5 Human Impacts on the Environment: Crash Course Ecology #10

Key Takeaways

at this point people have been studying the impacts that humans have had on the world around us for solid 50 years and while it's hard to get a handle on exactly how the choices we make every day affect the environment there's no question that our lifestyles our cars our need for more farmland and our love of all kinds of plastic stuff are putting the hurt on ecosystems all over the world human activity all by itself just people doing what they do could be responsible for the extinction of nearly a thousand plant and animal species to date most of the over the last century and even if you don't particularly care about the barar lion or the St Helena Olive or the passenger pigeon or anything else we've driven into Extinction the thing is we need these other organisms the ecosystems of the world are working very hard for us every day filtering water sucking carbon dioxide out of the air producing all the food we eat all very important ecosystem Services benefits that the natural world provides Us for free so having ecosystems and keeping them intact is important not only for the organisms who live in them but also for us the animals who rely on them for thousands and thousands of things that we could never do for ourselves over the next two episodes we're going to look at these systems and how our actions are affecting the ecosystems that we need for our survival basically we're messing up the environment six ways from Sunday but to make it easy on ourselves let's start with the top [Music] five you often to hear about all the different ways that our behavior is affecting the biosphere extinctions climate change deforestation acid rain desertification pollution and more but you're asking oh well why are all those things bad what's going on how is this stuff turning the earth into sausage I don't understand well I do understand which is why I'm qualified to make this video so let me lay it on you the services that ecosystems provide for us all the dirty work they do can be broken up into four different categories there are things that we could never ever ever do duplicate or work around no matter what kind of smarty pants technology we come up with first healthy ecosystems Provide support services that create and replenish the foundation of the Earth's biological systems these Services include recycling all of the compounds that are necessary for life through the carbon water nitrogen and phosphorus Cycles they also include other processes we've talked about before like forming new soils and producing atmospheric oxygen some ecosystems contribute more to these Services than others but none of them can get these basic jobs done unless they are intact two ecosystems also perform provisioning Services giving us the raw materials we need to live like the ocean provides food in the form of fish sticks and stuff and rivers and aquifers and other freshwater sources give us water plants and animals also yield all kinds of fiber that we use for clothing and shelter and all around us we find sources of fuel whether it's biomass in the form of grasses or wood hydr power in the form of flowing water where the carbon locked in millions of years old trees that were now re-releasing into the ATM atmosphere but I'm getting ahead of myself ecosystems also perform super important regulating Services moderating many of the Earth's systems that can get dangerous if they get out of whack like as we learned in biology fungi and other organisms take on the task of decomposing dead things in poop meanwhile plants help filter the water you drink and the air you breathe and provide flood control and they also absorb all that carbon you exhale and that your car belches out which in turn helps regulate the climate and finally number four ecosystems are just kind of awesome it's nice to be surrounded by happy plants and critters doing their business business nice robust ecosystems give us places to play scenes to inspire us and things to just discover and learn about these are their less tangible but still important cultural Services an interesting thing about ecosystem Services is that economists actually can and do calculate the monetary value they provide for Humanity if for example we had to do all of the things that ecosystems do for us it would cost us $46 trillion per year which is a lot consider considering that the output of the global economy is $66 trillion per year so yeah we should be happy that we're not we don't have to pay for all that but you'll notice that I keep saying that ecosystems can only serve up all this awesome sauce if they are intact by that I mean they specifically have to have their biodiversity intact because ecosystems are just a bunch of living and non-living things working together so unless their living parts are healthy they're basically just rocks and weather the main reason biodiversity is so important is that it makes ecosystems more resilient to that never- ending change we talked about a few weeks ago ecosystems with high biodiversity are way more resilient to disturbances than those with low biodiversity in a high biodiversity system if you take one species out of the mix it's less likely that the ecosystem will collapse take a hect a of Amazonian rainforest in that little patch of land there are more different species of plants and animal than there are in all of Europe so if a species of insect goes extinct there's less risk that the whole house of cards will fall than say in the soran desert where there are very few organ organisms so The Disappearance of one species could affect the entire ecosystem so the best way to understand our impacts on the environment is through how we affect biodiversity unfortunately it turns out that we've been doing a really bang up job of endangering some of