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How will the hydropower boom affect global river ecosystems?

December 1, 2014

Itaipu Hydropower Project on the Paraná River located on the border between Brazil and Paraguay. Image: Wikipedia


There are currently around 3,700 major new hydropower dam projects planned or under construction across the world, many of them in developing countries which lack widespread, reliable and affordable electricity supplies.  However, many of these same countries support biodiverse and relatively ‘natural’ large river systems, which raises questions of how to balance the potential ‘green’ energy gains from hydropower projects with the potential harm – barriers to fish migration, siltation, habitat change amongst others – they can cause to river ecosystems.

A new study ‘A global boom in hydropower dam construction‘, has been carried out by Professor Christiane Zarfl from the University of Copenhagen and colleagues at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) in Berlin, including BioFresh head Klement Tockner. The research team compiled data on future major hydropower projects to predict how much energy would potentially be produced if all projects were completed; and the potential impacts they would have on currently free-flowing river ecosystems.

The team found that despite a global ‘boom’ in hydropower developments, the extra electricity production “will not close the energy gap“, because energy demands will increase, due to growing human populations globally.  So despite the growth in global hydropower capacity – if all 3,700 dam projects were completed, the capacity would double to 1700 gigawatts (GW) within the next 20 years – the study predicts that the proportional hydropower contribution to overall energy production would barely alter (16% in 2011, 18% in 2040).  In short, the ‘boom’ in hydropower projects across the world – and their negative impacts on river ecosystems – will only keep pace with global energy demands, as opposed to providing a higher share of ‘green’ energy to overall supply.

The study shows the geographical spread of where new hydropower projects are planned, and so provides a basis for understanding where and how the various trade-offs and conflicts between energy production, freshwater biodiversity and human livelihoods are likely to take place in the future.  The maps below show: (1) the distribution of future hydropower projects, under construction (blue dots) or planned (red dots); and (2) the number of hydropower projects for each major river basin.   The maps show how the majority of hydropower construction will take place in developing countries and emerging economies, particularly along the Amazon basin in Brazil, the Ganges–Brahmaputra basin in India and Nepal, and the Yangtze basin in China.

Map (1): Global spatial distribution of future hydropower dams, either under construction (blue dots 17 %) or planned (red dots 83 %).  Image: Zarfl et al (2014)

Map (1): Global distribution of future hydropower dams, either under construction (blue dots 17 %) or planned (red dots 83 %). Image: Zarfl et al (2014)

Map (2): Number of future hydropower dams per major river basin. Image Zarfl et al (2014)

Map (2): Number of future hydropower dams per major river basin. Image Zarfl et al (2014)

Speaking to ECOS Magazine, Professor Zarfl said, “Hydropower is an integrated part of transitioning to renewable energy and currently the largest contributor of renewable electricity.  However, it is vital that hydropower dams do not create a new problem for the biodiversity in the world’s freshwater systems, due to fragmentation and the expected changes in the flow and sediment regime.  That is why we have compiled available data on future expected hydropower dams – to form a key foundation for evaluating where and how to build the dams and how to operate them sustainably.”

The study estimates that 25 of the 120 large river systems currently classified as ‘free-flowing’ would lose that status, as dam construction fragments and modifies their courses.  It suggests that “Worldwide, the number of remaining free-flowing large river systems will thus decrease by about 21 percent” – a decrease which is likely to be most prominent on South American rivers, which are some of the world’s most unique and diverse freshwater ecosystems.

The IUCN Freshwater Fish Specialist Group states that South America is the most diverse continent for freshwater fish species, globally, with an estimated 4,000 species (and roughly 100 new species found each year).  The Amazon, Mekong, and Congo basins, which will be heavily impacted by future hydropower dams, jointly contain 18 % of the global freshwater fish diversity, and the Balkans – a hot spot for future hydropower development – are an important region for freshwater biodiversity in Europe, as described by a recent IUCN report.

The dam wall on the Itaipu hydropower project. Image: International Hydropower Association, Flickr

The dam wall on the Itaipu hydropower project. Image: International Hydropower Association, Flickr

Freshwaters are already amongst the most threatened ecosystems in the world.  Hydropower developments can have negative effects on freshwater species in a number of ways – blocking migration routes, changing river flows and habitat, and dropping loads of fine sediment in areas where the river flow is slowed, potentially causing eutrophication and covering fish breeding sites.  Biodiversity loss as a result of hydropower projects has potentially negative knock-on effects for communities around rivers which rely on fishing for food and freshwater for drinking, washing and sanitation.

Despite being a low-carbon, renewable energy source, hydropower can significantly alter and degrade the rivers where it is implemented.  So, what is the solution to growing global energy demands?  Professor Zarfl and colleagues state that, “Even if the entire technically feasible hydropower potential will be exploited, which would correspond to a dam construction boom almost five times that currently estimated, hydropower would contribute less than half of the global electricity demand projected until 2040.”  

