Global South research: humpback whales and climate change

Humpback whale populations were decimated by whaling during the 20th century. Since the 1970s, when widespread protections outlawed humpback whaling, their numbers have started to recover. Now, however, they face a new threat: warming oceans brought about by climate change. Thanks to the recently launched Whales and Climate Program, Professor Marcello Vichi and Dr Subhra Prakash Dey from the University of Cape Town (UCT) will join scientists from seven research institutions in the Global South on a six-year project to better understand the effects of climate change on humpback whale populations and migration patterns.

For the last several years scientists and whale watching enthusiasts have noticed a puzzling new phenomenon occurring off the West Coast of South Africa: humpback whales have been gathering in their hundreds, in what have become known as super groups.

Professor Marcello Vichi, a marine scientist who specialises in understanding climate effects on marine ecosystems, explains that it is these kinds of questions that the Whales and Climate Program will seek to answer.

“Use of ocean models with whale observation networks can help us to understand how a changing climate is affecting humpback whales.”

“The concurrent use of ocean models with whale observation networks can help us to understand how a changing climate is affecting humpback whales, including phenomena such as the recent large aggregations of humpbacks, which we have observed off the Cape West Coast.”

Ground-truth data required

The Whales and Climate Change Program was spearheaded by Professor Alakendra Roychoudhury, an environmental geochemist based at Stellenbosch University (SU), in collaboration with Professor Brendan Mackey, director of the climate change response program at Griffith University in Australia.

According to Roychoudhury the Southern Ocean remains vastly unexplored.

“There is an urgent need for both seasonal and long-term observations from this vast expanse of ocean. A lack of ground-truth data provides a skewed picture in climate models, creating uncertainties. Recent observations of fluxes in carbon dioxide, a major driver in climate change, show that the Southern Ocean is behaving quite differently from what we understand from climatology and satellite data”.

The programme will include 25 researchers from five countries and a number of Antarctic voyages. Research teams from Brazil, Chile, Ecuador and Panama will investigate detailed movement of the South American west coast humpback whale population while South African-based researchers will analyse the combination of historic and more recent long-term datasets with future scenarios in multiple regions in the southern hemisphere.

Whales are ecosystem engineers

Over the past decade our understanding of the important role that whales play within ecosystems has also broadened.

Dr Olaf Meynecke, a whale researcher from Griffith University, explains that recent research shows that baleen whales are integral to re-fertilising the upper 80 metres of the ocean.

“This is the photic zone where light penetration drives primary productivity. Whales also act as recyclers, limiting iron micronutrients to the upper ocean by feeding on iron-rich Antarctic krill.”

Using data collected in different areas of the southern hemisphere will help to provide further clues as to the many-faceted way that humpback whales interact with their ecosystems.

Future scenarios for conservation

Mackey says the aim of a multi-year project such as this is to help establish a fundamental understanding of how changing ocean conditions are influencing the recovery of humpback whale populations.

“Climate change is drastically altering ecosystems and our oceans are experiencing fast changes, affecting all marine life. The project will develop adaptation scenarios for advancing whale conservation policies and programmes.”