The second session of the United Nations Ocean Conference ended on July 1 in Lisbon, Portugal, local time. The General Assembly adopted a new Political Declaration on Ocean Conservation, acknowledging the failure to achieve Sustainable Development Goal 14 – Underwater Life, namely, the conservation and sustainable use of the oceans and marine resources for sustainable development. At the General Assembly, States reaffirmed their commitment to urgent action to improve the health, productivity, sustainable use and resilience of marine ecosystems. This is undoubtedly an important event for strengthening the conservation of marine biodiversity, including cetaceans.
New findings from scientific expeditions
Every summer, humpback whales in the southern hemisphere complete juvenile breeding in low-latitude waters and migrate long distances to the Antarctic waters to feed. There is a Vimass In the South Atlantic Ocean, 1,000 kilometres off the coast of South Africa, it has long been considered one of the important feeding grounds for these whale populations on their migration journeys, but there are still a large number of gaps in research on the behavior of humpback whales in the area.
To fill the research gap and understand the two humpback whale populations that migrated through the Vima Sea Mountain, the Polar Dawn research vessel carried a scientific expedition in the South Atlantic Ocean in November 2019 with a research team jointly led by the University of Exeter in the United Kingdom and the University of Stellenbosch in South Africa. During the 11-day expedition, Aurora polaris recorded a total of 600 vocal signals from humpback whales.
After studying and screening these vocal signals, in April 2022, the research team identified for the first time a new type of social vocal signal from a humpback whale.
This new vocal signal is extremely short and sounds like a "boom" sound. Such signals are often found in right whales, and humpback whales are the first to record similar signals. Scientists speculate that this vocal signal may be related to reproduction or foraging, and the significance, frequency of use, and the behavior pattern behind such vocal signals will be the next research direction.
When studying marine mammals, especially cetaceans, due to the difficulty of visual observation, scientists often use passive acoustic monitoring as a data collection method, that is, monitoring equipment is placed in a certain depth of the sea, on a ship, or attached to the surface of the cetacean body for sound.
Of the 600 social vocal signals included this time, the most common is a low whup, which is usually emitted when the mother and juvenile whales are positioned against each other, and has also been found to be used in the foraging process, which confirms that the Vima Sea Mountain is an important foraging site.
The humpback whale is a whale that loves to "sing". Male humpback whales sing according to a certain beat, scale length, and musical phrase for about 6 months a year, and the ratio of percussion to pure tone in their singing is very similar to the ratio of both in Western symphonies. © Scott Portelli
Approach the Ocean Singer
Humpback whales are one of the species most adept at communicating through vocalization, and their vocal signals are divided into two types: social sound signals and songs (hereinafter referred to as "whale songs"). Whale songs are very complex vocal signals, and their structural composition includes units, phrases, themes, and movements. Males compete with the same sex by "singing" while attracting the attention of females.
The study found that when different populations meet on the way to migration, it will start the learning process of whale songs between populations. For example, male humpback whales in eastern Australia learn whale songs from humpback whales in western Australia every few years.
In addition to being a treasure singer in the ocean, as predators at the top of the food chain, cetaceans can be a good indicator of the health of ecosystems. Multiple studies have shown that cetacean species diversity is important, and if the species of whales are unified, the food web structure of marine ecosystems will undergo a series of changes. Fish stocks, including economic species, as well as seaweed at the bottom of the food chain, can be affected and can cause serious economic losses to surrounding fisheries.
Cetaceans, especially large cetaceans, have important implications for carbon capture in the atmosphere and can help us fight climate change. Whales promote the absorption and fixation of carbon dioxide throughout their lives. A whale's lifetime carbon dioxide is comparable to the total annual carbon uptake of thousands of trees, which is related to their large size, movement up and down in the water layer, and long-distance migration. When the whale dies and sinks to the bottom of the sea, it will not only bring a large amount of carbon into the seabed and seal it for centuries, but also bring a spectacular scene of "a whale falling, everything is alive", and the bones of the whale will continue to provide nutrients and habitat for deep-sea species.
Schematic diagram of the carbon sequestration function of whales. The yellow arrows represent cetacean excrement providing nutrients to the phytoplankton; The red arrows represent that carbon dioxide in the atmosphere is absorbed by phytoplankton; Blue arrows indicate oxygen produced by phytoplankton. © GRID-Arendal 2019
In 2019, the staggering economic benefits of cetacean conservation have even caught the attention of experts at the International Monetary Fund (IMF), conservatively estimating that the average value of the ecological services and contributions to the economy (such as whale watching activities included in tourism) over the lifetime of a large cetacean is more than $2 million.
The whale's dilemma
Commercial whaling began in the 11th century, and nearly 3 million whales were killed by humans throughout the 20th century, dealing a heavy blow to cetacean populations. As calls for an end to the slaughter of cetaceans continued to rise, and thanks to the combined efforts of many forces, finally, in 1986, the International Whaling Commission (IWC) declared a global ban on commercial whaling officially entering into force.
The number of cetaceans killed has dropped dramatically since the ban on commercial whaling, but cetaceans still face a serious threat. Climate change is affecting the survival of cetaceans on a global scale, and the IPCC 's Sixth Assessment Report Task Force II reports that habitat loss caused by climate change will directly threaten the survival of marine mammals, including cetaceans.
The intensity of human activity at sea is rising, the sea surface is getting noisier, and the sound of cetaceans is drowned out in the volume of ships and sonar, and cannot be heard. Human noise disturbance can degrade the cetaceans' hearing, which in turn can affect their navigation systems and, in severe cases, lead to stranding.
In addition, factors such as vessel collisions, entanglement of fishing gear, seawater pollution, and overfishing of fishery resources are also threatening the survival of whales, putting the slowly recovering cetacean populations in danger.
Let the whale song reverberate in the sea for a long time
To protect cetaceans and reduce the existential threats to which they are exposed, human activities must be properly planned and managed. Scientific research to fully understand the distribution, behavior, and threat factors of cetaceans is the basis for scientific planning and management of human activities. In addition, it is also necessary to improve the awareness and ability of practitioners in shipping, fishing and other industries to protect the ecology, which will help reduce the impact of ship collisions, fishing net entanglement and noise on cetaceans.
In order to more effectively protect cetaceans and all types of marine life, good networks of marine protected areas are also needed. Marine protected areas are recognized as one of the most effective tools for marine biodiversity conservation, and marine ecosystems can be restored by managing and limiting human activities within protected areas.
For the general public, vigilance in life, such as keeping a distance from whale watching, reducing the use of single-use plastic products, and buying sustainable seafood, can all add to cetacean conservation. As scientists gradually demystify whale songs, our small efforts and attempts can help whale songs reverberate in the sea longer.
The United Nations Ocean Conference has come to an end, and the journey to protect the oceans still requires us to forge ahead. In a month and a half, a general assembly will be held at United Nations Headquarters in New York to sprint towards the BBNJ (Conservation and Sustainable Use of Marine Biological Diversity beyond Areas of National Jurisdiction) Agreement, which is expected to provide a powerful tool for the conservation of marine biodiversity, and we look forward to its early conclusion and the early recovery of our oceans.