تأثیرات تغییرات دیرین اقلیم بر شکوفایی و افول سلسله های حاکم بر ایران و فرهنگ های باستانی جنوب شرق ایران از هزاره دوم پیش ازمیلاد، تا دوره ساسانی
آرشیو
چکیده
آسیب پذیری بالقوه جوامع اولیه در برابر بلایای طبیعی مانند خشک سالی، سیل و قحطی ناشی از تغییرات آب و هوایی موضوع مهمی است که نیاز به مطالعات دقیقی دارد. هدف اصلی این پژوهش بررسی اثرات احتمالی تغییرات دیرینه محیطی و اقلیمی بر سکونتگاه های عصرمفرغ در جنوب شرق ایران و سلسله های اصلی حاکم بر ایران براساس شواهد باستان شناسی و تاریخی مرزهای سرزمینی، رونق اقتصادی و سیاسی است. تطبیق تغییرات اقلیمی و فرهنگی در جنوب شرق ایران می تواند اطلاعات بسیار گران قیمتی را در اختیار محققین قرار دهد. در این راستا، پژوهش پیشِ رو سعی دارد پاسخ های مناسبی به این پرسش ارائه نماید که آیا تغییرات اقلیم بر جوامع باستانی جیرفت تأثیر گذاشته است یا خیر؟ و در نگاهی کلان تر تغییر اقلیم تا چه اندازه بر رونق اقتصادی و نفوذ سیاسی سلسلههای حاکم بر ایران تأثیر گذاشته است؟ در مطالعه حاضر با استفاده از ترکیبی از شاخص های ژئوشیمیایی و گرده شناسی، تغییرات دیرینه اقلیمی جنوب شرق فلات ایران درطول 4000سال گذشته بررسی خواهد شد. فعالیت های کشاورزی قابل توجه، بین 3900 تا 3700 سال پیش از حاضر هم زمان با شرایط اقلیمی معتدل در جنوب شرق ایران وجود داشته اشت. شرایط خشک همراه با افزایش گرد و غبار از 3300 تا 2900 سال پیش از حاضر بر منطقه حکم فرما بوده است. شرایط مرطوب در جنوب شرق ایران از حدود 2900 تا 2300 سال پیش از حاضر، هم زمان با شکوفایی حکومت های منطقه ای مانند مادها، اورارتوها، مانناها در نیمه غربی ایران و پس از آن شاهنشاهی هخامنشی در سراسر ایران بزرگ، کشاورزی گسترده را تسهیل نموده است. افول شاهنشاهی هخامنشی هم زمان با آغاز یک دوره خشک بوده است که برای نزدیک به 200سال، کشاورزی در جیرفت را کم رونق نموده است. جنوب شرق ایران بار دیگر بین 1550 و 1300سال پیش از حاضر شرایط مرطوبی را تجربه کرده است، که با رونق اقتصادی اواسط تا اواخر شاهنشاهی ساسانی هم پوشانی زمانی دارد.The Influence of Paleoclimatic Variability on the Rise and Fall of Iranian Dynasties and Ancient Cultures in Southeastern Iran from the 2nd Millennium BCE to the Sassanid Period
The potential vulnerability of primitive societies to natural disasters, such as droughts, floods, and famines caused by climate change, is an important issue that requires careful study. The main aim of this research is to investigate the possible effects of ancient environmental and climatic changes on Bronze Age settlements in southeastern Iran, as well as the main dynasties that ruled Iran based on archaeological and historical evidence of territorial boundaries, economic and political prosperity. Adaptation of climatic and cultural changes in the southeast of Iran can provide valuable information for researchers. In this regard, this article aims to answer the question of whether climate change has affected the ancient societies of Jiroft, and to what extent climate change has affected the economic prosperity and political influence of the ruling dynasties that have affected Iran. In the present study, using a combination of geochemical and pollinological indicators, we examine paleoclimatic changes of the southeastern plateau of Iran during the past 4000 years. Significant agricultural activities existed between 3900 and 3700 years ago in the southeast of Iran during moderate climatic conditions. Dry conditions with increased dust prevailed over the region from 3300 to 2900 years ago. Wet conditions from about 2900 to 2300 years ago facilitated extensive agriculture and coincided with the flourishing of regional governments such as the Medes, Urartos, and Mannas in the western Iran, and after that the Achaemenid Empire throughout Greater Iran. The decline of the Achaemenid Empire coincided with the beginning of a dry period that made agriculture less prosperous in Jiroft for nearly 200 years. Southeast Iran experienced humid conditions between 1550 and 1300 years ago, which coincided with the economic prosperity of the middle to late Sassanid Empire.
Keywords: Climate change, Sassanid, Bronze Age, Sediment core, Achaemenids.
