Box 2. Traditions in ecosystem conceptualization and
their influence on research and modelling
A critical factor in ecosystem research is resolution on what an
ecosystem is. Many theoretical and practical examinations of the
ecosystem concept have been presented since its inception (e.g., O’Neill
et al 2001) and although all have improved use and understanding of the
term, disparities among the prevailing philosophic and scientific
traditions of ecosystem science persist (Loreau 2020). Blew (1996)
outlined three major traditions in ecology, each rooted in relatively
distinct perceptions of the ecosystem concept and its primary
definitional criteria (see Table S1). Similar traditions persist in
contemporary ecosystem science (Baveye et al 2018, Zarnetske et al 2019,
Alahuhta et al 2020). Modified after Blew (1996), the three major
traditions include:
1) Biotic tradition. The biotic approach to ecosystem science
is organism focused and typically emphasizes either species or, more
often, communities as the most important expression of ecosystem
organization. Abiotic constituents are ranked with lesser importance and
may be employed to model or describe biotic patterning. Spatial
properties may be explicitly, or implicitly, recognized, and functional
relationships are inferred (O’Neill 2001). Such units are sometimes
called bio-ecosystems, ecological communities, or community-ecosystems
(Rowe and Barnes 1994). A prominent example is the IUCN global ecosystem
red list, which emphasizes biotically defined units for its operational
definition (Keith et al 2013).
2) Functional tradition. Under the tenets of this approach to
ecosystem science, the singular representation of holism and complexity
are an ecosystem’s functional features (Currie 2011). This approach
emphasizes the processes (e.g., respiration, decomposition, material
cycling), properties (e.g., energy balance, productivity, trophic
structuring), or products (e.g., biomass) resulting from interactions
between biotic and abiotic ecosystem components (Gignoux et al 2011).
Spatial properties may be explicitly or implicitly recognized (DeAngelis
and Yurek 2016), and biotic complexity is often generalized to trophic
levels, higher taxonomic ranks, or specific functional groups. Prominent
examples of this approach are process-based models of ecosystems at
local (e.g., Caron-Lormier et al. 2009) and global extents (e.g.,
Bonan and Doney 2018); ecosystem simulation models (e.g., Xia et al
2017); and mathematical models of individual ecosystems (e.g., Svirezhev
et al 1984) or meta-ecosystems (e.g., Leroux and Loreau 2012).
3) Abiotic tradition. Following principles of the abiotic
tradition, which is sometimes called the enduring featuresapproach, ecosystems are interpreted as ecologically homogenous areas of
terrestrial or marine geography (e.g., Zhao et al 2020). While biotic
variables may be employed to name, map, or describe ecosystems defined
through this tradition, biota are usually viewed as ephemeral products
of more enduring abiotic drivers, such as climate, landform, soil,
hydrology, and geology. These latter physical or marine geodiversity
features are considered the building blocks of ecosystems (Sayre et al
2009). This approach deemphasizes ecosystem function and dynamics,
focusing on steady-state expressions of ecological variability. Units
developed through the abiotic tradition are sometimes called
geo-ecosystems (Rowe and Barnes 1994) and they are most applied at
broader spatial scales. Biomes, ecoregions, ecozones, ecosites, and
landscape ecosystems are prominent examples of units developed,
following this tradition, in the contemporary literature (e.g., Yang et
al 2017, Keith et al 2022).