The Global Village literature, so full of economic wisdom, says little about the global and regional relationships of plant species in nature. We know about migrating birds and about cross-border national parks where animals may roam a little wider. But plant seeds have also been migrating without human intervention for many millions of years. The distribution areas for some plant species with above average wanderlust have widened greatly along natural distribution channels, with no respect for passport control! Some of these ancient plant migration routes have been cut off by development caused by humanity. Others have been lost due to natural climate changes, continental drift or maybe by some natural phenomenon even more surprising!
As a consequence some amazing botanical sharing links geographic areas very far apart on the globe. This means that plants of the same species may be found growing in the natural state in places remote from each other, with terrain in-between on which these plants simply cannot grow. The connecting routes or corridors, along which the natural distribution once occurred, have now disappeared. These breaks in the distribution area of plant species with unexpected reappearances far away not only suggest climatic or other interventions over long time periods, but create interesting notions of heritage sharing among diverse nations that seldom talk to each other.
Such phenomena seed the urges for international ecotourism involving unusual destinations: It is not only to see your much-loved plants in strange places that makes such trips interesting, but your familiar and favourite plant genera that are represented by different species in the far-off places; species that have evolved since the separation of the geographic areas. There are for instance the yellow wood trees, Podocarpus latifolius, of the Eastern Cape in South Africa that also grow above a certain altitude on the slopes of Mount Kenya; and South African ericas and proteas that are just as at home in the rain forest upper parts of this mountain.
But even more remarkable: There is a forest little known (to South Africans) in the Arabian Desert that shares an unexpectedly large number of (tree and other plant) species with South Africa. The genera mentioned in the text from which material for this story has been borrowed (See reference below), constitutes a fascinating diversity of (partly) shared knowledge among peoples who have never seen more than a fraction of their overall shared biodiversity.
This remote mountain on the south western escarpment in Yemen, the Jabal Bura, is a granite massif adjacent to a naturally forested valley with fascinating and inaccessible gorges. Some parts of the terrain has remained undisturbed by human intervention, at least until recently. The features of its inaccessibility must have contributed to its survival; some of the slopes exceed 70°! The rainfall is higher than in the surrounding arid areas and winter mists bring additional humidity to the deep valleys. For untold centuries a natural forest has been growing safely here; the forest canopy reaching a height of 30 metres in some places, and all made up of an exciting variety of indigenous trees. The surrounding area is described as sparsely vegetated with Commiphora, Acacia and Indigofera species, ranging from altitudes of around 400 m. to 2500 m. Little evolutionary diversification is said to have occurred in this forest since the botanical migration routes from the related feeding areas have been climatically removed long ago (Hall et al, 2008).
The habitat of the forest near Jabal Bura is, as can be expected, a rare one with a few species endemic to the area only and around 150 species prevalent overall. Trees that grow here in the natural state include the following well-known South African trees:
- Acacia mellifera (black thorn or swarthaak)
- Adenium multiflorum (Impala lily or impalalelie)
- Allophylus africanus (African allophylus or Afrikaanse bastertaaibos)
- Berchemia discolor (brown ivory, bruinivoor)
- Breonadia salicina (matumi or mingerhout)
- Carissa edulis (simple-spined num-num or enkeldoring noemnoem)
- Combretum molle (known in South Africa as velvet bushwillow or basterrooibos),
- Commiphora schimperi ( glossy-leaved commiphora or blinkblaarkanniedood)
- Dichrostachys cinerea (sickle bush or sekelbos)
- Euclea racemosa (sea guarri or seeghwarrie)
- Ficus ingens (red-leaved rock fig or rooiblaarrotsvy)
- Ficus sycomorus (sycamore fig or geel-riviervy)
- Grewia villosa (mallow raisin or malvarosyntjie)
- Maerua triphylla (small bead-bean, Zimbabwe)
- Nuxia oppositifolia (river nuxia or watervlier)
- Oncoba spinosa (snuffbox tree or snuifkalbassie)
- Piliostigma thonningii (camel’s foot or kameelspoor)
- Rhoicissus revoilii (bushveld grape or bosvelddruif)
- Rhus natalensis (Natal karee)
- Teclea nobilis (from Zimbabwe)
- Trichilia emetica (Natal mahogany or rooiessenhout)
- Ziziphus mucronata (buffalo thorn or blinkblaar-wag-‘n-bietjie)
What does this overlap in botanical heritage between countries far apart on the globe mean to people today?
One could firstly expect that such trees, straddling hemispheres and continents in their natural distribution, will have a firmer grip on survival than species with very restricted endemic areas. Conversely, plant species found in very small distribution areas and close to high density human presence are usually badly at risk, whatever the local people’s lifestyles; unless such plants become popular in the local people’s gardening activities. Biodiversity and gardening could thus be allies. Humanity’s inexorable spread over the earth raises the question: Is the idea of a remote area where rare plants might survive a tenable notion today at all? Or: will we never undertake to use our brains for curbing our numbers in a decent manner?
All of nature is at risk due to human impact on biodiversity. The 5 km tarred road built in recent times through the Jabal Bura forest has taken 10 ha or 13% of the forest away. More human footprint, less nature! We know that the Red Data List is getting longer, an infamous ‘world record’ we keep breaking with greater ease than any of the Olympic ones! At least the number of people agreeing to avoid this record is also growing! But is the population proportion that subscribes to this growing as well? Unlikely! As we multiply, we may soon reach a point where any conscious decision in this regard might be irrelevant anyway.
In South Africa we seem to share with Yemen the degrading of local forest quality, the shrinking of the retained indigenous forest area and the appearance of roads and other developments right in the middle of the prettiest places. Fortunately we also share some efforts at legislative protection for the natural assets in their current delicate balance with what the people over there are doing.
In the paper on the Jabal Bura forest, the authors recommend a visitors’ centre in the area of the forest to strengthen the protective process. This idea also seems popular in South African nature conservation practices. As the knowledge of the people improves, their attitude and ultimately their behaviour towards nature are expected, as a consequence, also to improve. (A reasonable assumption?)
Good communication is vital for spreading knowledge about biodiversity. Then we can at least work in the same direction wherever we are on the earth and learn from each other. It is a comfort to know that there are people with different languages, cultures and value systems far apart, but still sharing concerns in a global village sense for protecting global biodiversity in their living space. We’ll all share a good habit in doing this. The effort bridges the cultural divide, whether we might ever meet the people there or not. It strengthens the possibility of saving a little more of nature for a little longer. Or dare we aim a little higher? Achieve a little more?
[The Jabal Bura material has been obtained from:
Hall, M.; A.W. Al-Khulaidi; A.G. Miller; P. Scholte and A.H Al-Qadas (2008) Arabia’s Last Forests under Threat: Plant Biodiversity and Conservation in the Valley Forest of Jabal Bura (Yemen) EDINBURGH JOURNAL OF BOTANY 65 (1): 113–135 (2008) 113 Trustees of the Royal Botanic Garden Edinburgh doi:10.1017/S0960428608004976]