Introduction
This study aims to reconstruct the paleoclimate history in southeastern Iran by tracing the landscape changes and climate fluctuations since the Late Bronze Age and their impacts on human societies based on palaeo-environmental analysis of a wetland system. It will further evaluate the possible impacts of climate change on major ruling dynasties of Iran since the Late Bronze Age. An example of the latter would be following the territorial extent of major ruling dynasties from historical records, which would have been quintessential to society’s prosperity and growth coeval to favorable climatic conditions for agriculture and trade, and the development of city-states. The study involves a multi-proxy palaeo-environmental reconstruction using geochemical, and paleoecological proxies in a 250-cm long peat sequence near the archaeological complex at Konar Sandal near Jiroft, covering the last 4000 cal yr BP. The different proxies suggest changes in elemental concentrations, stable isotopes, and pollen records.
Materials and methods
Palynological analysis were done in Thirty-five subsamples at intervals of 1-10 cm at the Institut Méditerranéen de Biodiversité et d’Ecologie, Aix-en-Provence, France by procedure described by Gurjazkaite et al. (2018).
Geographical setting
Konar Sandal (25 km south of Jiroft in southeast Iran) is the main excavation site in the Jiroft Valley. Several high mountain chains surround it, some of them rising to 3700 m asl (Fig. 1). The Halil Rud stretches from north to southeast for almost 400 km through fertile agricultural land before draining into the Jazmurian playa south of Konar Sandal. The water level in the river fluctuates throughout the year.
Results
The sediment core was divided into six major units based on the sedimentological, geochemical, and palynological characteristics (Fig 2 and Fig. 3). The elemental ratios (Si/Al, Ti/Al, and Fe/Al) had relatively low values in Unit 1 (U 1; 250-189 cm; 4011-3548 cal yr BP). The first significant appearance of Cerealia-type pollen occurred in this unit extending from 3880-3700 cal yr BP (230-207 cm). The #948;13COM showed a distinct increase in Unit 2 (U 2; 189-164 cm; 3548-3293 cal yr BP). Unit 3 (U 3; 164-134 cm; 3293-2897 cal yr BP) was characterized by high elemental ratios (Si/Al, Ti/Al, and Fe/Al). The K/Ti ratio had the highest values in the entire core in Unit 4 (U 4; 134-106 cm; 2897-2302 cal yr BP). #948;13COM values were more negative in Unit 5 (U 5; 106-61 cm; 2302-1540 cal yr BP). Unit 6 (U 6; 61-10 cm; 1540-854 cal yr BP) was characterized by moderate values of different elemental ratios.
Discussion
Around 3950 cal yr BP a wet period prevailed based on elemental ratios, stable C isotope, and pollen (Fig. 3). Between 3900 and 3300 cal yr BP, mild climate conditions developed. significant appearance of Cerealia-type pollen and agricultural activities existed between 3900 and 3700 cal yr BP. Dry and windy conditions followed from ca. 3300-2900 cal yr BP with the driest conditions around 3200 cal yr BP coinciding with the regional Late Bronze Age cultural collapse. The driest conditions in this dry period occurred around 3200 cal yr BP, coinciding with the decline of the Jiraft Bronze Age civilization at the end of the Bronze Age. The long wet period extending from 2900 to 2300 cal yr BP with a high presence of Sparganium-type and intensive agricultural practices. Wet conditions in the Jiroft valley from about during this period, simultaneously with the flourishing of the powerful Medes and Achaemenid empires, facilitated extensive agriculture. The decline of the Achaemenid Empire coincided with the beginning of a dry period that made agriculture less prosperous in Jiroft Valley for nearly 200 years. The highest Ti/Al values coeval with the lowest #948;13COM values suggest an increase in Aeolian activity and dry conditions between 2100 and 1650 cal yr BP. The Jiroft Valley once again experienced humid conditions between 1550 and 1300 cal yr BP, which coincides with the economic prosperity of the mid to late Sassanid Empire (Fig. 4).
Conclusion
In the present study, using a combination of geochemical and pollinological indicators, we examine the paleo-environmental changes of the ancient Jiroft valley in the southeast of Iran during the past 4000 years and their possible effects on the settlements of the Bronze Age and the main dynasties that ruled Iran based on records.
The Jiroft Valley experienced wet conditions between 1550 and 1300 cal yr BP, which overlapped with one of the most extensive territorial boundaries in Iran’s imperial history (the Sassanid Empire in the early 7th century C.E.). Although mild conditions prevailed between 1315 and 854 cal yr BP, agricultural activities declined, probably due to weak succession and political instability. We evaluate the archeology and history of territorial borders, economic and political prosperity. Paleo-environmental reconstruction shows that the wet periods and increased agriculture in the Jiroft Valley coincided with the peak of political influence and economic wealth of the Achaemenid and Sassanid empires. Therefore, more detailed paleoclimatic records would be helpful for investigating the interplay of political and climatic factors in the development and decline of ancient settlements and imperial powers in Eurasian history.
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