Category: Aridity: Arid

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Dune Planting

Synonyms: Dune fixation, wickerworks

Dune grass planting is a dune restoration technique that reinforces dune stability by establishing vegetation capable of trapping, anchoring, and accumulating sand. This process is effective in both coastal and inland dunes, where wind erosion, overgrazing and sand mobility pose threats to ecosystem stability.

In coastal settings, grasses like marram grass (Ammophila arenaria) and lyme grass (Leymus arenarius) are essential for initiating and maintaining dune growth. Marram grass, in particular, grows vigorously in sandy environments, extending its roots both horizontally and vertically as sand accumulates. This growth pattern allows the grasses to trap sand and stabilize dune surfaces, reducing wind speeds at the ground level and encouraging sand to settle. By reducing the velocity of surface winds, the grasses create a self-reinforcing cycle of sand accumulation and root expansion. This process promotes the formation of “yellow dunes” further inland, while more resilient species like sand couchgrass (Elymus farctus) stabilize the vulnerable “foredune” zone nearest to the shoreline, where occasional seawater inundation occurs.

In arid, inland dune regions where desertification is a concern, planting drought-resistant vegetation such as Leptadenia pyrotechnica and Calligonum comosum serves a similar function. These species prevent sand from moving with the wind by creating dense root systems that hold soil in place. The combined horizontal and vertical growth of these plants enhances soil retention, improves the dune’s physical stability, and reduces the likelihood of sand encroachment on nearby agricultural or pastoral lands. By acting as windbreaks and anchoring loose sand, these plants encourage dune formation and mitigate the physical impacts of wind erosion.

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Dune Thatching

Covering exposed dune faces – or blowouts – with waste cuttings from forestry or other low-cost materials is a technique called dune thatching. It is used to stabilize sand, reduce trampling, and protect vegetation. When locally sourced, thatching materials are inexpensive, and the process requires no machinery or skilled labor. This method is typically combined with dune grass planting to further enhance dune stability. 

Properly applied thatch can aid dune recovery and provide resistance to erosion, although it cannot fully protect areas where waves frequently cause damage. The thatch slows surface wind speeds, encouraging sand to settle and accumulate. The effectiveness of this approach depends on the presence of blown sand, frequency of wave impact, presence of vegetation, and level of maintenance. Planting dune grasses after thatching can further improve dune recovery and stability over time. 

In this intervention we distinguish two types dune thatching:

  • Dune thatching with old (Christmas) trees:  Creating a natural barrier by digging in old (christmas trees) in a line parallel to the shoreline. This barrier promotes the entrapment of sand and in combination with dune grass planting this can stabilize dunes and promote formation of new dunes.

  • Dune thatching with millet stalk palisades: Creating physical sand barriers from dried plant palisades can be arranged in various ways depending on the level of sand dune destabilization. In heavily encroached areas, millet stalk palisades arranged in square grids can act as considerable wind catchment zones and prerequisite for revegetation. After two years, these palisades tend to fall apart and decompose and restored vegetation takes over the dune fixation function.
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Dune Fencing

Building semi-permeable fences along the seaward or the prevailing wind side of dunes encourages windblown sand to accumulate, reduces trampling, and protects both existing and newly planted vegetation. Various fencing materials can effectively enhance natural dune recovery. This type of fencing is often combined with other management practices to promote dune stabilization and minimize environmental impact.

The use of dune fencing for wind erosion control and dune stabilization has a long history. Its success relies on factors such as the fence’s void-to-solid ratio, the availability of wind-driven sand, the frequency of wave activity at the fence line, and the amount of vegetation present to help stabilize accumulated sand. Combining dune fencing with other strategies, such as Dune Planting or Dune Thatching, can help establish new foredunes and further enhance stability.

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Muvuca Direct Seeding

Similar names: Seed-based land restoration, Direct sowing

Muvuca direct seeding is a nature restoration method, where a mix of seeds from dozens of native species at different successional stages are planted simultaneously into the ground. The method mimics natural regeneration mechanisms such as seed soil banks and seed rain. Better known conventional practice is direct seeding’s popular counterpart – transplanting, which is a technique of moving plants from one location to another, usually to preserve the optimal condition of the seedlings. Despite providing more control over the plant’s growth, transplanting doesn’t allow for a high variety of plant seeds to grow simultaneously.