Hydropower water release.  Image: Global Water Partnership, Flickr

Hydropower water release. Image: Global Water Partnership, Flickr

Given this inability to keep up with demand, and the related environmental costs, is hydropower the most suitable response to global energy needs?  On average, life-cycle greenhouse gas emissions from hydroelectricity are more than 30 times lower than that of coal – potentially providing a key tool in mitigating climate change.  However,  how can we reconcile the potential climate benefits of hydropower with the potential harm it does to freshwater biodiversity?

The authors suggest that one solution might be to concentrate new hydropower developments on river basins that have existing hydropower projects, and are fragmented already – a new and perhaps pragmatic take on the old conservationists’ mantra of ‘preserve the best, restore the rest’.  For example, hydropower projects on the Rufiji River in Tanzinia – the last remaining large free-flowing river network in East Africa – might be moved to the Nile and Zambezi Rivers, which are already heavily fragmented today.  Whether this approach can account for spatial variation in energy needs, economic investment and political will is another matter.

The database of future major hydropower projects compiled by Professor Zarfl and colleagues provides a comprehensive new resource for conservationists, environmental planners and policy makers to help guide how and where hydropower developments are planned in the future.  However, it remains to be seen whether the growing global demand for new hydropower supply can be reconciled with the threats developments pose to freshwater ecosystems in the future.

14th International Symposium on Aquatic Plants

November 25, 2014
Playfair Library, Edinburgh.  Image: Edinburgh University

Playfair Library, Edinburgh. Image: Edinburgh University

The 14th International Symposium on Aquatic Plants has been announced to take place at the Playfair Library in Old College, Edinburgh between 14-18th September 2015.  Registration and abstract submission is open here.

Organised by MARS colleagues at the Centre for Ecology and Hydrology in Edinburgh, the conference aims to: “promote debate on all issues relating to the science and management of aquatic vegetation. Interest in aquatic plants has been growing and diversifying and to reflect this there will be a wide Scientific Programme which will appeal to scientists and managers.”

The conference programme will include sessions on Ecotoxicology, Trophic Interactions in Macrophyte Beds, The Future of Invasive Species Management, Community Responses to Environmental Change in Space and Time, Aquatic Plants and Physical Processes, Restoration, Aquatic Plant Monitoring, Ecological Stoichiometry and Nutrient Cycling, Vegetation & Dams, and Fundamental Science.

Delegates will also be offered to opportunity to take part in a conference dinner and ceilidh at Surgeon’s Hall, and to attend a field excursion to Loch Leven to see an excellent example of successful lake restoration.

Follow the Symposium websitetwitter and the #aquatic plants15 hashtag for updates.

Key Biodiversity Areas: new IUCN report finds that Mediterranean freshwater ecosystems are inadequately protected

November 21, 2014

Three-quarters of the Mediterranean region’s most valuable areas for freshwater biodiversity lie outside of protected areas, leaving some of the most area’s most important and diverse freshwater ecosystems vulnerable to human threats.  This is the key finding of a new IUCN assessment reported to the recent IUCN World Parks Congress in Sydney, Australia.

The report suggests that at least 167 sites in the Mediterranean Basin –covering an area of 302,557 km2 – qualify as freshwater Key Biodiversity Areas (KBAs) .  Key Biodiversity Areas are an IUCN designation of the most important sites for biodiversity conservation worldwide, particularly important in maintaining species populations.  They are assessed globally using a standardised criteria based on how vulnerable and irreplaceable the populations of plants and animals they contain are.

The above video gives an introduction to freshwater Key Biodiversity Areas, and the new online BioFresh portal for accessing information on them.

Freshwater biodiversity is poorly accounted for in the global protected area network.  The new IUCN study provides crucial information on critical sites for freshwater biodiversity, and sets the foundation for a new protected area network in the Mediterranean Basin – a region rich in diverse and threatened freshwater life.

This work was undertaken in partnership with the BioFresh project.  Two BioFresh partners outlined the new study’s value:

Through this project we are putting freshwater biodiversity on the map in a region of the world where pressures on inland wetlands are rapidly driving species to the edge of extinction – a number have already been lost. The next crucial step is to build widespread awareness of these important sites and to stimulate targeted conservation on the ground” said Will Darwall Manager of the IUCN Freshwater Biodiversity Unit and project coordinator.

“KBAs are fragile freshwater ecosystems which must be properly managed as part of Integrated River Basin Management planning accounting for the wide range of uses of water across sectors” commented Jörg Freyhof, European chair of the IUCN/WI Freshwater Fish Specialist Group and co-author of the report.

