Project highlights

  • You will gain new insights into river ecosystem responses to climate extremes, including major droughts and heatwaves. 
  • You will have the opportunity to conduct innovative new flow experiments in state-of-the-art mesocosm facilities. 
  • The project is co-created with partner the Environment Agency, so you will have an opportunity to take up a placement opportunity as well as benefit from end-user engagement. 
  • You will have the opportunity to collaborate with a large team of international scientists as part of a new exciting NERC-NSF (USA) project exploring drought and temperature interactions in Icelandic streams. 


Across the globe, extreme events such as droughts and heatwaves have increased dramatically in frequency and intensity over the past 30 years, with potentially profound consequences for freshwater ecosystems. In some regions, river flows are shifting from perennial to intermittent, modifying the ecological connectivity among habitats within the river network. Where low river flows persist, connections to riparian ecosystems are likely to be enhanced as terrestrial flora and fauna colonise the riverscape, altering biodiversity and the structure and function of food webs. Less is known about the effect of heatwaves on river life but long-term studies suggest the impacts can be long-lasting and profound. Despite the growing prevalence of extreme events, research on their effects in streams and rivers lags far behind other environmental stressors (e.g. acid pulses or pesticides) and has focused on community level responses. Far less is known about impacts on functioning, how aquatic-terrestrial linkages may change, or ecosystem recovery from drought and heatwave pulses.   

The successful candidate will join a team undertaking research to address these research gaps and conduct flow / temperature manipulation experiments in a new state of the art mesocosm facility at the University of Birmingham (see Fig .1 below). These experiments will be combined with sampling and analysis of long-term records of flow, temperature and biodiversity in streams monitored by the Environment Agency, our project partner. The project also links with a major new study evaluating the impact of global change (warming and droughts) on rivers in Iceland.  

The results of the research will reveal how river biodiversity and ecosystem processes are affected by extreme events in an era of rapid global change, and will be used to help inform and guide climate change mitigation and adaptation policy. 

A photograph of the Ecolab facility on the University of Birmingham campus.

Figure 1: You will have the opportunity to use artificial stream channels in the Ecolab facility on the University of Birmingham campus. 

CENTA Flagship

This is a CENTA Flagship Project


University of Birmingham


  • Climate and Environmental Sustainability
  • Organisms and Ecosystems


Project investigator

Mark Ledger, University of Birmingham, [email protected]


Kieran Khamis, University of Birmingham, [email protected]

Dr Thomas Aspin, Environment Agency, [email protected] 

Dr Daniel Read, UKCEH, [email protected] 

How to apply


The project will test the effect of low flow and high temperature regimes on ecosystem functioning and food webs, including aquatic-terrestrial links. The doctoral researcher will:  

  1. Use artificial streams in the Birmingham EcoLaboratory facility (see Fig. 1 below) to replicate elements of natural flow regimes and simulate plausible future scenarios of occurrence (e.g. more frequent or intense events) of drought and heatwaves. State of the art sensor networks will monitor effects on water quality and ecosystem processes.  
  2. Work with our Environment Agency colleagues to quantify the effects of extreme events on river ecosystems using historical data collected across the spectrum of UK river typologies. 
  3. Collaborate with researchers in the USA and Iceland by taking part in Icelandic fieldwork to explore how stream subject to global warming might affect the response of stream ecosystems to extreme events as part of a wider international research effort.  

Training and skills

The successful candidate will receive interdisciplinary training in hydroecology from staff and students within the School of Geography Earth an Environmental Sciences (GEES), University of Birmingham, and will also gain knowledge through collaboration with an international team of researchers as part of a linked NSF-NERC project based in Iceland. More specifically they will be trained in the use of mesocosms for global change research. Our project partner the Environment Agency will provide training in dissemination of findings to various stakeholder groups. A good understanding of experimental design, data science and statistical analysis will also be achieved.  In addition, there will be scope to develop expertise in environmental sensing using the sensor network at the EcoLaboratory facility. The school supports a large, vibrant and well-resourced community of postgraduate researchers. As part of this community you will have access to a wide range of training opportunities tailored to early career researcher development, focussing on transferable project management skill, personal development, research practice and careers.  

