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Ecology of Sinai
| Soil and climate determine the occurrence and spread of plants and animals. This fundamental ecological tenet assigns to geology and geography an important role in the survival of plants and animals. The ecology of Sinai, as well as the marine biology of the Red Sea, demonstrate this very clearly. On land, the paucity of species in the spatially restricted Sinai area creates clear-cut relationships. In the Red Sea, the geological formation of the seabed and the geographical location are the decisive factors. Observation of the flora and fauna in Sinai makes it clear that the peninsula is a genuine land bridge between Africa and Eurasia. Here plant species from four major neighboring regions mix. Most of the plants belong to the Sahara-Arabian region. The most important and best-known species are the camel thorn (Zilla spinosa), the various kinds of goosefoot (Hammada spec, Anabasis spec) and bean capers (Zygophyllum spec.), and tamarisks (Tamarix spec.). The biblical story of manna, the bread from heaven, is associated with the tamarisk. This legend, handed down by Sinai monks, comes close to being a miracle, since the manna harvest is very scant and only very seldom possible. Manna is the honey-like excretion of lice, which pierce the capillary tubes of tamarisk branches. At first the drops are crystal-clear, then they turn milky and finally brownish. From the Sudanese region come the acacia, the caper bush, the ben-oil tree (Moringa peregrina), Leptadenia pyrotechnics, and the poisonous Sodom-apple (Calotropisprocera), which can all be found mainly in the warm lowlands of the gulfs. In the coastal waters of the Gulf of Aqaba and at Ras Muhammad grows the mangrove (Avicennia marina), its northernmost location in the world. Persian and North African grassland species like primula (Primula boveana) and pistachio (Pistacea atlantica) grow in the cooler and more humid climate of higher mountains and plateaus. Surprisingly, only a few species of Mediterranean flora can be found in Sinai, in spite of that region's proximity. In former times Mediterranean plants were widespread in Sinai, but now they persist only in specific places. This indicates a changing climate that long ago made Sinai drier and drier, a phenomenon evident in the neighboring Sahara as well. Limited Mediterranean species are the Phoenician juniper (Juniperus phoenicea), which can be found at the rare places with plenty of water in North Sinai, the sand cherry (Ephedra campylopoda) and the olive tree (Oka europaea). Marjoram (Origanum isthmicum) has a very small range of distribution of only five square kilometers on Gabal Halal. Zoogeographically, Sinai is full of overlaps and intersections that have created an interesting mixture of fauna. Since animals, unlike plants, can move-and in some cases quickly cover long distances - the boundaries cannot be as sharply drawn as for flora (Fig. page 42). Beside wolves, ibexes, red foxes, dormice, partridges, and rock doves from the southern Palearctic region, there are also species typical of the tropical African region such as Tristram's grackle (Omyikogmathms tristramii), the common bulbul (Pycmouotms Irmeogemjs), the sunbird (Nectarinia osaea), and the rodent-like relative of the elephant, die rock hyrax (Procaria syriaca). In former times there were ostriches here. Sometimes their eggs are still found in the desert sand. Leopards, only recently exinct as well as hyenas and jackals, must have crossed the Sinai land bridge as they spread to Asia. In Sinai the dull-colored partridge (Perdix perdix), which lives mainly in northwestern Europe, meets the brightly-colored chukar (Alectoris chukar), which lives mainly in southeastern Europe, Arabia, and Persia. A main characteristic of Sinai's flora and fauna is their poverty of species. The total number of species of ferns and flowering plants is recorded as 820-900, including thirty-four endemic species found only in Sinai. In comparison, more than 1,400 species are estimated to exist in the Sahara, and that number of species could be found in a tropical rain forest in an area only a few kilometers square. The situation is similar for animals, though there are no reliable data available. The small number of species is a direct consequence of climatic factors. Life-threatening water shortages combine with high temperatures by day, extreme variation in temperature between day and night, and the effects of wind to make every habitat an extreme one. In the desert water is the factor that determines the survival of animals and plants. Even in places with occasionally plentiful water, difficult living conditions prevail. Due to high evaporation, the dissolved soil minerals accumulate and the water becomes very salty. Consequently, desert inhabitants - whether plants, animals, or humans - have had to adapt and develop strategies of survival in order to settle permanently. When species that do not have these adaptations are found in such an environment, two explanations are possible. Either there are better living conditions within a restricted area, or the last representatives of a species are eking out a miserable existence as so-called relict species, witnesses of a formerly humid climate. In Sinai, examples of such species are the Mediterranean plants and water insects such as Gyrinidae and Dytiscus species, water scorpions, and dragonflies, as well as water snails of the family Lymnaeidae, which to our surprise we found in the winter rain ponds of mountain wadis. Individual adaptations to desert life can be inferred by observing the plants and animals. Open spacing between plants is an expression of the struggle for water. Even very small plants may develop superficial root systems of up to one hundred square meters in order to use the scant, barely absorbed water. There is simply no place in between for other plants. Alternatively, larger plants develop deep roots in order to reach the ground water. Acacias with roots reaching down thirty-five meters have been found. Before an acacia can grow to this size it has to succeed in a hard struggle for survival. First of all, the seed needs enough water for germination. If the young plant grows well in a succession of good years, it is exposed to numerous feeders like gazelles, goats, and camels, which crave the fresh green and hinder growth. Even