Emeritus Professor John Raven, from Dundee University has a warning about the productivity of our the oceans. In 1798 Malthus published the first edition of his book on population, warning that human population growth could not grow indefinitely because resources would run out. Technological fixes to this problem are hailed as the answer but there are limits. Mobile phones, for instance, need trace elements such as indium which have to be mined and are a finite source.
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