Understanding the interactions that link societies, environment and climate is of crucial importance for anticipating the consequences of current global changes. The exploration of these interactions in the past through retrospective studies is the keystone of this investigation.

  The recent story of these interactions can be approached through historical and archaeological archives. But with respect to more ancient times, the scarcity of reliable written and archaeological sources requires an investigation of natural archives (e.g. lake sediments, peat, speleothems). Lacustrine sedimentary records retain information about such interactions in a generally continuous and well constrained time frame, and they record all the conditions that prevailed in their surroundings. Deciphering such interactions involves interdisciplinary studies (e.g. palaeoecology, archaeology, sedimentology), each approach providing different and complementary information.





   Lacustrine archives hold autochthonous (i.e. originating from the lake itself) and allochthonous (i.e. originating from the subaerial environment), organic and inorganic content, ranging from the microscopic to the macroscopic scale. The evolution of some of them can be measured throughout the core, and can tell the dynamics of societal, environmental and/or climatic changes through time. According to to their calibration level, they are called tracers or proxies.

   The recorded evolutions can result from different factors. For example, the progressive disappearance of a forest cover can be the consequence of climatic changes, of human-driven clearing, or both. With a multiproxies/multitracers approach, through the comparison of independant and complementary parameters, causes and consequences of each evolution can be tracked, and explained.



   Here is a simplified example of a few parameters that can be measured in a sedimentary core which, when considered all together, can give information about the evolution of climate, environment and human activities:


   At first glance, and when compared two side-by-side, these different parameters do not seem perfectly correlated. But a cross comparison highlights that they are all strongly interlinked, allowing to give a precise insight into past landscapes.


   According to the available parameters, the oldest part of the core (phase A) reveals a phase of humid climate (isotopic measurements). The magnetic susceptibility signal indicates a low range of detritism, which is in accordance with the biomarker content that attests of a large forest coverage, while no farming activity is detected.
  Immediately after the phase A, while the climate is becoming drier, the first farming activities are recorded. These two factors can explain the decline of the forest coverage.


  
   The cultural practices going with farming activities as well as the reduced forest coverage can explain the increase of detritism recorded in the core.
   Contrasting with the precedent one, the phase B thus reflects an agricultural landscape. The type of biomarkers can provide more precise information, tracking for example pastoral activity or the exploitation of the produced resources (e.g. hemp retting, as illustrated here).
   These measured parameters are then compared with historical and archaeological archives, when available, which strengthen the interpretations.

   Of course, a multiproxies/multitracers analysis is not limited to the few parameters shown here. Adding supplementary parameters will bring new perspectives on the palaeoenvironmental reconstitution, and will refine the understanding of the set of interactions linking societies, environment and climate.