A fire coral that experienced severe bleaching in 2016. Photo courtesy: The Ocean Agency By Gabriel Grimsditch

The ocean is giving us a climate warning, but it is going unheeded. Underwater heatwaves caused by climate change and ocean warming have been killing coral reefs around the world in recent years. But this disaster has not received the same attention as many other global tragedies.

Coral reefs are extremely valuable and biodiverse marine ecosystems that provide huge value to people around the world. Often described as the “rainforests of the sea”, coral reefs provide a home to at least 25% of all marine species despite covering only a tiny fraction of the ocean, making them one of the most biodiverse ecosystems on the planet.

Like forests, coral reefs also sustain the livelihoods of hundreds of millions of people around the world and contribute to national economies.

The ecosystem services provided by coral reefs include revenue from tourism, food security from fisheries, coastal protection against storms and flooding, and even genetic material for life-saving medicines.

Economic impact

These have been estimated to contribute at least US$ 375 billion per year to the global economy. In Kenya, coral reefs are also extremely important to coastal communities.

A fringing and lagoon coral reef system runs from Vanga at the Tanzanian border up to Malindi. There is then a break in the reef due to the sediment coming from the Tana and Galana rivers that stops coral growth north of Malindi and south of Lamu. Another distinct coral reef system then runs from Lamu to Kiunga at the Somali border.

The total Kenyan coral reef area is about 639 km2, and there are at least 13,000 artisanal fishers on the Kenyan coast, plus their families, who depend on coral reefs for their daily food and income.

In these coastal households, coral reef fish can provide over 80% of household income . Furthermore, Kenya’s coral reefs protect beaches from large waves, erosion, and storms, and thus protect the whole infrastructure of coastal tourism. Tens of thousands of jobs in Kenya depend on healthy and vibrant coral reefs.

Most vulnerable ecosystem

However, our coral reefs are in danger. They are the most vulnerable ecosystem on the planet to climate change. According to the Intergovernmental Panel on Climate Change (IPCC) , they may be the first ecosystem on the planet to disappear completely if warming persists unabated. This is due to a phenomenon known as “coral bleaching”.

Corals are small and relatively simple animals in the same phylum as jellyfish (the cnidarians) that form colonies, build skeletons and form the basis of coral reefs.

An individual coral polyp may only be a few millimeters or centimeters in size, but they are the great architects of the ocean and the structures (or reefs) they build can stretch for thousands of kilometers. Coral reefs have been around for at least 240 million years, but modern reefs today are estimated to have formed between 5,000 and 10,000 years ago, after the last ice age.

The tiny architects depend on an even smaller microscopic algae that lives within the tissue of the corals. The micro-algae, like plants, photosynthesize and gain energy from the sun which help the corals build their skeletons. Imagine having thousands of small solar panels in your skin.

In return, the micro-algae get to live in the coral tissue safely. This elegant and amazing symbiotic relationship is the basis for the growth of coral reefs, and for building the spectacular homes for thousands of marine species.

But like all relationships, the one between corals and microscopic algae can be broken when it becomes stressed.

The symbiosis is especially vulnerable to temperature increases. When the ocean warms above the average temperature that the corals are accustomed to, even by as little as one degree Celsius over the span of a few weeks, then the corals and micro-algae become stressed.

Cause for worry

The relationship is broken, the corals expel the micro-algae, and the white coral skeleton becomes visible as the coral has lost its colour. Whole reefs can go from displaying the vibrant colours of healthy corals to a ghostly white as the corals lose their colour, lose their energy and eventually die due to the heat. Hence the term “coral bleaching”.

The first major global coral bleaching event that shocked the world was in 1998. The El Niño event warmed up large areas of the world’s oceans. In the space of a few months, the bleaching moved through the ocean and killed an estimated 16% of the world’s corals .

The 1998 bleaching event was devastating to coral reefs in Kenya, as the live coral cover dropped from healthy reefs with over 40% live coral cover to about 8% on average. It took more than two decades to gain 10% coverage.

Today, average live coral cover across Kenya is estimated to be at about 18% . Since 1998, coral reefs around the world have recovered slowly. However, coral bleaching events have increased in frequency and intensity, as the world’s ocean has warmed due to greenhouse gas emissions and climate change.

In 2010, there was another global bleaching event. From 2014 to 2016 the longest and most widespread global bleaching event in history was recorded, impacting almost every coral reef region and causing widespread devastation.

Kenya not spared

Kenya’s coral reefs have been impacted as well, and they have never been able to recover to their previous health and glory.

The Great Barrier Reef in Australia, the largest coral reef in the world, has already lost 50% of its live coral. These repeated bleaching events have transformed the world’s coral reefs.

Due to warming trends in the ocean it is expected that by the middle of the century all coral reefs globally will experience bleaching conditions on a yearly basis , threatening extinction.

Of course, climate change is not the only threat to corals. We also lose coral reefs due to pollution, coastal development and overfishing or destructive fishing such as dynamite fishing. A combination of these impacts in addition to bleaching events means that we have lost up to 50% of the world’s coral already.

The remaining 50% is at high risk of loss this century due to climate change. This will have profound impacts on the livelihoods of hundreds of millions of people who depend on coral reefs, often in the poorest and most vulnerable countries. 

So, what can be done? First and foremost, coral bleaching is a result of climate change. Coral reefs are sounding the alarm as to what may happen to other planetary ecosystems as the world heats up.

We need to decarbonize the global economy and seize opportunities for economic growth that do not rely on burning fossil fuels and greenhouse gas emissions.

There are opportunities for green growth in the wake of the global COVID-19 pandemic, and this is a make-or-break moment for the world’s climate. Achieving, and even going beyond the Paris Agreement on climate change, is imperative for the future of coral reefs and the people who depend on them.

Scientists have been sounding the alarm for decades, and journalists can also play an important role in raising awareness and consciousness.

Secondly, we need wise management of the sea. A recent study found that only 2.5% of the world’s coral reefs are actively protected. This is far too little if we want these ecosystems to survive.

Protecting coral reefs from local threats such as overfishing, pollution or coastal development can give them a better chance of adapting and surviving through climate change.

Benefits to local communities

Well managed Marine Protected Areas or Locally Managed Marine Areas that provide benefits to local communities can strengthen the resilience of coral reefs and coastal peoples.

The Convention on Biological Diversity Aichi Biodiversity Targets, agreed upon by all member states, call for 10% of the world’s marine and coastal areas to be well protected.

Kenya so far falls short of this target, with less than 1% of the country’s Exclusive Economic Zone falling within protected areas. Kenya’s coral reefs are also overfished, with up to 70% of the reefs fished to unsustainable levels .

However, there is a growing trend to establish of Locally Managed Marine Areas, managed by local communities in collaboration with civil society and government, which is proving successful in some coral reefs in Kenya.

A combination of Locally Managed Marine Areas and Marine Protected Areas can provide hope for a more sustainable future. Strong global climate change policy along with community-conscious coral reef protection and management at local levels will be needed if we want to continue to enjoy the many benefits that coral reefs provide to us in the future.