DESERT AS A REVERSIBLE TRANSITION

Nunes, J., Landscape Architect, PROAP – Landscape Architecture (joao.nunes@proap.pt) Ribas, C., Landscape Architect, PROAP – Landscape Architecture (carlos.ribas@proap.pt)Campos, T., Landscape Architect, PROAP – Landscape Architecture (tiago.campos@proap.pt)Sanz, B., Landscape Architect, PROAP – Landscape Architecture (proap@proap.pt)

In arid countries such as the UAE, characterized by extensive areas of drylands and increasing urban pressure in territorial and water resources, desertification process has been highly accelerated during last decades. Since 2002, the “Greening the Desert” program has been implementing different projects in order to combat desertification in the Gulf. Although well intentioned, some of the measures have been criticised for their unsustainability and high energy demand. This paper discusses desertification and land degradation and, more specifically, highlights the main causes and indicators of desertification in the UAE. Among others, hyper-aridity, over-exploitation of water resources, soil erosion and over-grazing are the most representatives. Throughout the hypothesis that the desert is not a condition but a state within an ecological process, this reasoning explains the possibility of reversing desertification process in arid ecosystems, which is graphically demonstrated with a theoretical curve relating energy input/time ratio. Along the “de-desertification” process, maximum energy inputs are needed to a reversal phase and a minimum energy input is needed for a maintenance phase. The less energy input needed during the process, the more sustainable and efficient the process becomes. This paper proposes an ecological landscape approach, figuring measures that sustain low energy inputs for greening the UAE deserts, based on a deep understanding of the desert ecosystem’s dynamics, the identification and manipulation of the natural limiting factors and the consideration of the interconnection between the site’s intervention scale and the larger scale of the territorial context, always considering landscape in its most inclusive conception.

Keywords: reversibility, desertification, de-desertification, energy input-time, ecological succession, resilience

1. Introduction

The present research presents some possible definitions of desertification in arid, semi-arid and sub-humid climates, identifying its main causes and, ultimately, appointing some significant landscape strategies to reverse this global process. The paper assumes that desert is not a condition but a state within an ecological process that can be reversed at the expense of landscape strategies, which stated between the energy inputs applied to the system and the time it takes to react.

Desertification was a major global issue during the twentieth century and it will remain on the international agenda in the present century. According to the International Institute for Sustainable Development’s (IISD) 1996 report, it affects about one sixth of the world’s population, seventy per cent of all dry lands and about one quarter of the total world’s land area (Figure1). According to United Nations Environment Program (UNEP, 1984), about six million hectares are irretrievably lost or degraded by desertification each year and about one hundred and thirty five million people are severely affected by this process.

In 1977, the UNEP defined desertification as “the diminution or destruction of biological potential of land which can lead ultimately to desert-like conditions”. According to this program “this process leads to reduced productivity of desirable plants, alterations in the biomass and in the diversity of life forms, accelerated soil degradation and hazards for human occupancy” (Lal, 1989).

Figure1. World’s desert areas or with tendency to desertification.

Later on, in 1994, the United Nations Convention to Combat Desertification (UNCCD) was approved in order to provide international guidelines for combating desertification1. From this convention, desertification was described as “land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors including climatic variations and human activities”.

Desertification can be defined as “a dynamic self-accelerating process, resulting from positive feedback mechanisms driving a downward spiral of land degradation” (Tivy 1990).

Land degradation, a possible synonym for desertification, encompasses soil degradation2, as well as, the weakening of natural landscapes and vegetation, as it is defined as the reverse of soil’s development or formation.

Human-induced land degradation includes overgrazing adverse effects, excessive tillage, over clearing, erosion and sediment deposition, extractive industries, urbanization, disposal of industrial wastes, road construction, decline of plant communities, the effects of animals and noxious plants, and pollution of the air with its effect on land (Houghton & Charman, 1986). In this regard, the best way to reverse land degradation is early action and prevention, rather than costly rehabilitation of degraded lands (Shahid, 2007)

Taking the United Arab Emirates (UAE) as a case study, this paper attempts to show an ecological landscape design approach to reclaim desertifying areas by preventing and/or reverting the land degradation process.

