Cascading impacts across the coupled climate, ecological, agricultural and socioeconomic systems

The complexity of climate risk can lead to cascading impacts across the coupled climate, ecological, agricultural, and socioeconomic systems, which may involve potentially unprecedented outcomes and feedbacks, nonlinear behaviors or tipping points. While advances have been made in understanding such interconnected risks, particularly within specific disciplines, significant gaps remain in our understanding and modelling of such risks, and especially of how they cascade across systems. 

Several of such examples of cascading impacts can be found across the world, just in the last few years. The Australian bushfires of 2019-2020, fueled by extreme heat and prolonged drought, caused massive biodiversity loss, widespread air pollution, and significant economic damages. The 2021 Himalayan glacier collapse led to catastrophic flooding, infrastructure damage, and disruptions to local livelihoods, highlighting the fragility of mountain ecosystems in a warming climate. The global food and energy crisis of 2022, driven by geopolitical conflict and the disruption of supply chains compounded by low crop yields revealed the vulnerability of interconnected supply chains, with far-reaching implications for global stability. The 2024 DANA flooding in Spain, caused by a record-breaking atmospheric instability event and delayed emergency response, resulted in devastating loss of human lives and damage to infrastructure, agriculture, and urban areas, which eventually led to civil unrest in the region. All these examples underscore the need for comprehensive risk assessment, modelling and projection that better captures how shocks may compound and cascade across systems leading to high-impact outcomes larger than the sum of their parts. 

Existing frameworks and methodologies frequently fail to account for nonlinearities and worst-case outcomes or compartmentalize risks, in part to make an extremely complex problem simpler. This limits our ability to capture effects and impacts cascading to and from other sectors and systems, resulting in an incomplete understanding of the systemic nature of risk. Here, we assess to which extent cascading impacts have been included in impact assessments across sectors given our current methodologies and frameworks, to which extent our current methodologies and frameworks are insufficient for the task, and the cases where, even though current technology may allow it, cascading risks may have been overlooked. We reflect on recent examples of cascading impacts and their drivers, and outline critical directions for improving their integration into future risk assessments.