David's theory of evolution Part Two:addendum (Evolution)

by David Turell @, Sunday, December 08, 2019, 19:43 (119 days ago) @ David Turell
edited by David Turell, Sunday, December 08, 2019, 19:58

A reminder top predators rule balance of nature:

http://nautil.us//issue/34/adaptation/the-ecologist-who-threw-starfish?utm_source=Nauti...

"just three months after he began removing the starfish, Paine could already see that the community was changing. The acorn barnacles had spread out to occupy 60 to 80 percent of the available space. But by June of 1964, a year into the experiment, the acorn barnacles were in turn being crowded out by small, but rapidly growing goose barnacles and mussels. Moreover, four species of algae had largely disappeared, and the two limpet and two chiton species had abandoned the plot. While not preyed upon by the starfish, the anemone and sponges populations had also decreased. However, the population of one small predatory snail, Thais emarginata, increased 10- to 20-fold.

"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.

***

"Estes and Palmisano saw other striking differences between the two communities around each island: Colorful rockfish, harbor seals, and bald eagles were abundant around Amchitka, but not around otter-less Shemya. They proposed that the vast differences between the two communities were driven by sea otters, which were voracious predators of sea urchins. They suggested that sea otters were keystone species whose negative regulation of sea urchin populations was key to the structure and diversity of the coastal marine community.

"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 the regulation of kelp forest by sea otter predation on herbivorous urchins was very strong support for the HSS hypothesis and for Paine’s keystone species concept.

"In ecological terms, the predatory sea otters have a cascading effect on multiple trophic levels below them. Paine coined a new term to describe the strong, top-down effects that he and others had discovered upon the removal or reintroduction of species: He called them trophic cascades.

***

"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: Proper balance with top predators means everyone survives properly and every one eats. I'm sure God understood this when when He set up the bush of life. Dhw's worry about a delay to reach humans is totally illogical in view of what we know about top predators. God chose to evolve humans and set them up as top predators as the bold above notes. All that God did was logically required.


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