Troubled waters ahead on Australia’s “humpback highway”

© Shutterstock / Earth Theater / WWF

It’s a global conservation success story. Humpback whale populations, once hunted to near extinction, are bouncing back, so much so that right now, the Australian Government is assessing whether to remove the Humpback whale from its threatened species list. WWF has advised the government to hold off – for now, taking a precautionary approach and delaying this assessment by an additional five years. Chris Johnson, Global Lead for WWF’s Whales and Dolphins Initiative, explains why.

Humpback whales are one of the ocean’s most inspiring species. I’ve been lucky to study them first-hand in the Antarctic, floating beside these ocean giants in a tiny inflatable rubber boat surrounded by icebergs on a frozen sea. As Global Lead for WWF’s Whales and Dolphins Initiative, it’s my job, along with my colleagues, to protect these animals for future generations – something I am deeply passionate about. So, it’s difficult for me to comprehend that these very waters were once killing fields for this magnificent species.

Hunted to the brink of extinction

During the 20th century, more than 2 million whales were commercially harvested to near extinction in the southern hemisphere, including the western and eastern Australian subpopulations of humpback whales. When the Australian east coast whaling industry ended in 1963 – with whaling officially coming to an end in Australia in 1978 – the population of humpbacks had been reduced to a little over 100 individuals.

Following whaling’s demise and concerted conservation efforts since then, humpback whale populations are recovering, growing at a rate of about 10 per cent a year. The Australian Government has played a major role in this success story, investing over the years in science, monitoring and policy at the International Whaling Commission and other international fora. Importantly, it also established the Australian Whale Sanctuary under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), which protects whales, dolphins and porpoises in Australian waters.   

Collisions, entanglement and a cacophony of noise

These highways are becoming increasingly complex and dangerous to navigate. An ever-expanding fleet of shipping traffic – from super-tankers to cargo vessels – in humpback breeding grounds and along migration routes is increasing the risk of direct (and often fatal) collisions, with whales struggling to avoid vessels’ paths – not an easy task given some of the world’s busiest shipping lanes directly overlap with their habitat. Meanwhile, underwater noise pollution created by exponentially increasing volumes of shipping traffic is drowning out whales’ ability to communicate with each other. In other parts of the world, underwater noise from ships has forced humpback whales to change their foraging activities and singing behaviours significantly.

Add to this, the very real impacts of bycatch. Each year, along the Australian coastal humpback highways, unlucky individuals become entangled in nets or fishing gear. In an assessment of entanglements off the Western Australian coast, for example, humpback whales were the dominant species involved in more than 90 per cent of entanglements with the West Coast Rock Lobster Managed Fishery – a rope-based fishery that occurs in their migratory pathways.

Globally, an estimated 300,000 whales and dolphins are killed each year as a result of fisheries bycatch. Not only does it cause avoidable deaths and injuries, but the fishing methods can be harmful to the marine environments where they are employed.

The Southern Ocean, a climate change hot spot

Antarctic marine ecosystems are also undergoing rapid, unprecedented transformation. Migrating south from Australia to forage on krill, humpback whales contend with rapidly changing environmental conditions influenced by climate change, ocean warming and ocean acidification that are shifting prey distributions. Modelling predicts that suitable krill habitat, as well as krill populations, will shift southward by the end of the 21st century.

For baleen whales feeding almost exclusively on krill – including humpbacks – these southward shifts in krill distribution are likely to impose high energetic costs on migrating whales, with effects on body condition, reproductive fitness and population abundance. Take into account additional threats along humpback whale migration routes globally, such as oil and gas development and pollution, and it’s just too soon in our view to be declaring humpback whale populations safe.

Protecting “blue corridors”

Working with partners, WWF is mapping routes of migratory whales moving through international waters, national seas and coastal areas and between key breeding and foraging areas, analysing the overlapping emerging threats, and highlighting opportunities for governments to take action.  

Over the next few years, WWF’s Protecting Whales and Dolphins Initiative will be ramping up efforts to reduce these threats and protect important highways and “blue corridors” for migratory whales such as humpbacks so they can continue to make safe passage on their yearly journey back home to Australia. In the meantime, we urge the Australian Government to err on the side of caution and keep the humpback whale on its threatened species list for now.

Important areas for humpback whales (Megaptera novaeangliae) in Australian waters.