by John Jestico –
Climate change is defined as a “change in the long-term weather patterns that characterise the regions of the world”[1]. Changes to the Earth’s climate have occurred at various points over its’ 4.7-billion-year lifespan due to natural processes. However, contemporary climate fluctuations are being driven by human processes instead. As such, I believe that climate change has been humanised- shaped into an issue that supersedes social and economic, and national borders- a distinctly global issue. Any changes in the Earth’s climate have wide-reaching and substantial impacts on most, if not all, aspects of the natural world in which we live [2]. There are many examples of this, but I will focus on the impact a warming world is having on its largest ecosystem- the oceans, and the fragile ecosystems within them.
Divers install sensors on a coral reef. Image: Curt Storlazzi, USGS Pacific Coastal and Marine Science Center. Public domain via Wikimedia Commons
The Research
“Climate Change and the Oceans – What does the future hold?” authored by Bijma et al, speculates on the future of our oceans, if the current trend of warming and acidification persists. Bijima states that our oceans are slowly becoming more acidic because of the increased amounts of atmospheric carbon being absorbed. Oceanic pH levels are currently decreasing at a rate of 0.02 pH units per decade- deceptively small, this rate of change is approximately 100 times greater than any other in the geologic past [3]. Furthermore, the ocean itself is warming; by at least 0.6 degrees in the past century [4]. Increasing warmth and acidity are critical influences on the marine ecosystem, which has grave implications for both marine and human life.
What does this mean for the ocean, and for us?
Coral reefs are an extremely important marine ecosystem, (covering 0.1% of the ocean yet support 25% of all marine species), having a significant influence on the diversity, composition, and abundance of reef-associated wildlife [4]. However, they are extremely fragile- at the mercy of the marine environment.
The survival of coral reefs depends on the establishment and healthy growth of coral polyps, (polyps being tiny, carnivorous invertebrates that form the coral itself); without this, new reefs cannot form, nor degraded reefs recover. Research conducted on the growth of coral in warmer, more acidic conditions (specifically 1 degree warmer and 0.2-0.25 pH units lower than current levels) showed that growth of coral was reduced by a third.[4] Under these conditions, it becomes increasingly difficult for damaged reefs to recover, and new reefs to take root.
This will cause a significant loss in oceanic biodiversity, as demonstrated in Figure 1- the positive correlation between fish and coral species richness: a reduction in coral species richness would be reflected in decreasing fish species, in turn reducing the biodiversity of the coral reef, causing the ecosystem to collapse, with further impacts on oceanic food webs: disrupting fish stocks, damaging fishing industries. Furthermore, coral reef tourism is worth $36 billion globally [5] – many stand to lose their livelihoods if we fail to act.
To conclude, the consequences of losing our coral reefs are devastating to both the natural and the human world; marine ecosystems will suffer from the losses to their biodiversity, and for those who base their livelihoods around those ecosystems, this is practically a death sentence. Swift, precise action must be taken to avoid further damage.
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References:
[1] S. Vijayavenkataraman, S. Iniyan, Ranko Goic (2012)A review of climate change, mitigation and adaptation,Renewable and Sustainable Energy Reviews, 16, 878-897.
[2] Middleton, N. (2018). The Global Casino : An Introduction to Environmental Issues. (6th ed.). Milton: Routledge.
[3] Jelle Bijma, Hans-O. Pörtner, Chris Yesson, Alex D. Rogers (2013) Climate change and the oceans – What does the future hold? , Marine Pollution Bulletin, 74, 495-505.
[4] Komyakova V, Munday PL, Jones GP (2013) Relative Importance of Coral Cover, Habitat Complexity and Diversity in Determining the Structure of Reef Fish Communities.
[5] Mark Spalding, Lauretta Burke, Spencer A. Wood, Joscelyne Ashpole, James Hutchison, Philine zu Ermgassen (2017), Mapping the global value and distribution of coral reef tourism, Marine Policy, 82, 104-113.
[6] Holger Anlauf, Luis D’Croz, Aaron O’Dea (2011), A corrosive concoction: The combined effects of ocean warming and acidification on the early growth of a stony coral are multiplicative, Journal of Experimental Marine Biology and Ecology, 397, 13-20.
