposure in determining risk and impact. The salient points concerning water vulnerability in Europe are listed below;

i.    Exposure and vulnerability are key factors determining risk to hazards and associated impacts;

ii.   Extreme and non-extreme weather or climate events affect vulnerability to future extremes by modifying resilience, adaptive capacity and coping capacity;

iii.  The severity if climate extremes impacts depends on the level exposure and vulnerability to extremes;

iv.  Attention to temporal and spatial dynamics of exposure are particularly important when designing risk management policies that may reduce risk in the short-term, but increase long-term vulnerability (e.g. dike systems reduce flood exposure, but encourage settlement patterns that could lead to an increase in flood risk);

v.   Climate change leads to changes in the frequency, intensity, extent, duration and timing of extreme weather and climate events, and can result in unprecedented extremes;

vi.  Exposure and vulnerability are dynamic, varying across spatial and temporal scales;

vii. There is limited to medium evidence of climate-driven changes in magnitude or frequency of floods at regional scales – however, there is medium confidence that projected rainfall increases will lead to increases in certain catchments;

viii. There is medium confidence that droughts will intensify in the 21st century, particularly in southern Europe, the Mediterranean and central Europe;

ix.   Extreme events will have the greatest impacts on sectors with close links to climate, such as water, agriculture and food security;

x.   There is high confidence that changes in climate have the potential to seriously affect water management systems, however this is not necessarily the most important driver of change at the local scale.

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Box 3.3 The United Kingdom Climate Change Act 2008 – Climate Change Risk Assessment 2012

The United Kingdom has undertaken an extensive climate risk assessment (Department for Environment Food and Rural Affairs 2012) that assess the potential impacts and opportunities of climate change to key themes that affect future UK development and security. The need to embrace long-term planning and better understand risks is viewed as critical in ensuring a resilient society and environment. This will be achieved using a risk-based approach, with the government leading a National Adaptation Programme to be published in 2013. The key risks to water and freshwater systems identified within the themes considered for the UK include:

Natural Environment - the direct and indirect impacts of climate change on the natural environment could be significant by the 2050s, potentially further exacerbating existing pressures on ecosystems and contributing to the further decline of some species. Key impacts include i) low water levels and reduced river flows leading to increased concentration of pollutants from agriculture, sewage and air pollution damaging freshwater habitats and other ecosystem services; ii) warmer rivers, lakes and seas impacting on biodiversity and the productivity and functioning of aquatic and marine ecosystems; iii) possibility of algal blooms, ocean acidification and species range shifts impacting on marine habitats, species and ecosystem services; iv) changes in timing of seasonal events and migration patterns can result in mismatches between species such as predator-prey/host relationships.

Agriculture & Forestry – could be affected by both extreme weather events and gradual climate change, particularly beyond 2050. Key impacts include i) higher summer soil moisture deficits, increasing demand for irrigation to maintain crop yields and quality; ii) crop losses and other impacts on high quality agricultural land due to flooding and agricultural land lost to coastal erosion; iii) increased competition for water resources in the summer owing to reduced summer rainfall and the need to address unsustainable abstraction; Drier conditions and any increase in the frequency of drought will reduce agriculture and timber yield and affect woodland condition.

Buildings & Infrastructure - buildings and infrastructure will be affected by both extreme weather events and long-term gradual change in the climate. The challenges arise from higher temperatures and changing rainfall patterns.

Business &Services - main water related risks and opportunities to the Business sector are related to flooding and water resources.

Health & Wellbeing - will be affected by both extreme weather events and long-term gradual change. The main challenges arise from higher temperatures (on land and sea), changing rainfall patterns and rising sea levels

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The impacts of climate change on freshwater ecosystems are difficult to discern due to the complexity of the systems and the uncertainty concerning the effect of climate change on the hydrological cycle. What is generally agreed is that increases in temperature and changing precipitation patterns will lead to changes to the quantity, quality and timing of freshwater flows in the environment. These changes can have a range of eco-hydrological impacts upon freshwater systems outlined in table 3.3.

Table 3.3 Key eco-hydrological impacts of climate change

Source: WWF / Le Quesne et al. 2010

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3.3.4.      Land use change

Amongst many aspects of global change, land use change has a key human-induced effect on ecosystems ((Lambin et al. 2001)). Changes in climate and land use can result in large changes in ecosystem service supply often going together with an increased vulnerability of these ecosystems. The provision of many ecosystems services relies directly on land use ((Metzger et al. 2006)). When socio-economic scenarios and climate models are combined on the local scale and for the next decades the socio-economic changes often seem dominant in their effect on future land use and land use changes (Schröter et al. 2005). Metzger et al. (2006) made scatter plots for different categories of ecosystem services for different European regions and different socio-economic scenarios. The vulnerability shows a tension around economic growth in southern Europe. Economic growth can indicate more technological developments, infrastructure, equity and power, combined in a higher adaptive capacity (Metzger et al. 2006). At the same time, the socio-economic scenarios with the largest economic growth are the ones with most pronounced land use changes and largest negative potential impact on ecosystem services (Metzger et al. 2006)

