Farewelling coral reefs
Karen Middleton We hear much about trying to contain temperature rises to 2 degrees above pre-industrial levels. Why is that the magic number?
Ove Hoegh-Guldberg The 2-degree guardrail came out of the 2009 Copenhagen meeting. When you looked at how ecosystems were responding, you got into an unmanageable area at 2 degrees above the pre-industrial period, which was where the CO2 concentration had been stable for a long time. The trajectory we’re on today could raise temperatures by as much as 5 or 6 degrees on history. One of the problems with 2 degrees is that generally people have the idea that it’s a guardrail. You go up to the edge of 2 degrees and look over it and see where you don’t want to go and it’s all very safe here. But it’s more like a slippery slope. Things get progressively worse until they become unmanageable. At the latest Conference of the Parties, the UNFCC [United Nations Framework Convention on Climate Change ] governing framework started to say, “well actually we want to keep things well below 2 degrees, and hopefully aim for 1.5 in the long term”.
KM And where are we now?
OHG We’re about a degree above the pre-industrial period.
KM So we’ve got half a degree’s leeway left.
OHG: To keep to that half a degree would be a massive decarbonisation of almost everything we do – energy, transport, food production and so on. Key to this is not just the amount of temperature change; it’s the system’s stability. If we don’t take care of fossil fuels we very quickly get into a situation where things change. Anything like that puts a lot of stress on biology but also on our economic systems. If you’re constantly having increasing temperatures and challenges then you’re not going to be able to build an economic system that will last 50 or 100 years.
KM What do you think of the 2015 Paris agreement on climate change?
OHG The 2009 Copenhagen climate meeting that came before Paris had a top-down approach. China had a very different opinion to the Americans, the small island states to the larger economies and so on. They didn’t reach agreement. The Paris 2015 deal was countries pledging what they could do, realising this was a very serious issue. If you add the pledges up, we go to 3 to 4 degrees above pre-industrial, which is clearly not enough. But every five years, countries must come together and adjust their emissions reductions and they can only make greater cuts – you can’t go backwards. If you want to do that, you leave the agreement.
KM Well, the United States president, Donald Trump, says America is going to pull out. How significant is that?
OHG Having such a big player withdraw, there’s definitely a stumble in the road. But I think it’s likely to be a smallish blip and it doesn’t negate the huge amount of action at the subnational level in America, like the state of California.
KM Do you think we’re past arguing about the science? And are events like the hurricanes in the Caribbean and southern United States likely to generate more climate debate?
OHG The Intergovernmental Panel on Climate Change is this very arduous process where scientists meet and bring all the latest science published in peer-reviewed literature and reach a consensus about it. That’s about as solid as you can get. Now there are parts of it we don’t know, but the fundamental understanding that changing greenhouse gas concentrations in the atmosphere is disrupting weather patterns across the world is fact. You can’t unpick that one. You might still discuss whether every storm is a consequence of climate change. Over the last couple of years we’ve become certain that it’s not the number of storms changing, it’s the impact of each one. That’s what we’re seeing across the Caribbean and South Asia. You’re getting those normal storm systems coming through but they pack a bigger punch.
KM You predicted 20 years ago that we were going to be in a diabolical situation. Are you saying, “I told you so?”
OHG I wish I’d been wrong. A very simple model that I put together with people from the European Union showed what temperature was likely to do and we knew the temperature at which coral reefs got into trouble and they crossed each other around mid-century. I remember thinking at the time, “I hope this one’s wrong.” In the last couple of years we’ve had back-to-back bleaching events. Reefs have disappeared from many places – the Caribbean has been particularly hit hard. Corals have gone from maybe 50 to 60 per cent of the bottom of the ocean to less than 5 per cent in many places.
KM Is this irreversible?
OHG Under normal, non-climate-change circumstances, reefs might lose corals due to cyclones for example. And if they’re given 10 to 20 years, they’ll bounce back. But what’s been happening with these bleaching events, which are similar to cyclones in killing coral en masse, is they’re now coming faster and faster. There’s not enough time for reefs to bounce back.