the highest biodiversity ecosystems on the planet in some cases we're having impacts on the organisms themselves directly in other cases we're affecting biodiversity indirectly by creating one or two changes in that ecosystem that Cascade into all kinds of problems for living things first let's look at that he a of Amazonian rainforest again because even though it's one of those super resilient ecosystems we're having serious impacts on it how well first by removing a lot of what makes a forest a forest trees According to some estimates we are clear cutting around 8,000 hectares of trees a day to provide land to graze cattle on and to harvest wood to make coffee tables or whatever when you cut down a hect Aire of rainforest suddenly a place where a few thousand species used to live turns into a place where just the a handful of species live some grass some weeds maybe some rats or mice some insects and you know some cows cuz man we love cows and when you take out so many of the living things on that hectare of land a bunch of things happen for starters you're not just affecting that ecosystem but neighboring ecosystems as well for instance all those trees that were cut down provided the service of regulating the flow of all that rain that rainforests get not only by absorbing some of it but also by slowing down runoff letting the water seep into the soil before slowly making its way into streams and rivers and ultimately the ocean but when those trees are gone the water hits the land and shoots off in the nearest stream causing erosion and washing minerals and chemicals all the way to the Sea where it affects marine ecosystems and when I say affect I don't mean in a good way this my friends is what's called a Cascade effect in this case caused by deforestation one of the most obvious observable human impacts in addition to causing more flooding and changes in water quality deforestation on a large scale can lead to another impact desertification or the spread of dry unproductive Ive Landscapes but cutting dries doesn't automatically turn a forest into a desert desertification is driven Along by additional factors like overgrazing by cattle and over irrigation so how can overwatering something make it turn into a desert well when we use groundwater to irrigate crops the natural salts and the groundwater build up in the soil eventually making it so salty that nothing wants to live there over time fertile land near desert ecosystems become overtaxed and the desert spreads and this is exactly what has happened in China over the past Century where overg grazing and the cities unquenchable thirst for water have caused the GOI desert to grow by 3600 Square kilm every year now these two impacts by themselves clearly limit the biodiversity of otherwise Lush ecosystems but because they also result in fewer trees that provide the all important Services of releasing oxygen and absorbing CO2 you know what domino is going to fall next the climate carbon dioxide the principal greenhouse gas it insulates the Earth so it stands to reason that the more CO2 there is in the atmosphere the warmer the Earth will be and the thing is we're reducing the size of forests at the same time as we're unleashing all kinds of greenhouse gases by burning fossil fuels this double whammy is much of what's driving global warming as a result we're seeing decreases in the levels of polar sea ice which means less habitat for polar bears seals and seabirds more tempered animals are moving closer to the poles and hotter drier conditions are causing more grass fires and forest fires and while the climate has changed many times in the past those changes usually took place over centuries or even millennia giving organisms time to adapt or move these changes are taking place within our lifetimes and it's kind of a huge deal and it's complicated it take me at least like 10 minutes and 52 seconds to explain it all in detail which is why I did that in another video by now hopefully you can see how one human impact can lead to another and how even indirectly they can end up reducing biodiversity but it's hard to overlook the more immediate impacts we can have on ecosystems one of the more in yourface ways we affect biodiversity is by introducing non-native species either intentionally or unintentionally again there are so many examples of this that you can learn more about it in another video I did but suffice it to say whether it's Kudzu in North America or can toads in Australia invasive species have a knack for out competing or outright eating native species to the point that it rocks the world of an entire ecosystem and finally probably the most direct impact we have on biodiversity is simply overh harvesting certain organisms we're over fishing the oceans to meet growing demand for po fish species like tuna while on land we're Exterminating important Predators like wolves to protect livestock those cows again and the less diverse those ecosystems are the more vulnerable they become to disturbances including those other four impacts I just mentioned and the fact is there's a bunch more where those came from because there's a whole separate set of effects that Humanity has in the biosphere that stem simply from us putting the wrong amounts of certain stuff in the wrong place at the wrong time that's what we call pollution so tune in next time when we'll explore what it really is where exactly it's coming from and what we can do about it thank you for watching another kind of depressing episode of Crash Course ecology and thanks to everyone who helped us put it together there's a table of content over there if you want to click to review anything or the links are down below in the description and if you have any questions or comments or ideas for us please leave them on Facebook or Twitter or of course down in the comments below