1 A total of one hundred and ninety one countries had ratified and accepted the guidelines of this convention in 2004: The UAE became a member in 1999.

2 Soil degradation lowers the current and/or the potential soil’s capability to produce goods or services (FAO-UNEP-UNESCO, 1979), causing the loss, or reduction, of soil’s functions and uses (Blum, 1997).

2. Desertification in the UAE

Situated in the Southeast of the Arabian Peninsula in Southwest Asia, on the Persian Gulf, the UAE3 are located within the arid west continent desert belt and therefore, environmental conditions are highly sensitive. Sensitivity is due to the delicate balance between numerous components of the arid natural systems such as climate, water resources, soil, vegetation, and biodiversity. Despite the little information available in specialized literature proving desertification in the UAE, there is an evident process of desertification due to both natural and anthropic stresses, especially enhanced during last decades4. The main causes of desertification in the UAE are outlined and discussed bellow.

2.1. Hyper arid conditions and climatic change

With extremely hot and dry summers – temperatures rising up to 48ºC in coastal cities and 50ºC in the southern desert regions –, mild to warm winters with sporadic rainfall – with annual average ranging between 120 and 200 mm per year –, and high evapotranspiration rates – averaging about 8 mm per day –, climatic conditions within the UAE can be regarded as hyper-arid. In this regard, the United Nations Environment Programme (UNEP) classifies the whole of Abu-Dhabi Emirate and most of the surrounding area as hyper-arid, belonging to one of the most inhospitable regions on earth (Middleton & Thomas, 1997).

Under these extreme conditions, desert areas are a dominant feature of the UAE landscape. Fully four-fifths of the land area is classified as hyper-arid desert regions, a very fragile series of ecosystems with unique features such as vast loose sandy deserts, oasis, long coastlines, islands and rangelands (Figure2) (Ministry of Energy of UAE, 2006).

Figure2. Arid ecosystems in UAE: coastal areas, desert areas and mountainous areas.

3 Bordered by Oman, Saudi Arabia and Qatar, the UAE spans approximately 83,600 square kilometers and is a federation of seven emirates: Abu Dhabi (the capital), Ajman, Dubai, Fujairah, Ras al-Khaimah, Sharjah and Umm al-Quwain

4 One accepts a great demand of an integrated and coordinated intelligent system between different environmental agencies and government departments, in order to share information for a better understanding of the desertification problem in the UAE.

In addition to these harsh environmental conditions in the UAE, it is estimated that climatic change will affect the near future distribution of the existing dry lands. Expected decreases in regional soil moisture can induce sub-humid areas to become semi-arid and semi-arid land to become arid. The Intergovernmental Panel on Climate Change (IPCC) notes that resistance to degradation and resilience will decrease as aridity increases (TAR, 2001), suggesting that the vulnerability of the desert ecosystems to arid conditions can increase significantly due to climate change5.

2.2. Over-exploitation of water resources

The UAE have the highest consumption of water per capita in the world, being eighty per cent of water consumption used for different greening projects (both agriculture and parks) and only thirteen per cent for domestic needs (Ouis, 2007). The high rate of water consumption is exacerbated by increasing population, urbanization and greening projects in the country. The volume of rainfall the UAE receives annually is not enough to meet the excessive and growing demands6. As a consequence, the extremely high rate of subsoil water demand, including non-renewable fossil water resources, is one of the today’s main environmental problems in the UAE and one of the most important threats for the future (Environmental Agency of Abu-Dhaby, 2007). Estimates shown by the National Drilling Company – United States Geological Survey (NDC-USGS) in 1996 revealed that, at the rate of abstraction estimated at that time, brackish groundwater might last for about two hundred and fifty years. However, the new abstraction rate in 2002, states that they will last for only fifty years.

