**3. Results**

#### *3.1. Evolution of the Shoreline Classification from 1955 to 2019*

Using aerial images of Bora Bora, the maps below (Figure 5) were produced to display the evolution in coastal categories (sandy beaches, rocks, trees, grass, road embankments, private embankments, quays, cf. Figures 3 and 4) from 1955 to 2019. Sandy beaches have remained constrained to the southern part of the island, but the southernmost tip was altered from a sandy beach to a private embankment in the 2000s. Along the rest of the island, the dominant coastal category has switched from trees to private embankments. Most changes occurred between the 1970s and 1990s, and the coastline classification has remained relatively similar since 2006.

In detail, the natural (sandy beaches, rocks, trees, grass areas, and mangroves) shoreline length has decreased by over 46% from 1955 to 2019, from 32.2 km to 17.2 km out of over 40 km of shoreline (varying length depending on the year and human-made changes; Figure 6). At the same time, the human-made shoreline length (quay, road embankment, and private embankment) has increased by 476%. The percentage of the shoreline transformed into embankments to stabilise public roads has remained relatively constant on Bora Bora, at 8–10% (total length: 2979 m in 1955, 4273 m in 2019), while the percentage of the shoreline as quays has increased slightly (1% to 5%). The extent of mangroves and grass areas have remained limited (<0.5 to 1% throughout). Overall, Bora Bora's coastline has undergone strong changes, transitioning from natural to mostly human-made categories from 1955 to 2019.

#### *3.2. Evolution of the Shoreline Position from 1955 to 2019*
