Climate-induced migration — Alles bleibt anders

Who wouldn’t enjoy a bright summer's day? But the climate crisis we are all living through has brought home the fact that there is a downside to constant sunshine — heatwaves, for instance, leading to drought and poor harvests. That is still the case today and was no different in the past.

But how did earlier societies manage to survive natural climate crises with the limited means at their disposal? That’s what we in the CRC 1266 are looking to understand.

Climate crises — now and then

Today’s climate crisis is one of the great challenges of our times. Rising global temperatures make periods of drought or extreme weather events more likely. More and more people worldwide are suffering the consequences and fleeing the worst affected areas. By the year 2050 up to 143,000,000 people may have become climate migrants.

Natural climate events occurred in the past that bear comparison with today’s climate emergency. Particularly notable are climate events that occurred between 2200 and 1500 BCE. Though their effects were felt nearly everywhere in the world, they were particularly consequential in the Mediterranean region.

Bronze Age climate crises

Our research shows that the southern portion of the Iberian Peninsula was rocked by three climate crises over the course of the Bronze Age. First, around 2200 BCE, near the beginning of the Bronze Age, there was a marked decline in winter precipitation. Later, dry summers particularly affected people in the south-east, where rain was a rarity for much of the period between 2000 and 1800 BCE. The summers, always dry, now often lasted from May to September. Another sharp decline in winter rain and snow occurred around 1600/1500 BCE.

Challenges of previous droughts

Declining rainfall and months of summer drought inevitably affected both arable and livestock farming as well as the supply of drinking water. This posed an existential challenge: how were families to be fed? Bronze Age people in the south of the Iberian Peninsula tried a variety of solutions to these everyday difficulties, some of which seem to have been more effective than others.

We can observe that around 2200 BCE, settlements and traditions in the south-west of the Iberian Peninsula seem to have been largely abandoned. This includes the use of the large earthworks typical of this region. Furthermore, finds of animal bones suggest that livestock farming became increasingly difficult and that wild animals were hunted in increasing numbers to make up the shortfall.

Los Millares (Andalucía)
c. 3200—2200 BCE

This settlement gave its name to the Chalcolithic culture of Andalucía. Chalcolithic settlements were usually built close to fields and pastures.
Los Millares (Andalucía)

Chalcolithic people buried their dead in large collective graves outside their settlements. Grave goods included richly decorated vessels.
Los Millares (Andalucía)

The settlement was suddenly abandoned around 2200 BCE. There are indications that it was destroyed in a great fire.

Excursion

Reconstructing seasonal fluctuations in precipitation in the Bronze Age
In order to reconstruct past precipitation, we must look for suitable archives. We usually find these in the form of sediment cores, but also in dripstones from caves. These archives are then examined for useful indicators. There are several possible indicators that can help us reconstruct precipitation.
On the Iberian Peninsula, plant pollen is one such indicator we use. Plants are sensitive to fluctuations in climate, which means that these fluctuations register in the spectrum of species found in pollen samples. Certain trees, for instance, cannot endure long periods of drought.
Another indicator is the quantity of matter of onshore origin (e.g. plant remains) found in maritime sediment cores. Such matter largely enters the seas via rivers, which carry more material at times of high precipitation.
The reconstruction of seasonal changes is based on modern findings that be applied to the Bronze Age. The rainy season in the Iberian Peninsula lasts from October to March. That is when many trees produce their pollen and rivers carry more onshore matter than they do in summer.

A climate crisis as a spur to innovation?

At the same time, an entirely new form of society was taking shape further east along the Mediterranean coast, where monumental structures were erected on hilltops and so-called Motillas in floodplains. These new societies are now known as "El Argar". By means of social change and technological innovation, they appear to have adapted to the climate crisis.

Motillas made it possible for the first time to extract groundwater. This not only ensured the availability of drinking water during periods of summer drought between 2000 and 1800 BCE, it even allowed wheat to be grown — as well as barley, which can cope better with dryness. The elites of this newly-established class-based society proceeded to distribute food throughout their territory. For the time being, famine was banished.

