This thing called life

The man on the land has the oceans in his hands

The fruits of the sea include our own health. lotus8/flickr

People who live far from the seashore still benefit from ecosystem services delivered by the oceans of our planet, and people who cannot see the sea still damage the oceans by impacting the water quality of rivers that flow to the sea.

A recent study by Glenn De’ath and colleagues has analysed the causes of the decline of coral in the Great Barrier Reef, and found that a large proportion of coral mortality is due to algal blooms that are caused by increased nutrient loads delivered by freshwater rivers and streams. This means that managing the health of the reef means convincing people who live on the land to take part.

What does the ocean do for you?

Some people believe that if they do not live on the coast, or spend time fishing, then conserving oceanic habitats or species has no benefits for them personally. But the oceans provide climate regulation by absorbing carbon dioxide, it produces oxygen for us to breathe, and seafood provides essential protein for a large proportion of people on our planet. These are things we will not miss until they are gone. We call them ecosystem services, and they are easy to take for granted.

A recent analysis by the Centre for Policy Development concludes that Australia’s marine estate provides over $25 billion worth of ecosystem services every year. That figure does not include the money produced from commercial fishing, boat building, marine tourism or offshore oil. The marine reserve network, which is widely undervalued, provides $2 billion of ecosystem services each year.

But putting aside areas of marine habitat is only one aspect of ensuring the health of our oceans. Much more needs to be done to protect ourselves from catastrophic consequences. And the Great Barrier Reef is only one component of our marine estate, but it is both visible and important, so recent research on the causes of decline in live coral is instructive.

Study of coral reef deaths

Based on 2,258 surveys from 214 reefs over 27 years, a study by Dr De’ath et al. quantified the mortality of coral across space and time within the Great Barrier Reef (GBR). They found a large decline in live coral across the GBR over this period, from 28% coverage in 1985 to only 13.8% coverage in 2012. But the damage is not evenly spread across the GBR: in the isolated north the impact is far less than in the developed southern end, where live coral coverage has fallen as low as 8.2%.

More interestingly, the researchers identified three causes of coral death: 1) bleaching, 2) tropical storms, and 3) crown of thorns starfish. At first glance it would appear that these are beyond human control, but on careful examination, all three may be linked to human activities.

Bleaching occurs when symbiotic algae that capture energy from the sun for their coral hosts are affected, causing the death of the coral itself. Bleaching is triggered by warm water events, which are increasing due to global warming. Tropical storms will always be with us, but the kinds of damaging cyclones that cause damage to reefs are also likely to increase in frequency with warming ocean temperatures. To manage either of these causes of coral death we need a global response to reduce greenhouse gases. In the past three decades, tropical storms and bleaching were responsible for about 58% of coral deaths in the Great Barrier Reef.

The third cause of coral decline is a starfish that can become super abundant. The crown of thorns starfish are voracious predators of coral, and 42% of coral mortality was caused by outbreaks of this single species. One way to reduce crown of thorns outbreaks is to ensure that their predators remain prevalent, and restrictions on fishing have had some impact on crown of thorns populations because fish eat starfish. But the outbreaks are not due to predator release, they are caused by prey abundance.

Crown of thorns starfish outbreaks are due to increased survival rates among baby starfish. Algal blooms provide superabundant food for the larval stage of starfish life, allowing populations to explode beyond the capacity of fish to clean them up. Algal blooms are the consequence of high nutrient and sediment loads from cleared, fertilised and urbanised catchments.

Nutrient loads are now five to nine times higher in rivers than before European settlement. The lesson is that the water quality of our freshwater systems directly affects the water quality of our marine environments. The same problems caused by nutrients in inland waters are caused by inland waters providing nutrients to the ocean: algal blooms fundamentally alter the food web. In this case, extra algae means more crown of thorns starfish, which means death for coral reefs.

Link between land and sea

The good news part of this story is the author’s prediction that if crown of thorns starfish are controlled, the Great Barrier Reef would be able to recover from the other two causes of coral death. This means that people who live on the land have both a responsibility and an opportunity to make a difference to global health.

Protecting marine habitats and environmental management of the Great Barrier Reef is not enough to save it. The ocean is not as distant from inland environments as most people think. You do not have to have an ocean view or be addicted to seafood to see the benefit of preserving our marine estate. Let me use myself as an example: my home is over a three hours drive from the ocean, I don’t eat fish at all (vegetarian for 33 years so far) and I am the first person to get seasick if I do get the opportunity to go boating. And yet I cannot ignore the plight of the reef that flanks our continent, or the waters that support life as we know it. As a thinking person I know that a healthy ocean directly impacts my family and my future.

People who live far from the ocean have the power to save or destroy this World Heritage Site. Saving our oceans starts on the land, in the home, in the factory and on the farm. What we pour down the drains or spray on our soil inevitably finds its way into our freshwater systems, and they deliver the bounty of our activities to the sea.

Better management of our rivers and streams will benefit the native fish and habitats close to our homes, as well as giving the reefs and seagrass beds and other marine habitats a fighting chance. The payback for us is those ecosystem services, at once invisible and indivisible from our own health and well being.

Unfortunately, ecosystem services, like fresh air and clean water and food security, are easy to take for granted. But we will miss them like mad when they are gone. Just remember that you are not powerless to make a difference, in fact, the truth is quite the opposite. Only you, and others like you (human beings, that is) have the power to protect planetary health. Caring for the world’s heritage begins at home, no matter how far you live from a World Heritage Site.