The bodies of water around the world have been experiencing unprecedented warming that is taking a toll on the ecosystems and marine life that inhabit them. One of the species that is suffering from this warming is wild salmon. That’s why, in Scotland, the River Dee Board and Trust in partnership with local fisheries have a plan to plant millions of trees along the nation’s rivers to help cool the waters.

Wild salmon prefer water temperatures that sit around 50 degrees Fahrenheit (10 degrees Celsius) and cannot survive the heat of waters at 91.4 degrees Fahrenheit (33 degrees Celsius). In 2018, the fisheries saw the lowest rod catch of salmon, when the water temperatures of about 70 percent of Scotland’s rivers reached a temperature of 73.4 degrees Fahrenheit (23 degrees Celsius) for at least one day, resulting in heat stress for the fish.

“These rivers and burns are the nursery ground for young fish and it’s the young fish which will be affected by summer temperatures—their feeding and growth rates are affected,” explains Lorraine Hawkins, river director for the Dee District Salmon Fishery Board. “If it gets hotter, we will see fish dying.”

Tree cover is an essential tool in helping cool the warming rivers, but according to Marine Scotland, only 35 percent of Scottish rivers have enough tree cover to achieve this cooling effect.

The River Dee Board and Trust has already planted thousands of trees along the River Dee and its tributaries since 2013, and they have plans to plant over a million trees more by 2035. The trees they plan to plant include juniper, aspen, birch, willow, and Scots pine.

The fisheries are also lending a hand to plant millions more trees along remote streams and rivers to help protect the wild salmon population.

Plus, the added trees will boost biodiversity, help control flooding, and manage nutrients for the soil and water.