2.3 Human Activity Impacts on Ecosystems

Overexploitation

Overexploitation is a major threat to ecosystems and therefore sustainability. It is the consumption of a natural resource at a rate greater than that natural resource can maintain itself. Overhunting of species (see "What Happened to All the Fish" as follows) is one of the clearest examples of overexploitation, but there are other forms. Land degradations are human-induced changes that impair the capacity of the land to sustain life. Deforestation and overgrazing exploit the land and result in the exceeding of sustainable yield.

What Happened to All the Fish?

Grand Banks Annual Catch (Metric Tons)

 

The Grand Banks along the shores of Newfoundland, Canada, were once so full of cod that explorer John Cabot remarked in 1497 that they appeared so thick that a person "could walk across their backs," and sailors reported to be able to catch them just by throwing buckets over the side of the ship. From 1850 to 1950, the fishing industry yielded an overall annual catch of about 200,000 tons of cod. With new technology in commercial fishing boats, catches of cod increased in the late 1950s and early 1960s, peaking at 800,000 tons in 1968. Commercial fishing was catching cod faster than their stock could replenish itself, and by 1975, the catch had declined to 300,000 tons. The catch continued at approximately this level through the 1990s but only through the use of more damaging fishing techniques. In 1992, the cod fishery off Newfoundland collapsed. It was estimated that the entire cod population in the Grand Banks at that time was only 1,700 tons. In response, Canada set an indefinite moratorium on fishing in the Grand Banks. This collapse devastated the local economy with the loss of forty thousand jobs in the fishing industry. In response, the federal government put up nearly $1 billion to assist with social welfare payments and retraining of people employed in the fishery trade.

The case of the cod in Newfoundland illustrates how the unsustainable harvesting of a resource, when the yield reduces the overall base of that resource, is not only bad for the environment but also bad for industry and for the economy. Overfishing and habitat destruction damaged nature's ability to provide fish in the Grand Banks. This resulted in a loss to a significant portion of the eastern Canadian economy and the members of the fishery communities experienced true hardship due to the overfishing. Prior to the overfishing that occurred during the second half of the twentieth century, the fish had supported seaside communities for hundreds of years.