Humans have been changing the climate for longer than we’ve been farming. We killed off the mammoths, which turned the tundra from grasslands into taiga covered in tiny low growth forest and dramatically reduced the albedo of lots of Northern Eurasia. Humans prefer grassland over forest which is part of why eucalyptus are so prevalent in Australia, they do better with fire than other trees. It has been posited that the Little Ice Age was because when 95% of the American population died there was a great deal less land management and deliberate forest fires, resulting in more than two centuries of above average carbon sequestration and a drop in temperatures.
Humans have been changing the climate for a long time.
Yes, but it is much, much, much faster now than any previous time. Plus we have the knowledge of its effects upon us directly and the ecosystem that we rely on to survive, combined with the technological knowledge & wealth in order to reduce the effects and mitigate the impact.
You come across as somebody who's trying to fallaciously prove how smart they are, so can dismiss any argument you think isn't worthy of your esteemed intellect. It's not a good look. Your username adds to the suspicion that you're just a troll.
There’s nothing to be gained here so I’ll apply the principle of conservation of energy and move on. When two arseholes blow hard all you get is a smelly room.
We've banned this account for breaking the site guidelines. Creating accounts to do that with will get your main account banned as well, so please don't do that.
That’s great, because our children will have no preconceived notions of a world with plentiful drinking water, food, and a variety of different species. To them it’ll just be normal, and they won’t know how bad our generation fucked them. It’s all about perspective. /s
> "'Chemically and culinarily, you should think of them as a wonderful hybrid between an artichoke and an egg, or an avocado and an egg may be a better comparison. Again, you ask somebody 10 years ago, "What do you do with avocados?" and nine out of ten times they're going to say guacamole. Now they're in everything, almost to a point of self-parody. Same thing with uni. They are full of fat and protein, so you can use them as a source of browning. You can incorporate them into a barbecue marinade or a yakitori marinade. You can use their fattiness to enrich doughs; they make some of the best brioche that I've ever tasted. I sweated down urchins with andouille sausage and used their fat to make probably the best dirty rice I've ever made.'"
They can accumulate toxins from bacteria or algea in their environment. I can't eat any shellfish (mollusca) because it's an instant allergy and impending vomit if I force myself to eat it.
You've got two dangers in shellfish, one is bacterial spoilage and another is domoic acid poisoning that comes from plankton metabolites concentrating up the food pyramid. I always eat uni live so that's not really an issue - actually I can't stand it in a restaurant because I've always had it straight out of the ocean and nothing compares to that. But domoic acid doesn't concentrate in them because they don't eat those plankton - you only really have that issue with mussels, some tissues in scallops, and the tomalley of crab and lobsters - and that's very seasonal and typically not an issue.
Tons of nutrient runoff into the coastline means certain beings will thrive: algae, jellyfish, and apparently urchins. We’re lucky the other substances in runoff aren’t doing even more damage.
The question I’d like to know is: why is uni still so expensive at sushi restaurants?
These purple urchin are a lot smaller than the commonly harvested red urchin, resulting in less uni. Even the urchin are starving due to overpopulation and loss of kelp.
There are only about 100 commercial operators along the California coast that are licensed to harvest and sell them. That number used to be around 500 and they have been winnowing the licenses down year over year.
It's partially related to the work needed to obtain them. There's very little edible meat in each one and the processes to obtain that seem to be largely manual.
Uni is phenomenal, but unless you're a true omnivore, I'd say it could fall into the "acquired taste" category. In some sense they're also one of the foods with the highest dynamic range. When it's good, it's heavenly, but when it's not, it is truly hork-worthy.
No one knows how to repopulate the sea stars. Marine biologists have been actively researching the causes behind the population decline for years. Some species like sun stars are now effectively extinct in the northeast Pacific ocean.
There is one marine production which, from its importance, is worthy of a particular history. It is the kelp, or Macrocystis pyrifera.
This plant grows on every rock from low-water mark to a great depth, both on the outer coast and within the channels. I believe, during the voyages of the Adventure and Beagle, not one rock near the surface was discovered which was not buoyed by this floating weed. The good service it thus affords to vessels navigating near this stormy land is evident; and it certainly has saved many a one from being wrecked. I know few things more surprising than to see this plant growing and flourishing amidst those great breakers of the western ocean, which no mass of rock, let it be ever so hard, can long resist.
