Why did lighthouse construction decline during the Dark Ages?

The construction of lighthouses declined during the Dark Ages primarily due to a significant decline in commerce. As trade networks across Europe diminished, the economic and logistical impetus for maintaining and building coastal navigational aids waned.1

This halt in construction persisted until the revival of trade in Europe, which began around 1100 CE. During the interim, coastal navigation often relied on alternative methods, such as lights exhibited from coastal chapels and churches, particularly in Great Britain, or the use of traditional pilot books and oral traditions to navigate coastal waters. It was not until the subsequent expansion of maritime activity and the development of more advanced navigational tools—such as the magnetic compass and portolan charts—that the systematic establishment of lighthouses regained momentum, led largely by Italy and France.1234