Navigating complex sustainability decisions
4 December 2025 - Dr Emre Usenmez, Course Director for the Master’s in Sustainability Leadership, introduces one of the themes taught in the programme. He explores the complexity of sustainability decision-making, highlighting how well-intentioned actions can create both positive and negative unintended consequences, and the trade-offs leaders must navigate using real-world examples.
When was the last time you heard someone say we should do this or that for sustainability? I am always struck by the degree of confidence such statements exude. When I hear them expressed, I can’t help but wonder about the trade-offs and the consequences. Sometimes those consequences may be positive, what we economists call positive externalities; other times, they may be negative. In class, we explore these, and I leave it to my students, the current and future sustainability leaders, to decide which trade-offs they would be comfortable with within their own unique contexts. Any other approach would probably be underpinned by what Frederick von Hayek refers to in his 1974 Nobel Prize lecture as “pretence of knowledge”.
These class discussions are not just academic exercises. I want my students to deeply understand critical interdependencies, and this is what we start our programme with. Complex adaptive systems can behave in wildly unpredictable ways because of interconnections we are not aware of. This is why not every action, even with good intentions, will have good outcomes – however defined. Sustainability leaders will likely to be more impactful if they develop the skills to understand more of the system and identify where a well-intentioned action can have serious unintended consequences. These consequences will not necessarily be all bad or all good but being able to identify them is an important skill for practitioners to have in their arsenal.
Unintended consequences – examples from real world “solutions”
Complex systems are everywhere sustainability leaders operate. Take, for example, the International Maritime Organization’s IMO2020 regulations, which require ships to use very low sulfur fuel oil or comply with alternative mechanisms that give the same effect as 0.5% fuel oil sulfur content. This has been introduced with a view to reduce air pollution and prevent 570,000 premature deaths globally between 2020 and 2025. Switching fuels may require upgrading engines, which is costly, so a common alternative is to use a scrubber. Scrubbers use sea water to clean a ship’s exhaust, and in the process they discharge water contaminated with sulfuric acid, metals and other contaminants back into the sea, which, in a way, shifts the problem from air to the marine environment.
The use of very low sulfur oil may also result in higher emissions of black carbon. This may have negative effects, including darkening the arctic and impacting its reflectivity, which in turn may accelerate warming and melting – a mechanism not yet fully understood.
On the other hand, the pollutant sulfur dioxide itself aids in cloud formation by acting as a seed for cloud condensation. It therefore has an indirect but considerable cooling effect on the climate as it catalyses the forming of highly reflective clouds. As a result, it appears that reduction in sulfur dioxide emissions corresponds to additional global warming. In fact, the magnitude of abrupt reduction in sulfur dioxide as a consequence of the IMO regulations seems to be such that it appears to effectively behave as geoengineering - with the consequence of considerable radiative warming.
This is just one example; here is another: rewilding initiatives. They aim to reinstate natural processes in the absence of human activities with a view to restoring and increasing biodiversity. Our colleagues at the Zoology Department have recently shown that rewilding in one region may nevertheless adversely impact other regions that are richer in species due to ‘leakage’, which in turn can drive extinctions – the opposite of such initiatives’ intended outcomes.
Or consider urban heat stress, which has an impact on the demand for healthcare services and energy consumption, and, at its most extreme, on mortality. The most common response by urban planners is often some form of tree planting or urban greening initiatives. From Atlanta to Doha, London to Shanghai, many cities have launched One Million Tree campaigns, while India piloted One Billion Trees Initiative for Moga, Jaipur, and Ranchi. These trees can provide urban cooling and contribute to urban air and acoustic quality improvements. Yet, our colleagues at the Sustainable Design Group at the University of Cambridge have recently shown that the same trees can actually warm the urban environment at night, especially if they are the wrong type of tree for that particular environment. It also turns out that, depending on the planting patterns and urban forms, trees may either improve the air quality and reduce mortality risk or contribute to localized pollution concentration and reduce air quality in street level.
Decision-making with “humble confidence”
What these examples illustrate is what we examine in our teaching: when decision makers are considering a “solution”, it may be prudent to understand the surrounding complexity and instead view that solution as a package of trade-offs. For this, I usually encourage my students to ask the following questions:
- Compared to what is this considered a desirable solution?
- Who and what might be positively and negatively affected by this solution?What kind of incentives would this create for the affected parties?
- What alternatives exist for the affected parties and how their behaviours may change as a result?
- In response to this solution what kind of substitutions may the affected parties engage in?
- Are the trade-offs acceptable to you as the decision maker?
- Who decides for whom?
These questions are by no means exhaustive. Nor will they necessarily lead to perfect solutions. They are, however, a step towards uncovering potential unintended consequences. This is what we aim with our assignments: through iteration, sustainability leaders learn and adapt as they plan for and act towards transforming their organisations and sectors by implement their assignments. To do so may require “humble confidence” – both the agency to act and the humility that we are operating in great complexity and do not have all the answers.
When sustainability leaders can develop deeper understanding of critical interdependencies, when they can understand the broader consequences of each action, and consciously decide, we are more likely to observe improved sustainability outcomes that are not just short-term fixes. This is why I focus on developing these skills. As my colleague Dr Lou Drake says, we do not seek to ‘teach’ students in our programme, but rather to provide the scaffolding and support for us to explore and learn together; and the more I do it, the less confident my pronouncements become.