Many years ago, I was talking to a friend who had been at a dinner party of some sort, at which a professional economist was present. He got into conversation with this bloke and the topic eventually came around to whaling and what it was doing to world whale populations. This topic was in the news at the time, either because Australia had done something to protect whales or because Japan or some other country was pretending their whaling had something to do with science. The economist seems unperturbed that some whale species could be driven to extinction, stating that it was acceptable ‘as long as the whalers make a profit from it’. That phrase is seared into my mind even though I only heard it second hand.
This sort of attitude, although it was from quite a while ago, is still abroad among many economists and certainly many in the corporate class. The nadir of this attitude is companies and their executives maximising their profits while extracting and burning fossil fuels which will heat the planet to an extent that much of it will become uninhabitable, and many people may die, while millions more will be displaced.
In a previous article, I wrote about the Carbon cycle1. However, that is just one of many biogeochemical cycles which operate on the planet. Apart from the Carbon cycle, the most important ecologically are the Water, Nitrogen, Oxygen, Phosphorus, and Sulphur cycles. Perhaps the most overlooked cycle is that of Iron2.
Iron comprises more than 30% of the Earth’s mass, and most is deep below the crust in the core of the planet. However, it is a ubiquitous element found in the atmosphere, the ocean, in rocks and in living organisms. It is an essential element for countless cellular processes and metabolic pathways in all organisms2.
The movement of iron through the biosphere is controlled, at least in part, by the actions of plants. Although considered a micronutrient for plants, iron is an essential trace element required for the production of chlorophyll2.
Because iron is an important micronutrient used by most organisms, and is required for respiration, oxygen transport in the blood, photosynthesis, nitrogen fixation, and nitrate reduction, its availability is vital for Earth’s living organisms, especially in aquatic ecosystems. This is because, despite its relatively high abundance on Earth, iron is a minor component of aquatic systems because of its relative insolubility in water at near neutral pH. Research has demonstrated that most areas of the open ocean have surface trace metal concentrations in the range of one ion of iron ion for every fifty billion to trillion water molecules. At that vanishingly low concentration, iron is very often the limiting nutrient for primary production (e.g., photosynthesis) in large expanses of ocean2.
Now, back to whaling. In the 20th century, the largest animals that have ever existed almost became extinct. The baleen whales—the group that includes blue, right, and humpback whales—had been hunted for a few centuries, but as whaling became industrial, hunts became massacres. With explosive-tipped harpoons that were fired from cannons and factory ships that could process carcasses at sea, whalers slaughtered the giants for their oil, which was used to light lamps, lubricate cars, and make margarine. In just six decades of the 20th century, roughly the life span of a blue whale, humans took the blue-whale population down from 360,000 to just 1,000. In one century, whalers killed at least 2 million baleen whales, which together weighed twice as much as all the wild mammals on Earth today3.
Those exterminated whales left behind an enormous amount of uneaten food, mostly Antarctic krill. Consuming this prey means that whales dramatically influence their ecosystems. In the past it has been difficult to work out the magnitude of their consumption, as this has been estimated using extrapolated metabolic modelling, but lacked empirical validation. However, a recent study actually tagged 321 specimens belonging to 7 species of baleen whale in conjunction with acoustic measurements of prey density. This allowed the researchers to calculate prey consumption on a daily and annual scale across the Atlantic, Pacific and Southern oceans. Their results indicated that prey consumption was three or more times that previously estimated from the metabolic modelling. From this they estimated that in the Southern Ocean, pre-whaling populations had consumed about 430 million tonnes of Antarctic krill per annum. Surprisingly, this is twice the current estimated total biomass of Antarctic krill, and more than twice the annual global catch of marine fisheries today4.
One would expect that the mass slaughter of whales must have created a paradise for their prey? In the 1970s, many scientists assumed that the former whaling grounds would become a palce where krill would flourish, but instead, later studies showed that krill numbers had plummeted by more than 80 percent. The explanation for this seeming paradox involves the element iron which, as noted above, all living things require to function. Much of the iron in the ocean comes from dust blown over from the land, but in the Southern Ocean, where ice covers much of the land, iron is harder to come by. Much of it is locked inside the bodies of krill and other plankton. Whales unlock that iron by eating the krill and defecating. This stimulates the growth of algae which stimulates the growth of phytoplankton, which stimulates the growth of whales and so on3.
The researchers estimated that the pre-whaling population of baleen whales recycled 12,000 tonnes of iron annually in the Southern Ocean, while today it is estimated to be only one tenth of that. The recovery of baleen whale populations to pre-whaling levels could restore much ecosystem functioning4.
Most people mostly see climate change as: more and worse bushfires; more and stronger cyclones; heavier rain in some places; lack of rain elsewhere; drying up of rivers, lakes and dams; aridification of grasslands; and coral bleaching. These are all things they can see on the television news or read about in newspapers. However, the effect of other human depredations on the natural world is often overlooked because they tend not to make it into the mainstream media. This is just one example of the effect these depredations have. The industrial killing of whales in their millions has no less an effect just because it remains unseen.