Coral reefs are being pushed to the brink. For the past two years, many of the world’s reefs have been hammered hard by “the longest and most widespread coral bleaching event on record,” according to the US National Oceanic and Atmospheric Administration. Since the 1970s, climate change, El Niño events, overfishing, pollution, and other pressures, have caused coral to decline at an unprecedented rate. As coral continue to be assailed from all sides, the question becomes: what happens to a coral reef when the coral disappear?

To get an idea, says University of Queensland ecologist Peter Mumby, look to Jamaica. In the 1970s, the Caribbean nation’s vibrant coral populations died. In their place grew seaweed forests.

Jamaica’s coral reef collapse was a complex process that started with decades of heavy fishing. In the decades leading up to the 1970s, overfishing depleted the region’s fish, including those that eat seaweed. With the fish gone, urchins gorged on the sudden abundance of algae.

Read on in Hakai Magazine.