After eight weeks they were collected and carefully inspected under a microscope to count the number of newly settled coral recruits. But if the stressful conditions persist for too long, they die.
The IPCC report released previous year stated that if the global surface temperature is permitted to rise by 2C, 99 percent of coral reefs across the globe will perish. Scientists predict that the gap between pairs of coral bleaching events will continue to shrink as global warming intensifies. The extent of damage is still within the realm of recuperation and the researchers will be returning to Lord Howe Island to evaluate if these corals get any chance of recovery.
It's not entirely clear yet the exact effects which coral bleaching will have on the reef, however it is clear that the damage occurring will be system-wide and likely cause significant changes to the reef's biodiversity.
"Babies can travel over vast distances, and if one reef is knocked out, there are usually plenty of adults in another reef to provide juveniles", Prof Baird said. "The mix of adult species is different".
Historically, after the damage from events such as bleaching or a hurricane, the remaining adult corals in the reef spawn trillions of larvae each year, which spread and slowly begin to revitalize the reef by replacing dead corals with new ones. In the introduction to the report, the authors note that environmental changes caused by climate change, "are increasingly challenging the capacity of ecosystems to absorb recurrent shocks and reassemble afterwards, escalating the risk of widespread ecological collapse of (the) current ecosystem".
With projected greenhouse gas emission levels, estimates are for the reef to experience extensive bleaching twice a decade from 2035, and annually after 2044.
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Leggat and other scientists from several Australian universities and the US National Oceanic and Atmospheric Administration found severe bleaching of up to 90 percent at Lord Howe's inshore, shallow lagoon reefs. "But now, the scale of severe damage from heat extremes in 2016 and 2017 was almost 1500km-vastly larger than a cyclone track".
Hughes said the only way to fix the problem is to address the root cause of global heating.
The recent bleaching in the area is proof global warming is affecting coral reefs around the world, reaching even regions that normally do not see similar events. These include polluted water, poor water quality, disease outbreaks, parasites and destructive fishing or tourism practices.
"We used to think that the Great Barrier Reef was too big to fail - until now", he said. A 2018 Science Advances study, for example, also came to a similar conclusion. The rate at which baby corals are settling on the Great Barrier Reef has fallen by almost 90 percent since 2016. "We show that coral recovery rates across the GBR declined by an average of 84 percent between 1992 and 2010".
The scientists are set to return to Lord Howe in the next few months to find out if some corals have been so severely bleached they can not recover. "The number of new corals settling on the Great Barrier Reef declined by 89 percent following the unprecedented loss of adult corals from global warming in 2016 and 2017".