Date of this Version
Published (as Chapter 20) in H.J.B. Birks, et al., eds., Tracking Environmental Change Using Lake Sediments, pp. 615–642; Developments in Paleoenvironmental Research 5; doi: 10.1007/978-94-007-2745-8 20
It is now widely recognized that reliable long-term climatic data are required to evaluate the impact of human activities on climate. Lake-sediment records are an important source of such paleoclimatic information, on timescales from years to millennia. However, unequivocal interpretation of biological climate-proxy data preserved in lake sediments can be very challenging. Here we review the different numerical approaches that are used to evaluate the sensitivity and reliability of species assemblages of aquatic biota (algae and invertebrates) extracted from lake-sediment records as proxies of past climatic conditions. The most common techniques used to assess this relationship between these proxies and climate include calibration functions that model the relationship across modern lake environments between species composition in the indicator group and particular climate-influenced aspects of their aquatic habitat, and assessments of the main directions of variation in species composition in relation to independent climatic data. Other statistical techniques, such as variation partitioning analysis, are used to assess the relative importance of climate versus other factors in influencing limnological changes seen in the sedimentary record. These techniques show that in climate-sensitive lake systems, the sedimentary remains of aquatic biota can be sensitive and trustworthy proxies, permitting quantitative reconstructions of past climatic conditions with high temporal resolution.