Mayans, drought, and GIS. But does it tell us anything?

For this project we attempted to look at the Yucatan Peninsula to see if we could find any correlative climate data that might give us new insight into the collapse of Mayan society. We searched around for data, though there seemed at first to be a paucity of good, usable climate data that we could use for the Yucatan. We initially tried using global temperature and precipitation data from NOAA. We found that ArcGIS doesn’t like .nc rasters, but QGIS will at least open them (Figure 1). However, the resolution was on the order of ~50km per cell, which means the Yucatan only has a few cells on it. But then we found some fantastic, comprehensive data from the National Commision for the Knowledge and Use of Biodiversity (CONABIO) in Mexico. However, this gave us nothing for Guatemala and one of the other sites was in Guatemala.

Figure 1 - .nc raster of precipitation in 2017 around the globe. Unfortunately I couldn't figure out how to work with this, or what each cell meant. But I did learn "how" to make a map in QGIS.

From this new data we decided to look at areas that could potentially have droughts based on precipitation and evapotranspiration shapefiles. The data had a range of values (e.g. 125 to 300 mm), so they were converted to rasters and reclassified to the maximum value. Then we highlighted areas of drought/deficit (evapotranspiration > precipitation) and areas of surplus (evapotranspiration < precipitation) using Con(“evap - precip > 0”, 0, 1) where 1 = deficit. These were then converted back into polygons, and the zero value removed. Now we had identified areas that might be at risk for drought. Today. Unfortunately, we can’t make any real inferences about the climate or conditions 1000 years ago based on this. The city of Calakmul is a site of Mayan ruins (Figure 2), but it is located in a neutral area, however, we can’t say anything about past climate based on this. The full report can be viewed here.

Figure 2 - Here we have highlighted areas of deficiency and surplus of water. Note that Calakmul, an ancient Mayan site, is within the neutral area. 

Figure 3 - This is essentially the same map, just made in QGIS. It is a work in progress trying to be able to do everything I can do in Arc in QGIS. It is far from perfect, but I am moving forward.