Following is a Q&A with Dr David Wachenfeld, chief scientist of the Great Barrier Reef Marine Park Authority in Townsville.
Q The 2016-2017 bleaching event: what effect did it have on people?
A The science has been telling us that climate change is the greatest threat to coral reefs, and the Great Barrier Reef specifically, for more than 20 years, and even though we couldn't predict the exact times of the heatwaves that caused these terrible bleaching events, we knew they were coming.
I think what's difficult, though, is for people to listen to science and forecasts of what will very likely happen in the future and have that really galvanise them into action. What's happened in the last few years is that the world has seen essentially a marine heatwave roll between the Northern and Southern hemispheres, from 2014 to 2017, and of course two years of consecutive mass coral bleaching in the Great Barrier Reef in 2016 and 2017.
For many people around the world, this means that climate change and the impacts on reefs are no longer a matter of scientific evidence or forecast. These are some things they've seen, and felt, and in some cases smelt in their own backyards. People have smelt coral die on a scale that they've never experienced before. And so the reality of their experience is very confronting. I think that really changes how people think about climate change and the need to adapt and the need to tackle the problem globally.
Q Can corals adapt to these rapid changes?
A So we've had coral reefs for hundreds of millions of years, and in that time they have adapted to changing conditions. They've been able to make those sort of changes and to adapt at time frames of hundreds of thousands to millions of years.
And we are now changing the climate by burning fossil fuels and other mechanisms - we are changing the climate many, many times faster such that things are happening in decades which normally take tens of thousands of years.
Now, corals are good, they can adapt, but they can't naturally adapt to something that is changing this much, this quickly, and that's why we're seeing so much global impact to coral reefs from climate change.
Q What are the impacts on people who rely on reefs for their livelihoods?
A The Great Barrier Reef is much more than just an environmental icon, it's also an economic powerhouse. It supports tens of thousands of jobs, contributes billions of dollars to the economy, but reefs globally support hundreds of millions of people.
They provide food, they provide employment, they provide income and they provide coastal protection. So when we think about impacts of climate change on reefs globally, we're actually talking about the impacts on hundreds of millions of the world's poorest, most vulnerable people, as well as the wonderful ecosystems that are coral reefs.
Q What sort of reef, not only the Great Barrier Reef, but in the rest of the world, will we have in the future if we don't get emissions to decline rapidly ?
A It's important to remember that we're already 1 deg C warmer than we were before the industrial revolution, before we started to burn fossil fuels, and at 1 deg C warmer we've seen global mass coral bleaching events.
We know from the scientific evidence that once we're 2 deg C warmer than pre-industrial (times), it is very unlikely that we are going to be able to do anything to save and protect our coral reefs.
So progressively what will happen is we will get more severe weather events, more severe cyclones, heatwaves, floods. Progressively these will damage our reefs more, reefs will lose their corals, corals will become increasingly rare, the fish communities, the other communities will change.
This will affect people, tourism industries will cease to function, fishing industries will cease to function, people will lose their jobs, they'll lose their food source - I'm talking at close to plus 2 deg C. This is what we can expect to happen.
So it is essential we do everything we can to protect the coral reefs locally, from pollution, from overfishing. But the biggest problem and most urgent thing we have to do is mitigate climate change, stop putting greenhouse gases into the atmosphere, adopt renewable energy and make sure we constrain climate change to somewhere between 1.5 and 2 deg C above the pre-industrial average. But the closer to 1.5 we get, the better off the Great Barrier Reef will be.