Vulnerability of Turkey to Desertification with Respect To
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Tr. J. of Engineering and Environmental Science 23 (1999) , 363 – 380. c TUB¨ ITAK˙ Vulnerability of Turkey to Desertification With Respect to Precipitation and Aridity Conditions Murat TURKES¨ ¸ State Meteorological Service, Department of Research, P.O. Box 401, Ankara-TURKEY Received 19.01.1998 Abstract Climatic factors that may lead to desertification in Turkey were investigated by analysis of the spatial and temporal variations of the precipitation and aridity index series, for the period 1930-1993. Semi-arid and dry sub-humid environmental conditions are dominant over the continental interiors and South-eastern Anatolia. Persistent dry conditions have been evident for the past two decades over a considerable part of Turkey. There has been a general tendency from humid conditions of around the 1960’s towards dry sub-humid climatic conditions in the aridity index values of many stations and of Turkey, in general. At some stations in the Aegean Region, there has been a significant change from humid conditions to dry sub-humid or semi-arid climatic conditions. With regard to climatic factors, South-eastern Anatolia and the continental interiors of Turkey appear to be aridlands that are prone to desertification. When other natural and anthropogenic factors, such as high topography, forest fires and unsustainable use of agricultural lands are also taken into account, the Mediterranean and Aegean regions could be more vulnerable to desertification processes in the future. Key Words: Precipitation, Aridity Index, Seasonality, Variability, Trend, Persistent and Periodicity Anal- ysis. Ya˘gı¸s ve Kuraklık Ko¸sulları A¸cısından T¨urkiye’nin C¸¨olle¸smeden Etkilenme E˘gilimi Ozet¨ T¨urkiye’de ¸c¨olle¸smeyi y¨onlendirebilecek olan iklimsel etmenler, ya˘gı¸s ve kuraklık indisi dizilerinin alansal ve zamansal de˘gi¸simleri 1930-1993 d¨onemi i¸cin analiz edilerek ara¸stırılmı¸stır. Yarı-kurak ve kurak yarı- nemli ¸cevresel ko¸sullar, karasal i¸cb¨olgeler ve G¨uneydo˘gu Anadolu B¨olgesiuzerinde ¨ egemendir. Israrlı kurak ko¸sullar, yakla¸sık son 20 yıl s¨uresince T¨urkiye’nin ¨onemli b¨ol¨um¨unde belirgin olmu¸stur. Bir¸cok istasy- onun ve T¨urkiye’nin kuraklık indisi de˘gerlerinde, 1960’lardaki nemli ko¸sullardan kurak yarı-nemli iklim ko¸sullarına do˘gru genel bir e˘gilim bulunmaktadır. Ege B¨olgesi’nin bazı istasyonlarında, nemli ko¸sullardan kurak yarı-nemli ya da yarı-kurak iklim ko¸sullarına y¨onelik ¨onemli bir de˘gi¸sim s¨ozkonusudur. Iklim˙ etmen- leri g¨ozetildi˘ginde, G¨uneydo˘gu Anadolu B¨olgesi ve T¨urkiye’nin karasal i¸cb¨olgeleri ¸c¨olle¸smeye e˘gilimli kurak alanlar olarak kendisini g¨osterir. Topo˘grafyanın y¨uksek olu¸su, tarım arazilerinin s¨urd¨ur¨ulebilir olmayan kul- lanımı ve orman yangınları gibi ¨oteki do˘gal ve insan kaynaklı etmenler dikkate alındı˘gı zaman da, Akdeniz ve Ege b¨olgeleri gelecekte ¸c¨olle¸sme s¨ure¸clerine daha fazla a¸cık olabilecek alanlar olarak d¨u¸s¨un¨ulebilir. Anahtar S¨ozc¨ukler: Ya˘gı¸s, Kuraklık Indisi,˙ Mevsimsellik, De˘gi¸sebilirlik, E˘gilim, Israr ve D¨onemsellik Analizi 363 TURKES¨ ¸ Introduction The United Nations (UN) first put the issue of surface, drought events, sudden and high-intensity desertification on the international agenda at the rainfall, shifting spatial and temporal distributions UN Conference on Desertification (UNCD) in 1977, of precipitation, high temperature and high wind as a global socio-economic and environmental prob- speed (Gbeckor-Kove, 1989). Most of these natural lem. The first international effort to combat de- changes may be considered in the context of climatic sertification had begun at the end of the great Sa- variability, including long-period fluctuations of dry helian drought and famine of 1968-1974, in which and wet conditions, persistence from year to year over 200,000 people and millions of animals died variations and secular trends. Thus, the aims of this (Lean, 1995). Developing countries, especially in study are as follows: (i) to give basic information on Africa, insisted that particular attention should be spatial distribution of mean precipitation totals, pre- given to desertification, during the preparations for cipitation variability and seasonality of precipitation, the UN Conference on Environment and Develop- and to examine the aridlands of Turkey by using an ment (UNCED) held in Rio in June, 1992. Then the aridity index; (ii) to analyse the long-term variations, world’s leaders agreed in Agenda 21 to call on the including trend and persistence in precipitation and UN General Assembly to set up an Intergovernmen- the aridity index series, and periodicity in the arid- tal Negotiating Committee to prepare a legally bind- ity index series; and (iii) to assess the desertification ing instrument by June, 1994. Finally, the UN Con- vulnerability of Turkey, taking into account the cli- vention to Combat Desertification in those Coun- matic factors, particularly precipitation amount and tries Experiencing Serious Drought and/or Deserti- variability, aridity, and long-term changes