Shifting baselines in ecology encapsulate the gradual and often unnoticed alterations in ecosystems over time, leading to a redefinition of what is considered normal or baseline conditions. A wide range of human activities, such as habitat alteration, pollution, invasive species, and climate change, can contribute significantly to these shifts, reshaping the structure and function of ecosystems.
In the present article, we describe the results of our investigation of publications involving field work in national parks in the US Northwest from the 1950s to 2021. Our rationale for selecting Western parks is because they contain relatively large intact landscapes with limited confounding anthropogenic influences, and it is a region where trophic cascades have been documented following the loss of predators. Western park biologists’ historical observations and age structure data for deciduous trees reveal substantial ecological impacts of ungulates following the removal of gray wolves and other predators. This has led to declines in long-term tree recruitment, influencing plant communities and ecological processes. The observed impacts in these parks, along with findings from other Western North American studies, suggest broader changes to ecosystem processes and lower trophic levels in areas where gray wolves have been extirpated or displaced.
