Why is that I might hear someone say, I would also hear that I am stupid or naive too. Why. Because the average run for a species is a million years, then they get replaced or they evolve. If a few unimportant spots on a food web go vacant, they will get filled by another creature, or they will be filled by already existing animals that learn to fill that need. If there is an exploitable resource, something will exploit it. Eventually. That is the key word. This is what evolution is, resource exploitation.
What scares me is elimination of trophies levels, particularly the lower ones. Like say the Asian Carp. The Asian Carp is a vegetarian and when it gets big, nothing eats it, and it gets very big. A lake has a very simple food web composed of fish primarily. It starts with the Sun. The sun feeds the plants, algae and phytoplankton. The zooplankton eats the phytoplankton and algae and vegetarian fish eat the plants. Minnows eat the zooplankton, small fish is eaten by bigger fishe until there is only a top predator fish. The Asian Carp would threaten this food chain by feeding on the plants, algae and phytoplankton in all its sizes meaning less food for the zooplankton and the minnows and everything else. I don't eat fish, but I know that less or no pike, pickerel, bass, trout or other large predator fish would be bad, because the fewer species at a specific level means that the food web is more vulnerable to a disease or disaster.
If all the top predators in the world disappeared, the food web might fluctuate wildly between years of over population, starvation and too much food availible, all the tropic levels would be affected this way until the food web stabilizes at a new equilibrium level. As the new top wanes and waxes, the mid levels wane and wax accordingly, over population above means near total elimination of the lower levels, lower upper levels mean a rebound of the lower levels.
The same is true if one lower level trophic levels is eliminated. Except if it is the only or the biggest species on a trophic level. Then it all falls apart. Losing one or a few species on a healthy food web will not cause the structure to collapse, but it will weaken the health of the food web. Elimination of a few species on a weakened food web can cause it to collapse, but only as far down as the disruption goes.
Eliminate the Sun, everything dies. Eliminate all the plants, everything dies. Eliminate the plant eaters, the plants live and everything else dies. Eliminate the top predators and everything lower survives. When you understand this, the elimination of the polar bear, or the wolf, or the lion, tiger or anything like that, is not a serious problem. It is a shame, but not a problem. If we humans continue to affect the world with no self checking, we can wreck every ecosystem and food web on the planet, but we can't destroy them. Even the worst case scenario, acidification of the oceans killing the pH sensitive oxygen producers and oxygen production is reduced to 50%, life on this planet will not end. Life evolved on this Earth that survived similar evolutionary bottlenecks and some of their ancestors exist today.
Survivors of that extinction include a branch of reptiles that include, Crocodiles and dinosaurs. It does not include Mammals. It does include birds. If we eliminate that trophic species, we may die. Humans can live with 7% oxygen but we don't move so well below 14% oxygen. Surprisingly plants don't work well in low oxygen either. Birds and the few other species would be virtually unaffected. The scavenger birds would initially do well the vegetarian birds would do well, the birds of prey would need to re-balance. Scavengers would need to diversify and either hunt or die off.
Interestingly fires to not burn well in 10% oxygen. The result would be is that dead plants would rot but not burn meaning the land and marshes would become carbon sinks. This would reverse the carbon problem we have now. The oceans would give up their carbon as the air loses its, the oceans would de-acidify and and if any form of the phytoplankton remained they would be able to flourish. If not the Earth might recover with Algae. The Birds would like the Darwin Finches, move into different roles. Birds would in very short order start to take up the roles that were vacated by the Mammals. There would not be a polar bear, but there might be a giant non flying owl that hunts penguins that live in the arctic. There might be large sea going Crocodile that never goes on land. It might eat plankton. A whale shark may have become larger or smaller. The point is that the world will do fine, even if we fuck everything up. The other point is that it will do well without us too. It is OUR choice wether we are present on this planet and it is our choice if we can live in the open.
This post was inspired by listening to a podcast of Science for the People, "Where does the Camel Belong?" http://www.scienceforthepeople.ca/episodes/where-do-camels-belong
It is about a book about the science of invasive species and asks the question: Are species invasions really bad? The answer is no, not really. Some are bad but most are neutral. And trying to do something about an invasive species after it has escaped, is pointless. The book chronicles a few of the many thousand species invasions and some of the efforts to contain and eradicate the offending species, and they have all failed. Even the fool proof plans have been foiled by nature.
For me, I hear something and it triggers something in my head and it rarely has little to do with the trigger, if you were wondering how the first part works with the inspiration.
It is important to realize that when an invasive species enters a food web that everything around it does not recognize it and ignores it, until they know it is not poisonous to them and they begin to exploit it. The Asian Carp, for example, likes warmer waters, so the cold Great Lakes may stunt its growth and the carp minnows may be food for longer and keep the population in check. As climate change works it's magic on the environment and warms the Great Lakes, it may warm faster than the cold adapted fish living their can adapt to the new ecosystem and the Carp may then flourish where the other animals cannot. A parasite that the cold water fish have, that they can live with and survive may infect the Carp and they might have no protection to it and that could limit their growth. The point is that there are possibly hundreds of reasons why the invasive fish might be kept in check without our intervention. Zebra Mussels another example. They invaded the Great Lakes years ago and they were going to be the bane of the lakes, until some animal, group of animals started eating them.
The book author makes the point that Humans want the world to stay the same as it was when they were born—not the way it was before humans got involved. Camels evolved in North America, they lived in North America for 40 million years, then a land bridge to South America developed and many Camels invaded there, four survive there today. The Bering land bridge opened up and two species of camel crossed and landed in Asia and Africa. Then another invasive animal crossed the same land bridge and killed all the camels in North America. Where do Camels belong?
The House Cat belongs in Africa where it evolved? The Cow belongs in Europe? Wheat belongs only in Iraq? Sugar, cotton and cannabis only belong in India? Horses in the mid east? Humans in Africa? Potatoes in the Andes? Apples and carrots in Afghanistan? Do you see it? The Polynesians carried Rats in cages with them on long journeys to release them on the islands they went to so they could have food to eat when they came back. We bring cats with us where ever we go, because we like them. They kill rats, well they kill everything smaller than them. We will put a stop to an air turbine project because it will kill a thousand birds a year, but the neighbour's twenty barn cats will kill a hundreds of birds apiece every year, but we don't stop them. And we get angry about an animal that hunts and kills the cats.
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