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Imaggeo on Mondays: Soil and water conservation in the Dogon Plateau, Mali

10 Jun

Velio Coviello, a scientist from the Research Institute for Hydrogeological Protection, Italy, and one of the winners of the EGU 2014 Photo Contest, brings us this week’s Imaggeo on Mondays. He sheds light on his winning image and the problems associated with conserving soils and water in Western Africa… 

This picture was taken on Mali’s Dogon plateau during the dry season, in the course of a late sandstorm day. Between November and March, a hot, dust-laden Harmattan haze frequently persists over the whole of  Western Africa. The Harmattan is a hot, dry wind blowing from the Sahara, carrying large amounts of dust and transporting it for hundreds of kilometers. Here, we see two men drawing water from a deep and narrow well excavated by hand. This latter is a task commonly carried out by children, who climb down to dig the well bottom.

Men and children drawing water for irrigation in the Dogon plateau during a sandstorm. (Credit: Velio Coviello via

Men and children drawing water for irrigation during a sandstorm. (Credit: Velio Coviello via

Mali has a low population density, most settlements are concentrated in the southern part of the country and along the Niger River, where the climate is less harsh and water availability is higher. In the north, Mali is arid and only those who raise livestock can make a living.

One of the most important tourist attractions in Mali is the Dogon Plateau, which sits in the central part of the country, east of the Niger River. The plateau gently descends westward to the river valley and ends in abrupt cliffs on the southeast. These cliffs reach an elevation approaching 1,000 meters at Bandiagara, the main village of the Pays Dogon (Land of the Dogon). These geological, archaeological and ethnological interests, together with the striking landscape, make the Dogon Plateau one of West Africa’s most impressive sites.

Ensuring the population has safe and sustainable access to water is one of the major challenges in the Sahelian region. Facing recurring drought events and encroaching desertification, Sahelian countries are currently heavily affected by climate change. Extreme rainfall events and high rainfall intensity are the main cause of soil erosion and land degradation. Consequently, high rates of soil transport can lead to reservoir siltation and the reduction of water availability for agriculture. To cope with these issues, traditional soil and water conservation (SWC) measures like hillside terracing, permeable rock dams, stone lines, earth basins, planting pits and earth mounds have been regularly employed in the Sahelian area. The Dogon Plateau is home to a broad variety of these measures, implemented to deal with the acute shortage of soil and water. As the population urgently needs support to preserve soil fertility and reduce soil erosion, SWC measures need to be improved and adopted more widely. However, most donors fund short-term projects without considering the maintenance that is needed to ensure SWC measures remain effective long-term.

The first lesson is that there is much to learn from the traditional ways of doing things and SWC projects should always begin by looking at what the people are doing for themselves. Secondly, the international cooperation actors should set up long-term funding programs improving the participation and inclusion of local communities. The final goal would be to ensure the stakeholders are not permanently dependent on international aids.

by Velio Coviello, Research Institute for Hydrogeological Protection (IRPI) and Italian National Research Council (CNR)

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

Geosciences Column: Could plants be a cheap solution to soil contamination in developing countries?

30 May

There are many ways to remove contaminants from the land, but it is a constant battle for scientists to find better and cheaper ways to the job. Recent research published in Soild Earth suggests plants may present a solution – one that’s particularly promising for poor areas. Jane Robb describes the findings…

Bolivia has a long and complicated mining history, going back to the 1500s. Untreated tailings are commonly left in rivers, causing widespread contamination of waters and soils downstream. These wastes often contain pyrite, which generates sulphuric acid when exposed to oxygen and water, leaching the surrounding rocks of heavy metals in a process known as acid mine drainage. Mines in Bolivia also use sulphuric acid in the mining process, which catalyses production of acid rock discharge. With growing conflict over the rapid environmental degradation that is causing public health problems across the country, the Bolivian government declared an emergency zone in the Huanuni watershed in 2009, just one of the areas in which heavy metal contamination occurs.

Acid mine drainage causing contamination of water and soils in areas close to Rio Tinto, Spain. (Credit: Carol Stoker, NASA)

Acid mine drainage causing contamination of water and soils in areas close to Rio Tinto, Spain. (Credit: Carol Stoker, NASA)

Soil heavy metal contamination has serious effects on microbial life and the taxonomic diversity of soils, not to mention the serious health effects that high concentrations of elements such as As, Cd, Cr, Hg and Pb can have. Other metals like Cu, Ni and Zn are also released, and although they are essential for growth, they can cause problems when present in high concentrations. While heavy metal remediation in soils is a highly researched topic, we can still do more. This year, Jorge Paz-Ferreiro and his team et al have assessed two techniques that use plants for mine waste remediation: adding biochar to the soil and planting hyperaccumulators (plants that can store heavy metals at levels 100-fold greater than common plants without reducing their growth) in the affected area. Both of these techniques could be applied to sites like Huanuni in the future.

