UN UNIVERSITY LECTURES: 16,17
The Mediterranean Crises
Director, Institut océanographique,
and Secretary General, International Commission
the Scientific Exploration of the Mediterranean
Sea (CIESM), Monaco
Climate Change: Is It a Positive or Negative Process?
Arie S. Issar
Holder of the Alain Poher Chair for
in Arid Zones, Water Resource Center,
Jacob Blaustein Institute for Desert Research,
Ben Gurion University of the Negev,
Sede Boker Campus, Israel
Presentations Made, respectively, at the UNU Headquarters
on 15 July 1996,
and at the Global Environment Information Centre (GEIC)
on 14 November 1996,
This report contains two environmental lectures given at the United Nations University (UNU) by two internationally renowned scientists. They are presented between the same covers as the topics, albeit very different, have much in common. Both of the lectures deal with global scale, long-term environmental change, with implications on water resources. Both of the authors have their background in the Mediterranean basin, a fact that becomes evident from their focus on that region. Both also take a broad view linking natural environmental change with the development of human civilizations.
Dr. François Doumenge, Director of the Oceanographic Institute in Monaco and Secretary General of the International Commission for the Scientific Exploration of the Mediterranean Sea (CIESM), gave a seminar at the UNU headquarters on 15 July 1996. His presentation, entitled "The Mediterranean Crises", takes a long-term historical look at a series of environmental crises that have affected the Mediterranean Sea. He then utilizes this perspective to paint a picture of the human-induced environmental changes experienced in recent decades in the Mediterranean basin and the Black Sea, which have now reached a point where a new crisis is in the making unless we make a concerted effort to act to prevent it.
Professor Arie S. Issar of the Water Resources Center at the Jacob Blaustein Institute for Desert Research, Ben Gurion University of the Negev, Israel, was the first lecturer to deliver a speech at the newly opened Global Environment Information Centre (GEIC) on 14 November 1996. GEIC is a joint endeavour of the UNU and the Environment Agency of Japan founded on the recommendations of the UN Agenda 21 to act as a centre for global projects, networking and information on issues and activities related to the environment. As evident from the title, "Climate Change: Is It a Positive or Negative Process?", Professor Issar presented a provocative view of global climate change, its natural and anthropogenic causes in a historical perspective, and the need for mankind to act in a proactive way to adjust to the effects of global warming.
It is our pleasure to be able to offer this report to a wider audience of those who did not have the chance to participate in these lectures. We hope that the report will provide interesting and thought-provoking reading, and that it will contribute to the realization that we all must take responsibility for our common future.
Dr. Juha I. Uitto
The United Nations University
The Mediterranean Crises
Dr. François Doumenge
I. Introduction: CIESM and Mediterranean Science
Upon the retirement of Jacques Cousteau, I had the privilege to be selected as his successor as Director at the Musèe ocèanographique in Monaco and also as Secretary General at the International Commission for the Scientific Exploration of the Mediterranean Sea (CIESM).
CIESM is a purely scientific international organization, founded by Prince Albert I in 1914, and as such, one of the oldest international scientific bodies. During his oceanographic studies, Albert I and his team of scientists found that the Mediterranean Sea is a small-scale model where we can study most of the large phenomena of the oceans. At that time, Prince Albert was a supporter of the international cooperation movement and a founder of the polar scientific organization as well as that concerned with the Mediterranean. He organized the first meeting of CIESM in Rome in 1914, where he made arrangements with the different Mediterranean governments to cooperate in scientific research, but WWI started some months afterwards and the first plenary assembly of the organization itself was held in Madrid (1920). From 1920 until now, except for a break between 1939 and 1950 due to WWII and its aftermath, CIESM has convened every two years in a congress covering all aspects of marine research developed in the Mediterranean basin. This research ranges from marine geology and geophysics to physical oceanography, marine biology, fisheries, chemical pollution and so on. So, in summary, CIESM is a large organization supporting and initiating multidisciplinary scientific research in the Mediterranean proper and also in the adjacent seas (Adriatic and Black Sea).
