Box 1: From individuals to communities - pathways for human
impacts on wildlife
The impacts of human disturbance, and many other stressors, occur not
only via directly altering the vital rates (e.g., survival, fecundity)
of a population but also indirectly via changes in the behaviour and/or
physiology of individuals (NAS 2017). When sustained, stressors can lead
to chronic impacts that erode the health and immune status of
individuals. Stressors may also have an acute impact on vital rates,
such as mortality resulting from an injury. These individual level
responses can then be scaled up to the population-level by considering
multiple individuals, and ideally their interactions, within a
population. Representing multiple interacting stressors requires the
explicit consideration of multiple mechanistic pathways through which
these stressors are acting. For example, the European mink (see 3.2) is
exposed to a range of stressors including the direct effects of road
mortality, which relates to individual movement patterns and habitat
connectivity, and indirect effects of wetland loss and competition with
American mink, resulting in behavioural and energetic impacts on the
population.
Community and ecosystem dynamics are important when identifying
appropriate conservation or management strategies, since a lack of
consideration can lead to adverse management outcomes (e.g., Buckley and
Han 2014; Zavaleta et al. 2001) . Despite this, these dynamics
are rarely accounted for in disturbance models, particularly mechanistic
models, likely due to the increasing complexity when considering
multiple populations or species. Nonetheless, the increasing impact of
human activities on ecological systems and their continued degradation
(IPBES 2022) emphasises the need for human disturbance modelling to
incorporate community dynamics. There are many approaches that can be
used to account for community dynamics (Geary et al. 2020), which
can be integrated with other quantitative approaches to leverage off the
benefits of each approach. For example, individual-based models can be
combined to create community models (e.g. Radchuk et al. 2013) or
can be integrated within matrix community models (Lytle & Tonkin 2023),
depending on the specific data available. Community models also lend
themselves well to energetics approaches (Szangolies et al. 2024), permitting mechanistic evaluation of community dynamics.
The mechanistic pathways of impact are not only relevant for studying
the impacts of stressors on wildlife, they can also be used to measure
the effectiveness and appropriateness of management actions. By
considering how management actions are intended to impact the target
population, such as through improved resource availability, ecological
models can help identify if management strategies will have their
intended outcome or if alternative strategies may be more worthwhile.
This may be particularly beneficial when considering community dynamics,
where unintended consequences are more likely to occur.