everybody its mr. Smith's and today we'll be covering topic 5.10 which is urbanization so urbanization is just the act of converting natural landscape such as forests or wetlands into urban landscapes which are cities or towns so today we'll discuss the environmental issues that occur with urbanization we'll talk about some of the causes and why it's expanding in the United States and many developed nations and then finally we'll talk about some of the solutions so our objective for the day is to be able to describe the environmental effects of urbanization we'll talk about how it can lead to something called saltwater intrusion and how it can lead to increased fossil fuel combustion and therefore co2 emission into the atmosphere will discuss how urban ization replaces pervious land with impervious land that means land that does not allow water to infiltrate into the ground and then finally we'll discuss why urban sprawl is occurring and that's this process of population distribution heading from done cities out to less dense suburbs our suggested science scale for the day is describing a disadvantage or a drawback with a potential solution for a problem so the first thing to know about urbanization is that is the removal of vegetation and natural landscape and the conversion of that natural landscape to an urban landscape so one of the problems here is that this replaces the soil the vegetation so could replace valuable ecosystems like wetlands or forests and it's going to replace them with impervious surface now impervious surface would include things like concrete and asphalt that you'd find on sidewalks and roads and buildings and impervious means that it does not allow water to infiltrate so water can't seep through the concrete into the ground beneath it it has to leave as runoff so if we look at this diagram here we'll see there's a substantial difference in the amount of runoff we produce in a city and in urban landscape versus in a natural landscape in a natural landscape as much as 50 percent of the rain water is going to either infiltrate the ground through shallow infiltration or through deep infiltration but in the city that'd be 15 percent and so the vast majority of that's going to be leaving as runoff and then we're going to get some evaporation as well so this disturbs the natural water cycle by it limiting groundwater recharge in cities and leading to lots and lots of what we call urban runoff stormwater runoff will be discussing the impacts of that and solutions to it in another video another big impact is co2 emissions so because we are producing cement and asphalt to actually build the city that process releases co2 we're also going to use a lot of machinery for construction remember those machines are on fossil fuels so that emits co2 we have deforestation because we need to clear land for the city so that's going to be the loss of future carbon sequestration those trees can't store carbon anymore after they're cut down and their decomposition after they're cut contribute even more co2 to the atmosphere and then finally as urban populations continue to grow more people produce more waste and so we need to dig more landfills into the ground and the products that we put into the landfill result in even more carbon dioxide entering the atmosphere and methane which remember is 24 times as warming as carbon dioxide another environmental issue caused by urbanization is something called saltwater intrusion so as many of the world's largest cities are located near the ocean we have a lot of population growth in coastal cities so the problem is that as the populations in these coastal cities grow they're forced to draw more and more water out of their groundwater resources what this does is lowers the water table and it decreases the amount of pressure that the groundwater has to exert back on the sea water so if we look at this diagram under normal circumstances the freshwater is at a higher level the water table is higher than seawater and so it exerts this kind of downward pressure that keeps the sea water from infiltrating in when we have excessive consumption the water table is going to be dropped the pressure and the groundwater is decreased and the saltwater is able to seep into the groundwater and that's going to contaminate this ground water source that people are using as fresh drinking water we have another scenario here where sea level rise can cause the same thing to occur so due to the warming of the atmosphere that causes the oceans to warm and something called thermal expansion occurs thermal expansion is when ocean level rises just because the molecules of water in the ocean get a tiny bit further apart and so that can raise sea level another issue that can raise sea level is the melting of polar ice caps and because these melts they add water to the ocean that just increases volume so increase the sea level so we can see here in the diagram as sea level starts to rise that salt water is able to overcome the pressure of the groundwater and it seeps into the fresh groundwater source and now it's contaminated with salt water so again as urbanization continues closer to the coast as we have population growth in urban cities that are near the coast we're gonna start to experience saltwater intrusion and that contaminates the fresh groundwater so it's no longer able to be used for drinking or for irrigation for agriculture so now we'll talk about some trends in population movement so we can see in this graph here that from 1950 to 2000 we have a dramatic shift from rural communities to urban communities and especially to suburban communities we'll talk about what that means and why it's happening