The founder's membership right applies to all the states which are a part of the Mediterranean fringe. Every coastal state has only to pay an annual fee in order to belong to the organization, and there is no vote required on a coastal state's entry. But from the foundation, scientists and governments working on the Mediterranean were very international, coming not only from adjacent states, but also from other countries. So it was necessary to make a separate rule for admission of a non-coastal state working for the advancement of science in the Mediterranean Sea. In such cases, after an application is submitted, a two-thirds majority of the Mediterranean states is required for admission. Currently, the membership comprises all the Mediterranean states, except Libya and Albania, as well as Romania and Ukraine for the Black Sea. As countries actively engaged in the Mediterranean, Switzerland, Germany and the Netherlands were elected to join the organization. The present total is 23 states.
CIESM is also a privileged forum, removed from political tensions. For example, during the conflict years between Israel and the Arab states, Israel could sit with other Arab members. More recently, during the Yugoslav crisis, Slovenia, Serbia-Montenegro and Croatia, notwithstanding their conflicts, were working together and in 1995 it was a consensus to hold the next CIESM congress in 1998 (these are hosted on a rotating basis) in Dubrovnik, Croatia. Looking over many years, CIESM has been the only place where scientific communications and sometimes joint research projects could take place between Israel and the Arab states without any problem. Other international organizations ask us to play the role of an intermediary. Thus CIESM has many connections with FAO, UNEP, UNESCO, as it is asked to host workshop meetings with the participation of different, conflicting states.
The main duties of CIESM are twofold. First, the organization is accountable to all the governments with respect to the main scientific problems of the area. Each member state receives by official channel expert advice, conclusions or observations about the present status and trends of the Mediterranean basin. This is an official duty, and every year a meeting is held to inform the states' representatives of current developments and recommendations. Second, CIESM groups about 220 laboratories and 2,800 scientists who are active members of scientific committees. These scientists are working in separate groups on different projects that we support financially. Consequently, CIESM has two different orientations, one political, the other scientific.
CIESM also circulates information. Since 1922, it has published more than 100 books on Mediterranean problems, official records and special treaties about some important questions on physical oceanography, geology and geophysics, marine biology, etc. (Note: the official language is French, and while English is often used, most publications are available only in French.)
My presentation will focus on the Mediterranean crises - geophysical, geological and biological - during different time scales - millions of years, hundred thousands of years, thousands of years, and decades. So, I must use a very broad multidisciplinary approach. What are the main problems and the main crises of the Mediterranean Sea?
II. Beginning of Its History - Messinian: State 0
To start, we must look at a state zero, when the Mediterranean Sea was dry and life disappeared during the Messinian (end of the Miocene) 5 million years ago (figure 1). At that time, there was a blockage at the Strait of Gibraltar and after some 100,000-200,000 years the basin had evaporated quite completely. Prior to that, during a period of one million years, between 6 and 5 million years ago, the opening of the Mediterranean was sometimes from the east and sometimes from the west, so during those one million years there was a balance. The Mediterranean basin was like the Sahara, but with a basic level at minus 3,000 m. As a consequence, on the bottom of the basin, there are giant rock salt deposits with a total volume of 1 to 1.5 million km3. The thickness of these strata is between 800 m in the Baleares basin to 1,800 m in the Levantine basin with sometimes 2,000-2,500 m. In another view these deposits could be seen as the most important reserve of oil and gas of all the world, but under 3,000 m of water!!
This endoreic salt deposit takes away 6% from the dissolved salts of the whole world ocean: consequently the polar water freezing point goes down as a consequence of 2% decrease of total oceanic salinity.
In the shallower areas of the Tyrrhenian basin, proto-Adriatic, Aegean basin, the sedimentation is gypsum and anhydride.
The basin was a pure desert, but on the fringe big "wadi" were running from the mountain borders to minus 3,000 m. They dug very deep canyons fringing the Gulf of Lions platform between Provence and Costa Brava, sinking from 200 m to 2,500 m. During the Messinian, the Mediterranean was functioning exactly like the present Sahara system, with large central salty chotts and sebkhas and wadi running from the mountains at the peripheries. So, 5 million years ago, at first we have state 0 for the Mediterranean sea life, because the basin dried; even though recently the possibility was considered that, based on research of Israeli scientists, perhaps some 5 or 6 fish species could have survived at the periphery even under those conditions, taking refuge in some sebkhas in the vicinity of the wadi detritic deltas.
