Scale‐Dependence in Ecological Systems

Abstract

Scale has a profound influence on how we conduct ecological studies, interpret results and understand the links between processes operating at different rates. All of these factors profoundly influence our ability to predict responses to change. The ecological patterns and variability we observe range from millimetres to across ocean basins and from seconds to the expanse of evolutionary history. Patterns apparent at one scale can collapse to noise when viewed from other scales, indicating that perceptions of the importance of different processes vary in a scale‐dependent manner. Moreover, rather than the environment simply providing an arena within which organisms are born grow and die, many organisms interact with the environment, altering it for both for themselves and for other species. Because of these factors, studying ecological systems is far from simple and scale needs to be considered in study design and analysis. Key Concepts The pattern you see depends on the scale at which it is studied. Threats from human activities occur at varying scales, from small point sources to large diffuse threats and changes in disturbance regimes across landscapes. How organisms interact with the environment depends on how they perceive it and how patchy it is. How an organism moves and how far it can move is crucial to how an organism perceives and responds to their environment. Many organisms can alter their environment, both for themselves and for other species. Connectivity between locations and habitats does occur not only for organisms but also for ecosystem processes and services. Because most processes are scale dependent, studies must explicitly consider scale in their design. Understanding both the scale of threats and the scale over which species live are essential for successful management and conservation.

Herbivory facilitates growth of a key reef‐building Caribbean coral

“…Ecosystem processes are often scale-dependent (Hewitt, Thrush, & Lundquist, 2010;Levin, 1992). External drivers and internal feed- 2015).…”

Wave stress and biotic facilitation drive community composition in a marginal hard‐bottom ecosystem

“…Apart from facilitation, many environmental drivers affect species distributions that ultimately set the local and regional species pool. These drivers occur in spatial hierarchies, they are connected, and they integrate the interplay of ecological processes that form the patterns we observe (Hewitt et al 2017). In the Baltic Sea, for example, sea salinity forms an upper-level driver that ultimately determines how deep into the Baltic Sea marine species penetrate (Remane 1934).…”

“…A local driver is formed by, for example, wave exposure that may affect focal response variables, such as species interactions. Ecological interactions, however, often cross levels of organization or scales, and the interplay of processes at different scales may be much more complicated than first anticipated (Soranno et al 2014, Hewitt et al 2017. Consequently, the inclusion of multiple scales in ecological studies is important in order to test predictions about the influence of processes on ecological patterns, as the effects of these processes may be highly context-dependent (Hewitt et al 2017).…”

“…Ecological interactions, however, often cross levels of organization or scales, and the interplay of processes at different scales may be much more complicated than first anticipated (Soranno et al 2014, Hewitt et al 2017. Consequently, the inclusion of multiple scales in ecological studies is important in order to test predictions about the influence of processes on ecological patterns, as the effects of these processes may be highly context-dependent (Hewitt et al 2017). Limiting the scope and focusing on only on a narrow set of scales may also lead to false conclusions (Hewitt et al 2017).…”

“…Consequently, the inclusion of multiple scales in ecological studies is important in order to test predictions about the influence of processes on ecological patterns, as the effects of these processes may be highly context-dependent (Hewitt et al 2017). Limiting the scope and focusing on only on a narrow set of scales may also lead to false conclusions (Hewitt et al 2017).…”