Why We Still Don't Understand How the Ecosystem Works

this video is kindly sponsored by surf shark the fastest and easiest vpn find out more later in the video hey 42 here as anyone who's lived through high school will tell you the world can be a ruthless place we humans seem to spend a lot of our time competing for things money power market share love and detention that last piece of birthday cake and with the world population growing faster than a herd of nymphomaniacal rabbits competition for resources is only going to get more intense but we are not only competing against each other there are thousands upon thousands of other species out there going about their daily business too two varying degrees we are also competing with all of them for basics like food water and land and so far it looks like we're crushing it according to research by the worldwide fund for nature wildlife populations across the world have declined by an average of 68 since 1970 mostly due to human impact so in the race for survival there's really no contest if this were a hundred meter sprint we'd be usain bolt and the rest of nature would be your nan on ketamine this level of domination may fill you with horror or a warm glow of genocidal pride but either way you don't need to be a genius to comprehend that running at this pace isn't sustainable since our planet has finite resources it's highly likely we won't be able to consume at our current rate forever if we're going to survive people need to find a way to conserve and replenish stocks of flora and fauna and opposite to the thinking that's guided us most of the last hundred years and beyond that does not involve getting rid of the creatures we consider our main competition for food from primary predators to pigs humans have a long history of hunting and killing goth species we see as a threat to our food supply even today this thinking underpins government policies for example after an international ban in place since 1986 japan recently announced a decision to resume commercial whaling part of the justification for this move was that whales eat huge amounts of fish as well as the fish's food tiny crustacean-like shrimp called krill the argument goes if we let whales have their way there won't be anything left for us at a glance this thinking makes sense but's research over the last few years suggests that having whales in the ocean actually increases not decreases the numbers of fish and krill and the reason why may take you completely by surprise if you enjoy documentaries about wildlife like me or anything else for that matter you should definitely use surfshark to unlock videos on streaming services that might not be available in your country surfshark runs on any device anywhere and it's packed full of features such as industry-leading uncrackable encryption ip and dns leak protection an internet kill switch of your vpn drops out and 24 7 customer support surfshark maintains a strict no logs policy and their network of 3200 servers in over 65 countries runs 100 on ram so they couldn't log your data even if they wanted to by using surfsharkvpn you can stay anonymous and secure online personally i use surfshark to watch netflix content from other countries such as the us that's usually blocked here in the uk by using the code 42 you'll benefit from an 83 discount plus free extra months for free all you have to do is click the special link in the description below don't miss out in case you hadn't noticed whales are big really big blue whales are the biggest species to ever exist on the planet yes even bigger than those dinosaurs with their ridiculously long necks and that big silly flying lizard i talked about recently they have a heart the size of a small car which can be heard beating from two miles away and some arteries are so large a small person can crawl through as you can imagine a creature this size needs to eat a lot one blue whale can eat 40 million krill a day but as you can also imagine what goes in must come out what i'm trying to say is whales are massive factories you've probably not spent too much time wondering about this that's why i'm here to ask all the really tough questions on your behalf but i think it's pretty easy to accept that whales produce a lot of pain enormous clouds of the stuff actually known as fecal plumes in a hypothetical process called the whale pump whales are fought to dive deep below the waves to search for food and then when they return to the surface to breathe they release poop plumes usually in the photic zone the upper level of the sea in which there's enough light for photosynthesis to happen because in sunlight is just more pleasant this fabulous feces is rich in iron and nitrogen which are rare minerals this high in the ocean strata and it acts as a fertilizer for microscopic marine algae called phytoplankton formed the foundation for ocean food webs acting as the food source for small fish and crustaceans who in turn act as the food source for bigger fish and so on so more whale poo equals more nutrients for phytoplankton equals more food for everyone studies suggest that ocean areas with higher whale populations have higher densities of phytoplankton fish and sea life all the way up the food chain the increased phytoplankton from the whale pump could also have other benefits phytoplankton absorb around 40 percent of the carbon from the atmosphere which is equivalent to four amazon rainforests and produce about half of the world's oxygen making it a major influencer in climate change so it could be that rather than threatening human food supply whales actually support and increase it and possibly improve the climate whilst they're at it too these huge blubbery beasts are able to have such an outsized impact due to an ecological process called a trophic cascade which describes what happens to a food chain and the ecosystem around it when a top predator is added or taken away imagine for example a simple free tier food chain with a carnivore at the top known as the predator a herbivore below called the primary consumer and plants at the bottom known as the primary producers until the middle of the 20th century it was widely believed that ecosystems were governed by primary producers essentially the size and diversity of a habitat as well as the sizes of animal populations at all stages in the food chain were determined by how much food there was at the very bottom of the pyramid usually in the form of plants or phytoplankton predators just weren't considered to play a particularly meaningful role if there were lots of primary producers there could be more primary consumers to eat them and then there would be more predators to eat them at least that's what was assumed the problem with this theory was if the entire ecosystem was regulated by food supply at the bottom of the chain what stops the animal populations in the middle from growing unstoppably and decimating all the green stuff the answer to this little puzzler emerged in the 1960s the theory of trophic cascades and along with it the concept of keystone species in a trophic cascade predators at the top of the pyramid are just as important as the producers at the bottom if you reduce the number of carnivores at the top the population of herbivores is likely to expand because there's nothing to keep it in check and more herbivores usually equals overgrazing of plants which can destroy an ecosystem because reduced vegetation causes increased soil erosion which in turn leads to silted up rivers and so on on the other hand having more predators at the top keeps the populations of herbivores under control which