(This story is authored by the lead author of a UNESCO report
A lot has changed since Captain Cook became the first European to try to navigate the Great Barrier Reef in 1770. It was the reports of Cook and naturalist Joseph Banks on their return to England that first alerted the scientific world to the existence of this biological marvel. The Great Barrier Reef is now one of the world’s most important coastal and marine tourism areas, but its future is at risk, and climate change is the primary long-term threat.
A World Heritage site since 1981, the Great Barrier Reef is one of the world’s most complex and diverse ecosystems, with at least 400 species of hard coral, 150 species of soft corals and sea fans, and more than 2,900 individual reefs and some of the most important seagrass meadows in the world.
It teems with marine life of all sorts, including more than 1600 fish species, seabirds, seahorses, whales, dolphins, crocodiles, dugongs and endangered green turtles. The reef extends for 2,300km along the coast of Queensland in Northeast Australia and has evolved over a period of 15,000 years.
The region is important for the indigenous heritage of First Australians who are Traditional Owners including Aboriginal and Torres Straits Islander people. Climate change threatens hunting and fishing as well as other traditional and cultural practices. Some sacred sites are also at risk for the more than 70 Traditional Owner groups for whom natural resources are inseparable from cultural identity.
Tourism is an important economic driver
Today, tourism (including touring, diving, beaches, sailing, fishing and cruising) is the most important economic sector in the GBR communities, contributing $5.2 billion dollarsto the Australian economy in 2012 and supporting 64,000 jobs, or about 90% of the total economic activity in the region. Visitors spent nearly 43 million total nights in the GBR region in 2012, of which nearly 2 million nights were on the reef, mainly at Cairns and the Whitsunday Islands.
Direct reef-related tourism alone contributes 4,800 jobs. Approximately 500 commercial boats operate bringing tourists out to dive and snorkel on the reef, and there can be negative impacts associated with this, including damage from fuel spills and walking and dropping anchors on fragile corals. Tourism infrastructure, along with other coastal developments, can cause habitat degradation and damaging pollution and sediment run-off. Australia is the world’s fourth largest coal producer and debate currently swirls around the risks embodied in plans to expand coal mining and coal shipping near the Great Barrier Reef.
Higher temperatures and ocean acidification threaten reefs
The biggest threat to the GBR today, and to its ecosystems services, biodiversity, heritage values and tourism economy, is climate change, including warming sea temperatures, accelerating rates of sea level rise, changing weather patterns and ocean acidification. Coral reefs worldwide are being directly impacted by warming waters and ocean acidification, and climate change is exacerbating other localized stresses.
Ocean acidification is occurring because of increased levels of carbon dioxide in the atmosphere. A significant portion of this CO2 is being absorbed by the oceans and the resulting increases in seawater acidity reduces the capacity of some marine life, such as corals, to build their calcium carbonate based skeletons. Significant drops in coral growth rate have been recorded in the last two decades for massive Porites corals on the Great Barrier Reef.
Worst ever coral bleaching
Other significant threats to the reef include coastal development, agricultural run-off pollution, port-based shipping activities, illegal fishing and outbreaks of the coral-eating crown-of-thorns starfish. Assailed by multiple threats, the status of the GBR has been assessed as being poor and deteriorating. Half of its coral cover has been lost over the last three decades.
Unusually high sea temperatures have caused nine mass coral bleaching events on the GBR since 1979, and until this year, the worst had been in 1998 and 2002 (Great Barrier Reef Marine Park Authority 2012, Steffen et al 2009, Hughes et al 2015). But higher water temperatures and a severe El Nino have been pushing corals into the danger zone all over the world in 2015-16, and the Great Barrier Reef is currently suffering the most severe bleaching episode ever recorded.
Coral bleaching occurs when higher than usual maximum temperatures disrupt the relationship between corals and the photosynthetic zooxanthelae algae that live in their tissues in a vital and mutually beneficial biological relationship. Bleaching can kill corals, but depending on the severity of the impact and local factors they can also recover. The same is true for coral damage from storms, but damaged or bleached corals and reefs need time to recover.
All indications are that bleaching events will become more frequent and tropical storms more intense with continued global warming, and that this combined with a continued trend in warming water and ocean acidification will be massively detrimental to the GBR. The current bleaching episode has affected more than 90% of the reef, with the worst damage being in the northern region where surveys have confirmed 50% mortality in some places.
Without global efforts to reduce greenhouse gas emissions coupled with local management responses to increase resilience, current projections suggest that coral cover could decline to 5-10% of the GBR by the early 2020s from 28% in 1985—a potential loss of 80% in just 40 years. Similar fears are associated with one of the other keystone ecosystems of the GBR, seagrass meadows representing 20% of the world’s 72 seagrass species.
These shallow-water habitats provide vital nursery areas for fish and shrimps, critical food resources for turtles and dugongs, and act as carbon sinks, sequestering organic carbon in marine sediments. The combination of agricultural runoff, fishery impacts and climate change may exceed seagrass beds’ natural abilityto adapt. Sea turtles too are at risk from climate change as high temperatures and sea level rise impact their breeding and nesting beaches.
A need for action
Spurred by the direct evidence of climate change already impacting the GBR, degradation of the reefs and the likelihood of much worse to come, the Australian government has begun to plan and implement actions to reduce the risk of future damage. At the core of the adaptation strategy are efforts to build ecosystem resilience, fill gaps in scientific knowledge, and monitor environmental, social and economic impacts of climate change. Collaborative management strategies are also being developed and tested with local communities, Traditional Owners, as well as with business and industry.
The GBR was also the first World Heritage property for which a comprehensive Tourism and Climate Change Action Strategy was developed. The strategy recognizes the vital importance that a healthy GBR ecosystem plays for the Australian economy and that the tourism industry must quickly come to grips with the problem.
Recommended actions include reducing direct impacts and greenhouse gas emissions from tourism companies operating on or near the reef; increased training and awareness for guides and operators; helping to raise public understanding of the threat, and; supporting scientific research and monitoring activities. The plan also calls for the industry itself to plan adaptive responses for declining reef conditions and to contribute to risk management strategies for climate disasters.
Despite these measures, international concern has continued to grow, however, that without a comprehensive response more in keeping with the scale of the threat, the GBR’s extraordinary biodiversity and natural beauty may lose its World Heritage values. The World Conservation Outlook 2014 published by IUCN (International Union for Conservation of Nature) assessed the status of the World Heritage values of the GBR as of “high concern” and experiencing a deteriorating trend.
The most recent strategy from the Australian government, the Reef 2050 Long-term Sustainability plan addressed this issue head on and has been designed to “ensure the Great Barrier Reef continues to improve on its Outstanding Universal Value every decade between now and 2050 to be a natural wonder for each successive generation to come”.
This article was originally published on Union Of Concerned Scientists Blogs . Re-produced with permission. Adam Markham is deputy director of the Climate & Energy Program and was lead author of a chapter on Australia that was dropped from a UNESCO report at the request of the Australian government.