See full version: The reef’s greatest threats
Climate change is the Great Barrier Reef’s biggest threat, causing rising sea temperatures, ocean acidification, and extreme weather events. The sequential mass coral bleaching we are witnessing on the Great Barrier Reef is the literal effect of climate change.
In 2015 nearly all the countries of the world signed the Paris Agreement on climate change, this set the ambition of keeping globally average temperature rises at 1.5°C. To hit this target we need to massively accelerate the transition away from carbon intensive energy such as coal and, secure major reductions in wasteful material use. To achieve this will require communities and businesses to engage.
Tons of plastic waste end up in our ocean every year; smothering coral and killing wildlife. But it's not the only form of waste devastating our reef. Sediment run off, which is of a result of agriculture, urban development and deforestation, ruins our reef’s water quality. This makes our reef more vulnerable to local stresses, like the crown-of-thorns starfish. more
Do your part to help improve overall coral reef condition.
Climate change will affect coral reef ecosystems, through sea level rise, changes to the frequency and intensity of tropical storms, and altered ocean circulation patterns. When combined, all of these impacts dramatically alter ecosystem function, as well as the goods and services coral reef ecosystems provide to people around the globe. more
Many serious coral reef ecosystem stressors originate from land-based sources, most notably toxicants, sediments, and nutrients.
As temperatures rise, mass coral bleaching events and infectious disease outbreaks are becoming more frequent. Additionally, carbon dioxide absorbed into the ocean from the atmosphere has already begun to reduce calcification rates in reef-building and reef-associated organisms by altering seawater chemistry through decreases in pH. This process is called ocean acidification. more
Contributing factors that increase greenhouse gases in the atmosphere include burning fossil fuels for heat and energy, producing some industrial products, raising livestock, fertilizing crops, and deforestation. Climate change leads to: [links]
Increased greenhouse gases from human activities result in climate change and ocean acidification. Climate change = ocean change. The world's ocean is a massive sink that absorbs carbon dioxide (CO2). Although this has slowed global warming, it is also changing ocean chemistry. here
In Australia, the iconic Great Barrier Reef’s long-term outlook has been downgraded in a grim new report by The Great Barrier Reef Marine Park Authority that warned businesses to “prepare for change” and changed the reef’s overall outlook from “poor” to “very poor”.
This affects the ecological balance of coral reef communities, warping the food chain and causing effects far beyond the directly overfished population. more
Live coral is removed from reefs for use as bricks, road-fill, or cement for new buildings. Corals are also sold as souvenirs to tourists and to exporters who don’t know or don’t care about the longer term damage done.
Careless boating, diving, snorkeling, and fishing happens around the world, with people touching reefs, stirring up sediment, collecting coral, and dropping anchors on reefs. Some tourist resorts and infrastructure have been built directly on top of reefs, and some resorts empty their sewage or other wastes directly into water surrounding coral reefs. more
Erosion caused by construction (both along coasts and inland), mining, logging, and farming is leading to increased sediment in rivers. This ends up in the ocean, where it can ‘smother’ corals by depriving them of the light needed to survive. The destruction of mangrove forests, which normally trap large amounts of sediment, is exacerbating the problem. [links]
These include cyanide fishing, blast or dynamite fishing, bottom trawling, and muro-ami (banging on the reef with sticks). Bottom-trawling is one of the greatest threats to cold-water coral reefs. here
A plastic bag caught on a coral reef. Image credit: Richard Whitcombe/Shutterstock
The devastating effect of blast fishing on a coral reef. Image credit: cdelacy/Shutterstock here
Other climate change impacts like rising sea levels, stronger and more frequent tropical storms, and altered ocean circulation patterns (El Nino) also severely affect the coral reefs. Due to the rise in sea levels, the coral reefs are predicted to end up much deeper underwater thereby receiving much less sunlight and growing more slowly. The stronger tropical storms cause much larger and more powerful waves which can break the coral branches, overturn the coral colonies and destroy the reef structure. here
Sediments can enter water bodies through various coastal development activities like mining, farming, logging, and building projects, and urban stormwater runoff. Sediments that are deposited on coral reefs can smother corals, thereby impeding coral growth and reproduction, posing a severe threat to the health of the coral reefs. An increased volume of suspended sediments lowers the water quality and the opaque waters in turn drastically reduce the amount of sunlight reaching the coral reefs and the lower benthic ecosystems.
Nitrogen-rich fertilizers, animal wastes, human sewage, and untreated industrial effluents trigger the explosive growth of harmful marine algae that blocks the sunlight and starves the water of oxygen, resulting in an imbalance in the marine ecosystem. The excess nutrients also support the growth of life-threatening microorganisms like bacteria or fungi, that can be pathogenic to the corals and make them more susceptible to diseases. Similarly, hot water released from thermal plants and oil spills can also be highly detrimental to the health of the coral reefs. [links]