Var den gamle Maya en advarselshistorie for landbruget? Måske ikke, foreslår ny undersøgelse

Mange mener, at klimaændringer og miljøforringelse fik Maya-civilisationen til at falde - men en ny undersøgelse viser, at nogle Maya-kongeriger havde bæredygtige landbrugsmetoder og høje fødevareudbytter i århundreder.

I årevis har eksperter inden for klimavidenskab og økologi fremholdt den gamle Mayas landbrugspraksis som gode eksempler på, hvad man ikke skal gøre.

"Der er en fortælling, der skildrer mayaerne som mennesker, der engagerer sig i ukontrolleret landbrugsudvikling," sagde Andrew Scherer, lektor i antropologi ved Brown University. "Fortællingen lyder:Befolkningen blev for stor, landbruget opskalerede, og så faldt alt fra hinanden."

Men en ny undersøgelse, forfattet af Scherer, studerende ved Brown og forskere ved andre institutioner, tyder på, at den fortælling ikke fortæller hele historien.

Ved hjælp af droner og lidar, en fjernmålingsteknologi, undersøgte et hold ledet af Scherer og Charles Golden fra Brandeis University et lille område i det vestlige Maya-lavland beliggende ved den nuværende grænse mellem Mexico og Guatemala. Scherers lidar-undersøgelse – og senere, støvler-på-jorden-opmåling – afslørede omfattende systemer af sofistikeret kunstvanding og terrasser i og uden for regionens byer, men ingen store befolkningsopsving kunne matche. Resultaterne viser, at mellem 350 og 900 e.Kr. levede nogle Maya-kongeriger komfortabelt med bæredygtige landbrugssystemer og ingen påvist fødevareusikkerhed.

"Det er spændende at tale om de virkelig store befolkninger, som Mayaerne opretholdt nogle steder; at overleve så længe med en sådan tæthed var et vidnesbyrd om deres teknologiske præstationer," sagde Scherer. "Men det er vigtigt at forstå, at den fortælling ikke kan oversættes på tværs af hele Maya-regionen. Folk levede ikke altid fra kind til kæbe. Nogle områder, der havde potentiale for landbrugsudvikling, blev aldrig engang besat."

Forskergruppens resultater blev publiceret i tidsskriftet Remote Sensing .

Da Scherers team gik i gang med lidar-undersøgelsen, forsøgte de ikke nødvendigvis at afkræfte langvarige antagelser om Maya-landbrugspraksis. Deres primære motivation var snarere at lære mere om infrastrukturen i en relativt understuderet region. Mens nogle dele af det vestlige Maya-område er godt undersøgt, såsom det velkendte sted Palenque, er andre mindre forståede på grund af den tætte tropiske baldakin, der længe har skjult gamle samfund. Det var faktisk først i 2019, at Scherer og kolleger afslørede kongeriget Sak T'zi," som arkæologer havde forsøgt at finde i årtier.

Holdet valgte at undersøge et rektangel af land, der forbinder tre Maya-kongeriger:Piedras Negras, La Mar og Sak Tz'i," hvis politiske hovedstad var centreret om det arkæologiske sted Lacanjá Tzeltal. På trods af at de er omkring 15 miles væk fra hinanden som kragefluer havde disse tre bycentre meget forskellige befolkningsstørrelser og regeringsmagt, sagde Scherer.

"I dag har verden hundredvis af forskellige nationalstater, men de er ikke rigtig hinandens lige i forhold til den indflydelse, de har i det geopolitiske landskab," sagde Scherer. "This is what we see in the Maya empire as well."

Scherer explained that all three kingdoms were governed by an ajaw, or a lord—positioning them as equals, in theory. But Piedras Negras, the largest kingdom, was led by a k'uhul ajaw, a "holy lord," a special honorific not claimed by the lords of La Mar and Sak Tz'i." La Mar and Sak Tz'i' weren't exactly equal peers, either:While La Mar was much more populous than the Sak T'zi' capital Lacanjá Tzeltal, the latter was more independent, often switching alliances and never appearing to be subordinate to other kingdoms, suggesting it had greater political autonomy.

The lidar survey showed that despite their differences, these three kingdoms boasted one major similarity:Agriculture that yielded a food surplus.

"What we found in the lidar survey points to strategic thinking on the Maya's part in this area," Scherer said. "We saw evidence of long-term agricultural infrastructure in an area with relatively low population density—suggesting that they didn't create some crop fields late in the game as a last-ditch attempt to increase yields, but rather that they thought a few steps ahead."

In all three kingdoms, the lidar revealed signs of what the researchers call "agricultural intensification"—the modification of land to increase the volume and predictability of crop yields. Agricultural intensification methods in these Maya kingdoms, where the primary crop was maize, included building terraces and creating water management systems with dams and channeled fields. Penetrating through the often-dense jungle, the lidar showed evidence of extensive terracing and expansive irrigation channels across the region, suggesting that these kingdoms were not only prepared for population growth but also likely saw food surpluses every year.

"It suggests that by the late Classic Period, around 600 to 800 A.D., the area's farmers were producing more food than they were consuming," Scherer said. "It's likely that much of the surplus food was sold at urban marketplaces, both as produce and as part of prepared foods like tamales and gruel, and used to pay tribute, a tax of sorts, to local lords."

Scherer said he hopes the study provides scholars with a more nuanced view of the ancient Maya—and perhaps even offers inspiration for members of the modern-day agricultural sector who are looking for sustainable ways to grow food for an ever-growing global population. Today, he said, significant parts of the region are being cleared for cattle ranching and palm oil plantations. But in areas where people still raise corn and other crops, they report that they have three harvests a year—and it's likely that those high yields may be due in part to the channeling and other modifications that the ancient Maya made to the landscape.

"In conversations about contemporary climate or ecological crises, the Maya are often brought up as a cautionary tale:"They screwed up; we don't want to repeat their mistakes,'" Scherer said. "But maybe the Maya were more forward-thinking than we give them credit for. Our survey shows there's a good argument to be made that their agricultural practices were very much sustainable."