2.3. Wind erosion

The UAE deserts are dominated by sandy soils and sand dunes of varying heights, continuously moving at different rates, therefore, aeolian deposits are predominant. Most parts of the country are subject to violent dust storms causing strong wind erosion (Shahid, 2007). Thus, it is demanding to understand the desert soil’s texture and to determine the mechanisms of particles movement in order to formulate necessary measures to reduce wind erosion.

After analyzing the particle movement mechanisms in surface deposits of UAE desert soils, it was deduced that particles ranging from 5 to 24 percent are displaced in the creep, 70 to 92 per cent in saltation and 2 to 8 percent in suspension (Shahid & Abdelfattah, 2005). This stresses that saltation moves the main mass of wind-blown particles, what ultimately causes dust storms and wind erosion in the arid environments of UAE.

2.4. Water erosion

Most of the UAE’s desert environment consists of sandy, sand dune soils, which absorb the rainwater due to its very high drainage capacity and, therefore, no water erosion occurs in these areas (Shahid et al., 2004).

However, more stable and cohesive soils in the highlands have shown signs of combined effect of wind and water erosion. Water erosion in the UAE occurs only during the intensive 5 In their climate simulations, the IPCC has determined that temperatures in the Arabian Peninsula region could increase by

1 ºC to 2 ºC by the 2030-2050 time period while precipitation levels could significantly decline (TAR, 2001; Al Shindagah, 2001).

6 Current demands in the Emirate of Abu-Dhabi are about 26 times greater than the volume of water which is naturally recharged within the hydrological system (Environmental Agency of Abu-Dhaby, 2007)

rainy season, mainly concentrated during winter months, from October to March. This process causes severe run-off flows in the sloppy landscapes in the form of rills and gullies – surface crusts that obstruct water percolation to root zones. The main consequence of soils subjected to water (and also wind) erosion is the loss of the organic matter layer and the nutrient-rich surface (Shahid et al., 2004).

2.5. Over-grazing

Deserts in the UAE are important ecosystems for traditional grazing by domestic animals. As a result of changes in nomadic practices, these regions have shown vulnerability to chronic overgrazing (Ministry of Energy of UAE, 2006). The pressure of overgrazing is mainly concentrated on the rangelands, resulting into a loss or reduction in plant cover beyond its bearing capacity (Zoebisch and DePauwn, 2004).

Rangelands and forests over-grazing are the main causes for flora’s degradation and accelerated erosion (Mousavi, 2006). In fact, it has been argued that future trends in human and livestock practices may have more impact on desert systems than climate change (Al Shindagah, 2001).

A study made by El-Keblawy, in 2003, shows the difference in number of species, species diversity, and plant cover density, when comparing in and outside limits of the recently designated as protected site in the Al Ain-Dubai road region. The dominant species within the reserve boundaries were the most edible. Outside the reserve boundaries these were absent, which indicates that they were preferential and overgrazed.

2.6. Salinization, Compaction, Sealing and Crusting

Soil salinization is a widespread natural feature of semi-arid to hyper-arid climates. In the UAE, soil salinization occurs mostly in coastal areas due to seawater intrusion into groundwater aquifers (Shahid et al., 2004). It is also verified in inland areas due to the use of improper irrigation techniques. As a consequence, local plant species that are not used to saline conditions are being replaced by halophytic ones, inevitably leading to loss of natural biodiversity.

There are other desertification indicators, namely: surface sealing; crusting and compaction in heavy, cohesive, flattened soils rich in silt and with dispersible clay contents. In these cases, dispersible clay in crusted soil at the expense of mechanical energy, such as a rain drop impact, breaks free of its aggregate and goes into suspension (Southerland et al., 1996). The clay is, ultimately, accumulated at the surface to form crust or is translocated into the soil as an internal sealing of pores or clogging. In addition, these processes interact with other soil degradation processes such as water erosion, decrease soil infiltration, and increase run-off, aggravating desertification problems (Shahid et al., 2004).

