Balance of nature; ecologists view (Introduction)

by David Turell , Thursday, June 02, 2016, 15:45 (3096 days ago) @ David Turell

It turns out in a community of animals the top predator controls the existing diversity:-http://nautil.us/issue/37/currents/the-ecologist-who-threw-starfish-rp-"All three scientists were interested in the processes that control animal populations, and they debated explanations circulating at the time. One major school of thought was that population size was controlled by physical conditions such as the weather. Smith, Hairston, and Slobodkin (hereafter dubbed “HSS”) all doubted this idea because, if true, it meant that population sizes fluctuated randomly with the weather. Instead, the trio was convinced that biological processes must control the abundance of species in nature, at least to some degree.-***-"HSS pictured the food chain as subdivided into different levels according to the food each consumed (known as trophic levels). At the bottom were the decomposers that degrade organic debris; above them were the producers, the plants that relied on sunlight, rain, and soil nutrients; the next level were the consumers, the herbivores that ate plants; and above them the predators that ate the herbivores.-***-"Altogether, the removal of the predatory starfish had quickly reduced the diversity of the intertidal community from the original 15 species to eight.-"The results of this simple experiment were astonishing. They showed that one predator could control the composition of species in a community through its prey—affecting both animals it ate as well as animals and plants that it did not eat.-***-"In 1971, Paine was offered a trip to one of those places—Amchitka Island, a treeless island in the western part of the Aleutians. Some students were working on the kelp communities there and Paine flew out to offer his advice. Jim Estes, a student from the University of Arizona, met with Paine and described his research plans. Estes was interested in sea otters, but he was not an ecologist. He explained to Paine that he was thinking about studying how the kelp forests supported the thriving sea otter populations.-“'Jim, you are asking the wrong questions,” Paine told him. “You want to look at the three trophic levels: sea otters eat urchins, sea urchins eat kelp.”-***-"Estes' and Palmisano's observations suggested that the reintroduction of sea otters would lead to a dramatic restructuring of coastal ecosystems. Shortly after their pioneering study, the opportunity arose to test the impact of sea otters as they spread along the Alaskan coast and re-colonized various communities. In 1975, sea otters were absent from Deer Harbor in southeast Alaska. But by 1978, the animals had established themselves there, sea urchins were small and scarce, the sea bottom was littered with their remains, and tall, dense stands of kelp had sprung up.-"The presence of the otters had suppressed the urchins, which had otherwise suppressed the growth of kelp. This kind of double negative logic is widespread in biology. In this instance, otters “induce” the growth of kelp by repressing the population of sea urchins. -***-"The discovery of trophic cascades was exciting. The many indirect effects caused by the presence or absence of predators (starfish, sea otters) were surprising because they revealed previously unsuspected, indeed unimagined, connections among creatures. Who would have thought that the growth of kelp forests depended on the presence of sea otters?-***-"Indeed, trophic cascades have been discovered across the globe, where keystone predators such as wolves, lions, sharks, coyotes, starfish, and spiders shape communities. And because of their newly appreciated regulatory roles, the loss of large predators over the past century has Estes, Paine, and many other biologists deeply concerned.-"Today, of course, one predator has more influence than any other. We have created the extraordinary ecological situation where we are the top predator and the top consumer in all habitats. “Humans are certainly the overdominant keystones and will be the ultimate losers if the rules are not understood and global ecosystems continue to deteriorate,” Paine says. The only species that can regulate us is us."-Comment: A perfect reason for the bush of life. As I've stated everyone has to eat for evolution to exist and progress. Ecosystems must maintain balance. The higgildy-piggeldy has full-blown purpose behind it.