The Muvuca system uses a high diversity of species and ensures longer-term operational efficiency, which in return enables mechanised restoration with reduced planting, low maintenance in terms of time and reduced costs. Planting can be done either manually or mechanised (using machinery such as tractors), which enables the scalability of the intervention. Furthermore, the grown plants through Muvuca become more robust and resistant to various weather conditions, which results in stronger root systems and overall healthier vegetation. Overall, Muvuca direct seeding can contribute to the scaling up of restoration efforts, while reducing costs and increasing the species diversity. Meanwhile, the demand for native species enables the promotion of conservation and well-being.

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Stone Lines

Similar names: Cordons pierreux, stone bunds.

Stone lines are stones grouped in the shape of a line and placed along contours. The stones can be of different sizes. The goal of these lines is to conserve the soil and reduce runoff, as they are used to slow down water runoff and break its velocity. Hence, they increase infiltration and retain sediment and seeds to make water and nutrients available for crops. Stone lines are most suitable for water harvesting on slightly sloping plains (up to 5%) in semi-arid regions. For slopes starting from 5%, stone bunds can be used (see eyebrow terraces).

Stone lines are an easy and cheap intervention if stones are available in the immediate surroundings. This intervention is widely used in Africa, both in dry and humid areas. Moreover, stone lines are often used in combination with Zai Pits intervention for the rehabilitation of degraded and crusted lands. It is applied in semi-arid areas, on sandy and loamy soils where the slope is lower than 5%. A great example can be seen in Niger, where the combination of the two techniques is applied to capture runoff, making infiltration more efficient and improving nutrient availability. The pits have a diameter of 20-30 cm, and a depth of 20-25 cm and are spaced about 1 m apart in each direction. Stone lines are spaced 20-25 m apart on slopes of 2-5%. With this layout stone lines are quite small, usually, three stones wide and only one stone high and they are placed, along the contour lines, by hand. Very often grass grows between the stones leading to a greater infiltration and helping the accumulation of fertile sediments. Maintenance-wise, stone lines need to be repaired annually, in particular after heavy precipitation events.

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Terracing

Terracing is a method of farming and soil conservation on hills and sloped lands. It was traditionally used by the Incas and is widely practised around the world today. It involves the building of platforms, and forming step-like structures along a slope. The main goal of bench terraces is to periodically interrupt the slope of the terrain with flat sections; this helps to decrease the speed of water runoff,  significantly reducing soil erosion and surface runoff. By slowing down water speed, this intervention stops the washing away of topsoil containing important nutrients and promotes better water infiltration and soil moisture. The flat benches of the terraces create more effective and productive areas to farm on steep terrain.

There are two main types of terracing techniques: graded terracing and level terracing. With graded terracing, the slope can vary along the length of the terrace to direct water in the desired direction; this is especially useful for less permeable land. With level terracing, the terraces follow a contour line and do not vary in slope along this line, this ensures that water is more evenly distributed along the terrace. Stone or wooden walls are often used to hold terraces in place, although a simple earth wall without supporting material can be used with slopes and terraces on the smaller side. This intervention is similar to Fanya Juu and Fanya Chini which are specific types of terraces.

Terracing offers several ecological and socioeconomic benefits. Ecologically, it prevents soil erosion by slowing water flow, allowing it to infiltrate the soil and retain valuable topsoil, which is essential for agriculture. Terracing also manages water more effectively by evenly distributing it across levels, conserving water, reducing irrigation needs, and promoting nutrient cycling. It creates diverse habitats for various plant and animal species, enhancing biodiversity. Additionally, terracing stabilizes slopes, reducing the risk of landslides by minimizing soil pressure and movement, especially in regions with wet seasons. Socioeconomically, terracing increases land productivity on slopes, allowing for larger crop beds and easier use of machinery, thus boosting agricultural efficiency.

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Vegetative Lines

Vegetative lines involve the planting of lines of vetiver grass following the contour lines, along stream banks and roadsides, to create a hedge. These hedges act like semi-permeable barriers, aimed to hinder surface erosion as they slow down run-off and retain sediments picked up by excess rainwater. This setup improves water infiltration and helps to increase the ground moisture level. Their root systems also help stabilise the soil and prevent further soil erosion. Thus this provides increased stabilisation of embankments, gully erosion, roads and slopes. Furthermore, water runoff and soil runoff reductions are observed, at around 57% and 80% respectively.