The present problem stems from the developments that occurred after the Messinian crisis, when, with the opening of the Strait of Gibraltar, the basin was filled again only by the Atlantic and not by the Red Sea. The present paradox and the explanation of the permanent disequilibrium of life in the Mediterranean come from the fact that the Mediterranean Sea is a subtropical remain of the Thetys which was repopulated by cold water species. That is the explanation of the present situation.
With the subsequent opening of the Suez Canal and with the upgrading of the temperature, tropical species can return and colonize the East Mediterranean basin, and they flush out the cold species which settled there but are not in their adapted habitat.
It is important to remember that from 5 million years ago the Mediterranean Sea has been a tropical area settled by cold-water origin species, and this is the paradox explaining the fragility and the incapacity of the present Mediterranean Sea to have a stable population.
III. The Last Glacial Episode and the Three Mediterranean Seas
A more recent major crisis was at 18,000 years before the present (BP) at the end of the last glaciation (Wurm). What was the state of the Mediterranean Sea at that time (figure 2)? First, the general oceanic level was about 120 m less than the present level 0. At the end of the Wurm time, the world oceanic level was down at minus 120 m because the continental boreal and Antarctic inland seas kept a huge volume of oceanic water locked up. The black colour marks what was between 0 and minus 120, i.e. what is now sea and used to be continental. You can see that the northern and central Adriatic Sea was emerged, the Black Sea, as a freshwater lake, was quite small, and there was a smaller passage at the Strait of Gibraltar, with only about 30% of the present capacity. So the water exchange between incoming water from the Atlantic and evaporation was reduced, and consequently Mediterranean water was not exchanging at the same rate as it is now. This exchange controls the potential life in the basin.
Looking at the average temperatures in winter and summer [February (figure 2A) and August (figure 2B)], it is very important to notice that at that time there was not one Mediterranean Sea but three: on the east side there is a subtropical area where the temperature was from no less than 15¡C up to 21oC during winter, and between 21oC and up to 25oC during summer. So this Levantine basin in the east remained tropical and the warmer species were able to survive in that small area. Then there is a wall of cool and desalinate water tongue running from the Black Sea, cutting off the Levantine basin from the Central basin like a thermic and chemical wall. The Black Sea water extended as far as the coast of Libya. The Central basin is like the present Mediterranean. During the winter, the temperature is up to 11oC and in the summer between 19oC and 24oC. The Wesotern basin was like the North Sea or the Sea of Norway with a temperature of 5oC to 9oC during winter and a very mild 12oC-16oC during summer. That is why there were subarctic fauna (whales, penguins, and seals), which explains why even today there remains in the Western basin a huge population of more than 3,000 blue whales.
IV. Sapropels - Abrupt Changes and Massive Mortalities within a Millennium
The last Mediterranean crisis was 8,000 years ago. The big problem that befell the Mediterranean Sea at that time was what we call a "sapropel" phenomenon. That is a general mortality of all marine organisms in a very short time with a changing of the hydrologic condition. That time was 6,000 years before Christ, which was just at the passage of Egyptian civilization from pastoralism to the Pharaoh state. The time of changing climate and changing hydrologic condition was also a time of changing history. The crisis of that time is strictly associated with the story of the deluge as well told by the Holy Scripture. We must note such a record and description of what happened in the Middle East and in the Mediterranean basin - the deluge and, as a consequence of the deluge, the general mortality of life in the seabed area. Why ?
Because heavy rain falling in the Middle East and in the Nile basins and on East African Rift Valley lake basins increased the capacity of the Nile to a level of running water as for the present Amazon. Because of this gigantic increased runoff, the eastern part of the Mediterranean Sea was covered by a superficial freshwater layer in no more time than 40 to 60 years - this surface layer 15 to 20 m deep caused a general mortality because of a stratification phenomenon: the freshwater lenses floating at the surface cut the communication between the atmosphere and the sea water, and so under the freshwater layer, life died from lack of oxygen. Sapropel formation was discovered in 1952, some 20 cm of black organic matter at the bottom of the Mediterranean Sea that caused quite a surprise. It was studied through thousands of drillings and it was discovered that in a very short time all the life in the Mediterranean Sea had died.