3. “Greening the Desert” program and the ecological crisis in the UAE

“Combating Desertification” program is the sum of activities leading to land’s integrated development in arid, semiarid and sub-humid areas for sustainable development. It aims to prevent and/or decrease land degradation; to rehabilitate partially degraded land; and to reclaim desertified land. The UAE analyse it from different perspectives based both on their environmental conditions as the vision of HH Sheikh Zayed Bin Sultan Al Nahyan in

improving UAE’s desert conditions. Therefore, the term “combating desertification” is used as compromise for the “Greening the Desert” program (FEA-UAE, 2002).

“Greening The Desert” is focused on natural desert environment conversion into productive agricultural land, guarantying its biodiversity and increasing its economic outcomes. Traditionally, in the UAE’s area it had only been possible to cultivate land near oasis and mountains. However, today large areas within the desert have been cultivated at the expense of intensive irrigation and other technologies that require constant care and high maintenance costs. This attitude of greening the Emirates, often described as ‘rolling back the desert’, is being promoted as a source and symbol of national pride, proving the significant scale of the ecological transformations (Ouis, 2007).

Greening projects are providing positive environmental impacts such as: halting degradation; sand stabilization and hydrological balance promotion; creeping sand control; microclimatic comfort improvement; environmental quality enhancement; habitat restoration; and aesthetic increase of the area.

Furthermore, afforestation was also considered as preventive measure for some of the desert territories, which with distinct degradation levels7. Nevertheless, well intentioned all these green development projects might be, they are also threatening desert ecosystems and causing numerous new environmental problems in the UAE.

With insufficient rainfall to support them, desert ecosystems are entirely dependent on irrigated water. A substantial proportion of this water is provided by scarce groundwater reserves, and at present, the subtraction rates far exceed natural recharges. The excessive use of groundwater will have serious consequences for years to come.

Water demands are also being addressed at the expense of sea water desalination, a process that requires great amounts of energy and releases great amounts of carbon dioxide (Al-Rashed & Sherif, 2000).

In addition, aside from water use implications, plantations development cause adverse habitat effects too. Not only local varieties of shrubs and trees are being planted, but imported ones from other arid areas as well. These latter have been artificially introduced and have found optimal conditions. However, it is predicted that these newcomers will oust the local flora and fauna, in long term.

Habitat fragmentation has also occurred due to great extensions of walls and fences enclosing plantations and, therefore, restricting the larger animals’ movement.

At this moment, it is also important to acknowledge that the economic costs of the implementation and maintenance of projects under the purview of “Greening the Desert” program come mostly from oil exploitation. And, accordingly to Ouis (2007) this is, perhaps, the major cause for today’s global pollution problems and, which will create severe climatic changes in future, threatening many environments around the world.

7 “Physical Geography of Abu Dhabi Emirate, United Arab Emirates”. Environment Agency Abu Dhabi, 2008, page 40

4. “Rolling back the desert” 8 in sustainable way

Artificial greening of arid ecosystems is expensive, risky, and the benefits are often short-lived. Ecological restoration is an alternative approach that attempts to minimize management intervention (and costs) by stimulating natural successional processes in order to develop stable structural and functional dynamics (Whisenant, 1995).

This paper attempts to demonstrate a vision for combating desertification and greening the UAE desert, supported by an ecological restoration approach. This reasoning is based on the idea that the desert is not a condition but a state within a natural process, and can be graphically demonstrated with the help of the theoretical curve of desertification reversal, presented below (Figure3).

As shown in the graphic, in order to invert desertification processes (by restoring degraded arid ecosystems) two sequential phases are needed: a reversal phase, requiring a maximum energy input and a maintenance phase, requiring a minimum energy input into the system.

Figure3 Curve of Desertification Reversal

This document explores the process of “de-desertification” and, more specifically, the relation between the energy inputs imposed to a system and the period of time required by it to react and reverse the process of desertification, therefore giving the possibility to the ecological succession to evolve towards afforestation (Figure4).

