The culture of seaweed for the food and cosmetics industry is central to many rural households in Indonesia. The activity has vastly expanded in the past three decades, but in some cases, an opposite trend is now emerging. Spaceborne images were used to monitor the recent collapse of seaweed farming around the small island of Nusa Lembongan, Bali, Indonesia. A simple semi-quantitative Seaweed Farming Index highlighted the different dynamics for four different sectors around the island, with abrupt or gradual changes starting in 2012. By 2017, seaweed farming had eventually vanished from the island, after sustaining local livelihoods for more than 30 years and influencing the zoning plan of the local Marine Conservation Area since 2010. Interviews of 50 exfarmers in 2018 identified the reasons of the changes: failed crop, low selling prices, shrinking space to dry algae against coastal development, and easy alternative jobs in tourism, although not necessarily providing better salary incomes. Tourism attracted half of these farmers, while another 25% went into building construction, itself largely driven by tourism development. The vulnerability of a complete shift to tourism was highlighted when tourism temporarily collapsed for several months due to threat of a Bali volcano eruption in late 2017. This prompted ex-farmers to consider returning to farming. This integrated case study based on remote sensing and household surveys highlights the fast-changing dynamics of Indonesia coastal socio-ecosystem due to largely to tourism development and natural hazards. The consequences for local management are discussed.