Ancient farmers survived climate change by switching crops, storing grain
Modelling tracks agricultural strategies across the Tibetan Plateau in the face of variable conditions. Samantha Page reports.
As the world prepares to face a massive new global warming event, researchers are looking to ancient agrarian communities to see how they coped with climate changes.
A new study combines data for six grain crops in central, south, and east Asia during the Holocene period, which began about 11,600 years ago, using a high spatial and temporal resolution model to determine how agrarian communities adapted to crop failure driven by climate events.
It turns out that ancient farmers coped by diversifying their crops, increasing storage, and trading grain in order to survive two climate disruptions 3000 and 1500 years ago.
In a paper published in the journal Science Advances, researchers, led by Jade d’Alpoim Guedes of the University of California, San Diego, US, look at the “crop niche” – the temperature band in which crops can be grown – for broomcorn, foxtail millet, wheat, barley, buckwheat, and rice.
They compare this data with the spread of the cereals across Asia and find that farmers reduced their risk of crop failure in a number of ways.
“Our models demonstrate that humans across Asia increased their resilience to growing levels of crop failure throughout the late Holocene not only through crop diversification, increased storage, and redistribution but also through economic specialisation and extensive strategies such as pastoralism,” the scientists write.
In some areas, households turned to storage to reduce the risk presented by harvest failure, stashing away as much as a year and a half of grain.
Diversification may have driven crop migration as well as helped communities withstand climate change.
For instance, beginning 4000 years ago, farmers on the northeastern Tibetan Plateau began growing less millet and more wheat and barley. This change coincides with cooling regional temperatures.
The researchers suggest that the farmers switched to wheat and barley, which are more cold-tolerant, to reduce the risk of crop failure, and consequent starvation.
They say farmers likely also used a “spatial diversification strategy”, growing millet in warmer basins and wheat and barley on cooler slopes, in order to withstand the former’s high failure rate.
Interestingly, Guedes and colleagues report that on the south-eastern Tibetan Plateau communities did not adapt to the changing temperatures and “the impacts of this cooling episode appear to have been catastrophic”.
“Many sites in the region appear to have been abandoned during this period of time,” they note.
The researchers say this is the first time these models have been used to offer such a specific look at climate impacts.
“Crop niche models allow us to move beyond hemispheric estimates of climatic impacts to scales that mattered to ancient farmers and can thus help archaeologists situate the culturally resilient strategies they developed in the climatic context in which they took place,” the study says.
The scientists also suggest that tracking crop diversification and risk-aversion strategies may be helpful for modern climate resilience efforts.
“Understanding how farmers coped with past changes in the mean state of climate may be crucial for understanding how we must adapt to a rapidly changing world,” they suggest.