For the Mediterranean, that crisis happened 8,000 years ago, but for the Black Sea a similar crisis is of more recent origin (figure 3). Until 7,450 plus or minus 130 years ago, the Black Sea remained a freshwater lake. But at that time it started changing. The sea level rose and Mediterranean Sea water entered the Black Sea basin. After a transition phase with the deposition of aragonites, there were thousands of years of a period of general death. Such a layer, from 7,450 to 2,720 years ago, can be correlated with some very straight data like the explosion of Santorin Island and the subsequent general coverage with and deposition of volcanic ash in the Mediterranean Sea that killed everything. Also shown are the percentages of CaCO3 and of organic matter. From 1,600 years ago until now, the present status is an adjustment period. So, the Black Sea is like a laboratory giving us the possibility of observation, of learning what happened in one general crisis.
During the Holocene, 450,000 years, the Mediterranean suffered 12 sapropel crises (Herman, 1989). All during the palaeolithic and neolithic times, great meteorological perturbations caused periodic collapse of Mediterranean marine life. These crises are very important to understand because they give an explanation of what could happen if we have a changed climate.
Figure 4 is a general synopsis and explanation of the different crises and changing hydrological conditions: 18,000 years ago when the level was at the lowest, 12,000 years ago, and during the sapropel crisis. This illustrates that hydrology, sedimentology and biology interact together, which demonstrates that without a multidisciplinary approach you cannot understand anything in the Mediterranean basin.
Some years ago after the Gulf war between March 1991 and October 1991 we saw a pre-sapropel situation coming very close to a disaster. During the Gulf war there were burning oil wells in Kuwait. These fires caused a lot of smoke and the smoke created a cloud running about 10,000 m and covering the Arabian Peninsula, the Persian Gulf, and reaching to East Africa. From March to June and July 1991, this cloud was causing a decrease in temperature due to very low solar insulation, and the temperature of the Gulf was decreasing to less than 15¡C. At the same time, there was heavy rain, monsoon rain, in eastern Africa. The monsoon front was just balancing and was established in eastern Africa and didn't move.
At a meeting of the Open Partial Agreement on Major Ecological Disasters in Ankara in July 1991, it was reported to the Mediterranean governments that if the oil fires weren't cut off, we would enter a pre-sapropelic situation with a strong potential for disaster: a very cold winter in the Middle East, no more rain in India, excess torrential rain in East Africa, the Nile rising up from the present low level to an Amazon-like level, keeping out the Aswan Dam and keeping out Egypt at the same time, causing a general mortality in the eastern basin. This situation showed that humanity can create a sapropel situation just by changing the local climate with an excess of some chemical product, in this case burning crude oil. Prior to the conference, the appeal to put out the fires came only to America, but after the July meeting more than 30 international bodies called for it and in November the fires were extinguished. Little by little, things returned to their original state, but during the 1991/1992 winter it was snowing and freezing more than usual, causing problems in the whole Middle East area. So beware, the sapropel is not just theory, the sapropel can return.
V. The Lessepsian Story - A Century of Man-Made Changes
We now leave the sapropel scale of 1-2,000 years (even though the mechanism can switch on/switch off in 50-60 years, no more) and look at another present crisis. The Mediterranean Sea is a warm sea populated by cold species. The present level of the Red Sea is about 1.2 m higher than the Mediterranean Sea, so the physical pressure pushes the sea water from the Red Sea to the Mediterranean basin. Now, the Suez Canal is like a Mississippi running from the Red Sea to the Mediterranean Sea with an open gate. The former high salinity barrier of Lake Ammer was changing after 50 years of desalinization of the bottom. From 1970 to 1980, when Lake Ammer bottom water was of the same salinity level as the Gulf of Suez (43-48%), the chemical barrier disappeared. Second, the Nile did not act anymore as a freshwater tap at the entrance of the Suez Canal because the Aswan Dam cut the Nile freshwater flow, to less than 10% of the previous level. So, the Suez Canal is an open gate (14.5 m deep and 325 m large) running a huge volume of water from the Red Sea to the Mediterranean. The result is Red Sea fauna entering more and more in the eastern Mediterranean - first discussed by Por (1978) because along the Israeli coast there was a change in fisheries, the fishermen catching more Red Sea fishes and crustacean species than those of the Mediterranean.
