Depending on the area and product, climate change has varying effects on agriculture, forests/forestry, and fisheries. Higher temperatures have an impact on product quality and the shifting of locations suitable for growing specific products. Higher temperatures, for example, can cause cracked grains in rice, which break apart more easily during milling. In some parts of Japan, heat can also reduce yields. Rising temperatures also mean a shift in the areas suitable for growing specific crops.
The invention of agriculture was a watershed moment in modern human history, after which humans began to live sedentary lives and formed a so-called “civilization.” However, for a long time, the environmental factors responsible for this revolutionary change in human lifestyle were unknown. A new study on finely layered mud at the bottom of a Japanese lake reveals that the answer to this puzzle lies in climate stability.
Agriculture’s development was a watershed moment in human history. It marked the beginning of sedentary living and the rise of “civilizations.” However, until now, the environmental factors that drove this revolutionary change in human behavior have been debated.
A new study on finely layered mud at the bottom of a Japanese lake reveals that the answer to this puzzle lies in climate stability. This theory, however, cannot explain why humans did not begin farming much earlier in tropical regions, where temperatures were already sufficiently high even during the coldest period of the last ice age.
Takeshi Nakagawa
One of the most widely accepted theories about the origins of agriculture is that a food shortage crisis caused by a climatic cooling event that began around 10,900 BC and lasted until around 9,700 BC drove humans to adopt agriculture to increase food production. This conventional theory is being called into question, however, because several radiocarbon ages of the plant remain that appeared to support the hypothesis were recently re-assessed, and the updated results suggested that the period of climatic cooling coincided with the decline and discontinuation of sedentary life, rather than the beginning of it.
Some researchers believe that the elevated temperature of the post-glacial age resulted in humans adopting agriculture based on archaeological observations that agriculture appeared to have originated independently in multiple regions within a few millennia after the end of the last ice age. This theory, however, cannot explain why humans did not begin farming much earlier in tropical regions, where temperatures were already sufficiently high even during the coldest period of the last ice age.
Very detailed climate reconstruction from ca. 16,000 BC to ca. 8,000 BC, based on analyses of pollen fossils included in the annually layered sediments from Lake Suigetsu, Japan, shed new light on this debate. According to the time-series reconstruction of the climate change through this period, as well as the world’s most accurate chronology of the sediment established by counting annual layers and radiocarbon dating of hundreds of leaf fossils, a research team, led by Takeshi Nakagawa of Ritsumeikan University, Japan, demonstrated that the first attempts of domesticating plants and constructing settlements based on agriculture coincided with periods of relatively warm and, more importantly, stable climate.
According to the team’s latest findings, the transition from the ice age to the post-glacial age was marked by periods of stability and instability. Plant domestication did not begin when the warm climate was established in ca. 13,000 BC; instead, it had to wait until ca. 12,000 BC, when the climate stopped oscillating in short intervals with large amplitudes.
Agriculture is a subsistence activity that necessitates forethought. However, in order to plan ahead, a stable future is necessary. Agriculture was too risky a practice when the climate was generally unstable because accurately predicting the weather in the future was impossible, making it difficult to select appropriate crops for agriculture. In such climatic conditions, hunting and gathering was a more reasonable subsistence strategy than agriculture because, unlike farmlands, the natural ecosystem contains a diverse range of species from which humans could expect “something” edible. As a result, the new findings by Nakagawa and colleagues call into question the traditional view that agriculture was a watershed moment in human history. Instead, depending on whether the climate was stable or unstable, agriculture and hunting and gathering were equally viable adaptation strategies.
Paleoclimatologists haven’t focused much on climate stability, partly because annually resolved natural archives of climate change are rare, and analyzing such archives at a high enough time resolution necessitates a lot of work. The unique sediments from a small Japanese lake, as well as the research team’s two-decade-long efforts to extract information from the sediments, paved the way for a new discovery that could change modern humans’ self-image.
