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Qasr-e-Shirin

The location and development of the last outbreak

The area under study lies in the lowest foothills of the Zagros mountains, which border the plain of Iraq, and forms part of a zone of infestation running north-west into Iraq, Syria and Turkey. In the neighbourhood of Qasr-e-Shirin the boundary of Iraq and Iran turns and runs S.S.W.-N.N.E. for some 200 km., crossing this zone, which to the north-west lies in Iraqi territory and to the south-east in Iran (Fig. 2). The zone narrows at this point and widespread infestation apparently does not occur for more than a short distance south of Mehran. Unfortunately I was unable to visit this southern area in the time at my disposal but it merits investigation.

Fig. 2.-The northern part of Qasr-e-Shirin district. (Topographical base in black, information on locusts, vegetation and climate in red; P=pistachia, Q=oak, cross-hatching indicates cultivation.)

There has been no serious infestation in this region since 1948 and no control since 1951 (see Table 1), except in 1958, near Mehran, where a few hopper bands were seen and destroyed by Desert Locust control teams. Details of the outbreak are not available for the period before 1949, but there can be no doubt that it followed the same general course as the simultaneous outbreak in Iraq, which reached its peak during the years 1946-1948. There is a suggestion from the Iraq figures that the plague developed first in the Mosul liwa and subsequently spread to the east and south-east, as Rooke (1930) reported in his discussion of the 1925-1929 outbreak, but this does not mean that either Diyala liwa or the adjacent Qasr-e-Shirin district lay only within the invasion zone. There can be no doubt that swarms originated within these areas.

The last outbreak appears to have ended abruptly in 1949. This must be attributed partly to the build-up in size and efficiency of the control organisations during the course of the outbreak and partly to weather conditions very unfavourable to the Moroccan Locust during the winter and spring of 1949. At the Moroccan Locust Conference held in Baghdad in February, 1950, both the Iranian and Iraqi delegates referred to cold and torrential rains at the time of hatching, while from Syria (Regional Conference on the Moroccan Locust, Damascus, December 1951) very cold weather and snow were reported. In Iraq in 1949 only in Kirkuk and Diyala liwas was extensive egg-laying reported and this was on a far smaller scale than in the preceding years.

Climate

There is very little reliable meteorological data from this district. Ganji (1955) gives the mean annual rainfall for Qasr-e-Shirin as 354 mm., but does not say for what period his mean is calculated. More detailed figures are available from the Iraqi side of the border: the mean annual rainfall for Khanaquin for the years 1935-1940 was 382 mm. while for the period 1931-1939 it was 305 mm. (Climatological Means of Iraq, Publication No. 7 of the Iraq Meterological Service). For the period 1936-1957, i.e., the period in which we are interested more particularly, it was 327 mm. (Dr. M. E. D. Poore, personal communication). This includes the wet winters of 1939-1940 and 1948-1949. Although the annual figures have not been available to me it is clear that there is considerable variation in rainfall from year to year, and indeed this is a feature of the whole region. The mean annual rainfall at Mandali, further south, for the period 1935-1940, was 385 mm. This is certainly higher than the true mean; the equivalent figure must be almost the same as for Khanaquin. Naft Khaneh, on the border, lies to some extent in the rain-shadow of the Kuz-e-Darekhan and appears to have a lower rainfall, which is unlikely to rise above 300 mm. Probably the whole of the area under study, below 600 mm., receives a rainfall of between 300 and 450 mm., with the exception of a small area near Naft-e-Shah, where it may be slightly lower. The rainfall distribution is Mediterranean in type, cool, wet winters alternating with hot, dry summers. The mean monthly temperatures and rainfall totals for Khanaquin, which has a climate slightly hotter and drier than Qasr-e-Shirin, are given in Table 3.

The distribution of locusts

No maps or records were available to indicate where in the district hopper bands or swarms had been observed in the past or the area in which solitary locusts still survived, while the lapse of time since the last outbreak and the scarcity of long established settlements made it difficult to obtain any useful information from the inhabitants. However, I was fortunate in having with me Ing. A. Farabash, Entomologist in the Ministry of Agriculture, who had studied the Moroccan Locust here ten years previously and was able to give me first-hand information. As hatching had not yet begun, this was practically the sole source of information on the extent of the area formerly affected, the only exception being the report of the Moroccan Locust Conference held in Baghdad in February, 1950, in which figures for the area in hectares baited in a number of named sectors in 1949 are given. Eggpods were looked for but they are difficult to find where the locust populations are of low density and, in fact, very few were collected. The approximate boundaries of the areas in which swarms or hopper bands occurred are shown in Fig. 2. These must be regarded as provisional. From the information I was able to obtain it appears that solitaries exist throughout most of this area-and almost certainly elsewhere-and that hopper bands and swarms developed from this solitary population in many localities. The probable extent of this gregarisation is indicated in Fig. 2. Again it must be regarded as tentative and preliminary.

