Silent But Deadly
Last year brought about the worst global coral bleaching event ever recorded. Climate change and its symptoms are daunting, especially since we face many large-scale issues on our planet already. But none the less, it’s important that we understand what is happening. Here, we will discuss green house gasses, where they come from, how potent they are and how we can reduce them.
While earth’s climate has always been changing, there has never been an occasion where temperature has risen so fast. This poses many problems for ecosystems, whose species may not have the opportunity to evolve adaptations fast enough to compensate for the temperature rise. This is where climate change relates to our tropical coral reefs. Most corals thrive in a water temperature of 22-28°C, and some can survive between 18-36°C (although unusual). Here on Koh Tao we typically have a water temperature of 29-30°C, and during the 2016 global bleaching event the temperature peaked at 32°C. Bleaching occurred around the entire island and whilst a good amount of coral did ultimately recover, we saw many colonies perish. In some cases entire fields of corals were lost, and with it the habitat which they provide.
You may be wondering what exactly is happening to a coral colony when a bleaching event occurs? Well, the symbiotic relationship with an alga called zooxanthellae is lost. The algae lives within the coral tissue and shares energy produced during photosynthesises. The algae provides colour to the corals which would otherwise only show the white of their skeleton, and provides corals with 75-95% of their energy requirements. During a bleaching event the algae dies or leaves the coral host.
So! Now we have covered what climate change is, and how it affects coral reefs. Now we need to look into the greenhouse gas effect. Essentially, earth is the nice life supporting temperature it is due to our atmosphere which is a thin layer of gases that cloak our planet and protect it. Greenhouse gasses (GHG’s) are gasses which have some level of global warming potential (GWP). They have the ability to impact how much heat energy is reflected off our atmosphere back into space, and also how much heat is held in. When we add additional greenhouse gasses to the equation, more heat energy is trapped within our atmosphere from the sun.
There are many greenhouse gasses, both natural and manmade. Carbon dioxide (CO₂) is often referred to during climate change discussions. It has natural and manmade sources. Carbon dioxide has a GWP of 1, and other GHG’s potencies are expressed in CO₂ equivalences. It’s ‘lifespan’ in our atmosphere is difficult to determine, as while some CO₂ is absorbed by carbon sinks such as the ocean (over a 20-100 year period). However about 20% of CO₂ emissions will remain in our atmosphere for tens of thousands of years. So whilst it is less potent then some other GHG’s, it potentially has a much longer atmospheric lifespan than others.
Methane (CH₄) is another potent gas that has had more light in the media in recent years. It has manmade and natural sources. The significant manmade sources originate from animal agriculture (particularly cows), landfills, manure management (agriculture contributing largely to this sum) and fossil fuel production, transportation and use. It has a GWP of 25 over a 100 year period, and a typical atmospheric lifespan of 12 years.
Nitrous oxide (N₂O) also has both natural and manmade sources. A large portion, 75% of this manmade source originates from agricultural soil management when nitrogen is added to soils through the use of synthetic fertilizers. It has a GWP of 298 and a lifespan of 114 years.
The last one is a biggie, the fluorinated gases. They are sadly the most toxic gasses in terms of GWP and have the longest lifespan by far. All of them are manmade and do not have any natural sources. On the plus side though, they make up the small portion of the GHGs that we emit into the atmosphere on a yearly basis. They include the fluorinated gasses and are emitted through a range of industrial processes listed below:
- Hydrofluorocarbons (HFCs) have a GWP of up to 14,800 and a lifespan of up to 270 years. This gas was developed as a replacement for chlorofluorocarbons and hydrochlorofluorocarbons (CFCs and HCFCs) which were depleting the stratospheric ozone layer for quite some time. These two are being phased out under an international agreement. They escape into the atmosphere through leaking refrigerants, but luckily there is already a new alternative being introduced called HFOs which is a similar gas which has a much lower GWP and a shorter lifespan, yay!
- Perfluorocarbons (PFCs) are a by-product of many industrial processes, especially those associated with aluminium and semiconductor manufacturing. Their GWP is 7,390-12,200 and they have a lifespan of 2,600-50,000 years.
- Nitrogen trifluoride (NF₃) has a GWP of 17,200 and a lifespan of 740 years in our atmosphere. Its sources include semiconductor manufacturing and the production of many household items including microelectronics, such as TVs, touch screens solar panels etc.
- Sulfur hexafluoride (SF₆) is largely used in electrical transmission equipment. It is by far the most potent GHG with a GWP of 22,800 and a lifespan of 22,800 years.
So what can we do?
There are quite a few greenhouse gasses out there contributing to climate change, and consequently to coral bleaching. On a more positive note, there are a few things you can do to help alleviate the problem. There are small choices we can make daily which impact the environment, such as the food we eat, products we buy and the way we live at home. Where it is possible, start eating less meat, and use home appliances more responsibly. Buy second hand wherever possible, as most products we currently are using rely on oil. Whether it is a household appliance, or your clothing, redirecting our money to second hand over new products is a powerful way to reduce the weight on the environment. Investing in good quality items when second hand isn’t an option is another positive change to make- the fast fashion industry in particular is one of the biggest polluters on the planet. There are also many more environmentally friendly brands hitting the shopping scene which can help this cause. Most importantly however, we need to cast our electoral votes wisely, and support governments which care about our future and will commit to emission reduction schemes.
Lastly, you can work with programs and organisations like our own. Whilst big change needs to come from governmental bodies, we need people on the ground that are willing to work towards preserving our reefs until those big changes come. There will be no use in future policies to protect our corals if no one is willing to stop them from vanishing in the mean time.
We need coral reefs for food, medicine, tourism (economic gain) and coastal protection to name a few of the many benefits provided by these beautiful ecosystems. Help us protect these wonderful and ancient marine networks.
https://www.citepa.org/en/air-and-climate/pollutants-and-ghg/ghg/2137-nitrogen-trifluoride-nf3
https://www.livescience.com/37743-greenhouse-effect.html
https://www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-climate-change-k4.html