8 Synonym to “de-desertification process” extracted from Ouis, O. “Greening the Emirates: the modern construction of nature in the United Arab Emirates”. Cultural Geographies 2002; 9; page 337.

Figure4 Ecological Succession under arid conditions

In this case, it must be acknowledged that traditional successional concept of vegetation returning to a predictable, relatively stable state, following disturbance may not be valid in several arid ecosystems (Westoby and others 1989; Friedel 1991; Laycock 1991). In fact, most arid ecosystems seem to have multiple and alternative stable-states (Friedel 1991; Laycock 1991). Besides, and according to Friedel (1991), movement between these steady-states, i.e. ecosystem recovery, requires significant management inputs. Thus, despite the amount of energy input needed in rehabilitating degraded arid ecosystems – corresponding to the reversal phase –, there is always a demand for management intervention, providing minimum energy inputs – corresponding to the maintenance phase.

The idea of combating desertification processes based on ecological restoration strategies that initiate autogenic succession9 are most appropriate for extensively managed arid ecosystems, which cannot be completely restored by artificial methods (Whisenant,1995).

5. Strategies for combating desertification. Case study in UAE

The restoration of desertified areas by a “de-desertification” process is based on a thorough study of the ecological systems in deserts. This process can only be successful through accurate understanding of the arid ecosystem functioning and identification of the ecosystem’s natural limiting factors10.

Restoration efforts should be focused on site’s specific attributes and objectives, but always considering interactions with the surrounding landscape, when understanding it in its most inclusive conception. Therefore, it is accepted here that the failure to comprehend restoration sites as integral components of a larger, highly interconnected landscape has often produced inherently unstable “restored” landscapes (Whisenant,1995).

Unique landscape combinations are formed from interactions of geomorphology, hydrology, colonization patterns, and local disturbances. The distribution of energy, materials, and species in relation to sizes, shapes, numbers, types, and configurations of landscape elements is what structures landscape. Landscape functions – or dynamics – are responsible for the 9 Autogenic succession uses are encouraged in this paper, rather than fighting against natural processes.10 Ecosystem´s natural limiting factors considered in this research are: water, soil, vegetation, and climatic conditions.

interaction between all the elements concerning energy, materials, water, and species fluxes (Forman and Godron 1986).

This research introduces a series of strategies that contribute to an ecological restoration landscape approach, which induces desertification process in arid lands reversal. In order to obtain credible and systematic data, even if of theoretical character, an application study in the UAE is presented.

These strategies’ main intention is to manipulate the limiting factors in arid ecosystems, in order to reverse desertification process. These strategies consider the interrelation between landscape’s different components and dynamics, considered essential when establishing and maintaining ecological systems. These different strategies present can be represented by different profile curves, depending on the energy/time ratios required to reverse the desertification process (Figure5).

Figure5 Different curves of desertification reversal, according to different ratios energy-time

Once again, it is important to stress the theoretical approach within these graphics. They are based on realistic reasoning and accurate comparative analysis, even though further research will be needed to obtain referenced data.

The different strategies are mainly focused on: (1) infiltration enhancement; (2) vegetation establishment; (3) soil improving processes; and (4) adequate maintenance and resources conservation.

5.1. Infiltration enhancement

With appropriate techniques, instantaneous infiltration can be substantially increased. On sites with deeper soil profiles – usually on the lower, less steep sections of hill slopes and in flat valley bottoms – a large portion of moisture is retained. This moisture improves the in situ plant development and plant growth on the rangeland. A smaller fraction of the water will penetrate the soil and enter the substratum to recharge the groundwater. On sites with shallow soils and high contents of large-size gravel, improved infiltration will directly increase deep percolation and groundwater recharge in the area. In these cases, the direct effects on plant development will be less pronounced (Zoebisch and DePauwn, 2004). To increase instantaneous infiltration, water-conservation measures that improve localized surface roughness11 – and thus increase infiltration’s opportunity – are recommended:

11 In this regard, Marinez de Azagra (2000) coined the neologism oasification as an antonym of desertification by soil erosion. This process entails the building of small earth structures to collect and infiltrate as much precipitation and run-off as possible by modifying a slope´s physiography in a convenient and non aggressive manner. As a result, better soil moisture conditions will prevail and chances of the establishment and growth of vegetation will improve (Azagra,2004).

