Geology for Global Development

Soils

Robert Emberson: Soil Erosion and Sustainable Development

Over the last few weeks we’ve introduced you to some new faces on the GfGD blog, including Robert Emberson, Heather Britton and Jesse Zondervan. Today, Robert (based in Victoria, Canada) writes on the connections between soil erosion and sustainable development, and poses the question – is soil one of our most threatened resources? 

When we talk about sustainable energy sources, most of the time we’re referring to renewable sources of electricity and heat. Geothermal, solar, wind or waves – these are all sources of energy that are, within practical limits, not exhausted by our use. However, all living species need more than just electricity and heat as energy; we need food to sustain us.

The vast majority of food for humans requires agriculture, whether vegetable crop or grazing species. Agriculture depends completely on fertile soil to succeed, but we often don’t think about soil as a resource that really matters. Crucially, however, the rate at which soil forms is vastly outpaced by the rate it erodes away in modern farming. For all intents and purposes, soil is a non-renewable resource, like fossil fuels.

A recently published UN study has highlighted this, estimating that 24 billion tons of fertile soil is lost annually every year – primarily in sub-Saharan Africa. The implications for sustainable production of food are obvious, with some studies suggesting we only have an average of 60 years’ worth of harvests left under the current practices.

We shouldn’t ignore the inherent potential of this crisis to exacerbate existing economic inequalities, too; according to the study authors “critically unbalanced land productivity trends in African cropland and grasslands are particularly concerning given expected population growth.”  This, in fact, highlights the most worrying trend; even as soil is eroded away, and the amount of cropland dwindles, the global population increases apace, with 9 billion mouths to feed estimated by 2050.

Farming in Uganda (Source: GfGD)

Moreover, the UN study emphasises that degradation of soil and loss of agricultural land increases the competition for already-scarce resources, which could lead to mass migration or social instability, further increasing the difficulty of implementing sustainable solutions.

So how has the problem become so acute? It is useful to first explain how soil erosion occurs naturally, before thinking about how humans have impacted the natural cycles. Roughly, natural soils form as the result of chemical breakdown of underlying bedrock, supplemented by organic matter decaying from dead plants and animals. In a stable system, the rate at which soils are produced is in balance with the rate at which water washes away surface material during floods and storms.

In some parts of the world, where warm, wet, conditions are ideal for plant growth and chemical reactions, soil can grow extremely fast – as much as 2.5mm per year, although the global average is nearer to 0.1mm per year.

Water is the primary agent that erodes the soil. Whenever rain falls, droplets can dislodge material, and these can be washed away downhill or carried in floodwaters over landscape. It’s no surprise, then, that soils through which water can more easily infiltrate are less likely to lose material to overland flow. However, humans have fundamentally altered this balance.

Natural forests allow water to infiltrate into soil quickly, but without root systems and porous soil this can be much lower. For example, in Wales scientists demonstrated that forested plots had infiltration rates 67 times faster than sheep pastures. Agricultural land is similar, or can be worse; if there are no crops to bind the soil together for some parts of the year, or if ploughing churns up the soil and allows material to be easily washed away, topsoil can be severely depleted in a single flood.

These two factors – lack of plant cover, and extensive tillage – are hallmarks of high intensity farming globally, but as the UN study points out, while this kind of farming has increased productivity over the last decades, it is increasingly unsustainable. Addition of fertiliser has increased the productivity, but masked the degradation of arable land. Moreover, in some regions it creates a viscous cycle, where loss of productive land leads to deforestation to access untapped soil.

Forests are key buffers against many slow and fast moving disasters; they can limit flooding, by encouraging water to infiltrate rather than running over landscape, and in doing so can allow more water to reach aquifers – thus limiting drought later. They also serve important roles in stabilising hill-slopes against landslides, and slow desertification. Given how long it takes for forest to regrow, it seems clear that the impact of soil loss will be felt for years to come.

So what can be done to prevent it? And how can geologists act to help address the problem, particularly how we can still achieve sustainability goals in the face of the rapid loss of life-giving topsoil? An integrative approach is certainly important. Soil is the interface where life, at a microbial and macro-scale, coexists with physical and chemical processes in the bedrock. Understanding how all of these fit together is crucial to build a clearer picture of the at-risk soil.

Sustainable rehabilitation of agricultural land has been achieved at a wide scale in some countries, like Ethiopia. Surface process geologists could help by producing maps of local and regional propensity for erosion, to help guide these efforts. Scientists from the Kenya-based World Agroforestry Centre have been hard at work producing for the first time maps of soil chemistry and health across sub-Saharan Africa, and these should similarly help to more efficiently utilise the soil for particular crops, and aid in crop choice for a given location, if appropriately combined with crop biology assessments.

The authors of the UN study explain that increasing the efficiency of agriculture would certainly alleviate some of the stress on croplands. Improvements in efficacy can be found at different points throughout the food supply chain; for example, the authors write that:

“Eliminating food waste would reduce the projected need to increase the efficiency of food production by 60 per cent to meet expected demands by 2050”.

