What can we do? Serious question.
Identify areas that are become more hospitable, and work on establishing reefs there.
Expand artificial reef building, to help make up for lost area.
Cut carbon emissions, and work on finding ways to sequester what has already been released.
No one thing will be the fix, but they all have a role to play.
Can the worlds aquariums store a fraction of the biodiversity of the reef?
> Expand artificial reef building, to help make up for lost area.
It would take a massive engineering effort to make a dent in the area the Reef covers.
2. You don't need to replicate the entire area. You only need to make refugia. There is a lot of ocean shelf that is relatively barren, but could support a thriving reef, if only there was structure to build on. It's a subject that is being actively worked on. http://www.reefdesignlab.com/about/ for one example.
It doesn't have to be money spent just for reef creation, either. Changing how we construct jetties, piers, and other near-shore structures to be more welcoming to reef life would make a genuine impact.
You've got to keep in mind that we're not 'fixing' the problem, here. We're punting, and trying to keep the ball in play as long as possible while we work out the truly long-term solutions our carbon problem presents.
1) Climatic feedback systems such as arctic ice melting, or permafrost methane have already been triggered. This means their effect will continue for centuries if not millenia.
2) Climate lag. There are a few decades between emissions and consequences in the climate. 40 years on averge from what I've read. This means we are now only seeing the effects from the 70s emissions, and we have emitted more CO2 in the past decades than in the previous 150 years before that.
3) Cooling from sulfate aerosols produced by industrial activity. It's unclear how much these are cooling the atmosphere but even a small number such 0.2ºC would be considerable.
Our only chance are very strong negative emissions.
The reason CO2 is going up, at an increasing rate, is largely because the biosphere's ability to absorb CO2 is diminished.
I believe the grim truth is this: the world's transformation would continue for a long time even if humans stopped producing CO2 tomorrow.
Preparations for the inevitable should be our focus.
We can do a LOT better in terms of pollution.
>Coral reefs play a critical role in the carbon cycle of our planet, by taking calcium ions and dissolved carbon dioxide from the water and turning it into calcium carbonate forming their hard skeleton. http://www.reefrecovery.org/coral-reefs/
But the metric of "does putting in all this money and effort to fix the problem we created give us something back in return?" is absolutely poisonous. It's that selfish "is preserving this environmental habitat that has been around for millions of years worth my time or money?" that allowed us to dig this grave in the first place.
What grave? Things are better than ever!
But I'll bite. What metric are you using to say things are better than ever?
We are using more renewable energy, less coal. Every year we add more solar/wind capacity than the past decade (just a guess). Soon, driverless electric cars will transport people autonomously, without creating any pollution, and road accidents will dwindle down to ~0.
More people have access to clean water, modern medicine, and we have treatments/preventions for the deadliest of diseases.
I mean, what's not to love?
Yes, we live with countless blessings. But this is in spite of continued industrial negligence and increasing international economic pressure.
In spite of the fact that our wages increasingly do not match our economic contributions, while the costs of living continues to rise just about everywhere in modern countries. In spite of increasingly militarized police states engaging in targeted socioeconomic suppression across the globe.
In spite of many, many things.
I want to have optimism for the future, too. But I'm not going to ignore the multitudes of problems we face today, and will face tomorrow.