Will Mauritius ever recover from the oil spill?

The grounding of the Panama-flagged bulk liner owned by Nagashiki Shipping on the eastern shore of Mauritius has resulted in an oil spill of a magnitude not yet experienced in that country. Media reports tend to portray it as an environmental disaster, but it is best understood in the context of ecological processes playing out at planetary scale.

Mauritius in context

Mauritius has a typical island economy. A small tropical paradise surrounded by the Indian Ocean, Mauritius is rated as a high-income country, with one of the most competitive economies in the African region. From a job creation perspective, a significant portion of the economy is related to tourism. Coral beaches and blue warm waters attract sun lovers with pockets full of hard foreign currency that sustain many local livelihoods.

Any impact on the relatively pristine aquatic ecosystem is thus significant, but let us put this into context. From an ecological perspective, we can distinguish different levels of impact, ranging from the immediate risk to local livelihoods to the national loss of revenue. But, while these are both very important, they hide the global significance of coral reef ecosystems. The Mauritian coral reef is the third largest in the world, so it is globally significant, and the repercussions of this event will affect us all.

Beginner’s guide to ocean chemistry

The first risk is related to the chemistry of all oceans. All aquatic ecosystems can be classified as either freshwater or salt water. The difference between the two is of fundamental importance, because freshwater ecosystems are driven by slight acidity (a typical pH of less than 7) while ocean ecosystems are driven by slight alkalinity. The average ocean pH is 8.1. This is of fundamental importance to planetary ecosystems, because of the presence of carbonate, a combination of carbon and oxygen. We can safely say that oceanic ecosystems are centred on the chemistry of carbonate, with the availability of carbonate for the building of coral and seashells directly related to even the slightest changes in acidity. The observed global trend is a gradual acidification of the oceans.

Why coral is important

Carbonate is the fundamental building block of coral. As ocean ecosystems are being stressed, their capacity to sequester atmospheric carbon is changing. Even the slightest change to pH makes a significant impact. The creation of coral (and seashells and other sea creatures) by precipitation of carbonate sequesters atmospheric carbon. On the other hand, the dissolution of carbonate resulting from ocean acidification releases carbon, which ends up in the atmosphere as carbon dioxide. So, the delicate balance of global atmospheric composition is directly linked to the health of coral reefs. The central issue is whether coral is a sink for carbon (a good thing for humans in the industrial era because it removes it from the atmosphere) or a source of carbon (a bad thing because it accelerates the rate of carbon release into the atmosphere). This balance poses a risk to all humans, irrespective of where they live.

Biodiversity

It is widely accepted that the greater the biodiversity, the healthier a given ecosystem is. One of the indicator species is the humpback whale that was severely depleted through overexploitation in the early 20^th century. Research conducted by Prof Ken Findlay has identified at least three migratory routes of humpback whales in the southern Indian ocean. More importantly, this work has shown that the humpback whale population in 2006 was in excess of 70% of its pre-exploitation size. He also recorded population growth of between 9% and 11% per annum, which is expected to plateau as the carrying capacity is reached. This is good news, because it tells us that if we use science-based policy, we can reverse the damaging effect of overexploitation and restore biodiversity.

Putting the oil spill in context

Seen through the lens of these three global risks – disturbance to ocean chemistry, coral as a source or sink of atmospheric carbon, and biodiversity – the oil spill is an accelerator of change, rather than a driver of change. While the visual impact is great, and the immediate loss of livelihoods massive, the capacity of the ocean ecosystem to absorb shocks is driven more by acidification and changes to the chemistry of carbonate. Provided that the spill can be adequately contained, and clean-up measures sustained, the return to the pre-spill status quo is likely to be rapid.

Of course, this does not diminish the importance of the spill as a local disaster, but it interprets the scale of that event in terms of macro drivers playing out at a planetary scale. Ecosystems are resilient, and can recover from extreme events if given a helping hand. The most important aspect of the spill relates to its impact on coral reefs, because these have truly global significance as either a source or sink for carbon, and are collectively under pressure. The oil spill pushes us in the wrong direction by creating yet another stressor, and this is the true impact.

But there is a positive

In the same way that COVID-19 has woken us up to issues of inequity, and a global deficiency in healthcare infrastructure, this oil spill can be seen as a wake-up call. It’s easy to ignore the microplastics that are wreaking havoc on the ocean, because they are so tiny that – quite frankly – we wouldn’t see them even if we were swimming around in them. But it’s hard to ignore 100,000 tons of gooey black oil floating on the surface of a previously gorgeous turquoise ocean. It’s a wake-up call – not just to prevent other oil spills, but also to work actively to reduce and prevent other forms of pollution so that marine ecosystems are better able to deal with disasters when (unfortunately not if) they happen.