CRF Blog

Getting serious about overfishing

by David De La Torre

In Getting serious about overfishing, The Economist reports on this important problem.

In 2013, the most recent year for which full data are available, 32% of the world’s fish stocks were being exploited beyond their sustainable limit, up from 10% in the 1970s, according to the UN’s Food and Agriculture Organisation. The amount of fish caught at sea has been pretty much flat for the past three decades, but the share of the world’s fish stocks that are being plundered unsustainably has continued to increase ….

Overfishing is not the only problem. Pollution, notably fertiliser run-off, damages a lot of marine ecosystems. There are estimated to be 5trn bits of plastic in the ocean, with over 8m tonnes of the stuff added every year. By the middle of the century the sea could contain more plastic than fish by weight, according to research done for the Ellen MacArthur Foundation.

Not all the harm comes directly from the land; some comes via the sky. Carbon dioxide accumulating in the atmosphere has so far raised the world’s average sea-surface temperature by about 0.7ºC. This has effects at depth; when seas warm up they become more stratified, making it harder for nutrients in the waters below to rise to where they are most needed by fish and plankton. Given this, it might seem fortunate that the ocean absorbs a fair bit of that carbon dioxide, thus reducing the warming. But doing so changes the ocean’s chemistry, making it more acidic. This is a particular problem for creatures with calcium-carbonate shells — which includes not just crabs and oysters but quite a lot of larvae, too. Acidification makes carbonates more likely to dissolve. [more]

For free classroom lessons related to biodiversity, see Are We Headed for a “Sixth Mass Extinction”? and also “Rachel Carson and the Modern Environmental Movement,” which is currently only in PDF and can be obtained from our Bill of Rights in Action Archive. You will have to register (if you haven’t already and it is free).