BBC Future

Power of Nature

How salmon help keep a huge rainforest thriving

The Great Bear Rainforest is the largest temperate rainforest in the world. This huge and pristine wilderness depends on an unlikely source for its long-term survival – the salmon which spawn in its rivers and creeks.

The Great Bear Rainforest is vital to the health of the planet. This enormous habitat covers 32,000 sq km (12,000 sq mi) on the Pacific coast of Canada, helping purify both air and water, and is an unspoiled home to grizzly bears, wolves and cougars.

The forest is the scene of one of nature’s most impressive migrations; the perilous journey of the Pacific salmon from the sea through the forest rivers to spawn in its creeks. The salmon run draws carnivores such as bears and wolves to the river bank, where they gorge on the migrating fish.

In this film, ecological economist Pavan Sukhdev, The Nature Conservancy’s lead scientist Dr M Sanjayan and camerawoman Sophie Darlington talk about the salmon’s unsung role in fertilising the forest. The bears who feast on the spawning salmon don’t eat on the river – they drag the carcasses far into the forest. The remains of the salmon contain vast quantities of nitrogen that plants need to grow. Eighty percent of the nitrogen in the forest’s trees comes from the salmon. In other words, these ocean dwellers are crucial for the forest’s long-term survival.

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