allows plants to flourish this is known as a top-down trophic cascade for a real world example in the kelp forests in the pacific ocean sea otters feed on sea urchins who in turn graze on the kelp in some areas otters have been extripated which means their numbers have been reduced to extinction within that region usually through excessive hunting where this has happened sea urchin populations have increased so much that the kelp has been almost totally deforested the opposite of this is known as a bottom up trophic cascade in which the primary producer at the bottom of the chain sets the limit for the rest of it because phytoplankton and plants rely on photosynthesis variations in sunlight can cause big issues affecting nutrient levels when there's an abundance of nutrients generally all trophic levels prosper together however a lack of nutrients at the bottom can decimate the entire pyramid all the way up to the carnivores at the top [Music] the most famous and arguably most interesting example of a trophy cascade is the reintroduction of grey wolves into the yellowstone national park in the united states when yellowstone was established in 1872 there was no legal protection on the wildlife in the park so tourists and hunters had the right to kill anything they wanted protective laws were put in place a few years later but predators were excluded so by 1926 wolves had been hunted to extinction in yellowstone but when the wolves disappeared populations of their number one prey the elk increased massively and hence the ecological conditions within the park drastically declined biologists were worried about erosion and the overgrazing of woody plants like willow aspen and cottonwood so population control programs were started which basically involves moving elk around or killing them because you know what us humans are like if we don't know how to fix something we just kill it these programs helped slow the negative impact on the territory but the vegetation and landscape didn't recover so in the 1940s campaigns began for gray wolves to be reintroduced into the park the general public tend to feel about wolves the same way they feel about say sharks or gonorrhea so there wasn't an overwhelming amount of support for having wolves back at yellowstone things began to change in the 1960s though the free love movements meant there was a lot more gonorrhea and better understanding of ecosystems meant there was more support for having wolves back in yellowstone in 1969 zoologist robert payne introduced the concept of the keystone species which describes an animal that's able to influence an entire habitat on its own all animals in a particular area may have their place in the trophic pyramid but not all of them can fundamentally shift the way that pyramid works keystone species have that ability they are essentially ecosystem engineers and the wolf is one of them a few short decades later in january 1995 14 wolves imported from canada were released into yellowstone national park it was a rare situation in which the trophic cascade from the reintroduction of an apex predator could be monitored and compared to the environment that existed before as a result scientists have spent the last 25 odd years studying the impact of the wolves at yellowstone and arguing about what all of it means one version of events popularized by a video that went viral no not gonorrhea was that the reintroduction of the wolves not only had an impact on the population of elk in the park but also elk behavior for the first time in 70 years elk needed to be more wary of attack and began to avoid areas where they felt vulnerable such as valleys and gorges so vegetation in those areas began to regenerate with some trees showing a five-fold increase in height in just six years deforested areas saw new growth of trees like willow aspen and cottonwood which in turn saw greater biodiversity with the return of the birds and insects who lived in those trees the resurgence of willow trees was a particularly big deal because these are favorites of beavers who eat willow and use it to build their dams and lodges like wolves beavers are a keystone species so they began to have a dramatic impact on the environment between 1996 and 2009 the number of beaver colonies in yellowstone increased from 1 to 12. and importantly they weren't restricted to the main rivers but began frequenting the smaller outlying rivers too the dams the beavers built created new habitats of their own with fish aquatic birds muskrats and other water mammals also the wolves killed coyotes which allowed populations of coyote prey to flourish which is mostly small mammals like mice and rabbits which in turn attracted species that hunt mice and rabbits like weasels foxes and birds of prey the carcasses that the wolves left behind after their feeding attracted scavengers like bald eagles and ravens bears also profited from having more carrion lying around and because there were now more shrubs there were also more berries but perhaps most amazingly of all the wolves even changed the behavior of the rivers due to more widespread vegetation growth and regenerating forests river banks were stabilized and soil erosion decreased leading to deeper less meandering rivers with more pools and less silt all of which was good for local habitats the primary message was even though there were only a few wolves to start with in 1995 the fact they were a keystone species in a trophic cascade meant they had the power to change not only the ecosystem of yellowstone national park but also the physical landscape of the environment itself that's a pretty amazing story but is it true scientists generally agree that trophic cascades are a genuine and credible phenomenon but zoologists biologists ecologists and gynecologists continue to argue about the wolves and beavers in yellowstone no one is debating whether wolves had an impact on elk populations since they returned to the park but what is questioned is whether they can be declared responsible for the shifts in vegetation and therefore the rivers the ecosystem at yellowstone national park is very complex and it's impossible to say for certain that one change at the top of the food chain is responsible for a linear change all the way at the bottom for example in the same period of time since wolves came back to the park grizzly bear and cougar populations have increased and bears specifically are a natural predator of elk calves hunting by humans is also responsible for smaller elk populations with thousands of animals killed when herds cross the border and leave the park for some parts of the year other elk have contracted diseases from the growing number of bison yellowstone has also experienced significant drought in recent years which has impacted animal populations but also revealed some facts about willow growth willows need water to flourish and the discrepancies in tree growth brought on by drought has highlighted that the rise and fall of willow density across the park can't be attributed to one single cause the science around trophic cascades is still emerging and it seems clear that stories about river-moving wolves and poop-plooming whales highly complex systems and ecological processes but they do shine light on how interconnected the different elements of the natural world are and if that's going to encourage humans to make better decisions about how and where we fit in i'm all for it thank you for watching

Channel: Thoughty2

Views: 347,120

Rating: 4.9401217 out of 5

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Length: 20min 15sec (1215 seconds)

Published: Fri Apr 30 2021