Primary, ancient, or old‐growth? Navigating the dimensions of ecological continuity in forests

Ecological continuity is one of the key conditions for biodiversity conservation. However, concepts used to describe ecological continuity in forests remain poorly defined. To clarify ecological continuity, we present a framework with two temporal dimensions (ancientness and old‐growthness) and one spatial dimension (contiguity). Ancientness refers to a continued forested state and relates to undisturbed abiotic conditions of soil and microclimate. Old‐growthness relates to the continuity of late‐seral structural features in the forest, including the presence of large and old trees as well as dead wood. Contiguity refers to the spatial continuity and extent of the forest landscape. We highlight that these three dimensions may—but not necessarily—coincide, with each leading to distinct and prominent biodiversity values and having different conservation needs. In addition, we explain the different temporal dynamics resulting in development and loss of ancientness and old‐growthness as a function of land‐use change and forest management.