Prevention is the best way to fight soil and water contamination from mining, but in countries such as Bolivia, the political and cultural environments can present barriers to progress in this area. The country’s history of low economic diversification, corruption and political instability (democratically elected governments only began in 1982), and rapid inflation have continually hindered development. In addition, low population growth, high incidence of disease and low life expectancy exacerbates the country’s economic position – 86th out of 179 countries in the World Bank’s GDP ratings in 2012. Bolivia’s principal commodity for export is natural gas, but until the 1980s mining of tin and silver were its top economic exports. Although mining is not as prevalent in the country as it was in the past, the country still suffers from the impacts hundreds of years of mine tailings have brought to the environment. For Bolivia, prevention is a small part of what needs to be done to tackle the problem of soil and water contamination.

The extraction, filtration or stabilisation of heavy metals using hyperaccumulators (a process commonly known as phytoremediation) is nothing new. In fact, it has been studied and used for years as a remediation technique with varying success. But with costs that are a fraction of that spent on traditional remediation techniques – at a few cents per square metre for cleanup or removal of material compared to up to $300 per square metre– phytoremediation could be a viable option for countries such as Bolivia.

Mining in Bolivia in 1981. (Credit: Wikimedia Commons user Meister)

Mining in Bolivia in 1981. (Credit: Wikimedia Commons user Meister)

Paz-Ferreiro’s team are the first to assess the possibility of using biochar in combination with phytoremediation to remediate heavy metal contamination in soils. Phytoextraction uses hyperaccumulators to take up heavy metals and transfer them to aboveground tissues, such as stems and leaves. This process takes the contaminant from the soil to the plant, providing a way to extract economically valuable metals while improving soil – and therefore crop – quality. Phytofiltration sequesters pollutants from waters through the plant’s root system, and phytostabilisation limits the mobility and bioavailability (availability to plants and animals) of polluting substances by immobilising them. While phytoextraction is the most common and promising technique, both filtration and stabilisation help remove contamination from soils and reduce the probability of heavy metals being stored within crops.

Although phytoremediation is currently used and holds a lot of promise, there are still issues associated with this technique. For instance, phytoremediation may not be suitable in areas of elevated contamination, as plants could begin to suffer from the soil’s toxicity, and many known hyperaccumulators produce low amounts of biomass, meaning that heavy metals are removed slowly. Information is also missing on how climate change could impact the ability of phytoextractors to take up heavy metals. Most importantly, research on phytoremediation has, to date, focused on laboratory tests – more data from field experiments is needed to inform scientists about the impacts of microclimate and soil type on the effectiveness of phytoremediation.

Modern mining in Seite Suyos, Bolivia, devastates the surrounding environment. (Credit: Wikimedia Commons user Mach Marco)

Modern mining in Seite Suyos, Bolivia, devastates the surrounding environment. (Credit: Wikimedia Commons user Mach Marco)

Biochar is formed from burning other organic materials – ranging from plants to manure. Biochars act on the bioavailable heavy metals in soils, reducing the amount that can be leached from the soil by crops. Heavy metals stick to the surface of biochar, and because they have a high surface area, they are the ideal medium for this task. Some biochars can also stabilise heavy metals by helping them precipitate as carbonate, phosphate and sulphate compounds. Unlike phytoremediation, biochar does not reduce the amount of heavy metals in the soil, but instead reduces the bioavailability of these elements.

As biochars effectively stabilise heavy metals, they reduce their ability to be taken up by plants, preventing phytoextractors from doing their job. This means that the use of biochar and phytostabilisors would be a more useful remediation approach. Paz-Ferreiro and his colleagues indicate that it could be possible to use biochar and phytoextractors together, if the biochar and phytoextractors target different heavy metals in heavily contaminated soils. Much larger, long-term trials are needed to see how well the two methods work together – something that will need to be tested in the lab and the field.

Today, the scale of mine-related contamination in Bolivia and the emergency zone of Huanuni is still staggering. To remediate contamination not only does the government need to address the continual contamination of soil and water, but also historical contamination. Paz-Ferreiro’s team have brought together two methods for soil heavy metal remediation that can help address historical contamination in areas such as Huanuni, and have hopefully paved the path for more research with these combined remediation techniques in the field.

