A new study has found that the damage caused by human activity to some of the world’s iconic coral reefs in the past 30 years is greater than at any time in the last 220 000 years.
Research by Associate Professor John Pandolfi, a Chief Investigator in the ARC Centre of Excellence for Coral Reef Studies (CoECRS) and the University of Queensland, sounds a warning that the world’s reefs have never experienced changes quite like the ones they are now facing.
Degraded reef in same Caribbean location, post 1980, covered by seaweed (rather than coral)
The paper published in the science journal ‘Ecology Letters’ found that coral reefs in the Caribbean island Barbados remained very much the same over a period of almost 100 000 years before humans appeared there. The startling finding however, is that the modern day reefs are now vastly different and dominated by completely different species compared to anything seen in its past.
“The reefs have shown remarkable persistence over tens of thousands of years,” says A/Prof. Pandolfi. “Our biggest fear is that humans have pushed them to a completely different state where they are far more vulnerable and susceptible to change than ever before. We have to be on guard.”
A/Prof. Pandolfi’s study looked at the preserved remains of entire coral reef communities that lived in the Caribbean up to 220 000 years ago. By looking at these coral reefs “frozen in time” he is able to see exactly what made up the structure of the ancient reef – the individual coral species and their abundances.
By comparing the structure of coral reef communities at four periods over almost 100 000 years he found that they were all remarkably similar. In each period the same species predominated and occurred in very similar numbers.
The four reefs built upward during sea level rise after sea level falls; an event where the community is completely wiped out as geological movements push the reef above the surface, and expose new seafloor to be recolonised. On each occasion the coral reef returned to a very similar community structure as before – a testament to its resilience to change.
However, indications that Caribbean coral reef communities persisted through hundreds of thousands of years of hurricane, climate and sea level fluctuations does not mean that we can assume that they will always persist, especially in the face of human impacts, he cautions.
“In the past you would have seen an overwhelming dominance of Elkhorn coral…. It was one of the most beautiful and striking features of the Caribbean reefs in [the distant past],” says Pandolfi, “now, [that species] has virtually disappeared and the same reefs are dominated by algae and seaweed.
“There are precious few large fish, turtles, dugongs, or sharks. It is totally different to the past.”
So different in fact that the once-persistent community structure has not returned for the past 3 decades. The species that once dominated are now almost completely gone and the structure of the community is like nothing Pandolfi has recorded in the reef’s past.
The dramatic change in Barbados and throughout the Caribbean is due largely to overfishing, erosion and coastal land clearing – the same sort of events impacting reefs worldwide, including the Great Barrier Reef (GBR).
The study warns that strong management efforts must be made to ensure that coral reef communities like the GBR remain fighting fit.
“This study is a warning bell that if Australia is not proactive in it’s coral reef management we will see similar changes in the GBR,” says Pandolfi. “If our reefs are going to survive the impacts of climate change, they have to be at the peak of their health.”
A/Prof. Pandolfi says Australia is uniquely positioned to set the standard for reef preservation worldwide and that research centers such as CoECRS are providing expertise to help protect our reefs and the reefs of our neighbours.
Associate Professor John Pandolfi, Chief Investigator, CoECRS, +61 7 3365 3050 mobile +61 0400 982 301
Professor Terry Hughes, Director, CoECRS, +61 7 4781 4000
Jenny Lappin, CoECRS, +61 7 4781 4222
Jan King, UQ Communications Manager, +61 7 3365 1120