- Contour stone lines and small boulder bunds – these measures increase instantaneous infiltration and reduce surface run-off. This is particularly important for high-intensity rainfall events, which usually lead to short-term peak flows that escape to the sea through the wadi12 system. Contour stone lines and boulder bunds are particularly effective for soil moisture and water-table replenishment (Zoebisch and DePauwn, 2004).They are recommended because of their simplicity, ease of construction, low maintenance requirements, and cost-effectiveness (Figure6);

- Graded storm water bunds and diversion channels – these measures intercept run-off at various stages along the slope – from the steep hillsides to the flatter gravel plains –, in order to slope and facilitate posterior infiltration. These structures must be developed to provide short-term storage of overland flow for increased infiltration, always according to sites’ specific features. The structures must be intermittently graded, so that any excess run-off that could destroy the structures is safely discharged. (Zoebisch and DePauwn, 2004). The structures should be made from stone and soil available on site, with minimum interference in the landscape and minimum cost;

- Groundwater-recharge barriers – at wadis level, recharge dams intercept wadi flow to provide groundwater recharge. Structure should be semi-pervious, such as gabions built with local materials in wadi branches to reduce the risk of destruction by heavy spate flows. For the main wadi, a major recharge dam is recommended. This sort of dams should be designed after all the other measures have been implemented and when their water-trapping efficiencies have been duly evaluated (Zoebisch and DePauwn, 2004).

5.2. Vegetation’s establishment

Vegetation is re-established by natural regeneration, following the improvement of the soil-moisture’s character. However, this process requires livestock exclusion during rehabilitation period, from two to five years. Useful seeding and adapted species will speed up the restoration process on these sites. After establishment and evaluation of the bearing capacities, both specific and seasonal, a range-use plan may be developed to ensure sustainable use of the natural resources. This will include irrigated fodder production required livestock population support during drought periods(Zoebisch and DePauwn, 2004).

Different strategies of plantation can control different erosion problems:

12 Wadi is the Arabic term traditionally referring to a valley. In some cases, it may refer to a dry (ephemeral) riverbed that contains water only during times of heavy rain or simply an intermittent stream.

Fig.6 Small boulder bunds

- Trees Contour Ridges – one successful plantation technique to effectively control surface runoff involves establishing parallel vegetation bands along contour lines. A dense vegetation belt not only stops or slows down runoff, but also traps soil particles suspended in the water that have been removed from the more exposed areas between the strips. Strips spacing depend mainly on slope’s angle and local erosion conditions. The primary consideration for species selection should include native plants, as contour strips reduce a percentage of the land out of cultivation, even though they are intended to increase productivity of the total area. Many different species can be used, often in combination;

- Gullies reclamation – vegetation can also reduce bank or channel bottom erosion as long as the water flow is not too powerful. Gullies present special problems, because they often occur on steep slopes, and even brief peak flows can cause serious damage. To prevent gullies formation along waterways, banks should be lined with trees and shrubs. Trees, shrubs, and other mechanical methods can be combined and established within the gullies to further erosion control and to help rebuild the removed soil layers with optimal results (Figure7).

