Impacts of El Nino events on ecosystem services provided by Colombian mangroves The current El Niño event in the tropical Pacific region is forecast to be one of the two strongest since records began. There is increasing evidence of links between the El Niño-Southern Oscillation (ENSO) and climate change. Climate change is putting increasing pressure on many ecosystems, making them and the communities that depend on them for their livelihoods more susceptible strong El Niño events, such as the 2015/16 event.    Mangrove conservation has been proposed as a form of Ecosystem-Based Adaptation (EBA) to help protect livelihoods in the face of climate change, providing co-benefits for biodiversity and local communities. However, this strategy may be rendered ineffective if the impacts of extreme El Nino and La Niña events threaten the survival and functioning of mangrove systems and their socio-economic consequences. It is therefore particularly urgent to quantify the impacts of El Niño on mangroves and their socio-economic consequences on the local communities; the current El Niño event provides a transient opportunity to obtain these critical baseline data.  Colombia is being affected severely by El Nino. There is a dearth of data for coastal regions, yet the impacts of both El Niño and La Niña on coastal communities in areas vulnerable to both droughts and floods have been severe, with shortages of fish and degradation of mangrove systems. Mangroves provide a range of ecosystem services that support livelihoods, including provisioning services such as fisheries, wood, agriculture and transportation, and regulating services such as flood protection, sediment regulation, erosion regulation and carbon storage. The status of mangroves and their intimate link to human well-being and poverty alleviation provides a unique opportunity to quantify the broader impacts of El Nino events.   In partnership with Grupo Laera and INVEMAR in Colombia, we will quantify the impacts of the current El Niño event on mangroves in two contrasting mangrove systems in Colombia - La Boquilla, which is a relatively high energy system, facing the open sea, and Cienaga Grande de Santa Marta (CGSM), which is a low energy, lagoonal system. Working with our partners, we will collect empirical data on the status of the mangrove system and the following ecosystem services: fisheries, flood and erosion regulation and sediment regulation. We will combine these data with quantitative and qualitative data on the economic and social impacts of the current El Niño event, and supplement them with time series environmental data from a series of monitoring stations maintained by INVEMAR, the Colombian Marine and Coastal Research Institute.  We will derive economic values associated with key ecosystem services from the mangroves using a combination of market-based and spatial value transfer approaches. We will work with local community groups and stakeholders (via workshops) to develop and refine our models of ecological and physical properties of the mangroves into integrated ecological-economic models, and use a future scenarios-based approach to examine the ecosystem and livelihood impacts of various anthropogenic pressures and internal changes within the mangroves.   The work will enhance the environmental and socio-economic evidence base of the impacts of the current El Niño event in Colombia and, through the development of co-produced models, contribute to a better understanding of resilience of these systems and the livelihoods they support, to future El Niño events in the region. The Global Challenges Research Fund (GCRF) supports cutting-edge research to address challenges faced by developing countries. The fund addresses the UN sustainable development goals. It aims to maximise the impact of research and innovation to improve lives and opportunity in the developing world.