Paleoecology uses the data of fossils or subfossils to reconstruct the ecosystems of the past. It includes the study of fossil organisms in terms of their life cycle, their interactions, their natural environment, their manner of death and burial. Paleoecology's aim is therefore to build the most detailed model possible of the life environment of those organisms we find today as fossils; such reconstruction work involves complex interactions between environmental factors (temperature, food supplies, degree of solar illumination etc.) Much of this complex data is distorted or destroyed by the post-mortem fossilization processes, adding another layer of complexity.

The environmental complexity factor is normally tackled through statistical analysis of the available numerical data (quantitative paleontology or paleostatistics), while post-mortem processes as a source of information are the field of application of taphonomy.

Most paleoecological studies focus on the Quaternary Period (the last 2 million years) because older environments are less well represented in the fossil record. Most concentrate on the Holocene period (the last 10,000 years), or the last glacial period of the Pleistocene (the Wisconsin/Weichsel/Devensian/Würm glaciation of the ice age, from 50,000 to 10,000 years ago). These studies are useful for understanding the dynamics of ecosystem change and for reconstructing pre-industrialization ecosystems. Many have pointed to the importance of using paleoecological studies as a basis for conservation ecology.