Just as there are many approaches to ecological research (e.g., population, community, landscape, ecosystem, global ecology; descriptive, deductive, experimental ecology, etc.), there are several approaches to paleoecological research, resulting in several types of paleoecology. One division is based on the biological scales of study ranging from the paleoecology of individuals (adaptation, evolution) to population, community, landscape, ecosystem, and global paleoecology. Other types of paleoecological research can be taxonomically based or habitat based as individual paleoecologists often study particular organisms (e.g., vertebrates, insects, and diatoms) or work in a particular habitat (e.g., wetlands, lakes, oceans, and deserts). The major division within paleoecology, however, concerns timescales and time periods.
Ecologists are primarily interested in timescales of hours, days, weeks, months, years, or decades (so-called real time as these timescales lie within the realm of direct human experience and observation). In contrast, paleo-ecologists are interested in timescales of hundreds, thousands, or millions of years. The major division within paleoecology is between deep-time paleoecology and Quaternary-time paleoecology.
Deep-time researchers use fossils from pre-Quaternary sediments to study the distribution, evolution, and dynamics of past biota over timescales from thousands to millions of years. Research emphases are on adaptation, evolution, extinction, and biogeography. Quaternary-time (Q-time) researchers use techniques from paleontology, sediment geology, geochemistry, and isotope analysis to reconstruct past biota and environments and to study biotic responses to environmental change at Quaternary timescales (decades, hundreds, or thousands of years) during the last 2 million years of Earth's history. In practice, much of Q-time paleoecology is centered on the past 50 000 years, the period over which radiocarbon dating can be used to provide a chronology. The Quaternary has witnessed many major climatic oscillations between temperate interglacial and cool glacial stages. It has also witnessed the evolution, cultural diversification, and global spread of humans. The last few hundred years have seen the increasing role of humans in altering Earth's biota and environment, resulting in the so-called Anthropocene in which we live today where there is detectable human impact on the atmospheric composition and climate.
Deep-time biologists are usually called paleontologists or paleobiologists, whereas Quaternary biologists are often called paleoecologists.
A real-time ecologist may ask why study paleoecology and what can paleoecologists contribute to contemporary ecology? There are many reasons for studying paleoecology and integrating paleoecology into ecology. These are given as follows:
1. Present-day ecology benefits from a long-term perspective. Paleoecology provides direct evidence for ecological dynamics over long timescales that supplements ecological observations and tests ecological theories about succession and community dynamics.
2. Paleoecology can provide valuable insights into ecological legacies from human activity and environmental change. Ecological legacies are properties of an ecological system today that can only be explained by events or conditions absent from the system today.
3. Paleoecology provides a long-term context for current ecological phenomena and landscape patterns. Many ecological processes occur over decades to millennia (e.g., succession, migration, and pedogenesis). A long temporal perspective is essential to understand factors that determine the rates and causal mechanisms of these processes.
4. Reconstructing past environments is important to evaluate the extent ofnatural environmental variability, to place current environmental changes, particularly climate, into a long-term context, and to detect if current changes lie within the range of natural variability.
5. Understanding past climatic change and studying the response of organisms to those changes can contribute to predicting biotic changes in the future.
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