This transfer phenomenon was named Lessepsian migration, from the name of the famous constructor of the Suez Canal, Ferdinand de Lesseps. The Lessepsian province resulting from this migration is shown in figure 5. You can see that we are returning to the pre-Messinian situation. With the entrance of plenty of new fishes and invertebrates in a very short time (25-30 years), the biological balance of the eastern Mediterranean has been changing very fast. Every year are discovered five to ten new species from the Red Sea and from the Indian Ocean. You can see that mankind was able to return to a geological situation. This is very interesting and a test of the fragility and the capacity for change of the Mediterranean Sea.
VI. Black Sea Disasters
The fastest changing part is the Black Sea. It is a model of what happens in a crisis. We are scientifically fortunate, but as part of mankind we are unfortunate to have that example. What happened in the Black Sea in recent years? The economic development of big industries and intensive agriculture in the eastern European area, Soviet Russia and the Danubian states caused a drastic reduction of the inflow of fresh water with the increase of fresh water used for irrigation and industries. So the present Black Sea is returning to a pre-glacial state with a low inflow of fresh water and the entrance of too much salt water, changing the balance. At the same time, the remaining fresh water is heavily polluted with phosphates and nitrates and also heavy metals.
As a consequence a general mortality has affected not only fish and shellfish but also seaweed. As an example, the Black Sea was very famous for a large meadow of more than 11,000 km2 of five kinds of red algae (Phyllophora sp.), but from 1950 to 1980 there was a general regression until a quasi-total disappearance occurred.
So the Black Sea was completely disturbed by the chemical and physical intervention of man. The result was that only a few remaining organisms survived. And such surviving capacity was giving them the possibility to bloom and make a general invasion of all biotopes, i.e., when 90% of the organisms died, the remaining 10% of the organisms exploded and colonized the whole water body.
In the Black Sea it was a local jellyfish, Aurelia aurita, that exploded between 1987 and 1989 (see figure 6; unit: billion tons of jellyfish), but in 1988 something new happened. It was another jellyfish which competed making another bloom. This jellyfish, Mnemiopsis, is an American jellyfish of the Nantucket area which was accidentally introduced into the Black Sea: perhaps American ships visiting Odessa and the Sebastopol harbours transported the jellyfish in the ballast tank and released them during the exchange of water. Mnemiopsis reached complete saturation. The fisheries of the Black Sea collapsed by more than 90% from 1 million tons to 100,000 tons. In only a few years everything can change, a first crisis with a local species and the second with an exotic one. Figure 7 shows the changes in the general balance of the basic trophic population. From 1978 to 1988, the balance was the peak of jellyfish but the phytoplankton remained. In 1991-1992 the amount of phytoplankton came down, Aurelia also went down but Mnemiopsis went up. This shows the general components of trophic change in the Black Sea and is proof that in a very few years everything can change.
VIII. Mediterranean Bottom Life in Question?
Another conclusion on a more general topic: we study now what happens in the deep seas, we study the balance between the surface and the bottom. And we note that the next eutrophication process, the next sapropel process can be predicted in a very few years. The remainder of life in the depths depend on the balance between the oxygen content and the oxidation coming from the surface by way of minerals or organic carbon.
Winter oxygenation with the prospect of keeping life in the depth of the Mediterranean basin is quite simple. In winter, the cool air from the north decreases the temperature of the surface. The high density winter water sinks and goes down and brings down the oxygen of the surface and this gives the depths the capacity for life. If there are no more cool winters, there is no more life. It is the cool winters of the northern Mediterranean that give the depths life. If you have climate warming - and right now we have quite creditable data for a warming - you don't have the currents resulting in the downward transport of oxygen nor the upward transport of minerals to the surface. Now you have a cycle of oxygenation and fertilization - winter cooling gives oxygen to the depths and summer returning the water from the depths to the surface without oxygen but with minerals (potassium, phosphate) and organic matter - and with that cycle of oxygenation and fertilization you have life. But if the cycle is cut, life is interrupted and there is death.
