Ecosystems in the Global Water Cycle

A floating village on the Tonle Sap Lake, Cambodia. Over 1 million people live in the greater Tonle Sap area, making their living primarily from the lake fisheries. ©Vladimir Smakhtin

 

An ecosystem is normally defined as a complex of all living (plants, animals, microorganisms) and non-living (soil, climate) components interacting as a functional unit in a certain area. Each contributes to maintaining the overall ecosystem’s health and productivity. Ecosystems such as forests, wetlands and grasslands play an important role in the global water cycle. Recognizing this role and the interactions between the two is critical to managing water resources sustainably.

It is often conceptualized that ecosystems provide a range of “services” that can be categorized as: i) Provisioning that refers to consumer goods, such as food and water; ii) Regulating that includes, among others, water purification and preventing erosion; iii) Habitat that provides the environment for life cycles of species or maintains genetic diversity, through quality and quantity of natural vegetation or substrate for fish and iv) Cultural that refers, for example, to the aesthetic, tourism and spiritual services (TEEB, 2010).

The estimated economic value of ecosystem services globally, made in 2011, was $124.8 trillion, which was close to double the global gross domestic product in the same year (Costanza and others, 2014). It is widely acknowledged now that various ecosystems, both aquatic and terrestrial, are in decline, primarily due to economic development. There is no shortage of statistics. Since 1900, the world has lost around 50 per cent of its wetlands (WWDR 3, 2009). Between $4.3 and $20.2 trillion per year worth of ecosystem services were lost between 1997 and 2011 due to land use change (Costanza and others, 2014). An estimated 20 per cent of the world’s aquifers are being over-exploited leading, among others, to land subsidence and saltwater intrusion (Gleeson and others, 2012). Over half of the world’s large river systems are adversely affected by dams (Nilsson and others, 2005). Inefficient use of water for crop production has caused salinization of 20 per cent of the global irrigated land area (FAO, 2011). The decline of ecosystems results in a range of adverse impacts on humans, since billions of people live in water scarce regions, and/or areas with high water quality risks (Guppy and Anderson, 2017; Veolia and IFPRI, 2015)

It is common today to hear in scientific discourse about “payment for ecosystem services”, “ecosystem approach”, “green and grey infrastructure”, “nature-based solutions”, and many other terms that directly or indirectly involve the notion of ecosystems (Lautze, 2014). This discourse is a reflection of the growing concern about the status of global ecosystems and increasing understanding of the critical role that ecosystems play in development at large, and in water resources development, in particular.

As a natural [e.g. aquatic] ecosystem is being modified, some of the original services and associated benefits extracted from it are being lost and replaced by benefits from the introduced modifications themselves. However, there is a “tipping point” in this process where the sum of all benefits from an ecosystem reaches the maximum, and when further modifications will only decrease the total flow of benefits (Acreman, 2001). This point is very difficult to identify in practice, which is, perhaps, one of the many reasons for continuing ecosystem decline.

Identification and quantification of services provided by ecosystems may also be important in the political context. For example, a conflict over water in a river can be seen as a conflict over who gains and who loses access to the provisioning service(s) of the river. Tradeoffs between ecosystem services in various water resources development projects, large and small, and associated social conflicts are rather common, as in the case of irrigation and nature conservation, or hydropower production and habitat maintenance.

Ecosystem services, including those provided by aquatic ecosystems, are critical for the survival and livelihoods of the rural poor, and their loss may result in increased poverty. The concept of payment for environmental services is often put forward to address the issue. In a river basin, an urban centre downstream can pay rural communities upstream for storing extra water through managed aquifer recharge structures to reduce the risk or magnitude of flooding (Pavelic and others, 2012), or for various soil conservation practices designed to reduce the sediment inflow to downstream reservoirs. Such schemes are quite difficult to implement though. More importantly, the issue of “ecosystem services” and ideas around putting a price tag on nature may be and are being contested (Kosoy and Corbera, 2010). Also, it is hardly possible to compensate for damage done to an ecosystem due to water resources development, e.g. in cases when a place of water pilgrimage is permanently inundated, or riverine capture fisheries are totally destroyed by water pollution or river fragmentation.

Ecosystem degradation is also a significant source of increasing water-related risks and extremes, such as floods and droughts. Ecosystems can provide natural (“green”) infrastructure that can perform some disaster reduction functions, and therefore partially substitute or augment “grey” (built) infrastructure that targets the same purposes. Combing “green” and “grey” infrastructure, for example in the context of integrated flood and drought risk management in the same river basin, can lead to cost savings compared to grey infrastructure solutions alone (WWDR, 2018). Also, green infrastructure provides functions and benefits that can directly improve the performance of grey infrastructure and can help reduce risks to the latter. It is, however, unlikely that ecosystems alone can achieve the same risk reduction effect as grey infrastructure or totally replace it in the future. Therefore, advocating for ecosystems alone may be too simplistic for water-related disaster mitigation, and can potentially lead to ineffective policies (McCartney and Finlayson, 2017).

There are a number of challenges to large-scale implementation of ecosystem-centric approaches in water management. They include, among others, an overwhelming dominance of grey infrastructure solutions in the current instruments of many States, lack of quantitative evidence on how ecosystem-focused approaches perform, and a lack of capacity to implement such approaches. Many of the above-mentioned concepts are complex, or not yet well developed for practical applications, or simply not known to practitioners and policymakers. Hence, while the science discourse around ecosystems is vibrant, it has not yet caught up with the needs of practice and policy.