View into the groundwater well of Motilla del Azuer, depth approximately 20 m.

Motillas

Motilla del Azuer (Castile-La Mancha)

Motilla del Azuer is the largest complex of its kind to have been discovered to date. So far, some forty-five such structures have been identified in the region’s floodplains.

c.2200—1500 BCE
Motilla del Azuer (Castile-La Mancha)

The Motillas were probably built to reach vital ground water supplies in times of drought. In order to do so, wells had to be dug to a depth of 4—20 m.

c.2200—1500 BCE
Fuente Álamo (Murcia)

Fuente Álamo is a typical hilltop settlement of the El Argar culture. Hilltop sites were easy to defend and allowed for easy control of the surrounding countryside.

c.2200—1550 BCE
Fuente Álamo (Murcia)

Agriculture was virtually impossible in the immediate surroundings of the hilltop settlements. However, large granaries in the settlements are indicative of regular deliveries of grain.

c.2200—1550 BCE
La Bastida (Murcia)

La Bastida is another typical hilltop settlement. In addition to their location, such settlements were defended by strong protective walls.

c.2200—1550 BCE
La Bastida (Murcia)

The dead were buried in small urns within their dwellings. The difference in burial goods suggests the existence of several social classes.

c.2200—1550 BCE

Possible climate migration and its challenges

In spite of these considerable challenges, the people in the south-east of the Iberian Peninsula definitely remained where the sun shone. Yet there are also indications that groups from the south-west of the peninsula sought to escape the sun around this time. Perhaps they even became part of El Argar society.

Whether as a consequence of immigration or not: the society grew rapidly. This meant that a fundamentally dry region had more and more people to support. Dramatic decline in winter precipitation, setting in around 1600/1500 BCE, almost inevitably caused the El Argar society to collapse. Even doubling down on the cultivation of barley (already intensively pursued) could not save the El Argar culture, and the region was largely deserted around 1500 BCE.

In El Argar society, the dead were buried in small graves within their dwellings.

Excursion

Indications of climate migration in the Bronze Age Iberian Peninsula
Unfortunately, bronze age people were not yet able to record their experiences in writing. That is why, when addressing the question of possible climate migration, we must once more rely on indicators. Fortunately, we have several at our disposal.
The distribution of radiocarbon dates tell us that, as the climate crisis set in around 2200 BCE, human activity in the southern Iberian Peninsula shifted from the Atlantic to the Mediterranean coast. A plausible explanation may be migration.
Moreover, work carried out by international researchers show that some of the people within El Argar society came from other regions. This can be deduced from strontium isotopes or remains of DNA in human bones.

Ausgrabung

Kiel University students carrying out a magnetometric survey of the Monte da Contenda earthworks in Portugal.
Excavation of the great earthworks at Perdigões (Portugal).
Excavation of the great earthworks at Perdigões (Portugal).
Excavation of the great earthworks at Perdigões (Portugal).
Drilling for sediment cores for climate reconstruction near Seville.
Drilling for sediment cores for climate reconstruction near Seville.

Climate migration today

A global problem

Climate migration is one of the great challenges of our time. Across nearly all continents, people are trying to escape extreme weather events, droughts or rising sea levels. People in Africa, Asia, South America and the Pacific are particularly affected. Yet in Europe too each summer brings new heat waves, forest fires or floods. In Germany, the Ahr valley suffered severe flooding in 2021.

The root cause of global warming is clear, it is the result of growing emissions of greenhouse gases such as carbon dioxide or methane. Global warming triggers a chain reaction, with rising sea levels and extreme weather events causing floods, and droughts and heat waves leading to poor harvests and deaths. If we want to help climate migrants, we must tackle climate change.

Julien Schirrmacher is a palaeoclimatologist at the Institute of Pre- and Protohistoric Archaeology, Kiel University. Since 2016 he has been studying the effects of climatic changes on ancient societies in the Iberian Peninsula. He is particularly impressed by the ingenuity and adaptability displayed by people at the time in dealing with the challenges posed by a changing climate.

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