MARS Experiments: Low Flows in Nordic Rivers

November 14, 2014
The experimental channels.  Image: Aarhus University

The experimental channels. Image: Aarhus University

Over the last few weeks we’ve been introducing the experiments that the MARS research team have been carrying out across Europe to understand the effects of multiple stresses on freshwater ecosystems. This week we turn our focus to Denmark, where a team led by researchers led by Annette Baattrup-Petersen and Daniel Graeber from Aarhus University are investigating the effects of low water flows on freshwater streams.

Low stream flows, the build up of fine sedimentation, and eutrophication – caused by dissolved nitrogen and phosphorus – are the main stressors of stream ecosystems in Nordic agricultural landscapes.  In these experiments, the MARS researchers seek to understand how these stressors affect small stream ecosystems in these landscapes, particularly focusing on how the stressors might interact. Research in this area is particularly important given that predictions of future climate change suggest that many rivers in northern Europe will experience longer periods of low flows, due to changing precipitation patterns and climate warming.

Experimental channel diagram.  Image: Aarhus University

Experimental channel diagram. Image: Aarhus University

The MARS team are currently conducting a series of measurements and experiments, seeking to couple stream ecosystem structure to ecosystem function, from which the potential effects of stress on ecosystem services can be derived. The research team have constructed 12 experimental stream channels, 12 m long, 0.6 m wide and 0.3 m deep, which are designed to simulate natural small stream ecosystems and the effect of multiple stressors. The stream channels consist of a series of runs and riffles with sediment typical for such habitats.  They are fed by stream water, which results in natural water chemistry and also brings new algae, water plants and invertebrates into the experiment (as would happen in a real stream). The flow of water down the channels can be controlled to simulate normal and low stream flows.

low flow channel close up

Runs and riffles on the experimental channel. Image: Aarhus University

The MARS team are focusing their attention on two key components of small stream ecosystems: benthic invertebrates and benthic algae, with a focus on primary production and nutrient uptake as ecosystem functions. Benthic algae are the main primary producers in small stream ecosystems and provide food for grazers, such as benthic invertebrates, as well as oxygen for all animals and fungi. Benthic invertebrates are the main food source for fish in Danish small streams and can control the growth of benthic algae by feeding on them. Therefore, the combination of all elements of a stream ecosystem defines its capability to take up and therefore retain nutrients.

To measure primary production in the sediments and on stones, the team use specially made experimental chambers, and take samples for algal biomass and composition and benthic invertebrate density and composition. To measure nutrient uptake, the team initiate short-term nutrient releases for ammonium, nitrate and phosphorus, and measure the ecosystem response.

A stone covered in sediment in an experimental channel.  Image: Aarhus University

A stone covered in sediment in an experimental channel. Image: Aarhus University

Three stressors in the experiment:

The three chosen stressors are likely to have several effects on the interaction of benthic invertebrates and algae in the experiment.

Low flow is likely to result in a reduction of densities of typical stream benthic invertebrates (mayflies, stoneflies) many of which are grazers. Similarly, due to less physical abrasion on the streambed, low flows are likely to result in higher benthic algae growth. Combined with the reduction of stream benthic invertebrates, a higher primary production can be expected and due to the longer residence time (i.e. the amount of time a particle spends in a system), nutrient uptake should also increase.

Eutrophication is known to increase the biomass of benthic algae due to higher nutrient availability and will likely result in higher primary production and higher nutrient uptake. Based on existing scientific literature, eutrophication is likely to have minimal effects on benthic invertebrates.

Fine sedimentation severely affects benthic algae simply by covering them and by removing suitable habitats (coarser sediment), which are buried by fine sediment. Fine sediment also affects benthic invertebrates by clogging the room between coarser sediment particles and removing the access of scraper invertebrates (see the FSC guide to invertebrate feeding methods) to their food source (benthic algae). Finally, fine sediment delivers a large amount of organic matter to the stream, which is expected to strongly increase benthic respiration – which removes oxygen – and thus may counterbalance the effects of algal primary production.

We will keep you updated with the results of this experiment, and the others that the MARS team are carrying out across Europe. You can find links to all the MARS experiment blogs here.

Small is beautiful: the overlooked importance of small freshwaters

November 4, 2014
A pond in Hampshire, Southern England.  Image Anguskirk, Flickr

A pond in Hampshire, Southern England. Image Anguskirk, Flickr

Small bodies of water such as ponds, ditches, springs, flushes and headwater streams pockmark many landscapes across Europe.  Whilst they might often be overlooked (stepped over, sometimes), there is increasing consensus that these small freshwaters are extremely important to the ecological health of the landscape.

European ponds, for example, support a larger proportion of freshwater biodiversity than lakes or rivers, and help ‘connect’ a landscape for species such as frogs and dragonflies by providing a series of ‘stepping stone’ habitats across the wider landscape.  In this way, small water bodies are important as part of what ecologists term the ‘landscape matrix’, providing patches of diverse habitat (often in urban and non-protected areas) which interconnect with other ecological processes across the whole landscape to shape its overall health and diversity.  Headwater streams (those right at the top of the river’s course) can provide spawning grounds for fish like the Atlantic salmon, and then sheltered ‘nursery’ habitats for their offspring.

