[Global] We need our oceans, and our oceans need corals. But it’s not going well for them. Last week, the National Oceanographic and Atmospheric Administration in the U.S. announced that extremely hot oceans have triggered a global bleaching event spanning the tropical Pacific, Indian and Atlantic oceans. Corals around the world are under a lot of stress. And we should care.
Corals are about much more than brightly coloured backdrops of tropical snorkelling holidays or the stage of films about cute little fish that need to be found (that’ll be Nemo, for those without children). Corals are vital to ocean ecosystems. Even though they cover only 0.1% of the ocean seabed, they are home to 25% of the species in the ocean. Coral reefs are often referred to as the rainforests of our seas and play as vital a role in this ecosystem.
Even many species we don’t often associate with reefs are linked to them. Most open-ocean fish such as tuna start their lives as larvae on coral reefs. The demise of the thousands of species of coral would harm the very foundation of the marine ecosystem.
Corals are surprisingly complex. They live in a symbiotic relationship with algae called Zooxanthellae. The corals receive energy and nutrients from the algae and, in return, provide them with shelter and habitat. Corals are, however, also rather picky: if they get uncomfortably warm, they expel the algae living within them.
Since the algae are responsible for the brilliant colours, the corals turn white without them. This is coral bleaching and if the algae don’t come back within a few weeks, the corals starve and die.
Like all marine species, corals and their algae have evolved over millennia under a certain temperature regime, to which they are now well suited. From fossil records, we know that corals have in the past lived in much warmer and much colder waters, as they adapted to past changes in climate. It is therefore clear that bleaching is much more about the pace of temperature rise than the total amount of it.
The bleaching episode now under way is only the third ever recorded and closely linked to the big El Niño that is currently developing. This new El Niño might even surpass the 1998 one, the biggest recorded so far, which also coincided with a global coral-bleaching event. Tropical ocean temperatures are already up by more than 2C. If this goes on for a few months longer (and most scientists expect it will), then thousands of hectares of coral will die.
Corals can’t cope with such extreme and rapid temperature fluctuations, especially as they already have trouble keeping up with the fast temperature rise that is the result of global warming.
Our climate is now warming faster than ever before. Even in the most extreme episodes in Earth’s history, when giant volcanoes spewed enormous amount of carbon dioxide into the atmosphere, the pace was slower than what we are responsible for by burning fossil fuels. And the corals can’t keep up. In some scenarios, we may lose all corals by 2050 because of bleaching.
It is not only corals where the pace of climate change is in some ways as important as the magnitude of change. Most attention in the discussion on climate change is on how high temperatures and sea levels will be by 2100. But we should not forget to ponder how we get there.
If we want to adapt to climate change, we also need to consider how quickly sea levels are going to rise and how quickly climate zones are going to shift. One thing is certain: both natural ecosystems and human societies will be able to adapt more easily when the pace of climate change is slower.
So what can be done about it? The ultimate goal of any climate negotiation, such as those at the COP21 climate change conference in Paris, just before Christmas should be to limit the effects of climate change altogether. But we should not lose sight of the fact that the route we take towards a sustainable future matters, so every bit helps.
The biggest uncertainty when it comes to forecasting what’s in store for our climate lies in what are called the emission scenarios. These state how much carbon dioxide and other greenhouse gases we might burn each year as a global society depending on different scenarios of how we tackle this problem. Creating emission scenarios is inherently uncertain because future political choices are unknown, and the ones drawn up by the Intergovernmental Panel on Climate Change (IPCC) have all kinds of shapes.
One scenario, known as business as usual, just goes up and up and up, which is exactly what we’ve been doing since the Industrial Revolution. Other scenarios have emissions rising for a while, before plateauing in the second half of this century. Others still have emissions going down in a few decades from now, in some cases even dipping into the negative territory.
However, all scenarios accept that there will be an increase in emissions in the next decade. This means that temperatures will keep rising for a while to come.
But every tonne of carbon dioxide not emitted reduces the pace of climate change. This is a very strong argument for taking action right now. The sooner we start truly transforming our economies to low-carbon ones, the smaller the impact of climate change will be.
Corals have been around for millions of years. A world without corals will be a very different one. Globally, 500 million people depend on corals for their food and livelihoods, and their estimated value is upward of $30 billion per year.
If we want to keep this unique ecosystem as healthy as possible, there is no time to waste in combatting climate change.
View original article at: Across the globe, corals are dying — Here’s why you should care