An interim framework for assessing the population consequences of disturbance

Abstract

Summary Changes in natural patterns of animal behaviour and physiology resulting from anthropogenic disturbance may alter the conservation status of a population if they affect the ability of individuals to survive, breed or grow. However, information to forecast population‐level consequences of such changes is often lacking. We developed an interim framework to assess the population consequences of disturbance when empirical information is sparse. We show how daily effects of disturbance, which are often straightforward to estimate, can be scaled to the disturbance duration and to multiple sources of disturbance. We used expert elicitation to estimate parameters that define how changes in individual behaviour or physiology affect vital rates and incorporated them into a stochastic population model. Model outputs can be used to evaluate cumulative impacts of disturbance over space and time. As an example, we forecast the potential effects of disturbance from offshore wind farm construction on the North Sea harbour porpoise (Phocoena phocoena) population. Synthesis and applications. The interim framework can be used to forecast the effects of disturbances from human activities on animal populations, to assess the effectiveness of mitigation measures and to identify priority areas for research that reduces uncertainty in population forecasts. The last two applications are likely to be important in situations where there is a risk of unacceptable change in a species' conservation status. The framework should, however, be augmented with empirical data as soon as these are available.

Bubble curtains attenuate noise from offshore wind farm construction and reduce temporary habitat loss for harbour porpoises

“…Since the impact accumulates over tens or even hundreds of turbines installed in a single wind farm and across several wind farms installed in the same area, the impact on individuals may become large enough to have an effect on the population. Establishing such population effects by direct observation is very difficult, and currently the most promising approach is to study population-level effects of noise on porpoises using population models, such as the individual-based DEPONS model (van Beest et al 2015) and the PCoD model (King et al 2015).…”

Impacts of Navy Sonar on Whales and Dolphins: Now beyond a Smoking Gun?

“…The most notable are the PCOD and PCAD models (see King et al, 2015 andHarwood et al, 2016 for details). One particularly enlightening study, on gray whales (Eschrichtius robustus), predicted that an energy loss of 4% because of disturbance events during the year of pregnancy would result in reproductive failure (Villegas-Amtmann, et al, 2015).…”

Harbour porpoise movement strategy affects cumulative number of animals acoustically exposed to underwater explosions

“…This involves a series of analysis steps, often referred to as the PCoD framework (e.g. see King et al 2015). One step involves estimating which and how many individuals are exposed to high sound levels, and this has been the main focus of our study: How many individuals of the North Sea harbour porpoise population are exposed to sound from underwater explosions and, as a consequence, are expected to have PTS or TTS?…”

“…Extreme levels of these anthropogenic sounds have the potential to disturb or injure marine mammals (Richardson et al 1995, Nowacek et al 2007, Southall et al 2007. Potential population-level consequences of sound are of particular concern (NRC 2005), which has led to the development and application of a general framework for estimating population consequences of disturbance (PCoD;NRC 2005, New et al 2014, King et al 2015, Harwood et al 2016). The PCoD model describes how changes in an individual's behaviour and physiology may affect its health and vital rates, and how this may ultimately influence population dynamics.…”

“…The PCoD model describes how changes in an individual's behaviour and physiology may affect its health and vital rates, and how this may ultimately influence population dynamics. To assess whether specific human activities have long-term population-level impacts, it is necessary to know the number of individuals and proportion of the population exposed to a level of sound that is associated with negative consequences (Thompson et al 2013b, Nabe-Nielsen et al 2014, King et al 2015. However, estimating the total number of individuals exposed to specific sound sources is challenging.…”