- Windbreaks – windbreaks are barriers planted to reduce wind velocities and to prevent, or reduce, wind erosion. In addition, they also provide shade; reduce evapotranspiration; and moderate extreme temperatures. Different from windbreaks, shelterbelts imply a wider vegetation strip, incorporating more tree and shrub rows than the ones found in windbreaks. In a shelterbelt planting, three zones can be recognized: the windward zone, from which the wind blows; the leeward zone, on the side where the wind passes; and the protected zone, in which the windbreak or shelterbelt effects are experienced). It is generally accepted that windbreaks or shelterbelts protect areas over a distance up to their own heights on the windward side and up to twenty times their heights on the leeward side, depending on the strength of the wind13.In reducing wind speeds, narrow barriers can be as effective as wide ones, moreover having the advantage of occupying less land. Is important to make a thorough study of the local winds and to know the direction and strength of the winds. Barriers should be established perpendicular to the direction of the prevailing winds for maximum effect. When the prevailing winds are mainly in one direction a series of parallel shelterbelts perpendicular to that direction should be established to protect large areas. A checkerboard pattern is required when the winds are originated from different directions. Windbreaks may be staggered so that they conform to the established boundaries such as borders of fields, roads, trails, stream, and other natural or man-made features (Figure8).

13 “Windbreaks and Shelterbelts”, Arid zone forestry: A guide for field technicians. FAO, 1989

Fig.7 Gully reclamation by contour vegetation

Figure8 Windbreaks and shelterbelts

- Dune stabilization – shifting and blowing sand causes great damage to entire settlements in arid zones. Conservation of existing grass and other plant covers is necessary to hold the sand in place. There are basically two approaches to dune fixation: biological and physical. Preference should be given to biological control measures whenever possible. However, some physical constructions are often needed for initial plant establishment. By breaking the force of the wind, the palisades keep the exposed sand from being picked up, and the sediment load already carried by the wind is deposited in or behind the barrier. Sand will become entrapped in such rows and ridges will gradually form. Plant growth then becomes possible in the protected areas behind the ridges. Project sites close to or within actual desert zones will require more intensive efforts to stabilize shifting dunes. In these cases, maintenance inputs will also be higher. The more exposed a specific location is to the wind, the more difficult it is to establish vegetation (Pytlik, 1989). Physical protection may often be needed and it should be acknowledge that native occurring trees and shrubs have great resiliency. In this sense, indigenous vegetation should receive priority over exotics, particularly for large-scale projects.

Figure9 Dune stabilization

5.3. Soil improving processes

Mulching is the practice which maintains soil structure, increase aggregate size and conserve moisture in soil’s upper layer. It cools plant root areas, reducing the amount of water plants loss through evapotranspiration. Moreover, this measure reduces weed growth and helps soil erosion control. In some countries of the Middle East, oil (petroleum) mulch –an oil-extracted material (hydrocarbon colloid) – is sprayed over sand dunes to assist with re-vegetation. The hydrocarbon colloid is a by-product of refineries and has no cost for the purpose of sand stabilization. Iran was the first country in the Middle East to introduce oil mulch for dune

stabilization, a method that has subsequently been adopted in other areas including Abu Dhabi (Khan, 1983). The mulch, when spread, extends to a depth of about 1 mm, reaching a maximum of 5 cm after 3 years in higher rainfall areas (Dehdashtian, 2009). According to recent research, no adverse effects were associated with use of oil mulch in Iran; and positive effects were noted in some cases in relation to soil organic matter, soil water holding capacity and the amount and activity of soil organisms (Pouyafar and Moghadam, 2006).

5.4. Adequate maintenance and resources conservation

There are several methods required for accurate maintenance and resources conservation, namely:

- Aflaj water system – this is an ancient technique by which underground tunnels are dug to channel water from distant sources to villages where it was needed. It is a tested method which helps conserve water and is still in use around the world today. Aflaj are still widespread in Oman, where there are currently more than four thousand channels with an annual flow of six hundred and eighty million cubic meters. The first aflaj built in the UAE was discovered in 1985 in Al Ain, and dates back to the Iron Age. Whilst some Gulf States may believe they have resolved their water scarcity problems through desalination, there is still a lot to learn from the ancient aflaj system, which not only supplies clean water, cheaply and effectively, but also transports and conserves large masses of scarce existing water in arid environments (Aburawa, 2011).