Another question is that if the surface water has not only oxygen but an excess of mineral salts the oxygen reduction cannot work. Figure 9 shows the critical level of the remaining life in the depths. If the present trend of excess salt at the surface and the present trend in warming remains there will be no more oxygen in the western basin around the year 2045 and in the eastern basin around 2055. The present trend is completely changing the capacity of oxygenation of the deep bottom and so we predict that if we don't change in 50-60 years we will have a general death.
Another fact: With a 3% rate of organic matter increase in the Mediterranean Sea, saturation of the surface water will be reached from the continents in the eastern Mediterranean around 2020-2025 (figure 10), so if the present trend continues, we must face the next large-scale biological crisis in 25 years' time. If the inflow of organic matter is controlled to maintain present levels, the crisis could be postponed until 50 years from now, and, of course, by reducing the inflow we can buy even more time.
In conclusion, you can see that the crises are not only scientific curiosities or something academic. Mankind has shown that it can change the environment and create crisis conditions in a very short period of time, as compared with the geological time scale. To save the Mediterranean Sea, we need to act quickly, and this requires political will more than anything.
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Climate Change: Is It a Positive or Negative Process?
Arie S. Issar
Many observations show that a major climate change is affecting our globe, mainly a consequence of the enrichment of the atmosphere by the gases of burnt fossil fuels. The author of this article investigated, during the last decade, the possible impact of climate change on the hydrological cycle and socio-economic systems. This was carried out in the framework of the International Hydrological Programme (IHP) by the Division of Water Sciences of UNESCO. I adopted the principle of "the past is a key for understanding the future", and used data related to changes in the natural as well as socio-economic environment during the past 10,000 years. This was in order to assess the possible scenarios in the future.
This research showed that the Middle East went through severe climate changes during historical times which had major effects on the welfare and thus history of this region. For example, I found out that it was not the ancient Mesopotamians, 4,000 years ago, nor the Arab conquerors of the Middle East, 1,300 years ago, that caused the desertification of this region. It was a natural change into a warmer climate which triggered this aridization.
Climate Variations during the Last 10,000 Years in the Eastern Mediterranean Region
The climate of the eastern Mediterranean region is affected by both the subtropical high pressure belt, mainly during the summer, and mid-latitudinal depressions during the winter. Summers are hot and rainless and winters are wet and cool. The level of precipitation decreases as one travels in a southerly and easterly direction (reaching 400Ð500 mm in the western coastal area, 1,000Ð1,500 mm in the mountains of north-west Lebanon, and 50 mm in the desert areas). Ambient air temperature increases in a directional pattern, similar to that of regional precipitation. (In northern Syria, the average January temperature is 5¡C and in August, it is 24¡C; in Beirut, 13¡C in January and 27¡C in August.)
During the winter, low pressure systems which form over the western parts of the Mediterranean and southern Europe penetrate the region and produce rainfall. These low pressure systems are often followed by the development of high pressure systems which cause clear and cold weather conditions.
During the summer, the weather is less variable, being affected by the semi-permanent surface heat trough centred over Iran and Iraq. This surface trough is coupled with an upper air high pressure system, producing stable hot and dry weather.
During the autumn, cool and moist air masses occasionally penetrate the country from the north and upon passing over the hot ground produce rainfall. Spring is characterized by frequent occurrences of khamsins and dust storms caused by the penetration of heat lows from North Africa, although some rainfall occurs.
Research of the climate changes during the last 10,000 years involved the construction of a standard diagram depicting the major climate changes. This included an interpretation of the d180 and d13C time series obtained from lacustrine carbonates in a core sample taken from the Sea of Galilee, and stalagmite samples taken from caves in the Galilee of northern Israel and archaeological data derived from a detailed study of the Negev desert. In addition, the results of studies on the palaeo-levels of the Dead Sea and Mediterranean Sea were incorporated.
