New evidence in Belize shows the ancient Maya responded to population and environmental pressures by creating massive agricultural features in wetlands, potentially increasing atmospheric CO² and methane through burn events and farming, according to geographical research at The University of Texas at Austin published in the Proceedings of the National Academy of Sciences.
“We now are beginning to understand the full human imprint of the Anthropocene in tropical forests,” says Tim Beach, the study’s lead author, who holds the C.B. Smith, Sr. Centennial Chair. “These large and complex wetland networks may have contributed to climate change long before industrialization, and these may be the answer to the long-standing question of how a great rainforest civilization fed itself.” Beach adds that “Even these small changes may have warmed the planet, which provides a sobering perspective for the order of magnitude greater changes over the last century that are accelerating into the future.”
Evidence acquired from 250 square kilometers of high precision laser imagery combined with excavation data showed that the Maya faced environmental pressures, including rising sea levels in the Preclassic and Classic periods — 3,000 to 1,000 years ago — and droughts during the Late/Terminal Classic and Early Postclassic periods — 1,400 to 900 years ago. The Maya responded to such pressures by converting forests to wetland field complexes and digging canals to manage water quality and quantity.
“These perennial wetlands were very attractive during the severe Maya droughts, but the Maya also had to be careful with water quality to maintain productivity and human health,” said Sheryl Luzzadder-Beach, the study’s co-author, who holds the Raymond Dickson Centennial Professorship at UT Austin.
Similarly, the researchers posit the Maya responded to large population shifts and changing demands for food production during the Late Preclassic to the Early Postclassic — about 1,800 to 1,000 years ago — by expanding their network of fields and canals in areas accessible by canoe to the broader Maya world. Within the fields, the researchers uncovered evidence of multiple ancient food species, such as maize, as well as animal shells and bones, indicating widespread protein harvesting.
The researchers hypothesized that expanding the wetland complexes added atmospheric CO², through burning events; and methane, through the creation of wetland farming. Indeed, the largest premodern increase of methane, from 2,000 to 1,000 years ago, coincides with the rise of Maya wetland networks, as well as those in South America and China.