- Conservation tillage – Tillage aims to create a soil environment favorable to plant growth (Klute 1982). Appropriate tillage practices are those that avoid the degradation of soil properties but maintain crop yields as well as ecosystem stability (Lal 1981b, c, 1982, 1984b, 1985a; Greenland 1981). Conservation tillage provides the best opportunity for halting degradation and for restoring and improving soil productivity (Lal 1983; Parr et al. 1990). In recent years interest in conservation tillage systems has increased in response to the need to limit erosion and promote water conservation (Hulugalle et al. 1986; Unger et al. 1988). Conservation tillage includes a number of tilling methods, used alone or in combination, to control wind and water erosion for minimum loss of the soil’s surface.

6. Conclusions and considerations

Arid ecosystems within the UAE are suffering serious desertification processes. In order to combat it, the “Greening the Desert” program has been undertaken at a national level since 2002. Although well intentioned, some measures of this program have also deepened desert ecosystems causing numerous environmental problems in the country during the last decade.

The proposed methodology, with its most accurate expression in the graphic desertification reversal curve, demonstrates that most of the projects implemented under this program actually require high energy inputs into arid ecosystems, normally translated into high demand of resources, such as water, and high implementation and maintenance costs.

This research is an attempt to highlight the fragility and the high environmental value of UAE´s desert ecosystems. By extending this reasoning to a wider range of arid climates and local specificities of many arid regions around the globe, the urgency to adopt new effective landscape approaches that will lead desertification process reversal towards more sustainable systems becomes clear.

Landscape approaches based on a series of strategies and measures with ecological repercussions were presented, considering more efficient uses of the existing natural resources and lower energy inputs required to achieve the “de-desertification” process.

It is sustained that this approach can only be successful through an accurate understanding of the arid ecosystem’s functioning and dynamics, the identification and manipulation of the ecosystem’s natural limiting factors and the consideration of the interconnection between the site’s intervention scale and the larger scale of the surrounding territorial context. All actions have territorial consequences and all consequences must be quantified and qualified, especially when considering landscape in its most inclusive conception.

The strategies presented in this paper are a contribution to landscape ecological restoration approach towards desertification processes reversal in arid territories, with a specific application in the UAE context.

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8. Main author’s biographies

JOÃO NUNES

Lisbon,1960

Founder and CEO of the Landscape Architecture Studio PROAP, which gathers a vast group of professionals in a cross-disciplinary team, with distinguished levels of expertise in landscape, in its most inclusive conception.

As International Director is responsible for the strategic, executive and tactical leadership of the three international offices: Lisbon (Portugal), Luanda (Angola) and Treviso (Italy). Develops PROAP’s conceptual and creative design and defines the strategic orientation of the research processes.

Has been lecturing at the Instituto Superior de Agronomia in Lisbon (Agronomics Institute, Technical University of Lisbon) since 1991. Currently also lectures at the Istituto Universitario de Architettura de Venezia, Politecnico de Milano, Politécnico di Torino, Roma La Sapienza, Roma Ludovico Quaroni, Facoltá di Architettura di Alghero.

CARLOS RIBAS DA SILVA

Lisbon, 1966

Partner at the Landscape Architecture Studio PROAP, which gathers a vast group of landscape architects, architects, designers and plastic artists, part of a core oriented by João Nunes.

Involved in PROAP’s strategic and financial direction and management, oversees research and design projects to assure technical coherence.

Frequently participates as guest lecturer in international workshops and conferences, representing PROAP.

TIAGO TORRES CAMPOS

Lisbon, 1982

Research Manager at the Landscape Architecture Studio PROAP, which gathers a vast group of landscape architects, architects, designers and plastic artists, part of a core oriented by João Nunes.

Managing Editor for PROAP’s publications. Jointly runs the international communication processes, manages graphic and written project information sent to media requests worldwide.

Participates tactically in the creative processes, review and critique of projects.

Frequently participates in international workshops and conferences, representing PROAP.