Learning from Passenger Pigeons and Cod

Passengers Pigeons once flew in flocks across the North Americas that were so large and dense they would darken the skies for hours.  At the turn of the 19^th century, their population was estimated at 5 billion and they made up ¼ of all the birds in the North Americas. 

But the land these flocks were flying over was changing rapidly and beyond all recognition. Slave colonies were being expanded which needed the cheapest protein sources possible, and nothing was cheaper than plucking tonnes of high quality protein out the sky. At the same time the industrialisation of the continent brought railways and logistics networks to allow this cheap protein to go straight to the market.

It probably remains one of the most perfect illustrations of the paradoxes that human development causes, as well as being one of the first.  The result was that the number of passenger pigeons started declining, while the slave plantations and industrial networks that supported them grew. Within a short time the numbers of passengers pigeons had fallen to a critical level, at which point the birds that had evolved to live in large social communities were unable to survive. The population decline was transformed into a population nosedive. By the turn of the century the passenger pigeons were extinct. Slavery was abolished which begs a curious question; was the collapse of slavery driven partly by the economics becoming less favourable due to the loss of a cheap protein source? The only survivor was the industrialised system which then went on to exploit other natural sources.

A similar argument played out in the cod fisheries in Newfoundland which were once world's most productive fishing grounds. The first European explorers described the waters as being so full, one just had to lower a basket into the water and it would come up filled with cod. Up to the 1950s the bounty of the Grand Banks was enough to supply local small-scale fishing, as well as feed millions of harp seals. 

But this happy picture was not to last. The Grand Banks fishery was destroyed by technological advances in fishing techniques in the 1950s and 60s. Small artisan fishing boats found themselves competing with trawlers modelled on the factory whaling ships that had devastated the last remaining whale populations.

The giant trawlers came from distant countries, attracted by the seemingly endless bounty of the fishery. Their huge nets took unprecedented amounts of fish, which they would quickly process and deep-freeze. The trawlers worked around the clock, in all but the very worst weather. In an hour they would haul up to 200 tonnes of fish; twice the amount a typical 16th century ship would catch in an entire season.

In 1968, the cod catch peaked at 800,000 tonnes. By 1975, the annual catch had fallen by more than 60 per cent. Catches of other fish species were also plummeting. In a desperate attempt to increase catches Canada extended its fishing limit for foreign vessels from 12 to 200 miles from the coast.

As cod catches declined, factory trawlers used ever more powerful sonar and satellite navigation to target what was left. This led to overall catches remaining steady throughout the 1980s. But traditional inshore fishermen noticed their catches declining. The government, most members of which owned shares in industrial fishing companies, refused to listen to them, or to the growing scientific warnings that cod was in crisis.  

Politicians also feared that cutting the quota would lead to politically unacceptable job losses, but their short-term thinking led to catastrophe.

By 1992, when the cod catch was the lowest ever measured, the government was forced to close the fishery. The moratorium put 40,000 people out of work in 5 Canadian provinces, and required a several billion dollar relief package to be disbursed to coastal communities.

In 1993 the moratorium, initially put in place for two years, was extended indefinitely. In 2003, the two main populations of Atlantic cod were added to Canada's list of endangered species. Recovery efforts are hampered by the trawling for other species that still goes on in the area, and which often leads to high levels of cod as bycatch.

Like passenger pigeons, the cod lived in huge shoals. Like the flocks of the passenger pigeons, the size of the shoals and population density was a critical factor in their survival. With a large population density, larger cod would predate on other fish and crustations that would otherwise threaten the cod nurseries.  Once the population density fell below a critical level, recovery is virtually impossible. Since the moratorium in 1993 still no reliable recovery in cod stocks have occurred, and what catches were allowed were still reported as declining in 2013.

The Passenger pigeons extinction and cod crash raise an interesting question for humanity. If these social animals have a critical population level, below which recovery is impossible and extinction becomes inevitable, what is the critical population for human societies?

Pre industrialisation, it would have been relatively low as food was abundant in the local environment and skills were honed to exploit and sustain these. Those tribes still living nomadically across the world at the beginning of the 20^th century were testimony to this, from the Australian Aboriginals to the Eskimos of the Arctic.

Post industrialisation and post climate change collapse, a very different scenario will emerge. Little natural environment will be left which can be exploited and sustaining this will be an almost impossible job. High quality food that was once free, such as passenger pigeons which could be plucked out of the sky or cod that could be scooped out of the sea, has already long since gone and will not return in a post climate change collapse environment. What foods we have today are already energy intensive and dependent on fossil fuel. In a post collapse society they will be even more so. This in turns means that a fossil fuel industry must be kept going which will be impossible without a large population to provide the equipment and manufacturing infrastructure.

So the dilemma of the passenger pigeons and cod stocks comes to haunt us. On the best and most optimistic assumption, the sustainable global population is considerably less than 1 billion if any degree of industrialisation is be maintained, most likely in the order of no more than 10 million. Once climate collapse hits us, it is maybe as low as 1 million people scratching out a living around the Arctic. However, if this is below the critical level that is needed for survival then that small band of survivors will succumb. So climate change imposes two conflicting targets, the sustainable population must go down while the critical level for long term survival goes up. Once these two levels pass each other, eventual extinction is unavoidable. 

See The Vortex of Violence and why we are losing the war on climate change