Abu Dhabi Sabkha

Description

The area of the coastal sabkha of Abu Dhabi is located on the southern coast of the Arabian Gulf, in the United Arab Emirates; west of the emirate of Abu Dhabi.  It has been developed over the past 7000 years due to the wind erosion of pre‐existing dunes and progradation of subaqueous, intertidal, and supratidal carbonate sediments. 

The Sabkha is a translation of the Arabic word (سبخه), geologically referring to any form of flat salt-encrusted desert that is usually lacks any significant plant cover due to the high concentration of salts and sediments where the level of groundwater is very low and may be zero in some locations. Sabkhas are geographically divided into two categories: Coastal Sabkha  and Inland Sabkha.

According to experts, Abu Dhabi’s coastal sabkha is as wide as 16 kilometres at some points and includes channels, inlets, islands and shoals. It has a slope that average 1:3000 and lies above the level of present-day high tide. In a depositional environment like the sabkha, with strong evaporation due to the air temperature of the sabkha area can reach 60' or more in summer, the pore waters become highly concentrated and are drawn towards the surface, causing the precipitation of evaporites - halite, gypsum and anhydrite, together with some authigenic minerals: aragonite, calcite, dolomite, celestite and magnetite.

The coastal sabkha of Abu Dhabi can easily be accessed today than in the past. It could be easily reached now from the west of the emirate of Abu Dhabi, between Al Dhabayah (Zubbaya) and Abu Al Abyadh islands.

Justification of Outstanding Universal Value

The Abu Dhabi coastal sabkha are some of the best unique and documented in the world, as a result primarily of their vastness; completeness; and because of early research undertaken on the by geologists.

It has been reported that the sabkha located south of Dhabeiya and Abu Al Abyadh Islands is the only complete sabkha in the world that represents the 4 main distinctive layers of sabkha, together in one site. These layers, from bottom to top are: lagoon mud (subtidat), microbial mat (intertidal), gypsum mud and anhydrite nodules (supratidal).

The anhydrite (CaSO4) –rich soil developed over a 70-cm-deep water table is mapped in Abu Dhabi Emirate as unique in occurrence in a wet zone over a water table. Anhydrite is observed as massive clayey material, soft nodules and seams.

Radiocarbon dating has indicated that the coastal sabkha of Abu Dhabi were formed over the last 7000 years (Evans et al., 1969). Coastal sabkha are represented by eight major sub-classes and create the highest landform diversity in Abu Dhabi Emirate (Boer and Gliddon, 1997). These saline landforms are a major feature of the Abu Dhabi coastline, covering 62% of the mainland coastal strip. The sabkha ecosystems of Abu Dhabi Emirate are unique, and are a valuable teaching resource for geologists, yet they are being degraded by infilling and fragmentation caused through development.

These interesting landforms representation of the Abu Dhabi natural coastline and require special zoning for their long-term conservation.

Criterion (viii): The nominated area is formed behind barrier islands of mostly oolitic sands where lagoon areas with high salinities and gastropod shell rich sands and aragonite mud can be found behind. The area is often flooded when the (Shamal) wind crosses the Arabian Gulf followed by strong storms causing surge around the barrier island. High evaporation rates lead to drawing up, through the capillary flow of saline groundwater that deposits minerals, salts, gypsum, anhydrite and dolomite on the surface and within the sediment of the sabkha. The decrease in the pore diameter grains resulted in a greater capillary flow and more moisture on the surface, due to the precipitation of minerals that fill the pores of the sediment. The high water table traps windblown sediments, which provide new pore space for further precipitation of minerals.  This process helps to keep the surface of the sabkha flat because it keeps the sediments damp enough to hold together without being blown by the wind process and it also leads to increasing surface elevation which leads to an increase in the sabkha area.

Statements of authenticity and/or integrity

Integrity of the site is demonstrated by the fact that it includes all the elements of an outstanding universal value of an area. The area is an uninhabited area and rarely visited by people other than geologists. The area is protected by an effective system of local and federal laws. The site will be listed within the Abu Dhabi Protected Areas Network and an Amiri decree will be issued to ensure strict protection of the site. The site will be managed by the Environment Agency- Abu Dhabi (EAD) and related stakeholders within the highest standards of protection and conservation, ensuring the authenticity, sustainability and integration of the site. The size of the property is adequate for the continuing functioning of the natural biological system to endure viable and for geological and geomorphological processes to operate undisputed. EAD is proposing the establishment of a managed protected sabkha geo-conservation area to the west of Abu Dhabi City with minimum investment; this Geo-Park would promote public awareness of the geo-heritage of the United Arab Emirates (UAE), whilst also acting as a centre for sustainable geo-tourism and a focus for research of this fragile sedimentary system.

Comparison with other similar properties

Sabkhas are found in many parts of the world, especially in the hot and dry regions with tropical climate, which are spread in North Africa, the Gulf States, Mexico, USA and Australia. All the Sabkhas share certain characteristics, they are confined to warm and arid areas and their surface is always close to the groundwater level, usually one meter deep. There are few sites in tentative list with sabkha features such as Khor Al-Adaid natural reserve (Qatar) and Chott el Jerid (Tunisia). The essence of the difference and uniqueness lies in the Abu Dhabi coastal sabkha are some of the best unique and documented in the world, as a result primarily of their vastness; completeness; and because of early research undertaken on the by geologists as well as it’s the only complete sabkha in the world that represents the 4 main distinctive layers of sabkha, together in one site. Some other sites in the tentative list like the Bar Al Hakman (Oman) and the great Desert landscape (Egypt) are desert landscapes that have significant geological characteristics but are different in composition and perfection from Abu Dhabi Sabkha. In this sense, Abu Dhabi Sabkha is a sole model of a complete hypersaline ecosystem in the world that would represent a well-managed geo-park and having it inscribed in the WH list will enforce the sustainability of its value and services, locally and internationally.