Geology for Global Development

Agriculture

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.**

Guest Blog: Could agroforestry do more to protect Rwandans from hazardous landslides?

Megan Jamer is a geoscientist from Canada, and an avid cyclist and explorer. Megan is currently travelling around East Africa on bicycle, taking in some remarkable sites and observing first hand the relationship between geoscience and sustainable development. Today Megan makes her debut on the GfGD blog site, writing on the relationship between agroforestry, landslides, and disaster risk reduction.

Some landslide interventions are hard to miss along Rwanda’s highways. There are gabions, and concrete drainage pathways, kept unclogged by women and men in fluorescent vests. Other strategies are more subtle. Where cassava or bean plots are mixed with banana trees or ringed within a hedge, this may also reduce the damage caused by landslides in this central African nation. Rwandan agroforestry is getting attention. The strategy, which combines trees and crops in the same area, is being used to work towards the 2020 goal of trees covering thirty percent of Rwanda’s total surface area. In 2014, more than half of new seedlings distributed by the government were agroforestry or fruit varieties. Food and land scarcity pressure Rwanda’s slopes, and agroforestry is one way to address the root causes of these shortages, protecting against landslides in the process.

A rural dwelling in the hills of northern Rwanda, excavated into the slope (author’s own).

The Problem of Landslides

At least sixty-seven people were killed last year by landslides and mudslides in the north and west, and in the capital, Kigali. Deadly or not, they cause wide-ranging infrastructure damage, harming public infrastructure and trading patterns, as well as hillside settlements and agriculture. Landslides here disproportionately affect the poor, who pursue subsistence agriculture on steep slopes or live in vulnerable urban areas because they have few alternatives.

In the ‘land of a thousand hills’, slopes are made more vulnerable by rainfall patterns that some say are difficult to manage. In The New Times last year, coffee grower Pierre Munyura said that in western Rwanda“we receive about the same amount of rainfall as ever, but the rain comes in heavier and more destructive bursts.” Rainstorms are considered to be the main trigger of landslides in Rwanda, but human activities prepare the slopes for failure. They are cleared and levelled for walking pathways, homes, latrines, small plots and gardens. Other areas are hollowed out for small-scale mining. The result of these activities is a complex pattern of slope disturbance and deforestation.

Hillside communities cultivate in a manner that reflects traditional knowledge, regulations, and the resources available to them (author’s own)

Similar environmental and human conditions come together on the slopes of Mount Elgon in Uganda, where the causal factors of landslides were investigated. The researchers’ prognosis was bleak: “The growing population density not only increases the risk of damage, but hampers the search for solutions for the landslide problem as well.”  Understanding occurrence is the first step in managing rainfall-induced landslides, says Dave Petley of The Landslide Blog, and here Rwanda has made big strides. Its Ministry of Disaster Management and Refugee Affairs (MIDMAR) published a National Risk Atlas in 2015, an analysis of the earthquakes, landslides, windstorms, droughts and floods that challenge Rwanda’s resiliency. The Atlas inventories hazardous landslides, estimates slope susceptibility, and shows maps of properties that affect landslide incidence, including rainfall, slope angle, ground cover and soil characteristics.

MIDMAR’s analyses estimated that nearly half of Rwanda’s population lives in areas with moderate or high slope susceptibility to landslides. These hazards are commonly small and localized, requiring community action, but “knowledge at the citizen level [about landslides] is still low,” says Dr. Aime Tsinda, a Senior Research Fellow at the Institute of Policy Analysis and Research-Rwanda. Translating information in studies like the National Risk Atlas into local knowledge is a slow process. While it’s underway, communities are motivated to adopt agroforestry because of a hazard they are already familiar with: poor quality soil.

More Trees!

Agroforestry is the ‘intentional integration of trees and shrubs into crop and animal farming systems to create environmental, economic and social benefits’. On cultivated slopes where agroforestry isn’t practiced, small plots drape over them, resembling smooth patchwork blankets. Like blankets, their soils can more easily wash away, creep or slide catastrophically. This is what happened last year, says J.M.V. Senyanzobe, a Forestry Lecturer at the University of Rwanda. “If you observe the concerned areas,” he says, “they were empty of trees, just grasses which are not strong enough to stop the soil from being eroded.”