The stem is round, slimy, and smooth, and seldom has a diameter of so much as an inch. A few taken together are sufficiently strong to support the weight of the large loose stones, to which in the inland channels they grow attached; and yet some of these stones were so heavy that when drawn to the surface, they could scarcely be lifted into a boat by one person. Captain Cook, in his second voyage, says, that this plant at Kerguelen Land rises from a greater depth than twenty-four fathoms; "and as it does not grow in a perpendicular direction, but makes a very acute angle with the bottom, and much of it afterwards spreads many fathoms on the surface of the sea, I am well warranted to say that some of it grows to the length of sixty fathoms and upwards." I do not suppose the stem of any other plant attains so great a length as three hundred and sixty feet, as stated by Captain Cook. Captain Fitz Roy, moreover, found it growing up from the greater depth of forty-five fathoms. The beds of this sea-weed, even when of not great breadth, make excellent natural floating breakwaters. It is quite curious to see, in an exposed harbour, how soon the waves from the open sea, as they travel through the straggling stems, sink in height, and pass into smooth water.
The number of living creatures of all Orders, whose existence intimately depends on the kelp, is wonderful. A great volume might be written, describing the inhabitants of one of these beds of sea-weed. Almost all the leaves, excepting those that float on the surface, are so thickly incrusted with corallines as to be of a white colour. We find exquisitely delicate structures, some inhabited by simple hydra-like polypi, others by more organized kinds, and beautiful compound Ascidiae. On the leaves, also, various patelliform shells, Trochi, uncovered molluscs, and some bivalves are attached. Innumerable crustacea frequent every part of the plant. On shaking the great entangled roots, a pile of small fish, shells, cuttle-fish, crabs of all orders, sea-eggs, star-fish, beautiful Holuthuriae, Planariae, and crawling nereidous animals of a multitude of forms, all fall out together.
Often as I recurred to a branch of the kelp, I never failed to discover animals of new and curious structures. In Chiloe, where the kelp does not thrive very well, the numerous shells, corallines, and crustacea are absent; but there yet remain a few of the Flustraceae, and some compound Ascidiae; the latter, however, are of different species from those in Tierra del Fuego: we see here the fucus possessing a wider range than the animals which use it as an abode. I can only compare these great aquatic forests of the southern hemisphere with the terrestrial ones in the intertropical regions.
Yet if in any country a forest was destroyed, I do not believe nearly so many species of animals would perish as would here, from the destruction of the kelp. Amidst the leaves of this plant numerous species of fish live, which nowhere else could find food or shelter; with their destruction the many cormorants and other fishing birds, the otters, seals, and porpoises, would soon perish also
A lot of comments are saying we could eat the urchins. Sure. But creating yet another mass food production from a single species is like what we did with cows - now we have an ecosystem with a single point of failure.
The only way to fix this is to have as complex and diverse a food web as possible. That way if one species goes down, like the way the sun starfish has, everything else doesn't collapse around it.
I freedive the Pacific coast on a weekly basis year-round. The little purples are actually tastier than the commercially harvested reds to me, but it's a lot less meat for just as much work. I don't see them really making this work commercially, especially as much as the states (especially California) limit commercial urchin permits.
Thing is, the environment will sort itself out. Two years ago the urchin blight was hitting SoCal extremely hard. This year isn't so bad, a lot of places have kelp coming back extremely thick, and the purples aren't creating any kind of apocalypse. While it's true that there aren't as many sea otters as there were in yesteryear there are plenty of reef fish that eat the urchins. Sheephead are very numerous and they love crunching those guys - in fact every time I gut one it's packed full of purple urchin debris. In five years I'm sure there'll be an imbalance with too many sheephead, and we'll have some other article to read and worry about.
That seems like a generalized gospel in the US : the environment will sort this out. The free market will sort this out. No worries, god's hand will sort this out.
I'm genuinely curious, are you taught this at some point ?
According to [1] and [2], Spain and California seem to have very similar levels of religious observance. Italy is substantially more religious, though.[3]
US as a whole doesn't seem to be far behind Italy though and it matters more where you grew up not that you currently live in California. As I understand people in US move a lot especially to more modern, richer areas like California bringing their upbringing with them.
Although I must admit religiosity might have different flavor in different countries. Polish flavor is less denying evolution, at least up to a human level, virtually no denying of age of earth and less feeling that God will take care of us somehow (probably influenced by our history).
Spain is not very religious.Even what look like religious manifestations from afar, are simply rooted in traditions/seen as culture. Very different from Italy, as far as I know.