By Jane Robb, Project Assistant, University College London


Paz-Ferreiro, J., Lu, H., Fu, S., Mendez, A., Gasco, G.: Use of phytoremediation and biochar to remediate heavy metal polluted soils: a review, Solid Earth, 5, 65-75, 2014.

Climate-proofing the Netherlands

28 May

Emerging Leaders in Environmental and Energy Policy (ELEEP) fosters transatlantic relations, forges dialogue, and promotes leadership across energy and environmental policy landscapes. Former EGU Science Communications Fellow and ELEEP member Edvard Glücksman reports back from the Netherlands, where citizens manage the continuous threat of climate-related devastation through a combination of creatively adapted urban spaces and innovative new technologies.

In late January 1953, a storm over the North Sea wreaked havoc, causing one of the most devastating natural disasters that Northern Europe has ever seen. The surge of seawater overwhelmed coastal defences, causing extensive flooding along the Belgian, British, and Dutch coastlines.

The infamous North Sea Flood claimed roughly 2,500 lives, and damaged or destroyed tens of thousands of houses. In the Netherlands, where roughly 70% of the nation’s territory lies at or below sea level, the flood submerged over 1,300 km² of the country’s territory, destroying around 10% of agricultural land and crippling its economy.

Rotterdam is Europe’s largest and busiest port. (Credit: Edvard Glücksman)
Rotterdam is Europe’s largest and busiest port. (Credit: Edvard Glücksman)

Climate-proofing with blue solutions

The nation’s history of flooding has shaped urban design and construction initiatives across the Netherlands. This trend is particularly striking in the Dutch city of Rotterdam, which lies in a delta roughly 7 m below sea level and is vulnerable to flooding from both seawater and heavy rain. Its complex system of dikes and seawalls have a one-in-10,000 years chance of breaking, high enough for the city to take pioneering steps towards developing sustainable water management practices in preparation for the most extreme future climate scenarios.

In the offices of the Rotterdam Climate Initiative (RCI), Lissy Nijhuis, Project Manager at Rotterdam Council, depicts the city’s climate adaptation strategy as one that has recently grown to embrace ‘blue solutions’ – mitigation strategies that allow humans to protect themselves against potential catastrophic flooding events, while continuing to live with and enjoy water. 

The Watersquare Benthemplein plaza discretely weaves flood management systems into the city’s urban landscape. (Credit: Edvard Glücksman)
The Watersquare Benthemplein plaza discretely weaves flood management systems into the city’s urban landscape. (Credit: Edvard Glücksman)

According to Nijhuis, these new solutions contrast starkly with conventional approaches, which rely on separating humans from water using the most robust and resilient physical barriers available.

The blue solutions approach means that, in recent years, the RCI has adopted a long-term strategy of ‘climate-proofing’ the city by subtly adding water management infrastructure to standard urban maintenance and redevelopment activities. Nijhuis explains that this is most effectively achieved by developing first with a practical, beautiful outcome in mind, and working backwards to adjust it to particular flooding mitigation requirements.

To that end, we visited the city’s notorious Watersquare Benthemplein pilot project, a water plaza that doubles as a flood buffer during heavy rainfall, pooling water from surrounding streets and thus relieving the most immediate pressure on public drainage systems. The construction, seven years in the making and used during our visit as a basketball court by school children, is a prime example of Rotterdam’s understated but highly effective water mitigation strategy. Other similar examples – built to reduce pressure on drainage sites in times of severe flooding – include car parks that double as water storage units and the presence of absorbent green roofing on houses.

ELEEP members gather in Rotterdam’s port area. (Credit: Edvard Glücksman)
ELEEP members gather in Rotterdam’s port area. (Credit: Edvard Glücksman)

Halving emissions by 2020

Earlier this year, ELEEP visited Hamburg and witnessed first-hand the city’s commitment to transforming previously flooded and industrial areas into hubs for the development of green architecture and urban regeneration. Likewise, the Drijvend Paviljoen (Floating Pavilion) lies at the heart of Rotterdam’s mission to climate-proof itself in a sustainable manner.

Comprising three connected, floating hemispheres, anchored within the city’s old harbour, the Floating Pavilion serves as a pilot project within Rotterdam’s ambitious plan to construct a future community of floating homes. The pavilion floats on a 2.5 m-thick layer of polystyrene, which allows for construction directly on the water and is made of materials that are hundreds of times lighter than those used in conventional buildings. The roof, for example, is made of a triple-layer of foil, filled with pressurised air that insulates and keeps the building warm.

