What do we really know about the impacts of climate change on sanitation?

This blog is by Leonie Hyde-Smith a PhD student on the WaterWiser CDT programme

Effective sanitation systems are crucial for public and environmental health, particularly in densely populated urban areas. It is widely accepted that the impacts of climate change will stress the effective functioning of urban sanitation systems. But is there sufficient evidence for this claim?

My PhD is about financing the adaptation of sanitation systems to the impacts of climate change, and I am part of the WaterWISER CDT. Initially, I assumed I could jump straight into the topic and immerse myself in the financial aspects of climate adaptation of sanitation systems. However, I soon realised that the evidence base for the impacts of climate change on urban sanitation systems was not as solid as I thought.

Some of the best known and most widely cited publications on the topic appeared to be based on expert opinions, anecdotal evidence and secondary data. This seemed to be particularly true for reported impacts on onsite sanitation systems in low- and middle-income countries. More robust data appeared to be available for impacts of changing climate (mainly rainfall) patterns on sewer systems in cities in high-income countries. Although urban sanitation uses various infrastructure types and service systems, current research appears skewed towards a small subset of cases.

Recognising that there has not been a comprehensive summary and assessment of the evidence base for the likely impacts of climate on the full range of urban sanitation systems or components of such, my supervisors and I decided to conduct a systematic literature review critically appraising the evidence for climate change impacts on ALL urban sanitation system types.

Crucially, we aimed to integrate the evidence for impacts on sewered and non-sewered sanitation and highlight the gaps in knowledge and rigour of assessment of climate impacts along the entire sanitation chain. To make the research more relevant, we wanted to explore how climate change may increase pressure on existing diverse sanitation systems, including household and city-scale infrastructure and services, which are often incomplete or poorly functioning. Therefore, we overlaid the knowledge about the failures of urban sanitation systems today with the stresses that a future climate will impose. We based our analysis on a recent review of urban sanitation, which articulates typical urban sanitation systems and corresponding failure modes based on the analysis of excreta flow diagrams.

We designed our search criteria to include evidence of climate impacts on road-based transport networks, an essential part of faecal sludge management systems.

We screened over 43,000 records and included 99 studies in our analysis and qualitative synthesis. Our findings confirmed that most research is focused on the impacts of climate change on centralised, highly engineered, high-cost sanitation options in high-income contexts.

We identified only scant data demonstrating how climate change will influence the functioning of onsite (faecal sludge management [FSM]) services. None of the studies investigated the impacts of climate change on a citywide complex sanitation system featuring a mixture of centralised sewerage and non-sewered decentralised sanitation systems.

Table of climate change impacts on urban sanitation

Table of climate change impacts on urban sanitation

Further, most evidence refers to infrastructure rather than operational components. To date, there is no adequate consideration of interdependencies with other sectors and combinations of climate effects. For instance, the available evidence for climate change impacts on urban transport systems is poorly connected to potential disruptions of faecal sludge emptying and transport under climate change.

Finally, we found evidence that contradicts past research suggesting that even poor households are generally able to adapt their onsite sanitation technologies to changing climate conditions by their own means.

In conclusion, to date, research neither adequately represents the variety of urban sanitation systems nor reflects the operational and management challenges of already stressed systems. Investments in infrastructure alone will not render a sanitation system ‘climate-resilient’. The current focus of research might influence the direction, quality and robustness of future adaptation and resilience measures.

The evidence suggests that households are not able to adapt sanitation to climate change without support – a planned public service approach at the city level is required to adapt both sewered and non-sewered sanitation systems to climate change.

Lack of understanding of climate change impacts on sanitation systems in rapidly evolving cities in low- and middle-income countries means that climate adaptation investments are likely to reinforce existing sanitation inequalities.

If you are interested in more details on this piece of research, our related paper has just been published: https://pubs.acs.org/doi/10.1021/acs.est.1c07424

This work was supported by the UKRI Engineering and Physical Science Research Council (EPSRC) through a PhD studentship as part of the EPSRC Centre for Doctoral Training in Water and Waste Infrastructure and Services Engineered for Resilience (Water-WISER). EPSRC Grant number: EP/S022066/1