“If you want to catch a fish, plant a tree.” I have written about the impact of what we do on land on the quality of the water along the coast and, therefore, the health of the marine life it contains. That has focused, however, on the trees’ ability to both hold together the soil and sediment around them, which both prevents the runoff of the soil and also everything that is in that soil. The saying about planting a tree to catch a fish is an old Japanese saying that I came across in a book about trees — not expecting to find a connection to fish.

The book I am referring to is “To Speak for the Trees” by Diana Beresford-Kroeger, and it documents a powerful story of a young girl who grows up in Ireland among the forest there and becomes a renowned botanist. She often brings in Celtic traditions into her understanding of the power of the trees and forests but also delves deep into the science beneath the trees, including their unexpected impacts on fish.

When leaves decompose, like the ones about to fall from this highbush blueberry last November in Augusta, they release an acid that bonds with the iron that is found in the soil. This compound then eventually washes into the water and provides iron that is critical to the growth of phytoplankton. Christine Wolfe photo

What I learned in this book is that when leaves decompose, they release an acid that bonds with the iron that is found in the soil. This compound then eventually washes into the water and provides iron that is critical to the growth of phytoplankton — the basis of the marine food chain. That means when you cut down forests along the coast, you cut out an important source of iron. It turns out that not all trees are equal in their production of this acid, fulvic acid, but that some are more productive than others. These “mother trees” produce many other important chemicals aside from fulvic acid that help to condition the soil for the growth of other trees, thus benefiting the surrounding waters even more because of their ability to recreate a forested area more successfully. I wonder if, in our efforts to prevent erosion, there are opportunities to identify, breed and plant these “mother trees” to help stabilize coastal areas.

In the same book, the author studies the common marine algae, Chondrus crispus, or Irish moss. I’ve written about Irish moss before for its edible potential. But here I also learned that it is also used for medicinal purposes. The gel that it produces not only makes good pudding but is also good for digestion, tuberculosis and as an antibiotic, according to Beresford-Kroeger. I had often wondered about this when squeezing jelly-like blobs out of various seaweeds with my kids who mixed them into what they thought were medicinal mixtures. I guess they were on to something after all. While Beresford-Kroeger confirms this in her lab, she first learned about these medicinal properties from the Celtic tradition of those she grew up around.

I haven’t ever studied the chemistry of plants, trees or marine algae, but rather have focused on the functions they provide like producing oxygen, stabilizing soil and providing hiding places. It turns out there is another world of knowledge entirely, both traditional and modern, that proves that there are more intricate and invaluable functions beneath the obvious. This book has been an unexpected bridge between the plants of land and sea (admitting that seaweed aren’t true plants) and a source of understanding the even greater depth of the connection between what happens on shore and what happens under the water.

This is all particularly top of mind as I watch every culvert run full and strong, carrying water from the land right into the ocean, and notice the closures of coastal areas to shellfish harvesting as a result of the very rainy June we just had. While I hope for a sunnier July, it has given me quiet moments to read good books like this one that have expanded my knowledge of coastal ecology.

Susan Olcott is the director of operations at Maine Coast Fishermen’s Association.