Students will be awarded CENTA2 Training Credits (CTCs) for participation in CENTA2-provided and ‘free choice’ external training. One CTC equates to 1⁄2 day session and students must accrue 100 CTCs across the three years of their PhD.  

Partners and collaboration

The project will benefit from links with the Environment Agency who will provide a placement opportunity, as well as access to long-term data records of flow and biodiversity in lowland rivers in their regions.

Further details

Further details on how to contact the supervisor for this project and how to apply for this project can be found here: 

For any enquiries related to this project please contact Mark Ledger, [email protected]. 

To apply to this project: 

  • You must include a CENTA studentship application form, downloadable from: CENTA Studentship Application Form 2024. 
  • You must include a CV with the names of at least two referees (preferably three) who can comment on your academic abilities. 
  • Please submit your application and complete the host institution application process via:   Please select the PhD Geography and Environmental Science (CENTA) 2024/25 Apply Now button. The CENTA application form 2024 and CV can be uploaded to the Application Information section of the online form.  Please quote CENTA 2024-B31 when completing the application form. 

Applications must be submitted by 23:59 GMT on Wednesday 10th January 2024. 

Dr Mark Ledger: 

Dr Kieran Khamis: 

Read about our EcoLaboratory: 

Possible timeline

Year 1

You will establish experimental mesocosms and communities; refine methodologies and design of experiments; implementation of experiments. Undertake a literature review of the research field and begin analysis of historical data from the Environment Agency. Field visit to Iceland.

Year 2

Run experiments; sampling and data processing. Placement with Environment Agency to analyse long-term data. Analyse Iceland samples in collaboration with US colleagues.

Year 3

Data analysis, reporting and write-up.

Further reading

Aspin, T.W.H., Matthews, T.J., Khamis, K., Milner, A.M., Wang, Z., O’Callaghan, M. & Ledger, M.E.  (2018) Drought intensification drives turnover of structure and function in stream invertebrate communities. Ecography. DOI: 10.1111/ecog.03711. 

Environment Agency (2018). New chalk streams strategy launched to protect ‘England’s rain forests’. Accessed on 26/09/2022. 

Lu, X., Gray, C., Brown, L.E., Ledger, M.E., Milner, A.M., Mondragon, R., Woodward, G., Ma, A. (2016) Drought rewires the cores of food webs. Nature Climate Change, 6, 875–878. 

Woodward, G., Bonada, N., Brown, L.E., Death, R.G., Durance, I., Hladyz, S., Ledger, M.E., Milner, A.M., Ormerod, S.J., Thompson, R.M. (2016) Extreme climatic events and their consequences for biodiversity, food webs and ecosystem properties in running waters. Philosophical Transactions of the Royal Society B: Biological Sciences, 371, doi: 10.1098/rstb.2015.0274. 

Ledger, M.E. & Milner, A.M. (2015) Extreme events in running waters. Freshwater Biology, 60, 2455-2460.Ledger, M.E. & Milner, A.M. (2015) Extreme events in running waters. Freshwater Biology. doi:10.1111/fwb.12673. 

Ledger, M.E., Brown, L.E., Edwards, F.K., Hudson, L.N., Milner, A.M., Woodward, G. (2013). Extreme climatic events alter complex food webs: evidence from a mesocosm drought experiment. Advances in Ecological Research, 48, 343-395. 

Ledger M.E., Brown L.E., Edwards F., Woodward G., Milner A.M. (2013) Drought impacts on the structure and functioning of complex food webs. Nature Climate Change, 3, 223-227. 

Ledger M.E., Harris R.M.L., Armitage P.D. & Milner, A.M. (2012). Climate change impacts on community resilience: experimental evidence from a drought disturbance experiment. Advances in Ecological Research, 46, 211-258. 

Woodward, G., Brown, L., Edwards, F.K., Hudson, L.N., Milner, A.M., Reuman, D.C. & Ledger, M.E.(2012). Climate change impacts in multispecies systems: drought alters food web size-structure in a field experiment. Philosophical Transactions of the Royal Society B, 367 (1605), 2990-2997. 

Ledger, M.E., Edwards, F., Brown, L.E., Woodward, G. & Milner, A.M. (2011) Impact of simulated drought on ecosystem biomass production: an experimental test in stream mesocosms. Global Change Biology, 17, 2288-2297.