Meat uses five times as much land for a given nutritional intake than the comparable vegetable option, so reducing the intake of meat, along with other nutritionally inefficient crops (like soy and palm oil) would distinctly reduce the amount of cropland needed to feed 9 billion people. These solutions are politically sensitive, of course, but scientists can make informed decisions about their own food choices, and encourage others to do the same.

Above all, given how important soil is to land surface processes, many geologists could ask themselves which aspects of their own knowledge might help alleviate this significantly under-reported problem. While we have alternative, renewable energy sources to turn to instead of fossil fuels, we don’t yet have an alternative to soil, and as such it’s perhaps imperative to think about soil as one of our most threatened resources.

Robert Emberson is a science writer, currently based in Victoria, Canada. He can be contacted via Twitter (@RobertEmberson) or via his website (www.robertemberson.com).

**This article expresses the personal opinion of the author. These opinions may not reflect official policy positions of Geology for Global Development.**

Volcanic and Biological Hotspots

Geology for Global Development followed Professor Iain Stewart’s BBC two TV series (June 2013), ‘Rise of the Continents‘ with interest. In the first episode, Iain mentioned something that really caught our attention – the strange volcanoes along the East African rift valley and their effect on soils and wildlife. 

Each year, as the rainy season transforms the Serengeti, a nutrient hotspot emerges: a small patch of grass that is exceptionally rich in calcium and phosphorous, essential nutrients for healthy calf development. Millions of wilderbeast are born here at the end of their mothers long migration, and for a short while, this hotspot hosts the largest concentration of grazing herbivores on the planet.

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A look at the Ol Doinyo Lengai lava down the microscope, under crossed polar light, reveals some unusual minerals (combeite, nepheline, aegirine, sodalite). Source: T Peterson, Mindat. More information here.

The grass in this part of the Serengeti is unusual because it lies on soil forged by one of Africa’s most explosive volcanoes, Ol Doinyo Lengai, known to the Maassai as the ‘Mountain of God’. As Iain Stewart squeezed droplets of acid onto the lava, bubbles of carbon dioxide were released, indicating the presence of carbonate minerals. This is the world’s only active carbonatite volcano. 

The sodium and potassium carbonate minerals of the Ol Doinyo Lengai lavas are unstable at the Earth’s surface and susceptible to rapid weathering. Within a few months of erupting, lava flows turn from black into a pale powder. The resulting volcanic landscape is different from any other in the world.

To form lava with such strange properties, the rock must have melted at low temperature and high pressure. At only 500-600 degrees, carbonatites are relatively cool by lava standards. The volcano is fed by the mantle superplume that stretches out beneath the rift valley, pulling Africa apart. The red sea will one day (in the very distant future) flood this plain, splitting the region in two.

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Ol Doinyo Lengai eruption 1966, from U.S. Geological Survey.

Ol Doinyo Lengai lies at the end of a chain of extinct volcanoes and its crater rim sits atop the products of previous eruptions. Evidence of previous activity is rife, so an eruption was never unexpected. Geologists suspected that a sudden increase in daily earth tremors felt in Kenya and Tanzania, reaching up to 6.0 on the Richter scale, were  indicative of the movement of magma through the Ol Doinyo Lengai. The volcano erupted shortly after, on September 4, 2007, sending a 5Km plume of ash and steam at least 18 kilometers downwind and covering the north and west flanks in fresh lava flows.

The eruption ruined crops and forced local residents, mainly herders, to flee with their livestock. The people living nearby are concerned that it will happen again.

The mantle plume beneath East Africa is of great environmental importance. This region of intense geological activity has resulted in problems with water contamination within the rift valley, as well as producing volcanic and seismic hazards. However, the strange nature of the carbonatite lava has created a nutrient hotspot – one that draws both animals and people into the region.

 

Recommended Reading:

Nasa have an information page on Ol Doinyo Lengai, which includes some very clear aerial photographs. 

The Ol Doinyo Lengai Website includes photographs and information on past eruptions.

GfGD at #EGU2013 – Day three

Mid-week at the EGU conference, and we’ve finally got all three GfGD reps in the same place at the same time for a photo!

Faith Taylor, Joel Gill and Rosalie Tostevin in Vienna

Another busy day, and we’ve picked out a few examples of the latest research being presented at EGU:

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The Link Between Rainfall and Cholera in Haiti

Prior to the devastating earthquake in 2010, cholera had never been reported on the small island of Haiti. The outbreak of the disease in the wake of the earthquake affected nearly 8% of the population and killed over one in a hundred. The disease is now endemic in the country and may never leave. The disease was most likely brought into the country by UN soldiers, who arrived to help the Haitian people after the earthquake – the DNA of the virus has been linked to outbreaks in Nepal.

