Wetlands in drylands: how good is the service?

Monday 17th November 2014

The Vaal River, South Africa: an important ecosystem service provider in a dryland setting

The Vaal River, South Africa: an important ecosystem service provider in a dryland setting

Around 1800, the world’s population reached one billion for the first time.  Just over 200 years later, this figure exceeds seven billion … and is still rising.  With such explosive growth, human activities such as agriculture, mining, dam building, manufacturing and urbanization have had profound, long-lasting, negative impacts on the natural environment.  Decades-old worries over air pollution, soil contamination, and the hole in the ozone layer almost seem quaint by comparison with ever-more-urgent concerns over issues such as groundwater depletion, species extinctions, and a warming planet.  At the same time, there is growing recognition that human wellbeing is partially dependent on a healthy natural environment.  Wellbeing includes the obvious physical aspects, but also more subtle mental aspects.  As an example, the term ‘nature deficit disorder’ has arisen amid growing concerns that humans, especially children, are spending less time outdoors, resulting in a wide range of behavioural problems (see http://www.bbc.co.uk/news/science-environment-17495032).

Against this backdrop, the term ‘ecosystem services’ has entered the scientific domain, and is defined as the benefits that people obtain from ecosystems.  The Millennium Ecosystem Assessment (MEA) – a four-year (2001-2005) collaboration involving more than 1360 experts worldwide – provided a state-of-the-art appraisal of the condition of the world’s ecosystem services, and assessed the consequences of ecosystem change for human wellbeing (http://www.millenniumassessment.org/en/index.html).  The MEA classified ecosystem services into four main types: provisioning, regulating, supporting, and cultural.  It also noted that although the human species is buffered against environmental changes by culture and technology, it remains fundamentally dependent on the flow of ecosystem services.

Diagram from the Millennium Ecosystem Assessment illustrating how many aspects of human wellbeing are dependent on provisioning, regulating, cultural and supporting ecosystem services

Diagram from the Millennium Ecosystem Assessment illustrating how many aspects of human wellbeing are dependent on provisioning, regulating, cultural and supporting ecosystem services

Alongside coverage of various terrestrial and marine ecosystems, the world’s wetlands (defined broadly by the MEA) received special consideration.  The marshes, fens, swamps, peatlands, shallow water bodies and rivers in tropical, temperate and arctic regions were noted as delivering a wide range of ecosystem services, such as fish and fibre, water supply and purification, flood and climate regulation, coastal protection, and recreational and tourism opportunities.  But within the voluminous MEA volumes (the specific ‘Wetlands and Water’ synthesis volume alone runs to 68 printed pages), just how comprehensive was coverage of wetlands in drylands?  Drylands are the world’s extensive hyperarid, arid, semiarid and dry subhumid regions, and so while ‘wetlands in drylands’ sounds like a contradiction in terms, wetlands in fact can form and persist wherever a positive water balance exists for at least part of the year.  In many drylands, this most commonly occurs where river inflows combine with other factors that serve to impede drainage, including tectonic faulting, swelling soils, and ponding by wind-blown sediments.  Many individual wetlands in drylands may be relatively small compared to some tropical, temperate and arctic wetlands, but collectively they can form across a diverse range of dryland settings.  More importantly, by dint of their presence in otherwise largely dry environments, the MEA recognised that wetlands in drylands may be disproportionately important in terms of biodiversity and other ecosystem services.

Critical reading of the MEA volumes, however, reveals that hard facts about wetlands in drylands are in short supply, and many assumptions remain untested.  For instance, given that many wetlands in drylands desiccate on seasonal or longer bases, how similar are they to their more-or-less permanently-saturated tropical, temperate and arctic cousins?  Do wetlands in drylands necessarily serve to improve water quality for downstream users, or might there be situations where water quality actually decreases downstream of wetlands (e.g. where dry season grazing increases fecal contamination of the desiccating water bodies)?  Are wetlands in drylands really stores of carbon and therefore important contributors to global climate regulation (e.g. through incorporation of atmospheric carbon dioxide into vegetation and ultimately organic-rich soils), or might dry season fires simply burn off the vegetation and organics, thus returning carbon dioxide straight back to the atmosphere?  And to what extent are the provisioning, regulating, supporting and cultural services actually compatible, or might there be potential for conflict, especially where wetlands are the subject of competing human interests?

To examine these and other related questions, colleagues and I recently convened a three-day workshop entitled “Wetlands in Drylands: Past, Present and Future Trends in Ecosystem Service Provision” near Parys, Free State Province, South Africa.  The workshop was funded as part of the Royal Society’s UK-South Africa Scientific Seminars Scheme.  The overarching objective was the establishment of a network of researchers to advance the science of wetlands in drylands, and to translate scientific findings into forms that can be assimilated by those charged with wetland conservation, rehabilitation and management.

The scheme paid for four UK and twelve South Africa participants to convene at the magnificent Stonehenge in Africa conference venue (http://stonehengeafrica.co.za/), located 6-7 km west of Parys.  Situated close to the epicentre of the World Heritage-listed Vredefort Dome – arguably the world’s oldest (2.02 billion years) and largest (greater than 300 km wide) meteorite impact crater – and with a lawn that slopes down to the north bank of the Vaal River, the venue was never going to disappoint.  While the visual impact of the surrounding impact crater is somewhat muted on account of its vast age and size (one really needs an aerial perspective and geomorphologist’s eye to fully appreciate its grandeur), the permanently-flowing pools and rapids, and the green, tree-lined islands of the Vaal present a magnificent sight, especially as they contrast so starkly with the surrounding, usually much drier, browner terrain.  In the MEA’s terms, surely the Vaal must rank as one of South Africa’s most important riverine wetlands, providing good service for locals and visitors alike?

