World Wildlife Day: Dr James Guest and the impact of global carbon emissions on coral reefs

Submitted by Salix on Tue, 03/03/2020 - 10:11

World Wildlife Day: Dr James Guest and the impact of global carbon emissions on coral reefs

This World Wildlife Day (3rd March), Salix is celebrating a reduction of 821,583 tonnes of carbon dioxide across the public sector per annum[1] contributing to UK and international efforts to minimise the impact of global warming on our planet. The effect of global warming is far-reaching, affecting fragile ecosystems such as coral reefs and putting local and global resources at risk.

We spoke to Dr James Guest, a coral researcher at Newcastle University, to discuss the impact of greenhouse gases on coral reef systems and the importance of reducing these.

Dr Guest leads a 5-year European Research Council funded research program called Coralassist that aims to test the feasibility of selectively breeding corals for heat tolerance.

The impact of global carbon emissions on coral reefs

One of the largest threats to coral reefs comes from the increasing amount of carbon dioxide and other greenhouse gasses being put into the atmosphere. Carbon dioxide traps heat, so the more of it we produce, the warmer the planet and the oceans become.

Tropical corals live in warm water that can fluctuate in temperature naturally over the day and throughout the year. However, in the summer, if an abnormal spike in temperature occurs which goes over the corals temperature threshold by one or two degrees, it exhibits a stress response that we call coral bleaching. Algae inside the coral, which have a symbiotic relationship (giving it nutrients and colour), can become stressed and die. This causes the coral to lose its colour, becoming ghostly white, and if these high temperatures persist the coral will eventually die.

Over the past 30 years there have been several mass bleaching events that led to widespread coral mortality. These events are increasing in their frequency and intensity. For example, in 2016 and 2017 the Great Barrier Reef in Australia lost an estimated one third of its corals due to heat stress. Imagine if we lost one third of the trees in Britain in the space of two years and you can picture what this is like.

Another long-term effect from increased carbon dioxide in the atmosphere is the acidification of the oceans. The rise in acidity in the oceans can lead shellfish and corals to grow more slowly. This threat is equally worrying but will take longer to have an effect.  

Coral research and intervention

In the past, people would manage coral reefs locally from the effect of human interference such as sewage, fishing, tourism and anchoring on the reef. Now, coral reef systems that are classed as ‘pristine’ and sit away from the impacts of human activity are being hit by global warming. There is now a need to reduce atmospheric levels of greenhouse gases as well as encourage local management.

My research looks at active interventions that may assist reefs to persist in the face of climate change. Our work involves identifying corals which have a relatively high tolerance to heat and then to give natural selection a “nudge” by selectively breeding these in the laboratory until they are ready to be introduced to the wild. We are currently finding out if this ability is genetic and if they can pass this heat tolerance onto their offspring. By artificially boosting numbers of more heat tolerant corals on the reef, we aim to provide reefs with a greater chance of survival during the next bleaching event. This, of course, does not replace the need to deal with climate change directly, but may give some reefs a helping hand in the meantime.

The socio-economic importance of coral reefs

All ecosystems play a crucial role and, although corals don’t cover a huge area, they are one of the most diverse and productive marine ecosystems. They are extremely important and offer several services such as providing a habitat for marine life, contributing to the food chain which supports fishing industries and the local economy and tourism through activities such as diving sites. They also protect shorelines and local communities by acting as a natural buffer against storms.

Deriving from the same family as jellyfish, corals are relatively simple but fascinating animals. They produce a skeleton of calcium carbonate, creating vast geological structures which can be seen from space. These skeletons are still there even when the coral dies, but they slowly erode over time if there are no live, growing corals.

Why it is important to act now

Around 20 years ago, many scientists thought local management of reefs was probably more important than dealing with global stressors on reefs. Now it is clear now not only do we need to focus on local management but changing our behaviour and working towards reducing our global carbon emissions.

It’s great to see people starting to change their behaviour by flying less, eating less meat and driving less, but we should also be looking for people to take action by encouraging larger systemic changes at national and international levels to drastically reduce emissions.

One of the main challenges is convincing people to take climate action seriously. When the school strikes started happening, I felt optimism in the fact young people were making a stance and influencing big changes. The effect of climate change needs to be included more widely in education, allowing the future generations to start (or continue) having conversations about it. I think it’s essential we speak to people who don’t yet believe that climate change is the most serious challenge facing society and explain why it is important. It makes a difference.


[1] Figures to date (from 2004). From the Salix about us page here.