A paradigm shift is underway, however, with ecosystems gradually being recognized as an integral part of development solutions. This shift is reflected in global multilateral sustainable development agreements, such as the 2030 Agenda for Sustainable Development (2015), the Sendai Framework for Disaster Risk Reduction (2015) and the Paris Agreement (2015). The focus on ecosystems is explicit in at least 3 out of the 17 Sustainable Development Goals (SDGs) of the 2030 Agenda, but implicit in many others. SDG 6 is a revolutionary step forward in the water development agenda globally. For the first time, it addresses not just the challenges of universal access to water and sanitation, including those remaining from previous decades, but also the issues of resource management, efficiency and freshwater ecosystems.

Target 6.3 of SDG 6 focuses on significant improvement of water quality globally. Target 6.4 promotes efficient use of water by different sectors of the economy. One of its measurable indicators calculates the level of water stress in each country, thus quantifying the pressure on renewable national freshwater resources. Water stress, calculated on an annual time scale, is defined as the total freshwater withdrawn by all sectors divided by the difference between the total renewable freshwater resources and environmental water requirements. The latter is essentially water allocated and provided for the sole purpose of maintaining a freshwater ecosystem in a healthy state (Smakhtin, Revenga, and Döll, 2004). Such an explicit acceptance of the water needs of ecosystems in the global development agenda came from the understanding that balancing the requirements of the aquatic environment and other uses have already become critical in many of the world’s river basins as population and associated water demands continue to increase.

Another related indicator—that of target 6.6—focuses explicitly on the extent of water-related ecosystems and was designed with the specific intention of protecting them, so that they can continue to provide ecosystem services for the well-being of humanity. This includes protecting wetlands, rivers, aquifers and lakes. The indicator for target 6.6 has an explicit link to the water stress indicator of target 6.4.

Although not as explicit, in indicators of target 6.5 on integrated water resources management (IWRM), ecosystem maintenance should naturally be part of it, if such management is to become truly holistic and integrated. To properly practice IWRM, each country or basin authority would need to know, for example, how much water is needed for each ecosystem, so that river water withdrawals and groundwater abstractions can be managed within sustainable limits.

All ecosystem-related targets of the SDGs are voluntary and are not quantified in detail. Many suggested indicators are very simplified models of more ambitiously or generally formulated targets. The time frame of the 2030 Agenda is a challenge in itself. So, it remains to be seen whether we will be able to honestly declare a victory with some of these targets, or whether we will continue quoting the gloomy statistics regarding deteriorating ecosystems. But surely, there is hope.

 

References

Acreman, Mike (2001). Ethical aspects of water and ecosystems. Water Policy, vol. 3, No. 3, pp. 257-265.

Costanza, Robert, and others (2014). Changes in the global value of ecosystem services. Global Environmental Change, vol. 26 (May), 152-158. http://www.sciencedirect.com/science/article/pii/S0959378014000685.

Food and Agriculture Organization of the United Nations (FAO) (2011). The State of the World’s Land and Water Resources for Food and Agriculture: Managing systems at risk. London, Rome, Earthscan and FAO. Available from http://www.fao.org/nr/solaw/solaw-home/en/.

Gleeson, Tom, and others (2012). Water balance of global aquifers revealed by groundwater footprint. Nature, vol. 488 (9 August), pp. 197–200.

Guppy, Lisa, and Kelsey Anderson (2017). Water Crisis Report. United Nations University Institute for Water, Environment and Health, Hamilton, Canada. Available from http://inweh.unu.edu/wp-content/uploads/2017/11/Global-Water-Crisis-The-....

International Food Policy Research Institute (IFPRI) and VEOLIA (2015). The murky future of global water quality: New global study projects rapid deterioration in water quality. A White Paper. Washington, D.C. and Chicago, IL. Available from http://www.ifpri.org/publication/murky-future-global-water-quality-new-g....

Kosoy, Nicolás, and Esteve Corbera (2010). Payments for ecosystem services as commodity fetishism. Ecological Economics, vol. 69, No. 6 (April), pp. 1228-1236.

Lautze, Jonathan, ed. (2014). Key Concepts in Water Resource Management: A Review and Critical Evaluation. New York, Routledge and Earthscan.

McCartney, Matthew, and Max Finlayson (2017). Exaggerating the value of wetlands for natural disaster mitigation is a risky business. The Conversation, 2 February. Available from http://theconversation.com/exaggerating-the-value-of-wetlands-for-natura....

Nilsson, Christer, and others (2005). Fragmentation and flow regulation of the world’s large river systems. Science, vol. 308, No. 5720 (15 April), pp. 405-408.

Pavelic, Paul, and others, (2012). Balancing-out floods and droughts: opportunities to utilize floodwater harvesting and groundwater storage for agricultural development in Thailand. Journal of Hydrology, vols. 470–471 (12 November), pp. 55–64.

Smakhtin, Vladimir, Carmen Revenga, and Petra Döll (2004). A pilot global assessment of environmental water requirements and scarcity. Water International, vol. 29, No.3, pp. 307-317.

The Economics of Ecosystems and Biodiversity TEEB (2010). The Economics of Ecosystems and Biodiversity: Ecological and Economic Foundations. Pushpam Kumar, ed. Earthscan, London and Washington.

United Nations World Water Assessment Programme (2009). The United Nations World Water Development Report 3 (WWDR3): Water in a Changing World. The United Nations Educational, Scientific and Cultural Organization (UNESCO), Earthscan, Paris, London.

 United Nations World Water Assessment Programme (forthcoming), The United Nations World Water Development Report 2018 (WWDR): Nature-based Solutions for Water. The United Nations Educational, Scientific and Cultural Organization (UNESCO), Paris.