Dark Nature : Responses of humans and ecosystems to rapid environmental changes

Impact of rapid environmental changes on humans and ecosystems An environmental catastrophe is poorly defined, but generally, from the point of view of an earth scientist, is thought to be either a specific brief event (earthquakes, volcanic eruption, tsunamis) or a pervasive evolution at the time scale of the century or less (epidemics, dry periods) over a large area, significant enough to be registered in the sedimentary, chemical or biological earth archives and to have an impact on society. The full scale of rapid environmental changes has not been recorded in the short period covered by the instrumental record. Therefore it is essential to turn to geological and archaeological archives that span a much longer timescale. In some cases of high resolution, they may serve as adequate surrogates for the instrumental record. The societal response (such as collapse, migration) to external forcing (such as strength, frequency of the event) has a non-linear nature. Unless good science is done (robust dating or duration control), it may be difficult to prove a causality. The amplitude of a catastrophe will be larger if it combines the following: 1) rapid onset and long duration, 2) large area, or large proportion of the settlement, 3) inflexible society unable to adapt, and finally 4) an already stressed society or environment. Two special issues of Quaternary International, each containing eleven papers, have been prepared on this topic. This first volume (the present one) concentrates on the impact of rapid and catastrophic environmental changes on humans and ecosystems. These papers present methodologies and case studies as well as a paper more directed to end-users. The second volume (Leroy et al., 2006) focuses on the responses of humans and ecosystems to rapid and catastrophic environmental changes. The investigations presented here explore the past capacity of humans to react to drastic changes affecting significantly their environment. Responses are related to population dynamics (migration), activities (land use, subsistence), societal structure, or belief. Holocene societies changed in depth within the neolithisation process: domestication of animals and plants, and emergence of civilisations are key elements in the study of human adaptation potential. The examples here present evidence of how a drastic change can stimulate social and cultural development, or can be the cause of a culture collapse or emergence. These studies provide caution regarding environmental determinism, and point out that no simple rules seem to govern human evolution. This volume begins with a paper by Walker and Surge on the development of an isotopic method to reconstruct past temperature and salinity from coupled analysis of shells and otoliths found in archaeological sites of southwest Florida dating of the last two millennia. The negative impact of agriculture on human health at the beginning of the Holocene in Europe is reconstructed by Larsen from the analysis of human skeletal remains. Sallares proposes that environmental changes altering mosquito-breeding sites in many southern European coastal wetlands favoured the spread of malaria during the Holocene. Ollive et al. present the results of their investigation of a Gallo-Roman town in the southern Upper Rhine Graben that has been affected by four major floods between AD 20 and AD 145/ 146. Dinis et al. investigated the Holocene infill of three coastal lagoons in central Portugal and their impacts on humans as well as the reverse. A study of pollen and dinoflagellates by Leroy et al., set in the framework of instrumental data and biological surveys, showed the link between fluctuating sea levels of the Karabogaz-Gol/ Caspian Sea system and their rapidly changing environment. Stancikaite et al.