Back in 1731, the Dutch economy was at the mercy of a clam. But not just any clam, mind you.
While your typical clam lives a life of security in its shell, the so-called shipworm has a tiny calciferous casing, from which erupts a skinny tube of flesh up to two feet long. Swarms of the things burrow into wood, be it ship hulls or piers or, unfortunately for the Dutch, wooden dikes.
The strange invertebrate had destroyed over 30 miles of Dutch dikes, and threatened another dozen miles. The Netherlands were in serious danger of flooding, and the economy was spooked. Peasants fled their farms and entered the cities, where they could find no jobs. Crews tried switching the wood out for tropical hardwood, to no effect. The only solution was to import stones and build dikes that way, at no small taxpayer expense.