Recently, much has been posted in the internet about the upcoming Alaska ban on felt soles on wading boots. Here is an informative piece about the science of felt.
We had Bill Klyn from Patagonia in the shop the other day, and he brought up a great point. Even if you do away with felt soles, you still have the laces and materials on the boot to transfer invasive species. Granted the sole is the largest contact area, the laces and other materials can still transfer invasives.