Refilling the coral reef glass

David Obura’s editorial in the 22 Sept 2017 issue of Science magazine ‘is the coral reef glass half full, or half empty?’ emphasizes what we need to do to save and then rebuild coral reefs, rather than give up on them. Go to the Science issue page here, to read the article or view it at right.

The challenge faced by coral reefs – from climate change and non-climate stressors – is unprecedented in human history. It is also unprecedented in the history of coral reefs in that prior mass extinctions have been due to natural drivers played out over scales of thousands to a few million years, while the current ‘sixth extinction’ is primarily due to novel human-induced threats – pollution, overfishing and climate change – intensifying within a period of only 10s of years.

These threats are so severe and planetary in scale that many scientists have identified a geological era, the Anthropocene, to signal that earth is moving out of the Holocene – the benign and reasonably stable geological era of the last 200,000 years that has enabled human society to flourish. Apart from the frozen poles and their oscillation during the Ice Ages, the climate of the planet in the Holocene has been so benign as to allow us to live just about everywhere else – save for in the oceans and at the tops of the highest mountains.

Coral reefs grow where a fine balance is met – temperatures are warm enough to enable rapid calcification and production of the skeletons that build the reef structure, but not so high that corals and their intra-cellular symbionts, zooxanthellae, cannot survive together. But the greenhouse effect, ramped up by human emissions of carbon dioxide and other gasses, is raising global seawater temperature. The rate is only tenths of a degree Celsius per decade, but this is several times faster than has occurred in the major natural climate changes in the past, and evidently too fast for corals and their symbionts to keep up with.

The editorial outlines a number of steps we have to take:

  • >>> implement the Paris Agreement to limit global warming to less than 2oC, and for coral reefs, even the 1.5C ‘wish’ in the Agreement may be too much.
  1. >>> invest in efforts to reduce all other stresses to corals – as far as possible pollution should be reduced to zero, and fishing kept at levels that doesn’t increase competition to corals from algae, or destroy reef structures. Marine protected areas – whether run by government, or by communities and businesses with a vested interest in maintaining reef health – are one of the most powerful tools we have, providing a strong focus for management of coral reef areas.
  2. >>> support innovative research that helps to identify what we can do to maximize the survival potential of reefs now (e.g. accelerate genetic adaptation to heat stress, find deep refuges from warm surface conditions, identify and ramp up protection for those reefs most likely to experience the lowest levels of climate threat) and to rebuild functioning reefs in the future when and if conditions improve (developing new restoration tools that will work at scale). But it is important to not over-claim what coral restoration techniques can do now – for the moment, they cannot restore the fisheries potential that pays for food and school fees in low income communities, though they can provide a focus for education, awareness raising and tourism.

But even more than these a critical prior step is needed – changing economic and financial priorities to promote protection and investment in reefs to maximize their health as key assets for economic growth. Without a value change in how countries approach economic growth we are unlikely to reduce any of the primary stresses – climate and non-climate alike – to low-enough levels for reefs to survive and recover.

Meanwhile, a range of local actions are possible everywhere where there are reefs ad people dependent on them. Even if we are uncertain about whether they will be effective over many decades, the relief they provide now for people’s daily needs is critical, and they will maximize the chance that if/when the large scale drivers are finally dealt with, reefs will be in good enough condition to survive and rebuilt.


These links point to some basic tips on what individuals can do to help reefs:

simple actions

how you can help

… and get involved with local efforts for marine conservation – whether with marine parks, schools, community groups or tourism …