The Mayan population for their subsistence intervened in nature, eliminating forests to create a network of wetlands in order to do agriculture. This activity may have contributed to increasing CO emissions2 and methane.
Like many of the civilizations that were increasing in population and in the face of inclement weather such as droughts or floods, the Mayans acted accordingly, converting forests into large-scale and complex agricultural structures through which water circulated to ensure irrigation of crops.
“These perennial wetlands were very attractive during the harsh Mayan droughts, but they also had to take care of water quality to maintain productivity and human health.", ExplainSheryl Luzzadder-Beach, co-author of the study published in the journalPNAS and researcher at the University of Texas at Austin (USA).
The new work is the first to combine images obtained by lidar - using an airborne laser scanner - with evidence from ancient excavations of four wetlands in the Rio Grande basin in Belize, covering an area of more than 14 km2.
The results reveal that one of them, the so-called Birds of Paradise, is five times larger than the one previously discovered. The scientists also found another even larger wetland complex in that country.
Thus the study shows that the Mayans had “earlier, more intense and far-reaching anthropogenic impacts ” in tropical forests than previously known. These large and complex networks of wetlands may have changed the climate long before industrialization, and these may be the answer to the question of how a great rainforest civilization fed."Says Tim Beach, lead author of the study and researcher at the American university.
Higher gas emission
To unveil the vast field of ancient wetlands and channel networks, the team obtained 250 square kilometers of high-precision laser images to map the ground beneath the swamp forest canopy. Inside, the scientists discovered evidence of multiple species of ancient cultivated foods, such as corn, as well as shells and animal bones.
The extension of these systems could increase carbon dioxide emissions with the burning of vegetation and methane
According to the researchers, the extension of these systems could increase carbon dioxide emissions by burning vegetation and methane. In fact, the largest increase in this last gas between 2,000 and 1,000 years ago coincides with the formation of these channels, as well as those of South America and China.
"Even these small changes could have warmed the planet, which provides a sobering perspective for the order of magnitude of the largest changes during the past century that will accelerate in the future," emphasizes Beach.
The researchers hypothesize that the Mayan wetland footprint may have been even larger and imperceptible due to modern plowing, degradation, and drainage. The findings add to the evidence of early human impacts in the tropics, and hypothesize increases in atmospheric carbon dioxide and methane from combustion, preparation, and maintenance of these field systems that contributed to the early Anthropocene.
Timothy Beach et al. "Ancient Maya wetland fields revealed under tropical forest canopy from laser scanning and multiproxy evidence"PNAS October 7, 2019.