KM You’re involved in a project, the 50 Reefs Project, which is attempting to effectively triage reefs around the world and work out which ones are saveable and which ones aren’t – a potentially controversial thing to do. Can you give us a progress report?
OHG This project came out of the certainty one gets, to some extent, from the Paris agreement. You’ve got another half a degree of change, then it is supposed to stabilise about mid-century. Even under that pathway, we still lose an awful lot of coral. We’d lose 90 per cent in some places of today’s coral by the time we get the Paris agreement in place. We’ve already lost maybe 50 or 60 per cent. If we can get as much of those coral resources through to the time when the climate is stabilised then biology will take over. Once it is constant again, corals will grow and do what they normally do, post a disaster. Then you have to say, “Where are those reefs that have the best chance of surviving a climate increase of 0.5 degrees?” The ocean isn’t heating up at the same rate in all places. There are some places where the currents have stalled, where it’s getting a lot hotter a lot quicker, like the equatorial Pacific, versus the coral triangle, which is this South-East Asian paradise for corals. The number of species there is something like three times that of Australia. So you start to go, “Oh, well if we’re going to preserve something we wouldn’t do it at the equator where it’s getting really, really hot – we should be going to South-East Asia.”
You do run into what appears to be triage, and I don’t think that’s the right word. I think it’s about another strategy being added onto the great things that are already going on in conservation. We will be releasing a list later this year and you have to ask the question: “What if the Great Barrier Reef’s not on it?” And it’s an interesting one.
KM Is it going to be on it?
OHG I don’t know. People much smarter than me are working on this problem in a very objective way.
KM It’s really the reverse of triage, because under triage the most dire injuries are treated first. This is saying, “We’re going to go for the ones with the best chance of surviving and leave the ones that are worst until last”.
OHG Yes, we’re trying to be smart about those investments.
KM So what are the benchmarks for establishing which are saveable?
OHG It’s got to not be changing too quickly. You don’t want them in the way of storms. You want them not to be remote. There are a lot of reefs in the world that are in the middle of nowhere, so the value of protecting those might be high in terms of unique species but it won’t be in a good position to re-spawn back onto damaged reefs. The team went through a really large number of data sets and came up with about five or six of these key characteristics and then ran a modelling system which is actually used with financial investments for spreading investment and risk to optimise a portfolio. Let’s say a country’s not on the list. That doesn’t mean it doesn’t have reefs that are worth preserving. It just means this is a set of 50 sites where you’re trying to ensure that this ecosystem gets through to the future.
KM What do you then do with the rest?
OHG We need to go in there and map the resources. On the Great Barrier Reef, that’s probably not an issue because we’ve got one of the best park systems in the world. But many places will be in countries that don’t have those resources. We’ll need to map them, the potential threats and the potential solutions.
KM How do you assess the current status of the Great Barrier Reef? How bad was the bleaching?
OHG The reef’s health has been rocky for some time. In 1998 we had 50 per cent of the reef bleached but only 10 per cent died. That’s 10 per cent of 40,000 square kilometres of coral – it’s still a large amount. Then it happened again in 2002 and then we had a bit of a break and then it came roaring back in 2016 and 2017, where not only much of the reef bleached but we lost almost 50 per cent of the corals over the last two years. If we continue to have warm summers like we had in ’16 and this year, the next one could wipe out the remaining coral. Now, I don’t want to sound doomsday, but that’s where we’re at right now. It’s still a wonderful place to visit. But if we continue on this trajectory it won’t be, very soon – within our lifetime. I think that this is the wake-up call that we need. If losing the Great Barrier Reef isn’t serious stuff, what is?
This is an edited transcript from A Month of Saturdays at the National Portrait Gallery. This week: Clover Moore at the National Library of Australia, 2pm, September 16.
This article was first published in the print edition of The Saturday Paper on Sep 16, 2017 as "Corralled reefs". Subscribe here.