Quantifying and discerning the origin of PYrenean environmental Changes: Abrupt Climate and HUman impact.

PYCACHU is an ambitious scientific initiative to test whether or not the humans impacted significantly the Pyrenean environment in the past and when they started to be the primary forcing of landscape change. This project is focused in the identification and characterization of paleoclimate and anthropogenic indicators in a key Iberian region, the Pyrenees, which is a transitional region that serves the bridge and boundary among Atlantic and Mediterranean climate influences, it is very sensitive to past climate changes and has a long record of human occupation. In spite there are many paleoenvironmental records in this region, from lake and speleothem sequences, the information provided up to now on climate variability is not quantitative, thus limiting our understanding of climate effects on the environment. On the other hand, the available archaeological data are not sufficient to determine when, how and where humans started to significantly modify the landscape throughout deforestation, first cultures or incipient grazing activities. Therefore, the separation among climate changes and human impact effects on the Pyrenean landscapes is not carried out up to now with enough resolution and robustness to truly understand the role played by these two forcings in the past, present and future of our ecosystems.

PYCACHU, through the study of new indicators in lacustrine sequences and speleothems from the Pyrenees, aims, on one hand, reconstructing climate variability in a quantitative way for the first time in the Pyrenees for the last 20000 years in a longitudinal and altitudinal transect. Fluid inclusions in speleothems, isotopes in cellulose, transfer functions with diatoms and chrysophytes from lake sediments and WA-PLS regression methods in pollen records are the new indicators selected to obtain such quantification. The analyses will be carried out using already available sequences and on two new lacustrine records from the westernmost sector of the Pyrenees: Tramacastilla and Aguas Tuertas, to complete a large W-E transect.

On the other hand, to study the human impact together with the usual indicators, we intend to carry out an innovative analyses based on ancient DNA in lake sediments to unequivocally detect the presence of plants and animals associated to grazing and agricultural activities from the onset of the Neolithization and covering areas of high altitude where human impact occurred, theoretically, later.

PYCACHU results from integrating several disciplines and research lines in a definitive effort to discern the role played by both human and climate in the past environmental changes in the Pyrenees, one of the most important challenges today to evaluate, and mitigate, the actual impact of climate change in vulnerable Mediterranean areas.