It will be seen that swarms or hopper bands were found at Bavesi in the north, to the east, south, south-west and west of Qasr, up the Gilan valley and generally throughout the lowlands as far south as Naft-e-Shah and for some 30-40 km. beyond. They were again found south of Mehran, for about 50 km. Only one swarm was reported from Bavesi and undoubtedly came from over the frontier; it is very unlikely that there was any development of gregarious populations in this district. Similarly it is doubtful whether gregarisation took place south-west of Qasr, to the west of the Alwand River, although here there appeared to be a scattered solitary population. This area, however, was heavily invaded. On the other hand, hopper bands appear to have originated in many localities scattered throughout the lowlands to the east of Qasr to within 7 or 8 km. of Sar Pul-e-Zuhab, on the southerly flanks of the range which runs between Cham-e-Dehra and Cham-e-Gilan about as far as Tang-e-Kora (south-east of this there were only solitary populations), and on the lower S.W.-facing slopes of the range bordering the Gilan valley to the south-west, as well as in the broken country at lower altitude immediately to the west of Qasr, and along the foothills past Naft-e-Shah to the south. It is unlikely that the development of the gregarious populations was so widespread here and almost certainly it did not occur near the frontier in the Naft-e-Shah area.

If this is the correct distribution, the localities in which gregarious populations developed from solitary ones are situated below 600 m. (except in the Cham-e-Gilan north-west of Tang-e-Kora, where the altitude is a little above this), and for the most part above 300 m. They lie in undulating foothill country, dissected, by numerous little valleys. They are all on Upper Fars-Lower Bakhtiari beds or soils derived from them, with or without a certain admixture of downwashed material. It is noteworthy that where they are found above 600 m. in the Gilan valley the Upper Fars-Lower Bakhtiari exposures are also at an unusually high altitude.

Vegetation

The oak forest has been heavily cut in this district, particularly at low altitudes or near roads and villages, and over large areas of the hills exists only as coppice scrub. On deeper soils it has been completely cleared. The only remains of Pistachia forest are isolated trees, often standing well beyond the present boundary of any existing scrub, which have been preserved by their proximity to a shrine or tomb. That these are the remains of continuous open woodland is suggested by analogy with Fars. The present boundary of the oak forest and certain conspicuous isolated trees are shown in Fig. 2.

Apart from the area under cultivation the rest of the district is grassland, with a variable dwarf shrub component, which is never large. Much of it has been derived from forest; the greater part is "moist" steppe. It has been heavily grazed for a very long time and over wide areas Hordeum-Bromus-Avena grassland has been replaced by Poa-Carex or even by Koeleria-Plantago grassland. Artemisia herba-alba is not abundant in the area, and probably only along the border, and particularly in the Naft-i-Shah area, was Artemisia steppe the original vegetation.

Land-use in the area

The whole of the area is inhabited by Kurds, mostly tribal, some of whom are settled in the villages, while others still practise transhumance, grazing during the winter months in the foothill country at low altitudes and moving into the mountains in summer. In recent years, however, there have been rapid and widespread changes in practice which have affected land-use. For various reasons (the increase in law and order following the strengthening of the Central Government and the betterment of communications, which has led to a reduction in tribal warfare, the closure of the border to migratory groups, official encouragement or even insistence on settlement, and the profit to be derived from smuggling), the population has become much more sedentary and there has been a great increase in the area of land under cultivation. Extensive tracts of land in northern Iraq and Syria, which had been steppe grazing for centuries, have been brought under cultivation in the last ten or fifteen years and the practice is spreading. Moreover there has been a real increase in population coupled with a probable decrease in the number of draught animals available for transporting the tents and equipment to and from the winter grazing grounds. A number of new villages have been founded, especially in the lower Gilan valley, and large areas of land south-east of Qasr-e-Shirin have only recently come under the plough.

