Reinventing Freshwater Metrics

I came across a recently published article outlining frameworks for a new water availability metric. Unlike most popular water scarcity indexes and metrics, this metric embraces the ecosystem services (ES) approach in recognizing human-environment relationships and the impacts of downstream ecosystem functions degradation. Particularly in line with the module syllabus, I feel like it is appropriate to comment on its findings before continuing the original aims of this blog. 

The paper titled 'Freshwater ecosystem services supporting humans: Pivoting from water crisis to water solutions' was published in Global Environmental Change by Green et.al. and introduces a new metric that incorporates both impacts at point of service and impacts downstream. Recognizing the importance of provisioning ES provided by freshwater ecosystems, the freshwater provisioning index quantifies the provision of freshwater ecosystem services. 

Summary

Freshwater Provisioning Index:

• Traces freshwater sources to point of service and delineates spatial extent of upstream provision areas and downstream beneficiaries
• Calculated by taking into account population density and infrastructure support
• Threat/vulnerability-based - 2 levels of threat identified
• Incident Threat - threat to ES prior to mitigation
• Residual Threat - reduction of incident threat by engineering/management intervention aimed at rehabilitation of ecosystem 

Main Findings:

• Strong positive correlation between level of economic/human development (HDI), downstream population density and incident threat to freshwater ecosystems
• Effective and efficient investments in water delivery infrastructure globally reduced incident threat to freshwater ecosystems with lower overall residual threat
• Countries with low HDI and highly dependent on freshwater resources often lack investments in infrastructure development and thus benefit little from threat reduction (ie. remaining red/yellow in residual threat in map below)
• Near entirety of the world benefits from freshwater sources which are comprised to some extent by anthropogenic activities

Regional Findings (Africa):

• Lack of development and low efficiency in infrastructure results in high residual threat on freshwater ES
• Freshwater ecosystems located upstream of large industrial/population hubs in Africa are among most threatened (indicated by red in map shown below)
• Land use/habitat change is the single most important threat to freshwater provision areas in Africa
• Management should embrace 'service area conservation' - protection of upstream freshwater provision sources (eg. Wetlands in Congo River Basin/Niger River Delta)
• Diseconomies of scale persist in water provision due to lack of appropriate delivery infrastructure and often high water tariffs

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Concluding Thoughts:

This index introduced by Green et.al. 2015 effectively addresses the importance and widespread spatial influence of ES. The positive correlation revealed between HDI and freshwater ecosystem threat also sheds light on a crucial point that the problem of water scarcity in Africa is one of distribution and not quantity. This was echoed in ethnographic studies indicating an overall decline in reliability of water delivery infrastructure over a period of 30 years (Thomson et.al. 2000), leading to high residual threat to freshwater ecosystems.

However, there were some major omissions. Firstly, the index fails to include the relationships between groundwater and the ES it provides despite clear importance of such sources in some SSA nations with little surface water. Secondly, the focus on threats only to provisioning services (ie.water supply) by downstream populations detracts attention to other forms of ES. This may lead to underestimation of threats faced by freshwater ecosystems which may not provide water to a large number of downstream users. Examples of this may include the Amazon Basin in South America, which as seen from the map above, were considered low threat under this metric despite widespread scientific concern of an Amazonian dieback. The same could be said for the Congo River Basin in Africa. Thirdly, population density was included as the major threat to freshwater provision zones, risks neglecting other stressors which may have a large impact to freshwater ecosystems. As the author identified as well, the index could be improved through including downstream volume demand and freshwater sources in storage (GW).

All these potential pitfalls of the metric highlights the challenge of quantifying ES and the difficulty in incorporating all relevant ES. Vollmer et.al. (2016) found substantial variation in the services selected/measured among different ES based freshwater indexes. Apart from water provisioning, other kinds of services provided by freshwater ecosystems have yet to be universally included in water assessments. Lastly, this also raises the question of how best to assess freshwater resources through an ES approach. There are considerable debate surrounding the reduction of services to monetary value and the economic valuation of ES which will be addressed in later posts.

The Physical Distribution of Water Across Africa

In this post, we will discuss the physical distribution of water resources across the continent.

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Global Climate Dynamics

It is far too often when one picture the African continent to immediately reduce it to an extensive piece of land that is eternally dry and water-scarce. In reality, high variability in precipitation and hydrology results in a myriad of different landscapes and ecosystems at different times of the year.