Bedrock rapids and boulders along the Vaal River at Stonehenge

Bedrock rapids and boulders along the Vaal River at Stonehenge

The journey to the conference venue was trouble free.  During preparations for landing at OR Tambo airport, I caught glimpses of some of the wetlands around Johannesburg’s sprawling peri-urban fringe, many of which purify poor quality water emanating from malfunctioning sewerage systems and gold mine dumps.  The plane had landed on time, and we breezed through customs.  After meeting some other workshop participants, we piled into a minibus for the two hour-drive drive southwest to Stonehenge.  As we trundled ever nearer, there was an African welcome typical of November: an ever-darkening sky, followed by spectacular lightning bolts and a torrential downpour.  Wet season thunderstorms were arriving in a land parched by an eight month-long dry season … over the coming weeks, river flows would increase, wetland water bodies would fill, and green shoots would lighten dampened soil.  In this instance, the downpour didn’t last longer than about 10 minutes, but the dark sky, lightning and thunder hung around, providing a constant threat of rain.

And over the next three days, torrential rain did return several times, often accompanied by lightning and thunder.  We didn’t see much sun, which at this time of year normally makes a welcome visit between thunderstorms.  These meteorological conditions lead to some sleep-disturbed nights and one short-lived power outage, while leaking roofs caused inconvenience in a few bedrooms and communal areas.  But these conditions didn’t affect the torrent of ideas emanating from the workshop activities, which included short presentations, small group discussions and round table debates.

Attentive participants during one of the session talks

Attentive participants during one of the session talks

Following some introductory sessions, the first two days considered wetlands in drylands and their ecosystem services from the perspective of the past, present and future.  To what extent did wetlands in the past serve as key hominin habitats and migration routes from Africa to other parts of the world?  How can we best translate wetland science into current wetland management policy?  Which wetland ecosystem services are most threatened by projected future climate changes?

At the end of day two, I arranged for the participants to visit two local contacts of mine, whose house is located along the margins of the Vaal just a few kilometers upriver of Stonehenge.  To complement a generous provision of wine and snacks, our hosts took us for a walk on one of the numerous river islands, and we chatted about the Vaal and other important South African rivers.  A lifetime of kayaking South Africa’s rivers, coupled with more than 10 years living by the Vaal, has sharpened their awareness of the quality of river and wetland ecosystem service provision, even if this is not a term that they would use.  And in most instances, the service is declining as a result of human activities, including active mismanagement.  In the case of the Vaal, as with many other river and wetland ecosystems, factors such as flow regulation, raw sewage disposal, and invasive vegetation have dealt severe body blows, precluding optimal service provision.

Worse still are some of the threats facing the Vaal’s larger sibling, the Orange River.  Having long researched the landscapes of the lower Orange valley, I had already become aware of the proposed run-of-the-river hydropower developments for some of the most scenic, pristine and inaccessible reaches, including the supposedly protected, much visited Augrabies Falls and the downstream, lesser known Ritchie (Oranje/!Gariep) Falls (http://standupjournal.com/opposing-hydropower-facilities-at-the-gariep-or-oranje-or-ritchie-falls/).  If a green light is given, the developments will divert water from some of the Orange’s bedrock channels, waterfalls and gorges so that it can be run through turbines.  Relatively small amounts of electricity will be generated, much of which is destined for consumption by Namibia.  The threats to river ecology, geoheritage, and the sense of wilderness in these reaches is being given lip service – at best – by the developers and their consultants.  Potentially, this represents yet one more body blow to an already weakened ecosystem.

The final day considered how new scientific techniques can best be employed in the study of wetlands in drylands and their ecosystem services, and concluded with a discussion of the way forward for our nascent research network.  Plans are for state-of-the-art publications, an online presence to support network activities, and a future workshop.  Much more needs to be done to promote research into wetlands in drylands and their ecosystem services, so that the types of questions posed above can be answered.

A busy agenda and a long list of ideas for post-meeting activities

A busy agenda and a long list of ideas for post-meeting activities

But during preparation for the final session – partly done during the middle of night as I lay awake listening to yet another thunderstorm – I had already found an answer to at least one of those questions.  A definitive ‘no’.  The various ecosystem services provided by rivers and wetlands in drylands are not necessarily compatible.  It struck me that the provisioning, regulating and supporting services often take centre stage, effectively sidelining the cultural services.  In the case of the lower Orange River, certain interest groups are listing hydropower generation among the provisioning services, and are prioritising this service to the virtual exclusion of all others, particularly the cultural services that include aesthetic, spiritual, educational and recreational opportunities.  The installations and infrastructure associated with hydropower developments will undoubtedly detract from all these cultural services, so one has to question this prioritisation.  Cultural services may be more nebulous than electricity generation, and less easy to monetise than megawatts, but in a world where a sense of wilderness is rapidly disappearing and ‘nature deficit disorder’ is now a recognized condition, what are the hidden costs?

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