This integrated project aims to reconstruct the environmental history of Belize using evidence from lake sediments. This is important because whilst a general picture for Mexico and Guatemala is now emerging, we know little about conditions in the southern Yucatan. This area is of particular interest because of the collapse of the Maya civilisation, which some archaeologists link to climate change.
Following initial surveys across Belize, a number of wetland sites were selected where conditions looked as if they would yield promising results. We were looking for relatively undisturbed sites, despite changes in their occupation and land use history. Wetlands and lake basins fulfil this requirement well since the process of sedimentation provides layers of material which can be dated and compared with archaeological evidence. Cores were taken over two years, at sites in the north (Booth's River, Honey Camp and New River Lagoons) and south of Belize (Aguacaliente Swamp).
Cores were photographed and x-rayed to give a visual record of change. Further analysis consisted of geochemical investigations (such as determining the amount of carbon, nitrogen, phosphorus and carbonates in the sediment, measuring the particle size and identifying minerals present), oxygen and carbon isotope determinations, magnetic susceptibility measurements and microscopic identification of pollen and diatoms (aquatic microfossils). These provide evidence both of local environmental conditions and human activity around each lagoon, and also any wider regional climate signal. The project used a wide range of analytical methods - designed to act as alternatives or to provide supporting evidence. These proxy measurements are necessary because similar work elsewhere has shown that reliance on only one or two methods has often been limited and unsatisfactory. To establish when changes took place, materials were sent for radiocarbon and lead isotope dating.
The results have given us the first comprehensive picture of environmental change in Belize over the past 10,000 years (the Holocene). During this time, our cores show that conditions have varied considerably in Belize. Some sites appear to have undergone many changes, others show considerable stability. This local diversity questions some generalised regional explanations (e.g. extensive droughts) for the Maya collapse. We find evidence of several dry periods during the period of Maya settlement, but not the drastic changes suggested by researchers working elsewhere in the Yucatan. Periods of forest clearance and soil input into the lagoon (signs of erosion) are also picked up in the analyses. Obtaining reliable dates for the cores has proved difficult, partly because of the nature of the lagoon sediment. Further radiometric dates are required if we are to make definitive comments concerning climate change and settlement, but this work has established the framework in which this can be pursued.
Several conference presentations have been made and academic papers are in preparation. These integrate the different facets of the work including associated research on pollen and diatoms. The study has also strengthened existing links with institutions in Belize such as the Programme for Belize, the Forestry Department and the University of Belize.
Further enquiries about this project should be made to Prof. Sarah Metcalfe