Indigenous sea gardens can buffer impacts of contemporary heatwaves

While societies around the world are grappling with the challenge of maintaining productive food systems that are resilient to climatic disturbances, Indigenous communities have been adapting to climatic shifts for millennia. Here, we investigated if ancestral clam gardens, intertidal rock wall terraces built by Indigenous peoples throughout the Holocene, can mediate the impacts of contemporary heatwaves. During a simulated heatwave, we found that clam garden sediments were on average 5.4 °C cooler than non-walled beach sediments at 5cm depth and spent 1.26 times more hours above the optimal temperature threshold for clam growth. By keeping sediments cooler for longer, a clam garden encompassed clams that had an 11-fold lower expression of toll-like receptor 1, a gene associated with bacterial infection. These results suggest that clam gardens can alter clam physiology at a sub cellular level. By keeping clams cooler and safer to eat than non-walled beaches, this study highlights the important role clam gardens across the coast of the Pacific Northwest can and will continue to play in maintaining Indigenous food security and sovereignty in light of ongoing climate change.