The development of shrimp aquaculture in Ecuador caused massive ecological damage, particularly in the mangrove areas. Consequently, the livelihood of the population linked to this ecosystem was disrupted. Faced with environmental dispossession, the population engaged in the defence of mangroves by articulating a national grassroots movement. In 2007, this movement implemented a novel identity politics strategy that linked mangrove ecosystem to indigeneity, and positioned itself as the ‘Ancestral Peoples of the Mangrove Ecosystem’ (PAEM). This paper focuses on the political economy of the shrimp‐farming industry in Ecuador, showing the interrelation between environmental dispossession, collective action and identity formation, and analysing how this novel political identity is understood by different members of this social movement. The work argues that PAEM refers to a category that is closely linked to the processes of mangrove defence, in direct opposition to the shrimp farmer's identity, rather than to an essentialized conception of identity based on ‘nativeness’.