Maya agriculture

At www.nature.com/news/2010/101105/full/news.2010.587.html we have the fruits of research by the Geological Research Association of America on Mayan agriculture. They lived in sprawling densely populated pockets in the Yucatan and their civilisation reached it's height between 400BC-900AD. They had to contend wtih recurring droughts and rising sea levels – which is an interesting insight considering the same thing was happening elsewhere in the world. Basically, the Maya chose a peculiar terrain to practise farming as it was rocky and short of good earth. It was however interspersed with large areas of marsh, or wetlands in modern speak. Not exactly the ideal environment to feed such a big population. After 20 years of research Timothy Beach, a physical geographer, and his associates, as well as some 60 actual excavations made to study and map different layers of soil in northern Belize in order to look at soil and water chemistry and take carbon-isotope analyses, they found evidence of rising water tables and the remnants of flood deposits. Fossilised plant remains show the Maya were growing avocados, a variety of grasses, as well as maize, and they constructed irrigation canals between wetland zones to channel water to fields elsewhere, new farmland. In digging out the ditches, repeatedly and on many occasions, the soil was heaped on to the adjacent land and created raised fields which kept root systems of their crop plants above the water table. The wetland system was immense and nowadays 40 per cent of the Yucatan peninsular has reverted to swamp or marsh. The Maya had modified the wetland zones and this became the breadbasket of their civilisation. Archaeology has tended to focus on the architectural ruins, or on the written records that have survived, and has generally ignored how so many people fed themselves. The paper appeared in Quarterly Science Review (2009) and is cached at doi:10.1016/j.catena.2010.08.014 (2010). It would be interesting if there is any connection, time-wise, between sea level rise in the North Sea bowl, and sea level change in the Caribbean around the coasts of the Yucatan. If so, what might cause global sea levels to rise in such widely diverse locations?