Do shells decompose and provide nutrients for the soil in places like sand dunes?
Shells don’t really “decompose” as much as they weather. And while this breakdown may provide some nutrients to certain species, it’s primary effect on sand dunes is raising the overall pH of the sand itself, making it more basic. Shells are composed of mainly of calcium carbonate, which is a strong base. As it breaks down, it makes the surrounding soil more basic as well.