05/27/2016 02:22 pm ET Updated May 28, 2017

The Cities Beneath Our Seas

If we fail to look after our coral reefs we will lose our shot at a healthier, brighter future

They've been called the 'tropical rainforests of the sea', the world's 'underwater cities' and even likened to Shakespeare plays.

If these analogies are the right way of looking at coral reefs, the world now stands to lose not just a life-giving ecosystem but also vital components of human society and of our common cultural heritage.

Coral reefs around the world continue to be impacted by over fishing and use of destructive fishing methods, sedimentation, careless tourism and coastal development. Against this backdrop the impacts of climate change are growing ever more severe, taking on the primary role in the destruction of one of the most vibrant and essential ecosystems on the planet.

Here, in the Maldives, we are witnessing this first-hand. Our archipelago suffered severe coral bleaching in 1998, from which recovery is satisfactory after 10 -15 years, although highly variable. Now the ongoing global coral bleaching event, the longest on record, has already caused bleaching of 50-100% across many shallow reefs in our country. The increasing frequency of large scale bleaching is of great concern to us.

These underwater cities, which provide a home for more than a quarter of all marine species, take centuries to form but only weeks to destroy, which is why it is so heart-breaking to see vast swathes of reef that were once pulsating with life turn barren and grey.

Globally, about 20 per cent of the world's coral reefs have been destroyed and scientists predict even greater losses in the years ahead as the seas warm and the oceans grow more acidic.

The reason this matters is simple. Coral reefs provide more than half a billion people with food, coastal protection, building materials and income. They supply our white beaches with sand, they form the barriers that break the ocean's waves, they protect our properties and they provide us with new medicines to treat diseases like cancer and HIV. The 30 million people who inhabit atolls depend entirely on coral reefs to live.

Nowhere in the world is this more evident than here, in the Maldives, a country built by corals, covering vast areas of ocean but never rising more than a meter and a half above the sea surface.

In the near term coral loss may impact travel, tourism and fisheries, which are the main contributors to the country's GDP and employment. Moreover, it will become increasingly difficult and costly to defend our people from storm surges. We have made and continue to make very significant investments in providing safe living space for our population, but these efforts will eventually be undone if we lose the coral reefs that are at the basis of all land in the Maldives.

Along with mangroves and sea-grass beds, coral reefs deliver the highest annual value in terms of ecosystem services of all natural ecosystems on the planet. One square kilometre of healthy, well managed coral reef can yield a catch of over 15 tonnes of fish and other seafood every year. In all, the Earth's coral reefs provide a global economic value - from fisheries, tourism and coastal protection - of at least $375 billion per year.

That is why looking after these ecosystems is essential if the world wants to fulfil one of the most noble ideals of our time - to conserve and sustainably use the oceans, seas and marine resources so we can promote sustainable development that lifts people out of poverty and provides enough nutritious food for people to lead healthier, better lives.

These are goals set out in the 2030 Agenda for Sustainable Development and they are goals that we can achieve if we learn how to look after the coral reefs that sustain us, feed us, heal us, provide us with jobs and drive economic growth.

This week, countries from all over the world met in Nairobi for the United Nations Environment Assembly - the world's most powerful decision-making body on the environment. Central to the discussion was the role coral reefs play in safeguarding the health and resilience of half a billion reef-dependent people.

It is vital that the world uses this opportunity to spur action that combats the tragic loss of these precious ecosystems while harnessing their vast potential in a way that enhances the lives of those who depend on them.

The science is clear. Unless we act now, more reefs will be lost. In the process, we will lose protection for our coastlines, we will lose our economic vitality, and we will lose a major source of our food. Ultimately, without these majestic underwater cities we will lose our shot at creating a healthier, brighter future.