Do you have a specific criticism of his post or do you just fully the hate the idea that there are systems structured such that for some set perturbations, they regain a stable equilibrium??
I hate the idea that people think the environment is a stable system. It very clearly isn't. There are literally tens of thousands of papers and studies demonstrating that it's changing and not returning to its prior state.
To argue that some change (eg sea urchin population) will return to its previous level in the face of that is stupid. I'm not saying it won't, but no one should state with confidence that it will, because we don't know.
As an environmental engineer, albeit one educated in the US, this is generally a pretty true statement provided you stop doing whatever it is that wrecked the environment to begin with.
I have seen some of the worst environmental atrocities caused by people with good intentions of "fixing it". Let it be, it's often halfway to sorting itself out if you'll just leave it alone long enough.
For a very specific and narrow definition of "sorted itself out" (I presume you mean that some wildlife has returned and some species flourish in the no-go zones) - there was a substantial amount of effort involved in minimising the ongoing harm, and people literally died as a result of the cleanup operations
To say that Chernobyl sorted itself out is to completely fail to understand what happened and what was done in the decades following it.
It would still sort itself out eventually, one way or the other. We can speed up the recovery and try to minimize the impact, but even if there's no humans left life would probably continue in some form. If some species are destroyed, others would evolve into the empty niche. That's how nature works. That's literally how we and all other life got to exist on this planet in a first place, as a replacement for someone else less lucky/efficient.
In order to save time and energy, sometimes every detail isn’t spelled out. “Sort itself out” presumably has a condition of not causing substantial harm to humans.
It’s obvious the world will keep on spinning with or without humans, or maybe not, and it’ll get eaten by the sun. But that possibility doesn’t need to be addressed every time.
For a complete and total failure of an industrial facility a death toll on par with a bad bus crash is far below the threshold of "substantial harm to humans"
Normally when something containing substances hazardous to human health and/or containing a lot of energy goes pop like that it's a lot worse. Strictly by the numbers the Chernobyl is not worthy of being called a disaster. We only hear about it because it is the worst case in its particular niche.
I must admit that I almost cry when the bunnys, blue-tits, bears and deer all together started pouring concrete and building the sarcophagous whereas singing heigh-ho.
Yeah, the argument I see most about climate change is "Do something to tackle climate change". And I wish I saw more of "Stop doing that to tackle climate change".
Both are fine, but definitely the latter is my preferred choice. Many unintended consequences can arise from adding more action on top of bad action, even if they come with good intentions.
Very religious compared to what country? Africa and South/Central America have us beat by a decent percentage.[1] Ireland, Poland, and a few of smaller European countries are 10% higher as well.
There is a difference between having an "official religion" and being religious. Most people in South America go to church, but are very irreligious. God for us is just something abstract that you accept for convenience. If you asked people if they believe that god requires them to do something, they will mostly tell that each one should care of their own life and religion should get out of their business. In the US, a good part of the population believes that religion should dictate social laws.
No, it's called paying attention and forming judgments from copious amounts of personal empirical data and drawing conclusions from that. I was pretty concerned when the kelp disappeared and the urchin barrens arrived, but it's pretty remarkable to see firsthand how the system has returned to the previous equilibrium so quickly.
Why am I the only person in this thread who has firsthand experience about this phenomena yet everyone wants to talk about it as a jumping off point for their straw-boogeymen about America, capitalism, and religiosity?
First, I appreciate the comment you made, which is fortunately at the top of the thread right now.
I don't understand why HN hasn't banned the America Bad comments by now given their prevalence in so many threads. It would not be tolerated if it were directed at most any other nation (China still gets a lot of that type of nation-level ad hominem commenting). Such low quality comments never contribute positively to a thread. People seem to throw them in as a cheap excuse to attack the US via tangents that are usually only connected to the discussion at a bare minimum level. And simultaneously they seem to often directly or indirectly insult the OP they're responding to in the process.
You seriously want to ban comments about limitations in America? Because america is really great or something? I read your comment and I think it's serious, please elaborate why comments about the us should be treated differently.
The moderation comments we post against nationalistic flamebait and slurs are the same for all countries. I've posted many such comments in response to comments talking about the US, India, China, Russia, South Africa, you name it.
If you see a comment that hasn't been moderated that should have been, the likeliest explanation is that we didn't see it. We don't (can't) read everything that gets posted here. You can help by flagging it and, in egregious cases, emailing us a heads-up at hn@ycombinator.com.
