They didn't have enough.

>The Swedish Navy planted oak trees on the island beginning in 1831 to provide strategically important timber for future ship construction. Once the timber was ready to harvest it was no longer required for ship construction.

https://en.m.wikipedia.org/wiki/Visings%C3%B6

Fun fact: the word "Holland" comes from "Houtland" meaning "Wood" land. There is almost no forrest left there now because they turned the trees into boats during their golden age.

It was the same situation for Spain. Its rise as a naval superpower in the 15th and 16th centuries came at a high environmental cost too. To build its fleet, including those iconic Spanish galleons, Spain logged high amounts of oak and pine, especially from northern regions like Cantabria and the Basque Country.

As ship production ramped up, there were growing concerns about resource depletion. To the point that by the late 16th century, Spain was forced to start importing timber from its colonies to keep up with demand.

What I find so chilling and reminding about this history is that to this very day, the spanish peninsula remains largely deforested because of that fleet they had 500 years ago.

We have forests, but not like the US. We had to carefully manage our forests in order to keep them.