the long, hard, sharp thorns do not keep them off. If a few rain-poor years follow, the dream of a beautiful big acacia is over. Sand provides fairly good water storage; so many plants are shaped to favor the collection of sand: they catch the windblown sand and build their own sand hills. Sometimes whole areas are covered with these hillocks with plants growing out like tufts of hair. Such areas can be seen on the drive to al-Tur south of Ras Sidr. The outward shape of many desert plants results from their effort to minimize evaporation, which, given the high temperatures and strong wind, is a critical problem. Small leaves, round shapes, and stocky statures are examples of this effort. The widespread bright green and very lush-seeming Syrian bean capers of the genus Zygophyllum, which belong to the succulents, show this adaptation very clearly. Their leaves have become round and juicy with smooth surfaces. The Syrian bean capers are real masters of adaptation because they have developed a number of mechanisms to survive successfully in the desert. Another way to minimize evaporation is to absorb water-binding salt into cell liquids. Desert water contains more than enough salt, but in the Syrian bean caper, the salt concentration is three times as high as in the desert water, which is already intolerably salty for 'normal' plants. With the high concentration of salt in their leaves, the Syrian bean capers are able to absorb even tiny amounts of dew moisture through their stomata and so attain a regular water supply. And there is a third strategy of the Syrian bean caper to minimize evaporation. Like every foliage plant it takes up carbon dioxide from the air through its stomata for photosynthesis. In the heat of the day, open stomata would lead to high evaporation, so the Syrian bean caper takes up carbon dioxide at night, stores it chemically, and keeps its stomata closed during the day. Meanwhile, sodium chloride can cause problems even for salt-tolerant plants, as too much of it damages the tissue. To prevent this, a number of species have developed glands in the leaves and stems that excrete salt, creating little crystals on the surface. These crystals effectively reflect the sunlight and thus serve as further protection from evaporation. The saltwort species of the genus Salsola, normally rather inconspicuous, stands out because of the tiny glittering white crystals on its small blue-green leaves. The well-known tamarisks with their needle-like branches and twigs are covered with a whitish coating that reveals itself as sodium chloride when tasted. A few examples of from the animal kingdom may complete this short discussion of strategies for survival in the desert. Dabb-lizards (Fig. page 40), large, monitor-like reptiles, are dark grayish-black in the morning. As the heat intensifies through the day, they change their color to gray-green or paler and finally to pale gray or even white. In the coolness of the morning, they gather warmth through their dark color. Later, the pale tinge prevents overheating by reflecting light. These impressive animals have further peculiarities that make their lives in the desert easier. They have salt glands in their nostrils that excrete almost-dry salt. By doing so, they retain water, which they would otherwise have to use to excrete salt through their kidneys. The dabb-lizards protect themselves against predators by squeezing tightly into crevices. In order to do this, they have air sacs behind their lungs which they pump up. Interestingly, these air sacs actually have another function: they are used to allow the air to circulate twice through the lungs. The oxygen content is therefore better utilized, and the breathing rate can be slowed, reducing water evaporation. The surprisingly numerous black beetles use color to similar effect. Although black may seem quite unsuitable for a hot sunny desert, in the morning after a starlit desert night when the temperature can fall quite low, the beetles" Mack color helps to absorb warmth, allowing them to get moving more quickly. Later when the day becomes too hot they bury themselves in sand. This is the only relief for a number of desert animals. Skinks, lizard-like reptiles, have adapted their body shape so that with their shiny, smooth, scaly skin they are able to 'swim' in the sand. The eyelids of skinks, as well as those of desert lizards, are transparent and protect their eyes like sand-goggles. The horned viper and its relatives have another solution to the problem of loose sand. By moving in sideways curves, these poisonous desert vipers worm their way through the sand and avoid unintentional sinking, crossing even the softest places. Many desert animals of different families camouflage themselves b\ adjusting their color to their surroundings. Hoopoe larks, coursers, or golden spiny mice are often first noticed when they run away. The normally conspicuous black-and-white male of the white-crowned black wheatear, for example, looks like a stone with a shadow in the high midday sun. It sits motionless on the ground and is first recognized as a bird when it flies up. The sand-gray female of the wheatear is even better camouflaged, and when incubating eggs she can be hardly distinguished from her environment. Frequently lizards scurry unexpectedly away before our feet, or grasshoppers fly up, so perfectly are both animals camouflaged against the ground by color and pattern. This is necessary as the open areas with scant vegetation are good hunting grounds for predators. The predator easily becomes the prey when a stronger predator approaches. On the other hand, sometimes there are conspicuous, brightly colored species in the desert, like the black and brilliant orange grasshopper (Poeki-locerus bufonius). This grasshopper is extremely poisonous because it eats poisonous plants like French cotton or henbane. It not only tolerates but actually concentrates the poison. The conspicuous color warns possible predators and scares them off. From an ecological point of view, one gets to know both the large biospheres of Sinai when wandering through the Tih desert in the north and the mountain zone in the south. The geological variety of Sinai creates such varied local habitats that these biospheres must be further subdivided in order to understand their colonization by flora and fauna. |
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