As opposite to European belief that nothing can be solved without at least one government's committee discussing it for a few years first. I'm European, but in practice I'd say Americans got it closer to the truth. Most of the things get sorted out and heal on their own just if us humans leave it alone long enough.
It might be worth considering in this discussion that there are different levels of what we refer to as an environment and levels of cause & effect.
Variations in local climate, populations booms & busts, freak weather events: these are all things that happen regardless of any global level climate change. A population fall or damage to a localised ecosystem can recover naturally. Nature is resilient and it is sometimes accurate to say that nature to return to what's typically normal for a localised ecosystem (reverting to mean).
The concern with climate change is that these events are more common and "normal" is harder/longer to return to due to a long term change in environmental variables. More storms means less time to recover; higher temperatures mean some species won't thrive where they used to. In this article there does not appear to be a strong claim that this bloom is directly casued by climate change, but the long term climate change might be making it harder for the ecosystem here to recover.
Just as a cold winter doesn't mean global warming is a myth, a localised ecological event doesn't mean that effect is permanant or signifier of how things will be elsewhere. A local view point (from the poster above) is useful in understanding this situation. For a global view, you need experts to take long term views at much lager scales than this article covers.
Solo night freedives for lobster, no deeper than 30 feet on shore dives just because it doesn't get that deep within a quarter mile of the surf. I usually stick above 50 during daytime out in the islands.
Nature
The Serengeti Rules
Season 38 Episode 2 | 53m 14s
I has some NICE biology science.
The first parts are all about starfish, mussels, sea urchins, kelp, and sea otters and how they do or do not balance.
The researchers formulate a theory of keystone species and illustrate that starfish and sea otters can be examples. Then they continue and, in fresh water lakes, count large mouth bass as a keystone species and, then, go to Africa and the Serengeti and count Wildebeest.
They propose that keystone species are a general phenomenon.
The beginning of the program, the first segment, on starfish in tide pools, shows a clever biology experiment that starts to establish the keystone idea. So, yes, without starfish, some mussels take over.
In the kelp forest of the ocean, without sea otters, the urchins take over, eat all the kelp, and the system ends up with only starving urchins. Looking at the video, the urchins do look purple.
Sure, for positive integer n and n species, have an n x n matrix A = [a_ij] where a_ij is the propensity or some such of species i to eat species j. Then get rates of predation, start with a distribution of the n species, and then with the matrix A push the distribution forward in time. Then, as just a math problem, might identify a keystone species in terms of the matrix A.
Of course, also see if the distribution converges. So, may be looking for eigenvectors with eigenvalue 1?
103 comments
[ 3.1 ms ] story [ 168 ms ] threadHumans have been changing the climate for a long time.
What rate of change is your baseline for ‘objective normality’?
If you really want to, compare the past 150 years with the previous 2000: https://www.nature.com/articles/s41586-019-1401-2
What should the rate of change be at? What should we be aiming for?
Give me a bounded interval.
Having the last word was a really poor effort at conserving energy.
https://news.ycombinator.com/newsguidelines.html
Try again?
Congratulations. You win the argument, and the internet.
Pointing out the problems without offering solutions isn't a very useful thing to do.
Edit: just tried it, I can downvote your original comment but not your replies to mine.
Is it 'getting faster' if 'much much faster' is faster than 'much faster'?
I don't have much patience for linguistic prescriptivists. If you are 'correcting' other people's sentences you understood exactly what they mean.
> "'Chemically and culinarily, you should think of them as a wonderful hybrid between an artichoke and an egg, or an avocado and an egg may be a better comparison. Again, you ask somebody 10 years ago, "What do you do with avocados?" and nine out of ten times they're going to say guacamole. Now they're in everything, almost to a point of self-parody. Same thing with uni. They are full of fat and protein, so you can use them as a source of browning. You can incorporate them into a barbecue marinade or a yakitori marinade. You can use their fattiness to enrich doughs; they make some of the best brioche that I've ever tasted. I sweated down urchins with andouille sausage and used their fat to make probably the best dirty rice I've ever made.'"
The question I’d like to know is: why is uni still so expensive at sushi restaurants?
https://www.pbs.org/wnet/nature/the-serengeti-rules-41dfru/2...
I guess you do what makes money.
This plant grows on every rock from low-water mark to a great depth, both on the outer coast and within the channels. I believe, during the voyages of the Adventure and Beagle, not one rock near the surface was discovered which was not buoyed by this floating weed. The good service it thus affords to vessels navigating near this stormy land is evident; and it certainly has saved many a one from being wrecked. I know few things more surprising than to see this plant growing and flourishing amidst those great breakers of the western ocean, which no mass of rock, let it be ever so hard, can long resist.