Outbreaks of cholera during the epidemic correlate closely with rainfall patterns. If we can predict rainfall patterns accurately, then maybe we can anticipate, and prepare for, the spread of disease. Enrico Bertuzzo and Andrea Rinaldo, based at the École Polytechnique Fédérale de Lausanne in Switzerland, have created a model that accounts for rainfall as the driver of disease transmission by washout of open air defection sites or cesspool overflows. Their model allows us to draw longer term predictions for the cholera epidemic in Haiti, and the same model could be adapted to help us understand epidemics of other water borne diseases.

“Geoscientists can do a lot for modern epidemiology”

– Andrea Rinaldo

The red line tracks cholera outbreaks, and the blue bars show the amount of rain that fell during the same time period. There is a significant correlation between the two.


Soils and Human Health

Soils have an important influence on human health. It is soil that enriches our food with essential vitamins and nutrients, but it can also exposure us to harmful chemicals and disease causing organisms.

Soil is closely tied to atmospheric cycles and can be influenced by changes in temperature, precipitation and carbon dioxide levels. Climate change could alter nutrient cycling and the carbon cycle, and in turn affect soils.

After 594 mysterious deaths in the united states, a deadly soil fungus that can lead to meningitis was identified in each of the victims. Infections were traced back to contaminated steroid injections, produced by a New England compound centre. Lynn Burgess, a professor at Dickinson state university, admitted that “we have no idea how a soil fungus ended up in a medical injection.”

Soil scientists and health experts are collaborating to try and forge a new academic field, looking at the link between soils and human health. This kind of cross disciplinary work is difficult because it doesn’t fit into our traditional research funding framework. Health and soil researchers are two groups that don’t normally talk to each other, so we need to encourage cross-disciplinary involvement if we want to increase our resilience to soil related health problems.

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Disaster Risk Management

The toll from natural disasters is increasing as populations rise. At the same time climate change is making the frequency and intensity of climate related events harder to predict. We cannot predict the precise location and timing of most hazards, but we can model risk, to help us understand how people and communities respond to events, and how countries prepare for the financial and human impacts of a disaster.

People in developing countries are more vulnerable to disasters – 95% of the total number of deaths in disasters last year occurred in developing countries. This is a result of the increased exposure and vulnerability of populations in developing countries.

“Natural Hazards are a necessary condition, but you need vulnerability and exposure before you have a disaster”

– Reinhard Mechler

Between 1980 and 2009, a total of 90 billion dollars was spent on disaster related activities. The majority of this money was spent on disaster response and relief, and under 5% was invested in prevention and risk management. The UK government’s Foresight report into Reducing the Risks of Future Disasters championed the idea that in risk management, prevention is better than cure. Investing in risk management and reduction makes financial sense. It is thought that the benefits outweigh the costs by a ratio of at least 4:1 in most cases. This means that for every pound we spend before a hazard occurs, we save four in disaster response operations.

“Even in times of fiscal austerity, disaster risk management should be a priority for government investment”

– Reinhard Mechler

Countries can reduce their exposure to financial risk in disasters by grouping together and pooling the risk. This can significantly reduce the cost of disaster management.

“Grouping countries together and pooling their risk makes financing losses much cheaper”

– Stefan Hochrainer-Stigler

How can we ensure decision makers invest the pot of money available for disaster related activities in the most effective way?

One problem we face is perceived risk from stakeholders. A fear of flying is common, but statistically, crossing the road puts you at a much higher risk – people’s perception of risk may not be proportional to the size of the risk. Disasters that receive the most press coverage tend to receive more funding.

“bias in risk perception can be a barrier for implementation of mitigation measures”

–   Nadejda Komendantova

Cyclone shelters have been built and maintained in Tamil Nadu, India, for the last 40 years. These shelters could have been easily adapted to provide protection from tsunamis, but tsunamis were not a hazard that worried stakeholders in the area. The tsunami in 2004 resulted in seventeen thousand deaths. Clearly, the decisions made in this case were not based on sound science but on perceived risk from stakeholders.

Nadejda Komendantova, a researcher in risk policy and vulnerability, thinks it would be good to have more communication between scientists researching natural hazards and policy makers working in disaster risk reduction. Geologists are able to quantify risk through studying the past activity of hazardous geological phenomena, for example, we can calculate the repeat time of earthquakes on a particular stretch of fault. This information is very valuable, and we need to make sure it is understood by decision makers and incorporated into policy.

Investment in disaster related activities needs to be based on facts not opinions. People are starting to recognise the importance of investing in prevention rather than cure, but we still need to put more emphasis on incorporating good geoscience into disaster risk management.

 

Joel Gill talks about his Multi Hazards Research

What are the chances of an earthquake triggering a landslide, which causes a tsunami and leads to flooding? Joel Gill, GfGD Director,  is researching the extent to which an individual hazard increases the probability of other hazards occurring as part of a PhD at Kings College London.

Joel Gill presents a poster on multi-hazards at EGU 2013