The impact of extreme weather in December to February 2014 on meta-population processes in European shags

Many climate models predict increased frequency of extreme weather events. Understanding the impacts of extreme weather on wild populations is therefore a critical aim in population, evolutionary and conservation ecology. Short-term impacts include high mortality, lost body condition and eruptive movements, potentially leading to longer-term effects such as poor breeding, missing cohorts and increased dispersal or migration. At the meta-population scale, weather-induced mortality in one location may cause downstream impacts elsewhere, especially in partially migratory systems where some individuals winter away from their breeding location while others remain resident. Spatial heterogeneity in weather-induced mortality and associated movements could then substantially reshape meta-population range and structure. Such demographic mechanisms and dynamics are particularly challenging to understand in long-lived, migratory species with protracted pre-breeding life-history stages that are hard to observe, and where locations of winter impacts and subsequent reproduction are separated. Yet such species may be particularly vulnerable to extreme weather since they recover slowly from high mortality events due to delayed maturity and slow reproductive rates. Understanding the impacts of extreme weather on long-lived mobile species is critically important since many are of high conservation concern. To fulfil the needs of policy makers, it is imperative that such impacts are understood and incorporated into population models used to inform currently ongoing policy decisions.

The UK's recent severe winter weather has created an urgent and valuable opportunity to quantify the demographic effects of this severe perturbation, using a partially migratory meta-population of European shags Phalacrocorax aristotelis that is already the focus of a long-term, year-round demographic study led by the applicants. Shags are long-lived, partially migratory coastal seabirds that experience high mortality during extreme winter weather. The north-east UK meta-population has declined by 50% during the last 20 years, and we have received numerous reports of dead shags and absences from typical winter locations following recent storms, meaning that a severe perturbation to the meta-population has doubtless occurred. Due to our recent work, we possess comprehensive data on meta-population demography (breeding success, survival, dispersal, migration) and distribution both before the recent severe weather and also throughout the storms to date. We therefore have a unique and extremely powerful baseline dataset. What is now urgently required is targeted data collection during the 2014 breeding season and post-breeding migration to quantify the degree to which cross-season demographic responses to perturbation are driven by spatial heterogeneity in survival, breeding success, dispersal or migration. We will answer three specific questions a) How did the spatial pattern of weather-induced mortality affect meta-population structure?; b) What are the downstream effects on breeding success of surviving individuals?; c) What are the downstream effects on dispersal and migration? Since shags are protected under EU law and potentially at risk from marine renewables developments, there is also a specific urgent need to provide updated evidence to inform currently ongoing policy decisions. Meta-population size, distribution and demography have doubtless been majorly reshaped, meaning that existing knowledge and population models are obsolete. Our fourth project objective is therefore to undertake immediate data analysis and provide the updated population models that are imminently required to inform effective marine spatial planning.

The UK's seabird populations are protected by EU legislation and are widely appreciated by the general public, yet many species have declined sharply over the last two decades. Much research has focussed on the effects of mean temperature, typically at annual or decadal scales. However, there is increasing evidence that populations are also affected by climate variability and associated severe weather events. Such effects need to be explicitly quantified since many climate models predict that the frequency and degree of severe weather will increase in the future. Our proposed project will make an important contribution to understanding the full demographic and hence population dynamic consequences of a severe weather-induced perturbation. . This research will impact the wider scientific community by providing insight into the short- and long-term effects on seabird population dynamics. By focussing on the meta-population scale, we are contributing to NERC's commitment to large scale research. Knowledge arising from this project will also benefit a range of other stakeholders:

1. Marine regulators (Marine Scotland and Department of Energy & Climate Change) and the Statutory Nature Conservation Bodies (Joint Nature Conservation Committee, Scottish Natural Heritage, Natural England, Natural Resources Wales) require better understanding of variation in European shag population dynamics arising from climate and weather in order to decide effective marine spatial planning policy. The consenting process for marine developments is significantly faster when regulators and their scientific advisers are confident in the evidence base regarding key protected species such as shags. Key policy makers are currently aware that existing knowledge and population models for shags have been rendered obsolete by recent weather-induced mortality, potentially substantially delaying commercial consents unless updated evidence can be rapidly provided.
2. The marine renewable industry will clearly also benefit from improved population models in achieving the goal of receiving timely consent for developments.
3. NGOs: organisations such as RSPB, National Trust and National Trust for Scotland will benefit from a greater understanding of the effects of extreme weather on the seabird populations that they are tasked with protecting
4. General public: extreme events resonate much more powerfully with the general public than temperature trends, and seabirds are a charismatic group of animals that attract enormous public interest and concern. We will take advantage of the opportunity the project affords to engage with both adults and children regarding the science needed to provide effective seabird conservation and the challenges and complexities of understanding how a changing climate is affecting the marine environment.
5. Tourism: seabirds contribute millions of pounds to the UK economy through the provision of wildlife experiences to tourists (e.g. Farne Islands, Isle of May), and tour operators are concerned about seabird declines and the role of climate and weather in these changes. This project will contribute to our understanding of these key events and provide tour operators with the most complete information available so they can plan for the future.