The stem is round, slimy, and smooth, and seldom has a diameter of so much as an inch. A few taken together are sufficiently strong to support the weight of the large loose stones, to which in the inland channels they grow attached; and yet some of these stones were so heavy that when drawn to the surface, they could scarcely be lifted into a boat by one person. Captain Cook, in his second voyage, says, that this plant at Kerguelen Land rises from a greater depth than twenty-four fathoms; "and as it does not grow in a perpendicular direction, but makes a very acute angle with the bottom, and much of it afterwards spreads many fathoms on the surface of the sea, I am well warranted to say that some of it grows to the length of sixty fathoms and upwards." I do not suppose the stem of any other plant attains so great a length as three hundred and sixty feet, as stated by Captain Cook. Captain Fitz Roy, moreover, found it growing up from the greater depth of forty-five fathoms. The beds of this sea-weed, even when of not great breadth, make excellent natural floating breakwaters. It is quite curious to see, in an exposed harbour, how soon the waves from the open sea, as they travel through the straggling stems, sink in height, and pass into smooth water.
The number of living creatures of all Orders, whose existence intimately depends on the kelp, is wonderful. A great volume might be written, describing the inhabitants of one of these beds of sea-weed. Almost all the leaves, excepting those that float on the surface, are so thickly incrusted with corallines as to be of a white colour. We find exquisitely delicate structures, some inhabited by simple hydra-like polypi, others by more organized kinds, and beautiful compound Ascidiae. On the leaves, also, various patelliform shells, Trochi, uncovered molluscs, and some bivalves are attached. Innumerable crustacea frequent every part of the plant. On shaking the great entangled roots, a pile of small fish, shells, cuttle-fish, crabs of all orders, sea-eggs, star-fish, beautiful Holuthuriae, Planariae, and crawling nereidous animals of a multitude of forms, all fall out together.
Often as I recurred to a branch of the kelp, I never failed to discover animals of new and curious structures. In Chiloe, where the kelp does not thrive very well, the numerous shells, corallines, and crustacea are absent; but there yet remain a few of the Flustraceae, and some compound Ascidiae; the latter, however, are of different species from those in Tierra del Fuego: we see here the fucus possessing a wider range than the animals which use it as an abode. I can only compare these great aquatic forests of the southern hemisphere with the terrestrial ones in the intertropical regions.
Yet if in any country a forest was destroyed, I do not believe nearly so many species of animals would perish as would here, from the destruction of the kelp. Amidst the leaves of this plant numerous species of fish live, which nowhere else could find food or shelter; with their destruction the many cormorants and other fishing birds, the otters, seals, and porpoises, would soon perish also
~ Charles Darwin, The Voyage of the Beagle (1845)
The only way to fix this is to have as complex and diverse a food web as possible. That way if one species goes down, like the way the sun starfish has, everything else doesn't collapse around it.
Thing is, the environment will sort itself out. Two years ago the urchin blight was hitting SoCal extremely hard. This year isn't so bad, a lot of places have kelp coming back extremely thick, and the purples aren't creating any kind of apocalypse. While it's true that there aren't as many sea otters as there were in yesteryear there are plenty of reef fish that eat the urchins. Sheephead are very numerous and they love crunching those guys - in fact every time I gut one it's packed full of purple urchin debris. In five years I'm sure there'll be an imbalance with too many sheephead, and we'll have some other article to read and worry about.
[1] https://en.wikipedia.org/wiki/Religion_in_Spain
[2] https://en.wikipedia.org/wiki/Demographics_of_California#Rel...
[3] https://en.wikipedia.org/wiki/Religion_in_Italy
https://en.wikipedia.org/wiki/Importance_of_religion_by_coun...
US as a whole doesn't seem to be far behind Italy though and it matters more where you grew up not that you currently live in California. As I understand people in US move a lot especially to more modern, richer areas like California bringing their upbringing with them.
Although I must admit religiosity might have different flavor in different countries. Polish flavor is less denying evolution, at least up to a human level, virtually no denying of age of earth and less feeling that God will take care of us somehow (probably influenced by our history).
For comparison, although I am not sure how well these reflect reality: https://en.wikipedia.org/wiki/Irreligion_in_Italy https://en.wikipedia.org/wiki/Irreligion_in_Spain
EDIT: I see others also replied in a similar vein.