one of the main causes is that people move from rural communities into urban areas for increased job opportunities for things like entertainment or cultural attractions so they're often sports teams there's big music venues there's just a lot going on in these dense urban areas that attract people to move there this can actually decrease people's individual environmental impact and that's because urban areas are more densely populated so they're more walkable it's easier to get around without driving as much typically homes are going to be smaller in these densely packed urban areas and so on a per person basis environmental impact can actually be minimized by living in more densely populated areas what we should know especially looking at this graph is that the highest growth currently is in the sub urban population and those are less densely packed areas that surround urban area so the shift in population from these dense urban areas out to the suburbs creates an issue called urban sprawl so again this is the movement now away from the densely packed urban areas out to the less dense suburbs that surround them so again examples of suburbs of Grand Rapids would be Kentwood Wyoming Forest Hills these are all less dense communities that surround the dense urban area so we'll talk about the causes for this one of the main causes is there's cheaper property values so you can buy a larger piece of land and a larger home for the same price in a suburb compared to in this densely packed city and that's because the demand for property is so much higher in these cities another issue is the affordability of cars and gasoline so they make it really easy to live out in the suburbs but still commute into the city for things like work or entertainment and then we get something called the domino effect so as you start to see your neighbors leave densely packed urban areas you're more likely to leave as well and this leads to a positive feedback loop where there are fewer residents in the city and so the tax base of the city declines when residents move out of the city they no longer pay taxes to the city so the city is forced to cut services they can't offer as many police patrols they can't offer as many bus routes they can't maintain their public parks in the same way and so what happens is more residents leave because they enjoyed these services and they're no longer available this is gonna leave businesses to start to move out into the suburbs as well because there's a lower consumer base for them there's fewer residents and then finally we get something called blight so you can see here in the diagram the neighborhood starts to decline because there are so many abandoned homes someone abandoned buildings and that just drives even more people to leave we call this a positive feedback loop because as more people leave the city budget declines even further so services are cut even more and even more businesses will leave which makes the blight even worse so the problem once it starts becomes kind of a vicious cycle where it feeds into itself and makes the urban sprawl even worse so now we'll talk about the role that highways and the gasoline tax play in this as well so as we expand the highway system it makes it easier to drive and easier to live in the suburbs but commute into the city as more people drive it increases our consumption of gasoline and there's a tax on gasoline and this gasoline tax revenue is actually used to build more highways and so as more highways are built we have an easier time commuting we drive even further that fuels more gasoline tax revenue and so we build even more highway so we have another positive feedback loop when it comes to the gasoline tax and the building of highways causing more driving causing more gasoline tax and the cycle just continues and continues so let's talk about some solutions of urban sprawl one solution is something called an urban growth boundary so this is a zoning law that a city can enact which says beyond this point there's just no more urbanization we're not building this city further out than a given point and this can kind of contain the sprawl of the city and force people to build vertically or to use old abandoned buildings that are already existing in the city and it can force cities to be more efficient with their land use and limit sprawl efficient public transportation is another way to mitigate or reduce urban sprawl if people have an effective bus system that's clean and on-time and affordable they're more likely to stay because they can decrease their cost for driving if the city is really walkable and they can easily easily get around they're more likely to stay and then finally we have something called mixed land-use so mixed land-use is this idea of combining residential business and entertainment buildings all in one area what this does is gives people a sense of place so they can live very close to where they work very close to where they go to restaurants and go to concerts and sports games and so all of this can just make a community feel more attractive to someone it can make people want to stay in the city rather than move out into the suburbs so our suggested sites go for practice up our Q 5.10 today is describing advantages disadvantages or unintended consequences of a solution so I want you to describe a possible solution to the issue of urban sprawl but then identify one possible economic consequence of this solution all right everybody thanks for tuning in today don't forget to like this video if it was helpful subscribe for future ape's video updates and check out other notes over here to the side and as always think like a mountain write like a scholar