Re-examining the past to inform future trait-based predictions
Ecology in the Anthropocene is characterized by the rise of cumulative
effects on ecosystems, and thus there is an urgent need to synthesize
current trajectories of ecological change, predict future ecological
outcomes in relation to multiple drivers of change, and importantly,
account for the naturally large number of components affected and
effecting change. The persistence or loss of species in novel
Anthropocene ecosystems will depend on several factors that may be
predicted using traits: (i) species’ potential responses to
environmental forcing (dispersal, establishment, persistence), (ii) the
capacity of species to affect community dynamics (i.e. interactions
strengths), and (iii) the combined effect of multiple anthropogenic
forces on organisms’ interactions with the environment and one another (
i.e. either additive, antagonistic, synergistic), and (iv) the type and
duration of stressors (e.g. Hillebrand and Kunze 2020). Further
applications of trait-based approaches to modelling and predicting
ecological change are needed, as well as validations of such models.
Ample testing grounds exist ideally where ecological processes are
reasonably well understood and where the impacts of environmental change
can be investigated in relation to that prior understanding of ecosystem
form and function. For example, numerous examples of community
reassembly and varying degrees of ecosystem modification are documented
in the literature, particularly on trophic cascades and ecosystem
engineers. These examples have helped to shape our understanding of the
processes and factors involved in generating ecological outcomes of
change; but hindsight also supplies much of what we know of the role of
focal species’ traits in driving ecological outcomes.
Using the growing body of existing trait data, ecologists are positioned
to build and test trait-based predictions through hindcasting ecological
outcomes in systems that continue to face rapid community reassembly.
Transition zone ecosystems— for example, regions at the boundaries
between tropical and temperate coastal ocean reef ecosystems in
Australia, Japan, the Eastern Pacific and Western Atlantic (see Vergés
et al. 2014), where prominent coastal warming and ecological mixing
zones persist—are areas where suites of species are readily being
redistributed due to environmental forcing. These boundary systems
provide excellent opportunities to construct and test trait-based
hypotheses of rapid ecological change. For example, the
‘tropicalization’ of temperate reef systems is occurring due to multiple
and interacting environmental drivers of change (notably climate change,
overfishing and the protection of ecosystems through marine park
designation) afford researchers expansive opportunities to propose and
test hypotheses across gradients in natural experimental setting (Text
Box 1; Figure 8). Studies of key filtering traits such as thermal
tolerance, larval starvation resistance, and predator avoidance
strategies for many marine species in these systems have explained
shifts in distribution and abundances of range expanders (Text Box 1;
Figure 8). Additionally, the warming of tropical systems will likely
lead to transitions to new ecological states not observed in living
human time scales. These systems represent a need for generalisable, and
trait-based predictive tools to forecast ecological outcomes beyond
recent ecological states. We suggest that focusing research effort in
this field on incorporating suites of traits into spatially-explicit
process models of transition-zone ecosystems are likely to yield the
most fruitful tests and validations of trait-based global change
predictions.