Vetiver grass can grow on slopes of > 50% and can be planted on a high variety of soils (red latosols, black cracking vertisols, roadside rubble, C-horizon gravels, laterites, sodic, and saline soils). Furthermore, vetiver grass is resistant to different types of climatic conditions: rainfall from 600mm to 6000 mm /year and extreme temperatures of -14°C to 55°C, and could survive several months submerged in water. Vetiver grass can support high levels of toxicity by manganese, aluminium and other metals and high levels of soil acidity, salinity, alkalinity, and acid sulphate conditions. All in all, they provide great solutions as they are non-invasive, fire resistant, and regrow quickly and be used as mulch, fuel (vetiver energy value is 55% the energy value of coal), and as fodder. Finally, vetiver grass is very efficient in stabilising Semi-Circular Bunds, Eyebrow Terraces or Negarim.

Very similar to the intervention described above is the so-called “Vegetative lines with cactus”. This intervention is based on the same principle as the Vegetative lines with vetiver grass, but it is suitable for drier environmental conditions (0 – 600mm). Like some other interventions, over time, this type of intervention can lead to the formation of terraces due to tillage and water erosion between the hedges.

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Fanya Chini

Similar names: Retention trenches, infiltration trenches

The name Fanya chini means “throw it downwards” in Kiswahili. It consists of trenches and earthen ridges facing downslope. This intervention aims to reduce soil erosion by breaking down long slopes into smaller sections. Thus, the speed of runoff will decrease, and water can infiltrate into the soil between the bunds. This will result in a reduction of nutrient leaching and increased water availability for crops. Fanya chini is common in areas with 300-600 mm of annual rainfall on 1-25% slopes. It is suitable for all types of relatively permeable soils (e.g. alluvial, red, laterite, brown, and shallow and medium black soil). Still, it doesn’t work very well with clayey soils or vertisols as these are not permeable.

One of the main benefits of Fanya chini is that it limits soil erosion from water runoff, and simultaneously improves water retention in the soil and increases water availability for crops. Furthermore, an increase in yield is observed, as well as improved soil fertility.

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Fanya Juu

Similar names: Terracing, Retention Trenches, Infiltration Trenches

The Fanya Juu technique is an agricultural practice that involves creating ridges along the contour lines of sloping land. The name Fanya Juu means “throw it upwards” in Kiswahili and is very similar to Fanya Chini as it consists of terrace bunds and ditches along the contour. This technique rapidly spread during the 1970s and 1980s and it is well known throughout Eastern Africa, the goal of Fanja Juu contour bunds is different depending on the environmental conditions of the areas within which they are applied. Their aim in semi-arid areas is to harvest and conserve rainfall, whereas, in sub-humid zones, contour bunds are constructed to discharge excess runoff. However, their main purpose is to prevent water and soil loss and to make conditions more suitable for plants to grow. 

Fanya Juu is suitable for slopes of 5-20%, similar to the ones that characterize Fanya Chini interventions. The species most often used in drier zones are Pennisetum Purpureum (Napier grass or Uganda grass) and Panicum Coloratum (also known in southern Africa as “white buffalograss”) and the harvest can be used as fodder for livestock. Fruit trees (e.g. citrus or bananas) can be planted either immediately above the embankment or below the ditch, where runoff tends to concentrate.

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Zai Pits

Similar names: Chololo pits (Tanzania), Zaï pits (Burkina Faso), tassa (Niger), agun pits (Sudan), kofyarpits (Nigeria), yamka (Kyrgyzstan), planting pits.

Zai Pits are small basins in which the seeds of annual or perennial crops are planted. The pits are then filled with Mulch, manure, compost or good soils to increase soil fertility and the capacity of the soils to retain water. Zai Pits can be beneficial for soil conditions and they are a very successful method which can allow for the growth of vegetation in dry areas. They are also very efficient in protecting seeds and soil organic matter from being washed away from water runoff. One of the major advantages of Zai Pits is that it increases water filtration, through the collection and concentration of water for the plants due to increasing termite activity. What is more, Zai Pits can collect more than 25% or more of run-off water. This as a result decreases water run-offs and evaporation. When looking at the bigger picture, Zai Pits can improve soil fertility and agricultural productivity of several crops and can increase production by up to 500% if well executed.

Zai Pits are an efficient method to increase yield productivity due to more water and nutrients available. This intervention is most suitable for flat or gently sloped terrains (0-5%) with a precipitation range of 350-600 mm/y.  Zai Pits can also work with other techniques such as stone contours and hand-dug trenches.