The agricultural practices in these areas are primitive and most cropping is on a simple cereal-fallow rotation. No fertilisers are used and only near long established villages and where there is perennial irrigation water is there any variety of crops. The possibilities of mechanical cultivation are being realised, particularly by the clan chieftains. According to Mr. Farabash, the plain north of Sar Pul-e-Zuhab, although settled ten years ago, was little cultivated and there were extensive areas under grass so tall and dense that it brushed the sides of his jeep as he drove through it. It is now almost entirely under the plough, most of it being cultivated by machinery owned by the clan chieftain. This cultivation was begun about 1953. The only patches of unploughed grassland remaining at the time of my visit were low, heavily grazed swards of Poa bulbosa and a few annual species, as, for instance, around the graves south of Tepe Reza Khan. The villagers say they keep rather fewer animals than formerly (figures are lacking) and graze them on the slopes of the hills. The inhabitants of Bavesi, a little further north, formerly migrated; only during the last five or six years have they finally stopped. The same thing appeared to be true of a number of other villages.

The distribution of cultivated land is shown in Fig. 2. It is of course not continuous in broken country: the level areas are cropped while the river banks, gulleys and steep slopes are left under grass. Nevertheless the total area under cultivation in the district has probably doubled in the last ten years. Not all this has been at the expense of steppic grassland. On the road from Gilan to Elam, for instance, just beyond the junction of the Shahabad road near Sarchaleh, there was very fine untouched forest ten years ago. Clearance began three or four years later and now there are considerable areas of hill slopes completely cleared and under cultivation. The original forest soils are rapidly eroding.

This increase in the area under cultivation has meant a decrease in the amount of land available for grazing and even allowing for a reduction in the number of animals, an increase in grazing pressure on the remaining land. The area between the Cham-e-Duchys and the Tang-ab, east of the Alwand River to the foot of the mountains, is largely uncultivated and grazed by flocks of the Simoun clan. During the winter months some sixty flocks grazed this area, between two-thirds and three-quarters of which appear to be sheep and the rest goats. This gives an overall density of about 3.5 sheep and goats per hectare, which is not too dense in a year of good rainfall but in a year of poor rainfall it must result in severe overgrazing. In fact, evidence of overgrazing is widespread, usually accompanied by more or less severe soil erosion, particularly where the Upper Fars beds have no superficial layer of limestone colluvial material to render the soils formed from them more stable. There is some evidence that there has been an increase in the rate of erosion in recent years in the area near the border south of the Tang-ab and probably elsewhere. In many cases gulleys can be seen cutting back rapidly through a pre-existing erosion pavement and there are signs that the vegetation is degrading. Large numbers of recently dead Phlomis bruguieri plants were found with practically no regeneration, and in some cases there were numerous young plants of Astragalus microthamnus, probably a species of the dry steppe, certainly in our area a species found in the most and habitats and open vegetation. In many places Poa bulbosa and Carex stenophylla are largely dead and a sparse low annual cover, in which Koeleria phleoides is prominent, has replaced them. The fact that the dead plants remain even in this erodible soil suggests that their death is recent. If the ground is examined in such places it is found to bear the footmarks of sheep and goats over almost every square inch of it. This increased rate of erosion and degradation probably began no more than five or six years ago.

The location of eggfields

Where the land has come under cultivation it is usually level or only gently sloping. When fallowed, the fields are rapidly covered with a vegetation which resembles the surrounding grassland in general botanical composition, though it is more open and more uniform. The perennial Poa bulbosa and Carex stenophylla (where it occurs) are slow to re-establish themselves on land once ploughed. A number of such cultivated areas were seen which had been the site of high density locust populations ten years previously.

Even in the zone climatically suitable for moist steppe, under heavy grazing and on erodible soils, even moderately steep slopes may be almost devoid of vegetation or covered only with a sparse, low, growth of annuals. The vegetation of the valley bottoms in which water collects and soil is deposited (if they are not gullied) may form a complete cover of taller species, again predominantly annual. Thus the mosaic pattern of the vegetation essential for the development of high density locust populations is present, but the extreme erodibility of the soils derived from the Upper Fars beds renders the steeper slopes unfavourable for oviposition. On even gently sloping land, however, sheet erosion induces a mosaic pattern, with a rather compact surface soil on the bare patches, which are very suitable for locust egglaying. It is possible that the greater part of the dense egglaying formerly occurred on such sites, which, as has been shown, are the first selected for cultivation.