When trees are cut down their roots decay, eventually rendering them ineffective soil binders. The slopes of Mount Elgon demonstrate the difference. Forested areas lacked evidence of landslides, even when they grew on slope angles and in soil types that contributed to slope instability elsewhere in the study area. Deforestation began as early as 3000 BC in what was Rwanda-Urundi! Reforestation and tree cultivation have been encouraged since the 1930s and it’s working: In 1996, an FAO agroforestry study exclaimed that “photographs taken in Rwanda in the early years of this [twentieth] century show landscapes almost devoid of trees, a stark contrast to the present.

Some Rwandans are motivated to plant because of what the trees themselves offer. Bananas are brewed into beer, coffee trees have been called ‘Rwanda’s Second Sunrise’, and eucalyptus and pine provide construction materials. Other trees are valued for their structure, for example marking plot boundaries. And it’s taken some convincing, but more people are trying out types of agroforestry that plant trees and crops together, in an effort to improve soil quality. There are techniques that do more to increase soil stability. This guide recommends mimicking the plant diversity of a natural forest as much as possible, or to plant tree rows within crops along topographic contours. Within Rwanda, living hedges were found to greatly reduce soil erosion, but landslide prevention wasn’t specifically investigated. Senyanzobe recommends a combination of reforestation between cultivated areas, and agroforestry species within crop areas.  Ultimately, “the sustainable solution is to plant trees as much as possible,” he says.

Outside of agroforestry, is there a way to reduce hazardous landslides in Rwanda? Enforcing rules about how people should excavate slopes or use terracing appropriately is difficult, especially in remote areas. Similarly, mass relocation of vulnerable hillside communities is unrealistic in mainland Africa’s most densely populated country. Large-scale agroforestry interventions, by contrast, are already underway. But because they aren’t undertaken to address landslides specifically, their effectiveness is currently limited.

Pieces of the Puzzle

Speaking to the effectiveness of agroforestry for any goal, “it needs to be implemented with sensitivity to people’s needs, priorities and sociocultural and economic conditions,” says the FAO. It’s not yet clear whether many Rwandans choose tree planting specifically for reducing landslide risk—today, selling the tree’s products or increasing soil fertility are more powerful motivators. If this is how communities prioritise, then agroforestry will be pursued to the extent that those benefits are gained. The damage by landslides may be mitigated, but as a by-product.

Obstacles to agroforestry being used for disaster risk reduction overlap with the challenges of agroforestry in general. One major hurdle in Rwanda is the belief that trees can damage crops by shading them, drying them out, or otherwise competing. Unfortunately this is sometimes true. Avocado trees can harm the crops closest to them. Pine and eucalyptus trees are resilient, but also invasive.

Making the most of agroforestry involves more conversations about the risk—and prevention—of landslides. On the heels of its efforts to understand occurrence of its natural hazards, Rwanda is trying to increase public awareness of landslides in a number of ways. In the official guide to primary school construction, choosing a stable slope location is a ‘must,’ and instructions are given to this end. Public radio broadcasts, disaster committees at the district level, and discussions during monthly community service day (umuganda) on topics including disasters are other examples. Currently, about a quarter of disaster-related spending in Rwanda is directed to prevention and mitigation.

Seedling distribution on National Tree Planting Day looks pretty good, but so does a new home. Recently, several high-risk families were relocated to ‘disaster resilient’ homes in collaboration with UN-HABITAT. Both of these events received media coverage, but were largely treated as separate topics.

The collapsed downslope shoulder of a road in southern Rwanda (author’s own)

These conversations in the media and during umuganda need to continue, but hopefully soon when there’s talk of landslides in Rwanda, trees and agroforestry will be a bigger part of the discussion.

Do trees keep you safer from hazards in your environment? Do you think that any tree planting is a good thing when it comes to landslides, or can it bring mixed results?

Guest Blog: Micronutrients, Hidden Hunger and Geology

DSC_0494In January 2015, GfGD took a small group of members to a discussion event hosted by the British Geological Survey, on best practice in international development. Ben Clarke and Eleri Simpson, then final year undergraduates at the University of Leicester (UK) joined the event to share about their fantastic work in Vanuatu. Here they write a guest blog about one presentation that caught their interest… 

Mélanges, magmas and micrites are all familiar terms in geology, but what have micronutrients got do with anything? Quite a lot it appears. This is one of the least known aspects of study that the British Geological Survey (BGS) undertakes, and formed one of many fascinating discussions held between BGS and GfGD on a rainy day in January.

