Two primary goals of landscape ecologists are to (1) evaluate changes in ecological pattern and process on natural landscapes through time and (2) determine the ecological consequences of transforming natural landscapes to cultural ones. Paleoecological techniques can be used to reconstruct past landscapes and their changes through time; use of paleoecological methods of investigation in combination with geomorphic and paleoethnobiological data, historical records, and shorter-term ecological data sets makes it possible to integratelong-term ecological pattern and process on a nested series of temporal and spatial scales. 'Natural experiments' of the past can be used to test alternative hypotheses about the relative influences of environmental change, biological interactions, and human activities in structuring biotic communities within landscape mosaics. On the absolute time scale of the Quaternary Period, spanning the past 1.8 million years, current distributional ranges of the biota have taken shape and modern biotic communities have assembled. Quaternary environmental changes have influenced the development of natural landscapes over time scales of centuries to hundreds of thousands of years; human cultural evolution has resulted in the transformation of much of the biosphere from natural to cultural landscapes over the past 5,000 years. The Quaternary extends to and includes the present and the immediate future. Knowledge of landscape changes on a Quaternary time scale is essential to landscape ecologists who wish to have a context for predicting future trends on local, regional, and global scales.