The most important conclusions which can be derived from the study of the standard diagram are as follows:
Curves of d18O and d13C time series obtained from lacustrine carbonates in a core taken in the Sea of Galilee and the corresponding palynological results, as well as d18O and d13C time series evaluated from results of 41 stalagmites taken in 10 caves in Galilee, Israel, were found to correlate with archaeological data derived from a detailed study of an area of 100 km2 in the plain of Beer-Sheva and Arad.
The conclusion is that climatic changes were the primary factor deciding the desertification of the semi-arid part of Israel.
The earliest cold climate phase signified by a marked depletion of the carbon and oxygen isotope compositions started at ca. 5700 BP and ended at ca. 5200 BP, namely from the mid to the end of the Chalcolithic period. Towards the end of this period and at the beginning of the early Bronze Age, a warmer climate trend began.
Starting from ca. 4600 BP, and extending to ca. 4200 BP, a relatively cold period followed. A warmer period started at ca. 4200 BP, i.e. the beginning of the Middle Bronze I Age.
A new phase of isotope depletion started at ca. 3200 BP (the beginning of the Iron Age). At ca. 2700 BP the isotope composition became heavier. This may speak for a new aridization phase but cannot be correlated with the number of settlements. A reduction is obvious at ca. 2500 BP. At that time, the first kingdom of Judaea terminated followed by a partial abandonment of the Negev. It is not clear whether this was due to the onslaught of conquering armies from Mesopotamia or to aridization. Shortly afterwards, a trend towards the depletion of heavy isotopes, most probably a result of a colder more humid period, took place. The period of heavy isotope depletion continued (with a short interval sometime at ca. 1700 BP) throughout the Byzantine period. At ca. 1400 BP, namely toward the end of the Byzantine period, the isotopic composition becomes heavier. Parallel to this, from archaeological excavation a gradual abandonment of the settlements was evidenced. During the first half of the seventh century AD, the Arab conquest of this area took place.
From the isotope curves of the Sea of Galilee, a depletion can be discerned between ca. 700 BP and 500 BP. This may correspond with the Crusader period, as well as the Little Ice Age. However, a problem in dating exists for such short periods. These changes were not reflected in the resettlement of the Negev.
The Impact of Climate Change on the Socio-economic Systems of East Asia
The climate of East Asia is dominated in winter by the polar continental air mass (PCAM), causing a northerly flow at the lower troposphere layer which comes from middle-high latitude cold and dry air. In the summer, the region is dominated by the tropicalÐsubtropical oceanic air mass (TOAM) and tropical continental air mass, causing a southerly monsoon. This is dominated by a lower troposphere layer which carries warm and moist oceanic air masses from low latitudes. There are two types of summer monsoons (the south-western and south-eastern), which influence different areas. Today, the south-eastern summer monsoons dominate most of China.
A close correlation between climate changes and the migration of the Chinese in historical times was found by several Chinese scientists. Their studies were based on a critical survey of the historical data, as well as a literature survey on information concerning Chinese lake evolution, history of agro-cities in the Chinese deserts, and flood reports of the Yellow River. The main migratory events coincided with social and political unrest, as well as invasions from the north by the Mongols. Accordingly all of these events were connected with severe climatic changes during the cold climate phases occurring in 1000 BC, 0-50, 300-600, 1100-1300 and 1600-1750 AD. The first period of migration was that of the Zhou (Chou) and was recorded at about 1000 BC. These people were western nomads who settled in what is presently north-west China, moved eastward, overthrew the rule of the Shang dynasty and established the Western Zhou dynasty. During this period an advance of the glaciers and a snowline of 100-300 metres in the mountains of Tibet also occurred. Some sand dunes were also active, and some lakes in western and northern China became more saline. During cold and dry periods a southward shift in the agro-husbandry boundary also occurred. Thus in 300-500 AD, the boundary was 200-400 km south of the former boundary, followed by warmer and more humid periods. An analysis of the production outputs and rainfall record for the last 30 years in the Inner Mongolia Autonomous Region suggests that there is a linear relationship between summer precipitation and herbage outputs. Low amounts of summer precipitation decrease the growth of herbage and, thus, carrying capacity of the plain drops. This causes famine to livestock and the people that are dependent on them. The general conclusion is, therefore, that the greenhouse effect will be positive for China's agriculture, as it will strengthen the monsoons, whereby the agricultural regions of China will become warmer and more humid.
