The implications of our Top-Down Systems

The Silliman and Bertness article shows the importance of the trophic cascade. The authors essentially talk about how although a bottom-up approach of nutrients in a system can have an effect on an ecosystem, the main method of regulation is the delicate balance and hierarchy of the food web, with the most important players being the predators in an ecosystem. So they figured this out by creating five experimental situations with different concentrations of a snail species (Periwinkle) feeding on a primary producer called Spartina. The reason that they had these different concentrations was to essentially emulate how the populations of the snail would be with or without predators; with the higher concentration of Periwinkle indicating an absence of predators, and the lower ones a presence of predators. The experiments showed that at high densities the Spartina got eaten up to 88% greatly decreasing primary production and nutrient richness in the salt marsh.It was stated also that “grazing by snails at the same density transformed one of the most productive grassland systems in the world (up to3,700 g dry wt C per year; ref. 10) into a barren mudflat within8 months” which shows that not only does this have a major impact, but that it happens very quickly. The experiments with the lower snail concentration showed a better rate of primary production which essentially implies that an increase in predators essentially has an increase in primary production of an ecosystem.

The findings of Silliman and Bertness are very informative to scientists and any environmental decision makers because it shows us what the most impactful determinant of an environmental ecosystem is, which is the constant regulation of organisms through a trophic cascade. It was pretty surprising to me that these findings were submitted in 2002 which to me seems relatively new in the grand scheme of human ecological impact. At the end of the article it talks about how humans overfish certain areas and how this has detrimental impacts on the ecosystem because of our removal of natural predators. This got me thinking about how vast our human impact is on virtually every ecosystem in the world. And from a food stand point it raises a very interesting ethical question of buying “wild caught” fish as so called healthier options when perhaps these options are probably more detrimental to the natural environment. I also wonder if we are a necessary predator in some trophic cycles. By now we have established ourselves as predators at the top of the world food chain. So by Silliman and Bertness’s findings if we disappear or drop in population will this in fact be terrible for ecosystems around the world? Perhaps this wasn’t always the case, but maybe after we shoved ourselves at the top of these trophic levels maybe we in turn changed the populations and now are invariably involved in consuming these secondary consumers. I know for example, that hunters do a great job of maintaining and regulating deer populations and that there are times in the year when the population of game goes up and to keep it healthy we have to kill deer for the sake of the greater ecosystem. There are a host of questions that can be asked about these findings but without a doubt, Silliman and Bertness do make us question what our role is in the worlds many trophic levels should be.