The solar-powered Floating Pavilion is a showpiece within Rotterdam Municipality’s goal of halving energy consumption and CO2 emissions in housing by 2020. It also allows stakeholders to better understand the potential challenges involved in drastically altering the city’s urban landscape, including for example how to interpret the city plan when the harbour areas becomes living quarters virtually overnight.

Rotterdam’s Drijvend Paviljoen (Floating Pavilion), a pilot in climate-proofing infrastructure. (Credit: Edvard Glücksman)
Rotterdam’s Drijvend Paviljoen (Floating Pavilion), a pilot in climate-proofing infrastructure. (Credit: Edvard Glücksman)

Rotterdam’s port is by far the city’s most prominent industrial feature. Europe’s largest and busiest port, it covers an area of 5,299 hectares and shifts nearly 12 million cargo containers per year. It also hugely impacts Europe’s energy landscape, serving as the northwestern European hub for the arrival, production, and distribution of conventional and renewable energy. The port, which has a capacity of nearly 7,000 megawatts, powers nearly a quarter of the industry and homes in the Netherlands. At the same time, twice as much electricity will be generated by other power plants in northwestern Europe as a result of coal, biomass, and natural gas imported via Rotterdam.

In a broad-ranging talk, Ruud Melieste, an economist within the Corporate Strategy Department at the Port of Rotterdam, explains the pressures faced by the port as it strives to improve sustainability credentials. Important, he explains, is the global complexity within which EU energy issues must be understood, and the pressures faced by power, chemical, and refining industries as cheaper alternatives, such as US shale gas, are found elsewhere.

In response, Melieste offers three potential future scenarios for Rotterdam and the rest of northwestern Europe. The first, known as the ‘power’ scenario, focuses on maintaining the domination of fossil fuels through large-scale, centralised energy generation. In this scenario, big countries and companies determine future events. A second option is the ‘fusion’ scenario, which focuses on maintaining a diverse portfolio of stakeholders and solutions, and aims to gradually alter the economy towards sustainable energy use, while using shale gas as a transition fuel. The third, ‘unlimited’, scenario is based on radical innovations and the acknowledgement that climate change is a truly pressing problem. Here, the transition to renewables is seen as an economic opportunity, driven by decentralised energy systems. The Port of Rotterdam is prepared, according to Melieste, for the possibility that any of these three scenarios could play out. The one most likely to emerge, however, remains unknown.

Ruud Melieste, economist for the Port of Rotterdam, explains the dimensions of Europe’s busiest port. (Credit: Edvard Glücksman)
Ruud Melieste, economist for the Port of Rotterdam, explains the dimensions of Europe’s busiest port. (Credit: Edvard Glücksman)

Although the basic idea behind Dutch climate protection strategies has persisted for over half a decade, the sites we visited in Rotterdam demonstrate that the city’s climate adaptation portfolio is slowly changing from a “dry feet at all costs” approach to one of integrative water management, where the duties associated with climate protection and the pleasures of urban space can more freely mix. The city and its port are central features in the supply of energy, water, and food to much of northern Europe. As a result, its pioneering climate-proofing efforts are in future likely to affect millions of European citizens, ensuring that extreme weather events, such as the storm of 1953, can be mitigated in the most sustainable and least invasive way possible.

By Edvard Glücksman, Associate Research Fellow, Environment and Sustainability Institute, University of Exeter

ELEEP is a collaborative venture between two non-partisan think tanks, the Atlantic Council and Ecologic Institute, seeking to develop innovative transatlantic policy partnerships. Funding was initially acquired from the European Union’s I-CITE Project and subsequently from the European Union and the Robert Bosch Stiftung. ELEEP has no policy agenda and no political affiliation. Edvard’s current project is funded by the European Social Fund.

GeoTalk: Want a record of historical floods? Ask the taxman

7 May

Extreme weather events, like catastrophic floods, are the malicious exclamation points of Earth’s chaotic and variable climate system; they arrive without warning and extract huge costs, both economic and humanitarian, from the communities they strike. Evidence suggests the frequency and severity of these events may be on the rise in a changing climate, but scientists struggle to place modern events in a longer historical context.

Information about the past hides in all kinds of places. The trick is figuring out how to extract it. Rudolf Brázdil and his team from Masaryk University in Brno have started using historical tax records from southern Moravia in the Czech Republic to reconstruct the flood history of the area, a test case for broader studies of this kind. At the EGU General Assembly, Brázdil sat down with Julia Rosen to explain his approach.

