Balance of nature: New Zealand fights back (Introduction)

by David Turell , Wednesday, August 24, 2016, 22:12 (3012 days ago) @ David Turell

My entry on extinction today shows balance of nature based on environmental changes. This article discusses how predators affect the system. in the ice ages large cats fed on young mastodons and maintained the balance:-http://blogs.scientificamerican.com/laelaps/sabercats-kept-the-world-green/?WT.mc_id=SA_DD_20160824-"The huge herbivores of the Ice Age were ecosystem engineers. Wherever they went, mastodons, sloths, bison, and their ilk changed the landscape by eating, defecating, trampling, and otherwise going about their plant-mashing business. But they were not isolated agents. Following out the engineer analogy, Ice Age megaherbivores had managers. These were the sabercats, hyenas, wolves, and other predators past.-***-"Many of the most iconic Ice Age herbivores were simply too big to kill. It's the same reason why lions don't often chase after adult elephants. Clawing into a pachyderm is a high-risk scenario, even considering the fleshy reward, and fossil evidence has suggested the same pattern held in the Pleistocene. Smilodon didn't take on adult mammoths and Megatherium, for example, but often targeted camels and bison instead. Large size was a refuge was most Pleistocene giants. But their offspring were a different story.-"In a new study surveying the effects of large carnivores stalking the Ice Age landscape, University of California, Los Angeles paleontologist Blaire Van Valkenburgh and colleagues found that the young of many large Pleistocene herbivores would have been right in the sweet spot for hungry carnivores.-***-“'nearly all Pleistocene predator guilds found outside of Australia included at least one and often two species of large sabertooth cat.” This pattern is directly related to the number of big herbivores there were to eat. Even in modern ecosystems, Van Valkenburgh and colleagues point out, the likelihood that three or more large carnivores might be present steadily increases. In addition to the herbivores creating more open habitat that give predators the opportunity to hide along the forested margins, there's simply more meat to carve up.-***-"While a solitary extant lion probably can't capture even a two-year-old baby elephant, the paleontologists found, a lone Smilodon, Homotherium, cave lion, or other large cat would have been capable of hunting a baby mammoth or mastodon in the two-to-four-year-old range. (A sabercat den full of baby mastodon bones in Texas supports this point.) The chances of the Pleistocene predators only got better if they formed a pride, and social strategy was a boon to packs of wolves and clans of hyenas, too.-***-"This is how the landscape was shaped by the subtle paw of the carnivores. Many paleontologists previously thought that Ice Age herbivores were too big to fail. That they existed at saturation levels because their size made them immune. But now Van Valkenburgh and coauthors have made a solid case that carnivores greatly influenced herbivore populations by preying on the young. This was violent, and even sad, but all a part of the constant ecological shuffle. Unchecked by carnivores, large herbivores can proliferate to destructive levels until they start eating themselves out of house and home. Smilodon, dire wolves, and other beasts of prey actually defended the plants - vegetation has no greater friend than a predator. That's how large carnivores have been keeping the world green for millions of years,.."-Comment: We have established that natural ecology always balances out, and that top predators are required to keep the balance. Humans are top predators now. we need to be careful to not disturb the balance.