James and Thibaud Aronson report from Dhofar, in southern Arabia. This remarkable region is a biogeographical and historical crossroads at a critical moment of change.
The Sultanate of Oman doesn’t figure on most people’s mental map. But once told that it sits on the southeastern rim of the Arabian Peninsula, between Yemen to the west, and Saudi Arabia and the Emirates to the north, they may visualize an endless sea of sand with pack camels ambling towards an oasis dotted with date palms. A large part of the country – which is half the size of France – does look like this and is part of the fabled Empty Quarter of Arabia – Rub al Khali. But we have come here to see Dhofar, the monsoon-affected and heavily wooded fog oasis that harbors some of the most unexpected and spectacular landscapes and ecosystems in arid lands worldwide.
One of the beautiful landscapes of Dhofar, southern Oman, in the remote Wadi Ahjawt.
From mid-June to mid-September, every year, Dhofar is thoroughly drenched by the southwesterly monsoon – khareef in Arabic. Not what you expect in a desert region! The steady stream of drizzle and fog, aka “horizontal precipitation”, during this period recharges hundreds of springs and temporary rivers (wadis in Arabic), supporting dense, lush woodlands and forests on the south-facing slopes, dominated by large and varied trees more typical of east and north-east Africa. This constitutes a giant vertical oasis of sorts, but as the monsoon goes over the ridgetops, it is stopped by the hot desert winds coming from the interior and the vegetation transitions to a sparse desert scrub in a matter of meters, in one of the best illustrations of an ecotone – or ecological frontier – imaginable.
The stark contrast between the slopes which receive the monsoon fogs, and the plateau beyond the escarpments, where the moisture is stopped by the desert wind. Jebel al Qamr, near the Yemeni border.
It is there, right on the threshold of the desert, that are found the Boswellia sacra trees that produce the finest frankincense in the world. This tree resin was one of the most prized commodities in ancient times, throughout Asia, Europe, and Arabia, and it is still highly prized today for many uses, including incense, ritual ceremonies, bath oils, and perfumes.
A wild Boswellia sacra tree in Wadi Aful.
Indeed, two thousand years ago, Oman was the meeting point for maritime traders and spice caravans, who traded between the Mediterranean region, east Africa, India, and China. They came to Dhofar to buy the Frankincense harvested by the Jibbali tribes of the escarpments, who to this day manage the Boswellia trees in a sophisticated agro-forestry system, where the ownership of each tree is carefully recorded. You can read about this in detail in Gary Nabhan’s excellent book, Camels, Cumin and Caravans: A Spice Odyssey.
Moreover, as one would expect in such a major historical crossroad, there are many intriguing questions here, for those with an interest in human ecology. For example, Wadi Hinna, connecting the coastal foothills east of Salalah and Jebel Qara, hosts a beautiful population of very old baobab trees, as well as equally ancient tamarind trees. Are they relicts, the last remnants of once much larger populations, or were they brought here as seeds or young transplants by traders and returning travelers hundreds of years ago? Together with our colleagues at the Oman Botanic Garden, we are working on a study of these and other enigmatic trees of Arabia, on which we will report more in due course.
Ancient baobab trees (Adansonia digitata) in Wadi Hinna, eastern Dhofar, the only population of the species found in Oman.
Equally old tamarind trees (Tamarindus indica) in Wadi Hinna,
and in Wadi Ahjawt. Both these trees are often found near ancient human settlements.
Besides its value for traders, Oman’s geographic position also makes it a genuine biogeographical crossroad for fauna and flora. Indeed, thanks to the monsoon, the humid slopes and wadis of Dhofar may be home to one of the last remnants of a belt of seasonally dry tropical forest that once stretched from sub-Saharan Africa to India, but which was almost entirely severed as Arabia became drier. Indeed, among the 900 species of plants found there, Dhofar hosts quite a few species whose nearest relatives – or populations of the same species, are more than 1000 km away, across the Red Sea in Africa or otherwise found only in India, Pakistan and Iran. There is also quite a large number of plants that are unique to the region, with over sixty endemic species and 2 genera endemic to Dhofar. For animals, it is also a haven for many species, such as the critically endangered Arabian leopard, and the fascinating Arabian chameleon.
The beautiful desert rose (Adenium obesum) which is related to the common oleander.
The Arabian chameleon (Chamaeleo arabicus), found only in Dhofar and southern Yemen.
However, despite its lush appearance, Dhofar’s vegetation is not doing well, for many reasons. This – like much of the world – is a region in transition. Over-grazing is worse than ever. Throughout the Middle East – and Africa, it is a sign of status for a man to have a large herd of animals. However, many Omanis today actually hold sedentary jobs in the cities and simply employ shepherds – often from Bengal, Pakistan or Bangladesh – to look after their livestock for a very small wage. Further, they feed the animals fodder, which is subsidized by the government and which is of dubious value long-term. This enables them to maintain their herds at unsustainably large numbers, and as they roam over the slopes, the cattle, goats and camels graze the vegetation well past the threshold of sustainability. As a result, in many areas, you will see trees with no leaves under 3 m (the height camels can reach), with additional branches cut, bent and often broken to bring them within reach of the domestic animals, and an understory cropped to less than one cm above ground level.
The effect of large, essentially uncontrolled herds of camels and other browsers on an Omani landscape.
Note the 3m high browse line, marking the limit of the camel’s reach into the tree canopy and the all but extinguished understory.
Shepherds then go further by breaking higher branches of trees, in this case the dominant species Anogeissus dhofarica, to bring them within reach of domestic animals. This technique, which can be applied with varying degrees of care, is illustrated here with a particularly regrettable example.
When the animals are kept out, as we saw in a few fenced off plots maintained by the Department of Forestry, you see instead rapid regrowth of tall native grasses, often over a meter high, hopping with insects and birds, in amazing contrast to the silent, rocky moonscape outside the exclosure. This is actually an interesting problem, from a restoration perspective. Indeed, as recently as the 1980s, parts of Dhofar were dominated by tall grasslands, the easternmost extension of a habitat type more characteristic of East Africa. These are the ecosystems most affected by the increasing grazing pressure and today they are all but gone. However, according to Dr. Annette Patzelt, Director of the Oman Botanic Garden, it is likely that these grasslands were anthropogenic, and only arose following local clearing of woodland and forest. Therefore, did they exist for long enough to become an integral part of the Dhofari landscapes, which would make them a valid target for restoration, or should they instead be abandoned, to focus on the woodlands they replaced?
The only way to prove the effects of overstocking livestock on a desert landscape is to keep the animals out. In Dhofar, the result speaks for itself.
Dhofar faces other problems as well, such as rampant road building and urbanization. But it is conceivable that better policies relating to further development could be implemented and accepted with relative ease. This issue of livestock, however, is a systemic problem pertaining to people’s perception of themselves and their relationship to land, which is a lot more complex to address and change.
One ray of hope is the terrific work in education and outreach being done by the team at the Oman Botanic Garden, who are documenting the flora and vegetation of the whole country and tracking its changes over recent times. They are also learning how to propagate hundreds of native species that have never before been cultivated as they prepare a monumental desert park and garden that will demonstrate all the ecosystems found in the country and help Omanis to better understand the richness of their country’s natural heritage. It is a first step for desert ecosystem restoration, which is emerging not only in the Middle East, but throughout the world.
Natural History of Ecological Restoration 