in precip- fication, Particularly in Africa, was adopted in Paris itation totals and aridity index values throughout on 17 June 1994. Turkey. It would be useful at the beginning of this study to differentiate between the terms of aridity, drought Data and Method and desertification, through the use of the terms ac- cepted for the Convention to Combat Desertification For the time-series analysis of precipitation and (referred to hereinafter as the Convention). Aridity the aridity index series, this study was carried out is the state of low average precipitation or available mainly with the use of annual and seasonal precipi- water in a region and, if the possibility of climatic tation totals and mean annual temperatures, which change is not taken into consideration, is a perma- were calculated from monthly values recorded at sta- nent climatic feature (Gbeckor-Kove, 1989). Arid- tions of 91 and 55 of the Turkish State Meteorolog- ity generally arises from persistent widespread atmo- ical Service (TSMS), respectively, during the period spheric subsidence or anticyclonic weather, and from 1930-1993. The lengths of records vary from 54 to more localized subsidence in the lee of mountains. 64 years for precipitation data and from 42 to 64 Drought is “the naturally occurring phenomenon years for temperature data. The year was divided ac- that exists when precipitation has been significantly cording to the basic seasons, namely, winter (Decem- below normal recorded levels, causing serious hydro- ber to February), spring (March to May), summer logical imbalances that adversely affect land resource (June to August) and autumn (September to Novem- production systems” (UNCCD, 1995). However, it ber). This precipitation data set has been broadly is a temporary feature caused by climatic variations explained already by T¨urke¸s (1995b; 1996b). Miss- and occurs not only in arid and semi-arid regions ing values in monthly station records were replaced but also in other climatic regions, such as in humid with estimates from nearby stations only if the gaps climates of mid-latitude regions. The term of de- in a station’s record did not consist of more than 5% sertification was defined at the Convention as “land of the total number of monthly values in that sta- degradation in arid, semi-arid and dry sub-humid ar- tion’s record. This was performed by using the nor- eas resulting from various factors, including climatic mal ratio method, as described in Singh (1992). In variations and human activities” (UNCCD, 1995). this procedure, three nearby reference stations were Major climatic factors that are likely to lead chosen by taking into account the highest correlation desertification include variations in climatic vari- coefficients (Pearson’s r), between the base station to ables such as precipitation, aridity and wind, or be filled and the possible reference stations. changes in aridity, increase in the albedo of the land Statistical evaluations of homogeneity for the an- 364 TURKES¨ ¸ nual and seasonal precipitation total series, and an- the homogeneity test, and checked the station files. nual aridity index and temperature series were ac- complished by the non-parametric Kruskal-Wallis This type of information is useful in deciding test for the homogeneity of means of the sub-periods whether a jump arose from a relocation of the sta- (Sneyers, 1990). For this study, homogeneity means tion, or because of a low-frequency fluctuation (or a that there is no jump in the climatic series of obser- strong persistence) in the series. For instance, using vations. Jumps consist of non-climatological abrupt additional information from the station history files, falls and/or abrupt rises in the series. For the homo- we found that significant inhomogeneities in the an- geneity test of precipitation amount series, annual nual and seasonal air temperature series of Antalya, and seasonal precipitation totals were expressed as Anamur and Fethiye stations had occurred owing to percentages of their long-term average. The Kruskal- relocation of the stations. In particular, relocation Wallis test was carried out for individual stations. of Anamur station in 1962 from the inner part of For a more accurate assessment, statistical results the city land to its present site on coast has had an from the homogeneity test were also checked by artificial cooling effect on the temperature variations means of plotted graphs combined with the infor- throughout the year, particularly in the annual (Fig- mation available from the station history files, which ure 1.a and b), summer (Figure 1.c and d) and au- were prepared especially for precipitation and tem- tumn series (see sub-sections method and trend for perature studies, and include necessary information sequential version of the Mann-Kendall test). This for about 80 stations, such as changes of meteorolog- cooling effect, which appears to be stronger dur- ical instruments and of the height and location of the ing summer and autumn months, is likely associated stations, in order to detect inhomogeneity in the se- with land and especially sea breezes, which are dom- ries.