Green tides in Brittany: What can we learn about niche–regime interactions?

• An ANT-based approach shows that niches are fluid and dynamic assemblages.
• Regime institutions are characterised by a range of inner tensions that niches can use to link.
• Alliances with regime actors shift as the niche evolves.
• ‘Hybrid actors’ within regime organisations moderate the niche–regime dichotomy.

The coasts of Brittany (France) have witnessed algae blooms leading to ‘green tides’ since the 1970s. These are a typical example of a persistent environmental problem linked to intensive agriculture. We focus on how a mature niche, which proposes an extensive farming system, has extended its network, linked with the regime and drawn in resources. Within the Multi-Level Perspective, this case study is used to better understand the dynamics of niche–regime interactions. Using an ANT-based approach, we show how the network around the niche has evolved over the decades, how it adapted its core message, built alliances with diverse actors at niche and regime level, and recognized opportunities created by landscape pressures. This active work of building bridges through reinterpretation, of enrolling regime actors, of seizing windows of opportunity, highlights the ‘social’ aspect of social–technical transitions.