Which august international body celebrated its 70th birthday by paying special attention to faecal plumes? And what, you might ask, are these plumes?
Blue whale in the Gulf of California. Photo credit: (c) Fabian Ritter
The International Whaling Commission is the body in question and at its recent meeting in Portoroz, Slovenia, for the first time ever it talked about the positive contribution made by whales to ecosystems. Specifically this relates to the ways in which whales enhance natural systems predominantly by bringing nutrients to them in their dung. This discussion, focused around a resolution led by Chile, represents real progress for a body originally set up to manage the killing of whales for oil and meat.
The discussion of dung marks a refreshing change from discussions focusing on how killing and culling whales might benefit fisheries interests. That's kind of an old topic for the IWC. Specifically, the notion that because whales are big, they must eat a lot of fish is a poor and artless caricature of how marine ecosystems function. Similarly, the notion that any fish that whales consume would otherwise have simply lept into the nets of fishermen, does not hold water. The great whales, for example, tend to mainly feed in polar waters away from fishing fleets - sperm whales feed at depth mainly on schooling squid, and many whale species eat marine animals that we do not take. I don't want to oversimplify something that is actually complex - and marine ecosystems certainly are - and there may be problematic interactions between marine mammals and fisheries in some places, but the notion that the whales are 'eating all our fish' is, simply put, a distraction from the real culprits for declining fish stocks.
Within the IWC it is often the developing nations allied with the whaling nations that comment on whales as a threat to their 'food security,' but this view has been discredited by leading fisheries biologists Daniel Pauly and Wilf Swartz in a report for the Humane Society International :
"The rapid economic integration of the world fisheries market over the latter half of the 20th century, combined with the expansion of the distant-water fisheries of the developed countries, fuelled by government subsidies, has resulted in the acceleration of the trend wherein fish caught along the coast of developing countries gravitate toward the markets of affluent developed countries. Indeed, one can speak of fish migrating from 'the more needy to the less needy.' Our analysis, which identified the final destinations of the fish caught within the Exclusive Economic Zones (EEZs) of the coastal countries in the South Pacific, Caribbean, and West Africa, shows that in all three regions, domestic markets accounted for less than half of the catch, with a majority of the catch supplying markets of affluent countries in the EU, Japan, North America, and increasingly China. The issues of economic development and food security in developing countries are multifaceted. The necessary debates, however, do not benefit from the confusion that the 'whales-eat-our-fish' argument generates."
So now, thanks to the 'Ecosystems Functioning' resolution brought by Chile and several other nations, the Commission is being asked to conceptualize whales in another way; are they actually a benefit to ecosystems? In fact, there is considerable evidence that they move nutrients from their feeding grounds to the breeding grounds and also from deeper in the water up into the light where their dung can fertilize the growth of plant plankton.
This is how marine biologists Joe Roman and James McCarthy put it in their landmark 2010 paper:
"It is well known that microbes, zooplankton, and fish are important sources of recycled nitrogen in coastal waters, yet marine mammals have largely been ignored or dismissed in this cycle. Using field measurements and population data, we find that marine mammals can enhance primary productivity in their feeding areas by concentrating nitrogen near the surface through the release of flocculent fecal plumes."
For example, according to Roman and McCarthy, whales and seals may be responsible for replenishing 23,000 metric tons of nitrogen per year in the Gulf of Maine's euphotic or sunlight zone (where photosynthesis occurs), "more than the input of all rivers combined."
This "whale pump" effect played a much larger role before the commercial killing of whales began, a time when marine mammal recycling of nitrogen was likely more than three times atmospheric nitrogen input. Notwithstanding, even with reduced populations, marine mammals provide an important ecosystem service by sustaining productivity wherever they are present in high densities.
There is even more to the potential positive contributions from whales to marine ecosystems than this. Consider how much carbon is locked in their huge bodies... consider that when they die this is often taken down into the abyss. In this case, the whales are like a 'swimming rainforest', locking away carbon and helping to counter climate change.
The IWC resolution calling for consideration of their roles in ecosystems productivity is modest in its request but huge in its implications for our relations with these animals