Nov 28, 2021
JERUSALEM WEATHER

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World leaders convened a few weeks ago in Glasgow, Scotland, to discuss alarming climate change that threatens humanity around the globe in the coming years – but little resulted from the deliberations. But this is not new: there was significant climate change at the end of the last Ice Age 10,000 to 20,000 years ago in the Land of Israel. 

 

Based on the identification of plant remains, researchers at Tel Aviv University (TAU) and Tel-Hai College in the Upper Galilee provide the first detailed reconstruction of the climate in the Land of Israel at the end of the last Ice Age (20,000-10,000 years before present). 

 

The researchers claim that significant climate changes characterizing the period, expressed by sharp differences in temperature and precipitation not only seasonally but throughout the year, were a major influence in the transition from a nomadic hunter-gatherer society to permanent settlement and an agricultural way of life. 

Dr. Dafna Langgut.
(Courtesy of Sasha Flit/Tel Aviv University)

The study also provides the first data related to the history of the region’s flora and its response to past climate change. The researchers believe that understanding the response of the region’s flora to the dramatic climate changes in the distant past can help preserve the regional variety of plant species and plan for current and future climate challenges. 

 

The research was conducted by Dr. Dafna Langgut of the archaeology department and TAU’s Steinhardt Museum of Natural History; Prof. Gonen Sharon, director of the master’s degree program in Galilee studies at Tel-Hai College, and Dr. Rachid Cheddadi, an expert in evolution and palaeoecology of University of Montpellier’s Institute of Evolutionary Sciences in France. The groundbreaking study was recently published in the leading scientific journal Quaternary Science Reviews under the title “Climate and environmental reconstruction of the Epipaleolithic Mediterranean Levant.” 

 

The study was conducted at the prehistoric archaeological site Jordan River Dureijat (“Jordan River Stairs”) on the shores of the Paleo Lake Hula. The site is unique for its exceptional preservation conditions that made possible archaeological finds making possible the discovery of the primary activity of its early local residents – fishing. Botanic remains preserved also enabled researchers to identify the plants that grew 10,000 to 20,000 years ago in the Hula Valley and its surroundings.  

 

Major processes in world history took place during this period – the transition from a nomadic to a settled lifestyle that occurs during a period of dramatic climate change. Sharon, who supervised the Madregot Hayarden excavation, explained: “In the study of prehistory, this period is called the Epipalaeolithic period. At its outset, people were organized in small groups of hunter-gatherers who roamed the area. Then, about 15,000 years ago, there was a significant change in lifestyle – the appearance of settled life in villages and additional dramatic processes that reach their apex during the Neolithic period that followed. This is the time when the most dramatic change of human history occurred – the transition to the agricultural way of life that shaped the world as we know it today.”

 

Langgut, an archaeobotanist specializing in the identification of plant remains, elaborates on the second dramatic process of this period, the climatic changes that occurred in the region. “Although at the peak of the last Ice Age about 20,000 years ago, the Mediterranean Levant was not covered with an ice sheet as in other parts of the world, the climatic conditions that existed nevertheless differed from those of today. Their exact characteristics were unclear until this study. The climatic model that we built is based on reconstruction of the fluctuation of the spread of plant species indicating that the main climatic change in our area is expressed by a drop in temperature (up to five degrees Celsius less than today), whereas the precipitation amounts were close to those of today (only about 50 millimeters less than today’s annual average). 

 

However, Langgut explains that about 5,000 years later, in the Epipalaeolithic period (about 15,000 years ago), a significant improvement in climate conditions can be seen in this model. An increased prevalence of heat-tolerant tree species such as olive, common oak and Pistacia, indicate an increase in temperature and rainfall. During this period, the first sites of the Natufian culture appear in our region. It could very well be that the temperate climate assisted in the development and flourishing of this culture, in which permanent settlement, stone structures, food storage facilities and more first appeared on the global stage.   

 

The next stage of the study dealt with the end of the Epipalaeolithic period, about 11,000 to12,000 years ago, known globally as the Younger Dryas period. This period is characterized by a return to a cold, dry climate like that of the Ice Age, causing a kind of climate crisis around the world. The researchers maintain that until this study, it was unclear whether and to what extent there was any expression of this period in the Levantine region.

Chart of fossil pollen grains. (Courtesy of Dr. Dafna Langgut)

“The findings that arise from the climate model presented in the article show that the period was characterized by climatic instability, intense fluctuations, and a considerable drop in temperatures,” said the researchers. “Nevertheless, while reconstructing the precipitation, a surprising phenomenon was discovered – the average quantities of rainfall that were reconstructed were only slightly less than those of today, but the precipitation was distributed over the entire year, including summer rains.”

 

The researchers claim that such distribution promoted the expansion and thriving of annual and leafy plant species. The gatherers who lived in this period now had a wide, readily available variety of gatherable plants throughout the entire year. This variety enabled their familiarity just before domestication. The researchers believe that these findings contribute to a new understanding of the environmental changes that took place on the eve of the transition to agriculture and domestication of animals.

 

Langgut concluded that “this study contributes not only to understanding the environmental background for momentous processes in human history such as the first permanent settlement and the transition to agriculture, but also provides information on the history of the region’s flora and its response to past climatic changes. There is no doubt that this knowledge can assist in preserving species variety and in meeting current and future climate challenges.”