Destructive Marine Heatwaves Are Wreaking Havoc On Australia’s Great Barrier Reef
Credit to Author: Carolyn Fortuna| Date: Fri, 27 Sep 2019 16:45:25 +0000
Published on September 27th, 2019 | by Carolyn Fortuna
September 27th, 2019 by Carolyn Fortuna
It’s a World Heritage site that humans have seen from outer space. It’s the planet’s biggest single structure made by living organisms. Home to 30 species of cetaceans, it is Australia’s Great Barrier Reef, and hundreds of miles of its most pristine northern sector are dead. Overheated seawater is the culprit, and we humans are responsible.
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Climate change is the greatest threat to the Great Barrier Reef and coral reefs worldwide. Current rates of greenhouse gas emissions will spur global average temperature rise, and a special report by the Intergovernmental Panel on Climate Change projects that 1.5°C – 2°C temperature rises will cause the health and viability of the Reef to diminish exponentially, with dire consequential effects on communities that depend on the Reef.
A position paper by the Australian government says that the worst is upon us. Only the strongest and fastest possible actions to decrease global greenhouse gas emissions, they argue, will reduce the risks and limit the impacts of climate change on the Reef.
In March 2017, the journal Nature published a paper showing that huge sections of an 800-kilometer (500 mile) stretch in the northern part of the reef had died the previous year due to high water temperatures, an event that the authors ascribed to the effects of global climate change.
Global analyses show climate change has contributed to a 5x increase in the frequency of severe coral bleaching events over the past 40 years. Multiple severe tropical cyclones and floods have had cumulative impacts on the Reef’s ecosystem, including seagrass meadows, coral reefs, and dugong and turtle populations. Pressures on the Reef and its ecosystem include runoff, dumping of dredging sludge, and cyclic population outbreaks of the crown-of-thorns starfish.
Other impacts such as rising sea level are projected to result in increased coastal erosion and inundation of critical nesting habitats, while changes in the patterns of ocean circulation will likely lead to shifts in the distribution and abundance of species in the Great Coral Reef.
Image retrieved from climate.gov
Global emissions of greenhouse gases such as carbon dioxide from the burning of fossil fuels, agriculture, and land clearing are causing climate change. It is estimated these human activities have driven an approximate 1°C increase in global average temperature above pre-industrial levels.
Continuing and rapid increase in global temperature increases the likelihood of marine heatwaves. Coral reef ecosystems depend on the health of reef-building coral species, which have limited capacity to endure heat stress. Increased sea temperature can directly cause mass bleaching and mortality. Associated impacts from altered weather patterns — such as more intense storms, tropical cyclones and flood events — ocean acidification, and rising sea level also damage coral reef ecosystems.
Strong global action to curb climate change is needed urgently to give the Great Barrier Reef the best its only chance of survival.
Image retrieved from Ocean Services at NOAA.gov
The widespread impacts of climate change on the Reef are already evident.
Coral reefs are important for many different reasons, including containing the most diverse ecosystems on the planet. According to the Queensland government, they:
Other reasons why they are so important include:
Reducing biodiversity through the extinction of species inevitably leads to the breakdown in ecosystem health and function. Healthy ecosystems are essential to provide us with:
Only the strongest and fastest possible action on climate change will reduce the risks and limit the impacts of climate change on the Reef. The required reduction in global greenhouse gas emissions demands an international and national response to secure a better future for the Reef.
The Great Barrier Reef Marine Park Authority outlines the following actions:
Even relatively small increases in acidity reduce the capability of corals and other calcifying organisms to build skeletons and shells, which, in turn, leads to a reduction in habitat available to support reef biodiversity. The weakening of skeletons of coral and other reef-builders further affects their capacity to resist and recover from physical damage caused by tropical cyclones.
These effects are likely to include loss of properties and infrastructure, loss of cultural and regional identity, and, unless urgent action is taken, subsequent declines in regional economies. Impacts on communities globally are likely to be significant, as more than 500 million people depend on coral reefs for their livelihoods and food security.
For the Reef and coral reefs worldwide, there is growing recognition that limiting the increase in global average temperature to 1.5°C — and ideally less — is critical to minimize significant environmental and societal costs from the loss of reef habitats. Coral reefs are projected to decline by a further 70-90% at a 1.5°C increase in temperature, with greater losses at a 2°C increase.
Due to the greenhouse gases already in the atmosphere, delays in taking strong action to reduce global carbon emissions decrease the likelihood of limiting the temperature increase to below 1.5°C. Of particular concern are projections that the Reef could be affected by bleaching events twice per decade by about 2035 and annually by about 2044 if greenhouse gas emissions continue to increase at the current rate.
If bleaching becomes more frequent and more intense, there will not be enough time for reefs to recover and persist as coral-dominated systems in their current form.
Carolyn Fortuna Carolyn Fortuna, Ph.D. is a writer, researcher, and educator with a lifelong dedication to ecojustice. She’s won awards from the Anti-Defamation League, The International Literacy Association, and The Leavy Foundation. As part of her portfolio divestment, she purchased 5 shares of Tesla stock. Please follow her on Twitter and Facebook.