The Mayan civilization is well known for its architecture, relatively advanced hieroglyphs, complex calendar and wildly successful agricultural practices. Mayans inter-cropped or cleared miles of forest and built vast underground water reservoirs to keep their crops and citizens flourishing. But about A.D. 900, their civilization fell. According to studies being conducted by NASA, the indications that their fall had much to do with overzealous agriculture are many and mounting.
Mayans grew a wide variety of plants to support their civilization. They grew root crops such as yucca (Manihot esculenta) and sweet potato (Ipomoea batata), vegetables such as corn (Zea maiz), beans (Phaseolus vulgaris) and squash (Cucurbita ficifolia), and fruits such as Maya nuts (Brosimun alicaetrum), papaya (Carica papaya) and zapote (Achras zapota). Tobacco (Nicotiana rustic) was grown for smoking, while bark of coral trees (Erythrina corallodendron) provided ink. Rattle box (Crotalaria longirostrata), Mexican marigolds (Tajetes erecta) and the shilo tree (Bombax mexicanum) were all grown for medicinal use.
The Mayans used cultural practices designed to gain the most from the evolutionary cooperation of the plants they grew. When converting an area for farmland, they nurtured some existing plants, neglected some and removed others. Desirable crops were planted in pockets where a few plants had been removed. Monoculture, or the practice of growing only one crop in a field, was not used. One famous growing technique, called the Three Sisters, involved planting beans, corn and squash together on a mound for their mutual benefit.
The Mayan civilization thrived in a region of Guatemala plagued with heavy wet seasons that drain into the muddy bajos (lowlands) followed by extremely dry seasons. The rain forest regulates some of this erratic weather, keeping rain patterns in check enough for the Mayans to plant their crops. NASA archaeologist William Sever believes that irrigation canals were used by the Mayans in the bajos to support their crops.
In the dry season, the Maya may have planted crops in the bajos with the help of the irrigation canals, then moved the agriculture upland when the wet season turned the bajos into bogs. Mayan civilization and agriculture lasted from 2600 B.C. to A.D. 900 A.D. The population, and thus agricultural demand, was at its peak during the classic era, from about A.D. 260 until the fall of the Mayan empire. Samples from the ancient sediment that collects in lakes near Mayan ruins shows that just before the collapse of the empire, tree pollen vanished and weed pollen count exploded.
Despite the fact that Mayans were far more selective planters, the agricultural demand on the surrounding area and the clearing of forests is thought to have contributed to a shift in weather patterns and water availability. This theory gains support from skeleton samples of late Mayan civilization that indicate severe malnutrition. Clearing out too much of the rain forest to make room for planting may have caused the collapse of the entire empire.