To argue that some change (eg sea urchin population) will return to its previous level in the face of that is stupid. I'm not saying it won't, but no one should state with confidence that it will, because we don't know.
https://en.wikipedia.org/wiki/Ecological_succession#Types
I have seen some of the worst environmental atrocities caused by people with good intentions of "fixing it". Let it be, it's often halfway to sorting itself out if you'll just leave it alone long enough.
To say that Chernobyl sorted itself out is to completely fail to understand what happened and what was done in the decades following it.
It’s obvious the world will keep on spinning with or without humans, or maybe not, and it’ll get eaten by the sun. But that possibility doesn’t need to be addressed every time.
Normally when something containing substances hazardous to human health and/or containing a lot of energy goes pop like that it's a lot worse. Strictly by the numbers the Chernobyl is not worthy of being called a disaster. We only hear about it because it is the worst case in its particular niche.
https://en.wikipedia.org/wiki/Dam_failure#List_of_major_dam_...
https://en.wikipedia.org/wiki/List_of_industrial_disasters
I must admit that I almost cry when the bunnys, blue-tits, bears and deer all together started pouring concrete and building the sarcophagous whereas singing heigh-ho.
Both are fine, but definitely the latter is my preferred choice. Many unintended consequences can arise from adding more action on top of bad action, even if they come with good intentions.
[1] https://en.m.wikipedia.org/wiki/Church_attendance#Attendance...
Why am I the only person in this thread who has firsthand experience about this phenomena yet everyone wants to talk about it as a jumping off point for their straw-boogeymen about America, capitalism, and religiosity?
I don't understand why HN hasn't banned the America Bad comments by now given their prevalence in so many threads. It would not be tolerated if it were directed at most any other nation (China still gets a lot of that type of nation-level ad hominem commenting). Such low quality comments never contribute positively to a thread. People seem to throw them in as a cheap excuse to attack the US via tangents that are usually only connected to the discussion at a bare minimum level. And simultaneously they seem to often directly or indirectly insult the OP they're responding to in the process.
https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...
If you see a comment that hasn't been moderated that should have been, the likeliest explanation is that we didn't see it. We don't (can't) read everything that gets posted here. You can help by flagging it and, in egregious cases, emailing us a heads-up at hn@ycombinator.com.
Variations in local climate, populations booms & busts, freak weather events: these are all things that happen regardless of any global level climate change. A population fall or damage to a localised ecosystem can recover naturally. Nature is resilient and it is sometimes accurate to say that nature to return to what's typically normal for a localised ecosystem (reverting to mean).
The concern with climate change is that these events are more common and "normal" is harder/longer to return to due to a long term change in environmental variables. More storms means less time to recover; higher temperatures mean some species won't thrive where they used to. In this article there does not appear to be a strong claim that this bloom is directly casued by climate change, but the long term climate change might be making it harder for the ecosystem here to recover.
Just as a cold winter doesn't mean global warming is a myth, a localised ecological event doesn't mean that effect is permanant or signifier of how things will be elsewhere. A local view point (from the poster above) is useful in understanding this situation. For a global view, you need experts to take long term views at much lager scales than this article covers.
Interesting.
https://www.pbs.org/video/the-serengeti-rules-41dfru/
is
Nature The Serengeti Rules Season 38 Episode 2 | 53m 14s
I has some NICE biology science.
The first parts are all about starfish, mussels, sea urchins, kelp, and sea otters and how they do or do not balance.
The researchers formulate a theory of keystone species and illustrate that starfish and sea otters can be examples. Then they continue and, in fresh water lakes, count large mouth bass as a keystone species and, then, go to Africa and the Serengeti and count Wildebeest.
They propose that keystone species are a general phenomenon.
The beginning of the program, the first segment, on starfish in tide pools, shows a clever biology experiment that starts to establish the keystone idea. So, yes, without starfish, some mussels take over.
In the kelp forest of the ocean, without sea otters, the urchins take over, eat all the kelp, and the system ends up with only starving urchins. Looking at the video, the urchins do look purple.
Sure, for positive integer n and n species, have an n x n matrix A = [a_ij] where a_ij is the propensity or some such of species i to eat species j. Then get rates of predation, start with a distribution of the n species, and then with the matrix A push the distribution forward in time. Then, as just a math problem, might identify a keystone species in terms of the matrix A.
Of course, also see if the distribution converges. So, may be looking for eigenvectors with eigenvalue 1?