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Precipitation across Africa is controlled by global patterns of atmospheric circulation and the Intercontinental Convergence Zone (ITCZ). The ITCZ is formed at the equatorial trough where deflected moisture-rich northeastern and southeastern trade winds converges after the completion of the Hadley circulation cell. The ITCZ migrates both north and south according to the axial tilt of Earth's orbit as shown in the figure below. This migration controls both intra-annual variability (seasonality) and spatial variability of rainfall across Africa (Taylor, 2004)

Geology and Elevation

Water is distributed across Africa as lakes, wetlands, rivers, swamped forests or reservoirs (Rebelo et.al. 2010). While the regulation of global atmospheric circulation determines precipitation and runoff patterns, the spatial distribution of water resources as lakes or wetlands is primarily determined by local geology and elevation. On the one hand, areas with a rise in elevation would induce orographic rainfall effects with increased precipitation in mountainous regions relative to low-lying adjacent regions. On the other hand, extensive low-lying, low relief surfaces favours ponding and the formation of lakes (eg. Lake Victoria) or widespread floodplains and the formation of wetlands.

Importance

In one of the most recent comprehensive study on the distribution of wetlands and rivers across sub-Saharan Africa, Rebelo et.al. (2010) concluded that lakes, wetlands, rivers and reservoirs is the dominant source of freshwater with a cumulative area of 1,448,771 km2, covering 6% of the African continent. 143 sites in sub-Saharan Africa are designated as Wetlands of International Importance at the RAMSAR Convention. One of the most alarming statistics taken from this publication is that >90% of the listed RAMSAR sites in the region are used for agricultural or fisheries purposes but >70% of which are threatened because of supporting agricultural or fisheries uses. This fully highlights the importance of an ecosystem services approach in which the quantification of monetary value of wetland systems and economic costs of wetland degradation is urgently needed.  

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Owing to global atmospheric circulation, surface geology and elevation, water resources across Africa is highly diverse and plentiful. However, due to seasonal and spatial variability, the distribution of water resources and thus the ecosystem services they provide are not evenly distributed across the continent. This means that different types and levels of access to ecosystems services exists across local regions. Power relations and problems of access will no doubt influence the valuation and economic incentive of ecosystem services which may lead to trade-offs which are detrimental to complex ecosystem functions or other ecosystem resources (Ryan et.al. 2016). 

The following questions will be addressed in the upcoming series of blogs:

1) What are the current status of provision of and access to freshwater ecosystem services in sub-Saharan Africa?

2) How will the provision of ecosystem services change according to changes to people's access of    ecosystems?

3) How does poverty alleviation, agricultural expansion and global environmental change impact the provision of and access to ecosystem services?

4) Is payment for ecosystem services and the economic valuation of ecosystem services the future for sub-Saharan Africa? 

Introduction - An Ecosystem Services Approach

Welcome to my blog! Over the course of my university module on 'Water and Development in Africa', I will be exploring and blogging about the relationships between water resources and various ecosystem services it provides. A wide range of topics and examples will be investigated, ranging from the physical processes generating ecosystem services to possible changes in the provision of, access to and types of ecosystem services provided by water resources in the future depending on environmental change, and socio-economic trends.

Ecosystem Services?

Popularized by the Millennium Ecosystems Assessment 2005, Ecosystem services is defined as:

  

'The benefits people obtain from ecosystems. These include provisioning services such as food and water; regulating services such as regulation of floods, drought, land degradation, and disease; supporting services such as soil formation and nutrient cycling; and cultural services such as recreational, spiritual, religious and other nonmaterial benefits.'

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The ecosystem services approach implies that any changes to the services provided will affect human well-being in some ways, linking the physical distribution of water to socio-economic impacts. Growing demand for ecosystem services may lead to either 1) development at the expense of another resource which may be of equal or even greater importance or 2) simultaneous growth in demand and degradation in resource itself. Despite relying on the provision of ecosystem services, management interventions rarely consider environmental impacts and often undervalues or completely disregard ecosystem services.

Freshwater as an 'umbrella service'

Water is essential to the healthy functioning of the hydrologic cycle and sustains a wide range of freshwater-dependent ecosystems. Water can be viewed as being the 'umbrella service', being the basis to services within both consumptive and non-consumptive uses. The following table taken from IIED, 2007 summarises some of the provisioning, regulating, supporting and cultural services provided by freshwater ecosystems.

Table 1 Source

The ecosystem services approach views ecosystems as provider of marketable goods and services. The concept of valuing nature in monetary terms is highly controversial and while it indeed provides economic incentives to preserve and protect certain ecosystems/resources, critics argue that a neo-liberal approach in commodifying nature may lead to unequal access or even irreversible damage to other natural resources (Gomez-Baggethunand Ruiz-Perez, 2011).


Although an ecosystem services approach is more integrative than approaches dominated by environmental determinism, it should be noted that issues of access and power relations between stakeholders are not directly implied and are often excluded in studies advocating for an ecosystem services approach. Critical issues of this approach will be investigated in later posts.