Jean Baptiste de Lamarck and Thomas Huxley believed that humanity could not cause the extinction of marine species (Roberts and Hawkins, 1999). This idea, based on the abundance of marine fisheries at the time, led them to believe that the sea was an inexhaustible source of food and wealth for societies that have access to them and that anthropogenic activities would have a minimal impact on populations (Pauly et al., 2002). This idea is still carried forward to the present day despite there being a drastic and, in some cases, irreversible changes to marine populations. This therefore means that, at present, marine species are at a far greater risk to extinction than we have so far assumed (Pauly et al., 2002).
http://www.nature.com/nature/journal/v418/n6898/full/nature01017.html
Global catches by fisherman have been declining since the 1980. Figure 1 shows fish catches between 1950-2002, and clearly show that the total number of fish caught has ben declining since the mid 1980s, or plateaued if china is included. This decline in catches indicates a decline in fish stocks globally and that action needs to be taken to reduce the anthropogenic impact on global fish stocks.
Figure 1: Graph to show global fish catches between 1950 and 2002.
What this graph does not indicate is that there have been vast technological advances within the fishing industry and that these may in fact be masking the true decline in fish stocks as fisherman are able to travel further to fish and target fish in a lower trophic level (Thurstan et al., 2010). These advances in technology and changes in the type of fish caught poses a greater threat to marine animals, one that was less prevalent throughout the history of the human interactions with marine life. As of 2003, there had been 133 reported cases of extinction within marine populations (Dulvy et al., 2003). These extinctions are entirely due to anthropogenic activities, be it through exploitation through the fishing industry, habitat loss through coastal developments, introduction of invasive species, climate change, pollution and disease. However, the association between invasive species and species extinctions are in most cases speculative, anecdotal or based upon limited field observations (Gurevitch and Padilla, 2004). This does not mean that human facilitated invasive species are solely contributing to the extinction of species however it has been seen that their presence comes hand in hand with threats such as habitat change and exploitation. According to Clavero and Garcia-Berthou (2005) 91 of the 680 extinct species identified by the IUCN are directly attributed to the presence of invasive species. This again shows that the threat of invasive species is significant, however when considered in combination with other threats, as discussed with respect to marine species above, their presence becomes a very serious issue. Thousands of years ago this issue would not have been so prevalent. Since the expansion of global population and the globalisation of the world, our impact on such threats has enhanced the vulnerability of certain species to extinction. Our role as facilitator has clearly had a dramatic impact on aquatic, combined with our increasing demands for fish in our fiscally driven global economy.
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