The coexistence approach (Mosbrugger and Utescher, 1997) is an efficient and reliable method for quantitative terrestrial palaeoclimate reconstructions from the Cenozoic palaeobotanical record. It is based on the assumption that fossil plant taxa have similar climatic requirements as their nearest living relatives. The aim of the coexistence approach is to find for a given fossil flora and a selected variable the climatic interval, in which all nearest living relatives of the fossil flora can coexist.
Quantitative terrestrial paleoclimate reconstructions in the Cenozoic based on Nearest Living Relatives of the fossil taxa
Fossil remains from the upper part of the Miocene Rhenish Main Seam (Northwest Germany, Middle Miocene) and their relatives in the Mississippi Swamp Forest.
Taxodium (pollen, wood, leafes)
For this purpose we have started in 1990 the Palaeoflora database project, which actually contains for over 6000 Cenozoic taxa (macro and micro) nearest living relatives and their climatic requirements. As algorithm for the analyses the Program ClimStat is used.
For all types of fossil floras the coexistence approach thus allows for the rapid quantitative reconstruction of 10 different climate parameters, including mean annual temperature, temperature of the warmest month, temperature of the coldest month, mean annual precipitation, mean precipitation of the wettest month, mean precipitation of the dryest month, mean precipitation of the warmest month, relative humidity, potential evaporation, as well as the ratio of mean annual precipitation over potential evaporation.
The reliability and resolution of the coexistence approach are tested with various techniques and proved to be very good; for instance, the resolution with respect to the mean annual temperature can be up to 1° C. Applications to various modern and fossil floras have demonstrated the advantages and disadvantages of the coexistence approach.
A short course on the application of the CA is available at the NECLIME website.