Controlling Other Species' Populations - Why does it matter?

Perhaps the best known example of this is the total collapse of the 100 year old sustainable scallop fishing industry along the Atlantic Coast of the USA. This study from scientists at Dalhousie University - https://www.sciencedaily.com/releases/2007/03/070329145922.htm - found direct links between overfishing of large shark species and population booms of their prey, including the Cow Nosed Ray. The knock-on effect of this is perhaps obvious, more rays means less of whatever rays eat. Rays eat scallops. These rays ate all the scallops. So the communities depending on this industry found themselves in deep trouble and the price of scallops sky-rocketed for the rest of us. Perhaps less obvious, is where it goes from there. Rays uprooting scallops from seagrass beds causes damage to the seagrass beds - this habitat is essential for the breeding and initial life phase of many species. Without healthy seagrass, these species can't maintain their populations, causing their predators to either go hungry or find something else to eat. It's like when you rip a teeny hole in your tights - soon it's a massive ladder that just keeps on running and your tights become pretty useless. Tights may not be essential to human life. But oceans are.

Scallops are also suspension feeding bivalves - they filter water and have a measurable positive effect on its quality - https://www.nap.edu/read/12802/chapter/9 - They protect shallow waters by removing inorganic particles and phytoplankton from the water column. This buffers the effects of eutrophication, clarifies the water and transfers nutrient rich particulates to the bottom where they can be used to support seagrass beds and other habitats that form essential nurseries for thousands of species.

Without networks like these working in harmony, fundamental changes to the ocean ecosystem start to affect the movement and retention of carbon within the sea - all living things contain carbon and the sea has absorbed more than half of all carbon emissions since the industrial revolution ( http://news.nationalgeographic.com/news/2004/07/0715_040715_oceancarbon.html ) - it can take a lot. But upsetting the complex network of the ocean ecosystem beyond a certain point leads, in the words of Marine Conservationist Professor Steve Oakley, to something "hot, sour and empty".