Shading reduces bleaching risk, but to be effective it must be reliable. Heavy cloud cover may offer protection to corals from increased ultraviolet light and ultimately from, bleaching, but clouds are not a reliable source of shade. On the other hand, topographical and bathymetric features are reliable year-round.
- Shading is important in certain locations such as Palau, the Philippines, and anywhere there are steep-sided limestone or volcanic islands that offer protection.
- Islands of high relief that are oriented along a north-south axis provide reefs with shade for half of each day.
- Steep-sided reefs with a north-south axis may also provide shade for half of each day.
- Aspect relative to the sun for steep-sided reefs in high latitudes may provide greater shading of slopes facing away from the equator.
- Limestone islands, or coastlines undercut by erosion at the waterline, may provide shade for reefs growing on shelves around their perimeter.
- Trees on steep islands further enhance their shading effect.
Shading Factor (1:15)
Rod Salm and Jamie Oliver discuss shading as a possible indicator that corals will survive a warming event.