Spatio-TEmporal Dynamics of Forest Response to ENSO Drought (STEED) Globally, almost half of all remaining tropical forest is allocated for timber production, illustrating the enormous economic asset that these forests represent to many nations. Additionally, these forests provide important societal and ecosystem services, from being sources of food through to climate change mitigation and generating income from carbon offset schemes. Compared to undisturbed forests, much less is known about previously logged and degraded forests that are regenerating. Critically, with increasingly smaller areas of undisturbed forest remaining, the economic and societal importance of disturbed forests has become greater in recent years. However, the resilience of these forests i.e. their capacity to respond to short-term perturbations (e.g. ENSO-induced drought) by resisting damage and recovering quickly, is poorly understood. If we are to manage tropical forests, both in terms of their initial exploitation and subsequent rehabilitation, we need to better understand how these systems respond to periodic drought at local to regional scales. Only then can we develop policies and practice that explicitly take into account the impacts of drought and protect the economic and societal benefits derived from these fragile ecosystems. To provide the evidence from which policy makers and practitioners can better plan forest management strategies we will examine the impact of the current ENSO drought on logged and degraded forests in Borneo, SE Asia, using a combination of ground-based and satellite remote sensing methods. In the field we will examine the response of trees to drought across a disturbance gradient, making use of a network of forest inventory plots that were established in the mid-1990s at the time of the last major ENSO drought to affect the region. In 2014 these plots were revisited as part of a long-term study into post-logging recovery of disturbed forests and as such represent a unique natural laboratory for comparing ENSO-induced changes in forest structure, composition and ecosystem functioning across a land-use gradient and addressing the interactions of logging disturbance and drought. We will revisit 25 plots at least four times during the 18 month project. At each plot we will measure a variety of leaf traits, canopy structure and tree mortality. This will be done by a joint team of UK and Malaysian research assistants who will harvest leaves and analyse leaf chemical properties in facilities at the Universiti of Malaysia. Additionally we will collect spectral reflectance measurements from the leaves. This will allow us to scale up our field observations to use multispectral satellite images to map forest response to the current drought across wider regions. In particular, we will make use of the new Sentinel-2 earth observing satellite to generate region-wide maps of current drought impact, whilst also producing a 20 year time-series drought index from NOAA AVHRR imagery. The latter will provide evidence of the temporal response of the forest to drought in comparison with non-drought conditions, whilst the former will allow us to map the spatial coherence of forest response, determining whether prior disturbance or other factors affect the resilience of forests to drought events. Finally, we will track changes in canopy structure and composition through observations from UAV-mounted sensors, from which we will examine the dynamics of liana/tree composition, which appear to change during drought conditions. With our project partners, the South East Asian Rainforest Research Programme and Permian Global, we will engage with a network of actors who are responsible for forest management across the SE Asia region. We will do this through dissemination activities including a workshop in Malaysia, where will present evidence of the impact of the current ENSO on SE Asian forests and provide a forum for discussion on how best to adapt forest management policy and practice to future ENSO events. 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.