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Due to the rise on population and the environmental pressures , as well as the rise of the sea level from 3,000 years ago, or the droughts of 1,200 years ago, the Maya civilization responded by turning tropical forests in compounds of fields of wetlands by digging canals to manage the amount and quality of water.
These wetlands were used as full-scale agricultural systems for growing avocado, corn, and squash, and were active during extreme natural disasters , such as droughts, and periods of population growth.
“These perennial wetlands were very attractive during severe Mayan droughts, but they also had to take care of the quality of the water to maintain productivity and human health,” explains Sheryl Luzzadder-Beach , co-author of a study just published in the PNAS magazine and researcher at the University of Texas .
The new article is the first to combine LIDAR obtained images – that is, with a laser scanner transported by air – with evidence of ancient excavations of four wetlands in the basin of Belize’s Río Bravo , which includes an area of over 14 square kilometers .
Results reveal that one of them, called Birds of Paradise , is five times bigger than the one previously discovered. In addition, scientists found another compound of wetlands even bigger in that same country.
Hence, the study shows that the Maya had “ earlier, more intense, and of more extension anthropogenic impact ” in tropical forests than it was known. “These big and complex wetlands networks could have changed the climate long before industrialization, and they can be the answer to how a great civilization nurtured from the tropical jungle ,” says Tim Beach , main author of the study and researcher of the University of Texas.
Higher gases emission
To unveil the vast field of ancient wetlands and the network of canals, the team got 250 square kilometers of high-precision laser images to map the soil underneath the canopy of the swampy forest. Inside, scientists discovered evidence of multiple species of ancient foods such as corn, but also shells and animal bones.
According to researchers, the extension of these systems could have risen the carbon dioxide and methane emissions with the burning of vegetation. As a matter of fact, the biggest rise of methane in the postmodern era, between 2,000 and 1,000 years ago, matches with the creation of these canals, as well as those from 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 biggest changes during the last century that will speed in the future,” highlights Beach.
Researchers pose the hypothesis of the Mayan wetlands’ footprint being bigger and imperceptible due to modern plowing, degradation, and drainage. The discoveries are added to the evidence of the first human impact in the tropics and pose the hypothesis of the rise of atmospheric carbon dioxide and methane linked to combustion and the preparation, and maintenance of these agricultural systems used in the early Anthropocene.
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