The Circle of Life
This blog post may not be what you expect since it is not about birth and death, but rather about transformation. How does altering one aspect transform a relationship and thereby an ecosystem? Let's jump right in.
Fish are one of the most important sources of nitrogen in a coastal forest ecosystem. Scientists can find the source of nitrogen by tracking its radioisotopes, a similar process is used in carbon dating. Some trees along the banks of salmon runs have a nitrogen content that is up to 80% originally from the ocean, which means that the forest vegetation relies on the fish! Ecosystems are incredibly complex, and I'd like to explain the above sentence to provide one example of how interconnected everything is.
Wolves like to dine on deer and when wolves are killed the deer population increases. Deer like to graze on stream banks and therefore the riparian zone becomes less dense, sparse vegetation causes the stream banks to erode which then causes the water to become murkier. As the water becomes more saturated with silt and other particles caused by the erosion the oxygen levels decrease, most likely this is because the bacteria attached to the sand, silt, and organic matter particles require oxygen to function and consume great quantities of it. Less oxygen in turn causes fish populations to decrease, and then bears have less fish to eat and therefore there are less fish carcasses, heavy in nitrogen to fertilize the ground. This slows the growth of trees, ground vegetation, shrubs, and berries. Now there is less food available for the deer and their population decreases, the riparian zone starts to grow back, and we have gone 180 degrees, give it some time and nature, like fashion trends, comes full circle.
Consider what would happen if wolves had been exterminated for some time but were now newly introduced to this ecosystem. More wolves means the deer population decreases and so more berries become available for the bears. The bear population increases, they eat more fish. At the same time the riparian zone becomes fuller since there are less deer grazing at the stream's edges and nitrogen levels are high. The deer now face another danger as they rely heavily on their eyesight to detect predators and with a dense riparian zone they can't see their predators as well. Now the wolf population is really happy, until they start to run out of their favourite meal...
This was only one example where I explained why fish are important to deer, trees, and much more. We could also have discussions about how cranes are important to wild pigs, how dogs effect jellyfish, and how woodpeckers effect the life of flies. Next time you go for a walk in the woods try to think of all the systems in place that make it the way it is and take time to wonder at nature.
The ideas expressed in this blog post were taken from, "The Secret Wisdom of Nature", by Peter Wohlleben.