To start with, how did this idea occur to you?

Existing hydrological series based on instrumental records are generally short. To study really disastrous events, which have a long recurrence interval, you cannot use just the period of hydrological measurements, you have to extend it into the past. We are working in the field of historical hydrology using documentary sources to reconstruct past floods and we recognised that we can use this so-called taxation data. In the past, in Moravia, if anybody was affected by any disastrous events – like a flood – they had the opportunity to ask to pay lower taxes. It was a complicated administrative process, and we are studying documents related to this process to reconstruct hydrometeorological events – including floods. The idea is to obtain the longest series of extremes as possible.

A painting from 1846 commemorating the tragic Elbe flood of March 1845 in Ústí nad Labem, NW Bohemia. The peak discharge of this flood was not matched even by the disastrous August 2002 event. (Credit: Museum of the City of Ústí nad Labem, Oil on wood, painted shooting target, catalogue no. U 334)

A painting from 1846 commemorating the tragic Elbe flood of March 1845 in Ústí nad Labem, NW Bohemia. The peak discharge of this flood was not matched even by the disastrous August 2002 event. (Credit: Museum of the City of Ústí nad Labem, Oil on wood, painted shooting target, catalogue no. U 334)

How do you actually infer flood histories from these data?

Using this data, you can recognise the time and place of an event and its impacts. That’s because the original aim of these documents was to describe damage for which affected people could obtain some tax relief. Generally, you can use flood marks to determine the size of events. For example, people identified the height of the water on the bridge, or on the wall of the house. In Prague (where I have worked before) there is a statue – the head of a bearded man – that was installed in the 15th century. People have characterised floods with respect to how much of the head was submerged, or if it disappeared entirely, since 1481. People knew, for example, that if the water reached the head, they had to leave their houses.

You also know the flooded area by which villages or settlements have been affected. It is difficult to precisely compare the magnitude of historical floods with recent floods because of the totally different character of rivers in the past. They were not regulated – they had many meanders and the character of the landscape was different as well. But we can still compare events from the point of view of the frequency of floods, their seasonality and impacts.

What are the challenges of working with this kind of data? What are its limits?

Every proxy is limited from different points of view. One limitation of our data is incompleteness, both spatially and temporally. For example, you could have a situation where nobody recorded such events, although this is not so likely when events are really strong. Second, perhaps someone recorded it, but original records were lost in fires or during reorganisation of archives. Third, of course, it is generally qualitative information. You need to understand the nature of these data by collaborating with historians and archivists. I am a climatologist, and for me, it’s extremely important to cooperate with such people because without them, there wouldn’t be any historical hydrology. On the other, they would never use such data for the purposes for which we are using it. It is a classic example of interdisciplinary research.

What did you find? Has the frequency of extreme floods increased or decreased?

We are more or less at the beginning of this project using taxation records in Moravia. I am just now evaluating everything, so it’s difficult for me to say now. However, I can give you an example from Bohemia (the western part of the Czech Republic) where we have worked before using other kinds of documents. There, the 19th century was an extremely active period for floods, followed by the second part of the 16th century. The second part of the 20th century was very quiet in the Czech Lands, there were really no important floods until the disastrous floods of July 1997 in Moravia and August 2002, in Bohemia.

The Long Bridge across the River Svratka in Brno where ice floes accumulated during the flood of March 1830 after the extremely severe winter of 1829-1830. (Reproduction of a colour drawing by Frantisek Richter, Brno City Archives, Collection of graphics, prints and reprints, no. 255R)

The Long Bridge across the River Svratka in Brno where ice floes accumulated during the flood of March 1830 after the extremely severe winter of 1829-1830. (Reproduction of a colour drawing by Frantisek Richter, Brno City Archives, Collection of graphics, prints and reprints, no. 255R)

What comes next?

For this project, the first step was tax records. The second step is family archives, which sometimes contain better information, and the third step is chronicles, then newspapers, and of course systematic hydrologic and meteorological measurements. This should form the main database to allow us to do our analysis and synthesis. Success will be if we are able to analyse in detail the spatial and temporal variability of hydrometeorological extremes for the last 350 or 400 years and to use this information for estimates of future extremes.

It will also be a success for us if our work gains acceptance within the international community. This will demonstrate that we are presenting new and interesting results and new methodological approaches that might be applicable on a broader scale. I believe these taxation data are available in many European countries and it would help to extend our knowledge about past floods in this area.

By Julia Rosen, PhD, Freelance Science Writer


The project is financed by the Czech Republic Grant Agency.


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