Correlation between the Eastern Mediterranean and Eastern Asia
Correlating the two regions, it can easily be seen that the cold, dry periods in eastern Asia correspond with the cold, wet periods in the Mediterranean region, while the warm, wet periods of China correspond with the warm, dry periods in the Mediterranean region. The period of 1000 BC is that of the Iron Age, followed by the Persian period of warmth and dryness which started to change in the Middle East already in 300 BC to a colder and more humid period, but had no impact until 0 AD. This continued throughout the Roman cold period. The Muslim period, which was dry and warm in the Levant, was warm and humid in China. The cold and wet Crusader period in the Levant was again a cold and dry period in China. The same happened again during the Little Ice Age.
These observations and conclusions are in agreement with the results obtained by the simulation runs of the GCMs for the glacial periods, as palaeoclimatic records adjacent to India and Africa show that monsoon maxima occur during interglacial conditions. Yet there is a price that the people of eastern Asia have had to pay for the good years, which is the loss of life and damage caused by floods. This is the forecasted scenario for all the monsoon countries in eastern Asia, and might also be true for southern Asia, i.e. India, Myanmar, Thailand and Sri Lanka.
The main conclusion from this research is that in all that concerns the Middle East, the coming global change will cause the further drying up of this region. This will aggravate, most probably, the already severe problems of water supply. This, on top of all other reasons, may endanger the flimsy socio-economic balance in this region, as it may cause hostilities due to debates over the rights of the use of water resources.
Yet, it is claimed that such a scenario is not mandatory, as the potential of water resources in the Middle East can still be extended. This statement is based on the results of investigations carried out by me on the water resources of the Middle East, as well as on many other arid countries of the world.
One of the results of these investigations was the finding of tremendous amounts of fossil water resources under the Sinai and Negev deserts, another was the locating of fresh water under the saline soils in the deserts of Iran. During the last three years, I have been involved in a regional project of development of non-conventional water resources, an aid to try and overcome the severe socio-economical problems of the new South Africa.
To reverse the existing foreboding scenarios in the Middle East, scientists and engineers have to advance new and non-conventional methods for the development of the already existing, as well as new, water resources, and come up with new methods of management and use of these resources.
This optimistic view is supported also by a survey of the history of the development of the water resources of Israel. This survey shows that even before the establishment of the State of Israel, politicians hostile to the Zionist plan for Jewish autonomy were expressing the opinion that the limited water resources of this area would not be sufficient to supply a new modern agricultural and industrial society. The innovations in all that concerns methods of water development and use introduced by Jewish scientists and engineers and adopted by the Jewish settlers have falsified this prophecy.
On the other hand it seems that the climate change may have a positive impact on countries with monsoonal climate especially. This under the condition that precautions are taken in time to reduce the damage inflicted by floods and to use the water in a positive way. One has also to take into consideration that the majority of the agricultural population of the world lives in these countries, thus if the surplus of water is turned into a beneficial resource, the greenhouse effect may have its positive aspects. In other words, in order to avoid the negative impact of floods, the recommended strategy for this case should be based on the "win or gain principle", i.e. that new projects should be undertaken that in case the greenhouse effect does take place these projects will mitigate its impact. On the other hand if it does not occur, then these projects will help to promote the economy of the region. In China, the main precautions are the dam systems which are being proposed to be built on the main rivers. There are many reasons why these dams should not be built. These reasons have been brought up mainly by people that are afraid of the negative impact on the environment. The results of the research presented in this paper bring up an additional argument recommending the building of these dams.
In order to pursue these strategies, it is suggested to create a UNU forum which will stimulate non-conventional interdisciplinary innovations in all that relates to the development, management and methods of the use of water in relation to the possible impacts of climate changes. This should be carried out through the promotion of brainstorming workshops in which creative scientists and engineers participate. The discussions and ideas expressed in these meetings should be published and distributed in order to encourage new ideas, methods and policies.
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