From fish to flowers: New research proves that salmon boost terrestrial plant growth

The relationship between terrestrial and marine environments within an ecosystem is essential. Newly published research from Simon Fraser University shows that salmon and marine plants increase both growth and reproduction in terrestrial plants. The findings, “Experimental addition of marine-derived nutrients affects wildflower traits in a coastal meta-ecosystem,” published in Royal Society Open Science show that nutrients from salmon carcasses can change the way that plants grow and reproduce.

Researchers from Simon Fraser University were motivated to understand how life in the ocean is connected to life on land. They conducted a large-scale field experiment in Haíɫzaqv (Heiltsuk) territory, on the central coast of BC, where they placed salmon carcasses and marine algae in a wildflower meadow and observed changes over three successive years to the plants that live there. 

The scientists found that nutrients from salmon cause two species of wildflower, yarrow and common red paintbrush, to grow larger leaves. Additionally, the authors found that common red paintbrush and another wildflower species, Douglas’ aster, have larger flowers, which has the potential to attract beneficial pollinating insects.  

“This study affirms what Haíɫzaqv, other coastal First Nations people, and local gardeners have known for generations: salmon make excellent fertilizer,” says lead author, Allison Dennert, PhD candidate at SFU and Salmon Ecologist for the Raincoast Conservation Foundation.

People have known for millennia that nutrients from salmon travel into forests and ecosystems. Western science conducted in the last two decades has often found a special isotope of nitrogen, known as the “salmon signature,” in a variety of terrestrial plants and animals. This research elaborates on this background understanding by showing a causal connection between salmon nutrients and the growth and health of terrestrial plants using an experimental and long-term approach.

This research is the first to make causal links between salmon and terrestrial ecosystems, which is a difficult task in the Great Bear Rainforest, an area with thousands of distinct salmon watersheds. Most studies examining nutrients from salmon in terrestrial ecosystems are necessarily observational and correlational, and conducting a field experiment let the researchers prove the causes and consequences of this phenomenon much more clearly.   

“Understanding the interconnection between ecosystems is incredibly important to our knowledge of how to protect them,” says Dennert. “Currently, lands and oceans are managed under separate federal and provincial jurisdictions. Both in western science and in management, we often think of the land and sea as separate and unconnected entities. This work affirms the idea that ecosystems don’t exist in isolation, and that what happens in one can influence the other.”