Since their arrival in New Zealand (about 800 years ago), the Maori have been burning the forests there on such a large scale that the effects can be measured in Antarctica, more than 7,000 kilometers away. According to research by an international team of geophysicists, published on wednesday in Nature.
New Zealand is one of the last areas to be colonized by humans. In the thirteenth century, the Maori arrived in New Zealand from Eastern Polynesia by canoe. At the time, about 90 percent of the islands were covered with forest. Almost immediately after their arrival, the Maori began to burn the dense forests on a large scale. This allowed them to move through it to hunt and create space to grow food, for example sweet potato, taro or yam. Today, only a quarter of New Zealand is covered by forest.
These forest fires release soot, just like the burning of fossil fuels today. The presence of soot particles in the atmosphere is – after carbon dioxide emissions – the largest climate influence of human activity. This is partly because these black particles absorb sunlight and thereby heat the atmosphere. The fires by the Maori appear to have taken place on such a large scale that the concentration of soot in the atmosphere in large parts of the southern hemisphere was greatly increased. The researchers demonstrate this using ice cores from Antarctica. The soot particles released by the fires traveled great distances by the wind and precipitated in Antarctica, where they are stored in the ice sheets. Temperature differences throughout the year provide a recognizable seasonal variation in snow composition. This allowed the researchers to count annual layers in ice cores. In this way, it is possible to find out how much soot has precipitated and when.
The researchers then used atmospheric models to calculate where this soot came from. Soot particles remain in the atmosphere for a relatively short time, only a few weeks, so the particles must have reached Antarctica within that time. Three candidate regions remained: Tasmania, Patagonia and New Zealand. The first two could be ruled out. At the time, not enough was burned there, according to charcoal remains from that time.
In any case, the indigenous peoples of Tasmania and Patagonia burned far less than the Maori. In these two regions, the amount of wildfires is much more closely related to climate variations, indicating natural wildfires. The sooty peak begins to occur in the year 1297, exactly during the period when the Maori inhabited New Zealand.
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According to Toon van Meijl, professor of cultural anthropology at Radboud University who specializes in the Maori, the forest fires started by the Maori have gotten out of hand: “Archaeologists describe it as an ecological disaster. The fires had huge implications for nature. More than 35 bird species have gone extinct, including many species of the famous Moa bird. Many fish also became extinct.” The Maori had not planned to start fires on such a large scale, according to Van Meijl. “It doesn’t match the Maori worldview. They have a balanced relationship with nature. They do not think that man is above nature, as we have found in the West since the Enlightenment. The Maori feel the presence of their ancestors in nature. You are not going to burn down your own ancestors.”
This is not the first study to show that humans already left their mark on the global environment before the industrial revolution. In 2018, for example, researchers at the University of Oxford showed that lead emissions during wars in the Roman Empire are reflected in Greenland’s ice. First author of the Maori study, Joseph McConnell, says in a press release of his institute, the Desert Research Institute in Nevada: “Even the most remote places on earth were not necessarily pristine before the industrial revolution.”