However, small water bodies have been largely ignored by freshwater scientists, conservationists and policy makers, meaning there are gaps both in our knowledge of their ecological forms and functions, and in their protection through policies like the Water Framework Directive.  There is growing awareness of the significance of small water bodies, shown by their inclusion in the European Environment Agency’s European waters – assessment of status and pressures and the European Commission’s Blueprint to Safeguard Europe’s Water Resources, both published in 2012.

As part of this increasing focus on small water bodies, The European Environmental Bureau and the Freshwater Habitats Trust recently released a report on a workshop which took place in November 2013 to discuss how small water bodies might be better managed and protected in Europe.

A key issue discussed at the meeting was how existing European legislation – particularly the Water Framework Directive, Birds and Habitat Directive and the EU 2020 Biodiversity Strategy – could incorporate small water bodies.  Another was the need for effective co-operation between different environmental managers across the wider landscape to better understand, monitor and manage the role of small water bodies in supporting biodiversity on a landscape scale.  Finally, small water bodies were seen as ideal habitats for engaging the public with conservation issues, given that ponds and streams are present in most landscapes, even those that are predominantly urban.

You can read the workshop report on the Freshwater Habitats Trust website, and find out more on the European Environmental Bureau website.

Introducing the SOLUTIONS project: an interview with Rolf Altenburger

October 29, 2014

When the MARS project was launched in the sunny climes of Mallorca in February 2014, Dr Christian Feld interviewed a number of freshwater scientists and policy makers attending the kick-off meeting.  In the above video, Christian interviews Rolf Altenburger from the Helmholtz Centre for Enviromental Research (UFZ) in Leipzig, Germany.  Dr Altenburger is deputy co-ordinator of the SOLUTIONS project which studies the effect of chemical pollutants on freshwater quality and ecological health, and aims to provide solutions to help manage and protect Europe’s freshwaters.

In this video, Dr Altenburger describes how the project’s focus on the impact of stressors on the freshwater environment links SOLUTIONS with the MARS and GLOBAQUA projects (see our earlier blog and interview here).  As Dr Altenburger explains, there are more than 100,000 chemicals in daily use across the world, which come from sources such as agriculture, pharmaceuticals, food additives, plastics and cosmetics.

Animals and plants living in freshwater ecosystems are increasingly exposed to a complex mixture of diluted chemicals (referred to as ‘cocktails’ by Dr Altenburger), which makes identifying and managing their effects – both individually and together – a difficult task.  This is further complicated by the sheer number of chemicals which are potentially harmful to freshwater ecosystems.  At present, the monitoring systems in place are not detailed or comprehensive enough to assess and manage the huge diversity and complexity of chemical ‘cocktails’ that are increasingly present in freshwater environments, many of which are new or unknown.

Chemical pollutants may interact with other stresses on freshwater environments.  For example, water scarcity (as seen on the Iberian peninsula) increases chemical concentrations in the remaining available water, which would otherwise be diluted by normal flows, with potentially harmful effects on water quality and freshwater life.  Understanding the impact and interaction of multiple stressors is a key EU research topic at present, in an effort to strengthen the Water Framework Directive, which is why the MARS, GLOBAQUA and SOLUTIONS projects are collaborating closely.

SOLUTIONS seeks to better understand, predict and manage the effects of chemical pollutants on freshwater environments.  Achieving this requires the development of a consistent framework to monitor and assess chemical pollution, particularly in increasing efficiency and speed of chemical identification from complex ‘cocktails’ and at low concentrations.

SOLUTIONS will produce computer models to help environmental managers and policy makers predict the effects of chemical pollution on freshwater biodiversity and water quality in the future, allowing forecasts to be made under changing economic conditions, new technologies, shifting human development and climate change.  This production of user-friendly resources and a common chemical knowledge base will also help will help bring chemical pollution up the European policy agenda ahead of the potential revision of the Water Framework Directive in 2019.  It will also help create early warning systems for future chemical pollution across the continent.

The models and tools developed by SOLUTIONS are being trialled and tested in three river basins across Europe.  New approaches to identifying river basin specific pollutants are being applied along the Danube basin in Central and Eastern Europe, following the extensive Joint Danube Survey 3 along the river in 2013.  In the Rhine basin in Central Europe, new wastewater and drinking water treatment technologies are being assessed, to understand their effects on chemical pollutants in the basin.  Finally, the risk posed by chemical pollution under water scarcity conditions are being studied in the Ebro and Llobregat basins in northern Spain.

More information on SOLUTIONS:

Project website
Project factsheet


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