Determining favourable conservation status for the UK’s birds: creating population targets to conserve biodiversity


The conservation of species in the current biodiversity and climate change crises requires the setting of population targets for species of conservation concern, in order that actions can be taken to ensure and retain healthy populations. Until recently, conservation biology often emphasised a reactive approach, focusing on stemming rapid declines in threatened populations and augmenting numbers of individuals in populations deemed perilously small. More recently, conservation organisations and others have advocated for the more proactive approach to maintaining all species in a favourable conservation status, ensuring that populations are large enough to allow long-term persistence and recovery (e.g., There is no universally accepted methodology to achieve this, which is a major problem, as favourable conservation status is a concept increasingly written into environmental legislation both in the UK and across Europe. This approach requires that target population sizes are defined. Commonly, targets are based on known abundances of species from a reference period, an approach vulnerable to shifting perceptions of what constitutes a favourable population size for a species (Rodrigues et al. 2019), particularly when monitoring of many UK species only commenced in the latter half of the 20th Century, a period by which many populations had already declined markedly from previous levels.

In recent pilot work between Durham, Natural England and RSPB, we explored approaches to define favourable conservation status based on the discrepancy between a species’ current range and their potential range in a simulated landscape without human impacts (Mason et al. 2021). Such measures are required in global assessments, such as the International Union for Conservation of Nature’s (IUCN) recently developed Green Status metric (Akcakaya et al. 2018; Grace et al. 2021a, b), which assesses species’ recovery levels, as well as the impact of conservation actions. As a result, the Green Status metric requires information on baseline populations as well as likely impacts of conservation, both current and potential future conservation, on species.

In this PhD, the candidate will explore a wider range of methods to estimate both current population sizes of species across the UK and those expected under various alternative scenarios, including past and future climate scenarios, human-free landscapes, and landscapes with increased quality and quantity of suitable habitat.

This PhD provides an outstanding opportunity to work at the cutting edge of conservation biology, with the potential to produce high quality publications, whilst also working closely with leading conservation organisations and practitioners. The PhD should also provide an excellent basis from which to continue into a career in applied conservation biology, or in ecological or conservation research.

The key objectives of the PhD are to:
• Objective 1: work with data from across the UK and Europe to relate species’ densities to habitats and their landscape context.
• Objective 2: use habitat-specific densities to estimate population sizes in current, future and human-free landscapes.
• Objective 3: use changing and potential population size information to explore approaches to evaluate favourable conservation status.
• Objective 4: use information on potential carrying capacities to identify areas where conservation management options could be applied to maximise conservation value for species across the UK.
• Objective 5: use all of the above information to explore the impacts of different baseline metrics, and of future climate on the perceived conservation status of species in different scenarios.


Objective 1: We have already collated much density information for birds in different habitats. We will augment this with national and international bird census information (from colleagues in British Trust for Ornithology and EBBC respectively) to produce a more detailed understanding of bird densities in different climate, habitat and land management scenario.

Objective 2 tasks: We will use information from Objective 1 to estimate densities, and hence population sizes, across the UK under past and current climate conditions, validating these estimates against field derived census data and estimates. Validated approaches will be applied to future and human-free scenarios, the former using species distribution modelling based on future climate and land-cover projections, and the latter using human-free landscapes derived from dynamic vegetation modelling under current climatic conditions.

Objective 3 tasks: Regional and national population estimates from the various models in Objective 2 will be used to estimate population sizes of UK bird and mammal species, exploring various approaches to evaluate which species are in favourable versus unfavourable conservation status.

Objective 4 tasks: For species in unfavourable conservation status in the current and/or future landscapes, we will explore scenarios and sites of land-use change that would improve their conservation status. The initial focus will be on individual species but there is also the potential to optimise solutions to maximise benefit for many species.

Objective 5: Finally, we will explore how outputs from the above objectives can inform developing metrics such as the IUCN Green Status index, and using projections from species distribution models to consider also the impacts of future climate change on maintaining species at favourable population levels.

Project Timeline

Year 1

Explore and augment existing data on bird densities. Explore the potential to use additional national census data for the UK and across Europe to better understand bird densities and their drivers. The major objective of year 1 will be to produce robust estimates of population size for our focal taxa across the UK/Europe.

Year 2

Explore, and potentially create refined maps of, human-free land-use scenarios across the UK, also evaluating the potential to create UK habitat information from earlier periods of human history (e.g. 20th, 19th century). These will be used to create various baselines that could be used to assess favourable conservation status for species. Explore, and potentially create refined maps of, human-free land-use scenarios across the UK, also evaluating the potential to create UK habitat information from earlier periods of human history (e.g. 20th, 19th century). These will be used to create various baselines that could be used to assess favourable conservation status for species. Create national and international populations estimates for species in various time-frames and scenarios (including future projections) and use these to assess species conservation status.

Year 3

Explore measures of land-use change/alteration that could be used to enhance conservation status for species in an unfavourable status. Evaluate measures that would maximise benefit across species.

Year 3.5

Finalise thesis chapters and papers. The expectation is that paper drafts will be created during the first three years, so that several chapters will have been drafted before the write-up period and the student will go into their PhD viva with at least one published paper.

& Skills

The successful candidate will join the very healthy and collegiate Conservation Ecology Group (, a group of 30+, mainly postgraduate, conservation scientists, with a diverse skillset, which will benefit the training experience. They will receive training in multiple transferable skills in ecology and biodiversity conservation. For example, they will learn to produce species distribution and abundance models, building on decades of previous modelling experience in the group. They will also, through close liaison with Case and project partners, learn about applied conservation and the application of theoretical ecology in the real world. They will be supervised by Prof Willis at Durham (& IUCN Climate Change Specialist Group Member) interact closely with Prof McGowan at Newcastle University, (& Chair of IUCN SSC Post-2020 Biodiversity Targets Task Force) as well as with our Natural England CASE partner and collaborating colleagues at RSPB. The student will have the opportunity to liaise closely with staff at both of the latter organisations and to tailor the outputs of the research to have genuine application for UK conservation, as well as to inform global perceptions (and measurements) of species recovery.

References & further reading

Akcakaya, H.R. et al. (2018) Quantifying species recovery and conservation success to develop an IUCN Green List of Species. Conservation Biology, 32, 1128–1138.

Grace, M.K. et al. (2021a) Building robust, practicable counterfactuals and scenarios to evaluate the impact of species conservation interventions using inferential approaches. Biological Conservation 261, 109259

Grace, M.K. et al. (2021b) Testing a global standard for quantifying species recovery and assessing conservation impact. Conservation Biology, DOI: 10.1111/cobi.13756

Hof, C. (2018) Bioenergy cropland expansion may offset positive effects of climate change mitigation for global vertebrate diversity. Proceedings of the National Academy of Sciences ,115, 13294-13299.

Howard, C. et al.(2020) Disentangling the relative roles of climate and land cover change in driving the long‐term population trends of European migratory birds. Diversity and Distributions, 26, 1442-1455.

Mason, T.H.E. et al. (2021) Using indices of species’ potential range to inform conservation status. Ecological Indicators 123, 107343

Pacifici, M. et al. (2015) Assessing species vulnerability to climate change. Nature Climate Change 5, 215-224.

Rodrigues, A.S.L. et al. (2019) Unshifting the baseline: a framework for documenting historical population changes and assessing long-term anthropogenic impacts. Phil. Trans. R. Soc. B, 374, 20190220.

Stephens, P.A. et al. (2016) Consistent response of bird populations to climate change on two continents. Science 352, 84-87.

Further Information

Please contact Professor Stephen Willis for further information.

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