Micronutrients are the substances we all need, in small amounts, to develop properly; from Vitamin A to Zinc they decide whether we develop and maintain an immune system, a fully functioning brain and even whether we can see or not. It seems imperative therefore, that we get enough of them. This isn’t the always the case, in fact it’s estimated that in excess of two billion people on Earth don’t receive enough 1. What’s more is the effect can be measured economically: economic loss associated with micronutrient deficiency (or hidden hunger) is thought to amount to 2.5% of India’s Gross Domestic Product (GDP) 2; to bring this into perspective this amounts to about £15 billion in 2007. But why? If children don’t receive enough Iron or Iodine, their cognitive development is impaired, they don’t achieve academically at school and they don’t become the scientists, doctors and business-people that the country needs to flourish. If adults don’t get enough Iron or Vitamin A, they become tired and are ill more regularly, straining any medical system that may exist and reducing productivity. It seems not just because of the day-to-day effects of such ‘hidden hunger’ on humans, but also the economic effects on entire countries to be in everyone’s interest to tackle the problem.

Picture5So where do we get these substances from? This is where geology comes in. We receive micronutrients from the foods we eat, but the concentration of them in food depends on the soil it’s grown in. If you want to understand the soil, speak to a soil scientist. Dr Michael Watts, a geochemist at the BGS works in partnership with scientists from universities in Malawi, Zambia and Zimbabwe to study the problem and to find simple solutions that can be easily implemented on a local level. Methods such as using enriched fertilizers and planting crops that more readily absorb micronutrients in the soil have the potential to vastly change lives on a local level, and if scaled up may produce enormous regional impacts. But for such schemes to be sustainable, it requires local initiative, and because of this the BGS aims to fund doctoral training programmes and PhD exchange schemes for African students so that in time these countries have the expertise to tackle the problems themselves.

It’s great to see that research like this is being so thoughtfully and effectively undertaken by the BGS but we can’t sit on our laurels, micronutrient deficiency isn’t just a problem in Africa: Bangladesh, Honduras, India and many other countries also suffer. Far more work is still required by the next generation of geologists, biologists, chemists and anthropologists to enrich our diets. It’s surprising what you might learn on a rainy day in January.

1 Kennedy, G., Nantel, G., Shetty, P. 2003. The scourge of “hidden hunger”: global dimensions of micronutrient deficiencies. Food, Nutrition and Agriculture (FAO). 1014-806X, (no.32) p. 8-16.

2 Stein, A., Qaim, M. 2007. The human and economic cost of hidden hunger. Food and Nutrition Bulletin, vol. 28, no. 2, p. 125-134

Dr Michael Watts will be joining the 3rd GfGD Annual Conference (Friday 30th October 2015, The Geological Society, Burlington House, London). He will be joining a panel discussion on geology and the Sustainable Development Goals. Information and registration details here.


Editors Note (3:10pm, 4th Sept 2015): There is an excellent blog on the BGS website also discussing this theme.

Back to Basics – Geology and International Development (Part 2/4)

How can an understanding of geology support and strengthen international development?

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#4 – Geotourism. Many geological features carry enormous value, not just in terms of their scientific importance, but also as an attraction to domestic and international visitors. Unusual rock formations, key geomorphic features, volcanic landscapes etc are all destinations that may help countries generate income and livelihoods. If it is done well, this can help support geoconservation of key sites for future generations and geoeducation – helping a range of people better understand their natural heritage. Our feature image today is from Zhangye, in the Gansu Province of China, showing the colourful Danxia landform.

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#5 – Agrogeology is the application of geology to agricultural practice, examining how soil nutrients, pH and soil structure can be improved using locally available, mineral-rich rock materials. Food security and sustainable agriculture is fundamental to global development. A key text, Rocks for Crops, outlining the principles of agrogeology, has been written by Dr Peter Van Straaten. You can find this –http://www.uoguelph.ca/~geology/rocks_for_crops/

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 #6 – Infrastructure development (e.g., roads, bridges, dams, ports, airstrips) requires a thorough understanding of ground conditions. Engineering geologists are an important part of the team attempting to assess soil and rock mass behaviour, determine slope stability and understand the hydrogeological regime in the area under development, in order to develop resilient infrastructure. Resilient infrastructure supports the fight against global poverty. Good transportation infrastructure, for example, enables better access to markets, education, and healthcare facilities.

 For more images and key themes, see Part 1/4 of this series and keep an eye on our Facebook page over the coming days.