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Water resources and spatial planning have for a long time been seen as 2 separate management problems (Valenzuela Montes and Matarán Ruiz 2008). A modern view on land-use policy aims at getting a sustainable harmonization of economic, social, cultural and environmental interests in the society at regional to local level (Viglizzo et al. 2012). Integrated water management regards the spatial correlations between water and spatial development and doing so take into account the WFD (EC 2000) as well as the EU Strategic Environmental Assessment Directive (EC 2001). Land use changes can seriously influence both low flows and water availability as floods and inundations, especially when land use changes means sealing of soils and transforming open areas – like agriculture or nature – into urban areas, industrial zones or construction sites often going together with increased soil sealing. Sealing of soils by impervious materials is, normally detrimental to its ecological functions. (Scalenghe and Marsan 2009) as these modifications are fundamental in determining the rate of water intake into the soil. Most soil sealing is anthropogenic covering areas permanently or temporarily. An example of this latest is plastic sealing in agriculture as protective cover to adjust soil temperature, to control erosion or to control weeds. The sealing of surfaces also has evident consequences on neighbouring areas, as they increase the amount and the speed of the runoff water, increasing the risk of ponding and erosion in the unsealed neighbourhoods (Scalenghe and Marsan 2009). In addition the proximity of unsealed areas to pollution sources such as roads exposes them to pollution (Wolf et al. 2007). But an unsealed soil, managed appropriately can buffer (smaller) flooding and mitigate or reduce the transfer of pollutants. When not managed appropriately they can exacerbate problems acting as a source of nutrients, pathogens and sediments polluting groundwater resources. (Haygarth and Ritz 2009)

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Changes in size of population (and the resulting size of households and changes in behaviour) as well as changes in the activities of different economic sectors may lead to urban and infrastructure expansion. As there is no precise information on soil sealing, often the evolution of built-up areas is used as a proxy (Scalenghe and Marsan 2009). Intensive impermeabilisation of urban areas also put additional pressure on sewage systems – by increased speed and amount of runoff - increasing the risk of urban flooding (Natale and Savi 2007). This can also have consequences for the water quality due to direct runoff and reduced filtering capacity water passing through the soil (Gaffield et al. 2003). In paved areas, impervious areas can be reduced with semi-pervious systems that allow water infiltration (Nehls et al. 2006). Other systems are adopted from agricultural techniques like amendments of gypsum (Singer and Shainberg 2004)or shallow tillage (disrupting the seal and returns infiltration).

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In general, forests and afforestation are seen as positive for the water balance and the hydrological cycle. Nevertheless, little is known about the quantitative changes in nutrient and hydrological budgets following changes in land use (Van der Salm et al. 2006). The same can be said for agriculture, where there’s a lack of integrated quantitative understanding of how agricultural modifications of the hydrological cycle regulate the prevalence and severity of abrupt changes in ecosystems (Gordon, Peterson, and Bennett 2008). Compaction as a result of intensification of agricultural practices (by livestock or machine wheels) affects water supply regulation (Haygarth and Ritz 2009).

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Water plays a major role in sustaining ecosystems services (Gordon, Finlayson, and Falkenmark 2010) and maintaining their resilience to cope with extreme drought or floods (Folke et al. 2002). Maintaining ecosystem services in an agricultural landscape is helpful in managing water resources (Rockström et al. 2010).While a River Basin Management Plan makes an overview of a whole river basin district, independent of administrative internal boundaries, IWRM should also focus on downscaling to smaller areas (generally below 1000 km²) when it comes to measures to identify win-win opportunities between upstream and downstream areas. An example can be upstream green water investments like water harvesting with implications for downstream uses like reduced sedimentation. (Rockström et al. 2010)

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Land use changes are complex phenomena in space and time. E.g. the scenarios set up by Metzger et al. (2006) were developed for analysis at European scale. While this overall picture is their strength, the ignored regional heterogeneity and the limited number of distinguished land use classes are a weakness. They (Metzger et al. 2006) clearly state that more specific ecosystem services, especially these related to biodiversity and nature conservation, are hard to asses in a European scale study.

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Land use has and will have an important influence on ecosystem services in Europe, although with large differences for different regions and across the services. (Metzger et al. 2006) Different land use scenarios and more or less (or different) land use changes have in most European regions a different potential impact on ecosystem services where the most notable distinctions are caused by the differences in between a more economic versus a more environmental friendly development (Metzger et al. 2006).

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