The Adaptive Capacity of the Peruvian Andes / / by Dan Teeling

Dan Teeling is a PhD student at the University of Reading, working with Prof Chris Vane at the British Geological Survey on a NERC funded SCENARIO DTP project. Dan's research focuses on the adaptive capacity of past communities to climate change in the Peruvian Andes over the last 2000 years. Dan’s project will help to fill the gaps in our current understanding of the timescales of human occupation in the region, and their response over the last two millennia to changes in climate and environment.

Team Peru at Lake Keushu, with the Nevado Huascaran in the distance. L-R Chris Vane (BGS) and Dan Teeling, Josie Handley, Frank Meddens and Nick Branch (University of Reading). Photo: Stuart Black

In Peru, and across most of South America, more than 80% of past and present populations have relied upon water sources from mountainous areas for agriculture and drinking water. The main source of this water is stored in mountain glaciers, high up in the Andes, which are retreating at an unprecedented rate. In turn, these glaciers feed upland lakes and mire systems from the glacial discharge. This makes them very sensitive repositories of past climate and environmental change.

The aim of the SCENARIO DTP project is to integrate isotope and palaeoecological data from a series of upland Andean lakes to determine the impact of pre-Columbian climate and environmental change on land use and human occupation for the Peruvian highlands. At present there are a few records of environmental change from Peru, these are mainly from larger lake basins such as Lake Junín and Lake Titicaca, karstic cave systems and tropical ice core records.

While these records make up most of the terrestrial records, there are surprisingly few other lake and mire sequences in the highlands of Peru, and certainly no records currently exist from the regions our study sites originate: the Cordillera Blanca and the Chillón Valley.

An example of sediments recovered from the Chillón Valley. The dark brown layers are organic peat formation. The pale sediments are possibly old lake sediments.

For the project to meet its aims, several techniques will be used. Isotopic analysis of organic biomarkers (coprostanols, n-alkanes etc) will be combined with stable light (C, N, S, O, H) and heavy (Pb etc) isotopes of organic and inorganic fractions to fingerprint human, animal and sediment sources in highland lake sequences in Peru. The project also aims to constrain the appearance and disappearance of major Empire States in Peru over the last 2000 years, such as the Wari (600-1100 AD) and the Inca (1438-1533 AD), and understand why their populations crashed.

To achieve these aims, a joint team of scientists from the University of Reading, the British Geological Survey, Cusichaca Andina and Universidad National Frederico Villarreal flew out to Peru to undertake the challenge ahead. Coring at altitudes of 3190m – 4570m proved to be quite a physical undertaking, nevertheless we managed to core ~60m of sediment from four different basins in the Cordillera Blanca and the Chillon Valley. In addition to the core material, we also bagged and logged 34 soil, nine plant, eight dung and four moisture samples from these sites, which will be used to quantify modern concentrations of pollen, n-alkanes, water availability and soil content as a comparison to the past.

Chris Vane looking very happy with himself after bagging his "highest ever poo sample" at 4500m above sea level. 

Back in the UK, the sediment cores will be processed (with the different analytical techniques, as outlined above) by myself in order to complete my PhD. The preliminary organic data from Loss on Ignition (all sites) and carbon isotope data (for Huarca) looks quite interesting and certainly holds potential for the time period we are interested in. Both the carbon and nitrogen isotope data shows that there are three distinct periods of isotopic shift – from C3 to C4 plants – hypothesised to be from agricultural practices. The carbon shifts would determine that the type of vegetation has changed from the grasses and sedges of the wetland, to crops like maize and quinoa. On the other hand, nitrogen may be telling us that there has been natural manuring of crops at the same intervals. There is still much more work to be done in the coming months, in order to uncover the stories hidden within the sediments.

Panoramic views of the two main field sites. Above: Cantamarca, Cillón Valley, Lima region. Below: Huarca, Cordillera Blanca, Ancash region.