[Music] hi awesome ap environmental science students this is mrs williams of science panda and today we are going to do the review of unit 9 which is the global change unit that includes topics such as climate change global warming and biodiversity issues stratospheric ozone is what we would consider the good kind of ozone it is ozone or o3 that is in the atmosphere to help absorb dangerous high-energy uv radiation uv radiation is the same kind of radiation that can cause sunburn can give you skin cancer over time and can also cause eye damage which is why we need to use things like sunblock now ozone if you look at the right side of the screen is formed through a specific kind of reaction so let's go through that ozone is going to be formed when uv radiation actually strikes oxygen molecules which is o2 and splits that oxygen molecule into two atmospheric oxygens or single o atoms notice that that atmospheric oxygen then reacts so follow the red arrow down on the right it's going to react with o2 to form o3 which is the ozone molecule now the reason that we're discussing ozone in general is because ozone depletion is a serious climate change issue so ozone depletion was first discovered in 1985 and it was discovered because there was basically a hole it was a giant hole in our ozone layer or thinning of ozone that formed over the antarctic pole so the south pole of the earth this thinning occurs seasonally and it's actually caused by man-made chemicals and this is why we discussed it in an environmental science course is it's anthropogenic it's caused by humans these chemicals are usually chemicals that are from the halogen family and they include things such as chlorine fluorine and bromine chlorine though is our primary concern when it comes to ozone depletion because chlorine is the major damaging component of cfcs or chlorofluorocarbons these are found in aerosols refrigerants and in manufacturing processes and they have been removed from typical use due to the montreal protocol we'll take a look at that in just a minute now if you look at our chemical formula on the right side of the screen this shows the reaction that chlorofluorocarbons cause that leads to ozone depletion so what ends up happening is that uv radiation which is naturally just from the sun in the atmosphere is going to cause our cfcs to decompose and that decomposition process releases chlorine which then reacts with ozone or o3 and it forms chlorine monoxide or clo now that chlorine monoxide is going to continue causing damage in the atmosphere because it will go react with other ozone molecules once it reacts with other ozone molecules it actually breaks it down and so what we're left with is cl plus two oxygen molecules now those oxygen molecules are great but they're not ozone and ozone is what we actually need to protect us from uv radiation so since the ozone layer thinning was discovered or the ozone hole as it's often called we have figured out a few ways to try to prevent further worsening of this problem one of them was to make sure we get rid of cfcs as much as possible this was done through the montreal protocol which was written in the 80s to help protect stratospheric ozone from further depletion by trying to phase out cfcs and replace them with other chemicals we could use as refrigerant and aerosol propellants and so on one of those is hfcs and hfcs are hydrofluorocarbons which are often used instead of cfcs they don't cause ozone depletion but they are very strong greenhouse gases meaning they do still retain heat in the atmosphere we'll talk more about greenhouse gases in the greenhouse effect in just a minute the reason it's so important for us to make sure that we are reducing this ozone depletion is to avoid the effects of uv radiation because remember that the ozone layer does protect us from that radiation so by trying to protect the ozone layer we are also helping protect humans animals and other organisms from incidences of sunburn skin damage skin cancer and eye damage such as cataracts so let's get into some details about what the greenhouse gases are and what the greenhouse effect is so first thing to know is that the greenhouse effect is naturally occurring it is supposed to be there it's what actually keeps our planet warm so what we will have is heat from the sun in the form of infrared heat enters earth's atmosphere and then it's going to reflect back out to space a lot of the time but greenhouse gases in the atmosphere actually trap some of the heat that's there from the sun within the atmosphere keeping the surface of the planet warm this makes earth hospitable for living things but when we have too many of what we call greenhouse gases and these are the gases that help trap that heat that heat trapping intensifies and the planet actually starts to create a warming trend over time now you should know that greenhouse gases are primarily going to originate from human causes or they are anthropogenic usually this source is going to be fossil fuel combustion we burn fossil fuels we produce carbon dioxide carbon dioxide is a major greenhouse gas so one of the laws that you should be familiar with for this class is the kyoto protocol which specifically addresses greenhouse effect and it is the agreement to try to reduce greenhouse gases worldwide based on the fact that we know that the majority of them are being produced by humans so let's dig a little bit further into what greenhouse gases actually are if you'll take a look at my chart on the right you can see i've got a list of some of the really common greenhouse gases their warming potential and their time in the atmosphere so these greenhouse gases include things like water vapor carbon dioxide methane nitrous oxide or n2o and cfcs their warming potential is talking about how much heat they're actually able to trap in the atmosphere so remember our greenhouse gases are helping trap that infrared heat radiation from the sun to warm the planet while the stronger their warming potential the more of that heat they're going to trap so notice that water vapors is very low carbon dioxide is kind of the base that we measure all of the other greenhouse gases after so notice its warming potential is one methane is significantly stronger than carbon dioxide and then nitrous oxide and cfcs are much stronger than that so what that means is cfcs are going to be retaining a great amount of heat in the atmosphere carbon dioxide is actually going to retain a lot of heat as well just because there is so much of it and then the time in the atmosphere is also going to affect how these gases affect warming over time so the longer they last in the atmosphere the more of an effect they're going to have so notice that water vapor's time in the atmosphere is relatively low and this is partly because water cycles through the hydrologic cycle so it's going to go through precipitation and evaporation and all of those stages so it doesn't contribute quite as much to warming as the other gases do ultimately the result of all of these greenhouse gases is global warming and this is what we are seriously concerned about because of the changes that we are seeing globally in climate and climate is not all changing the same the whole planet is not just warming equally we are seeing various changes depending on where you're located what we typically see if you look at the graph on the top right is that carbon dioxide levels vary seasonally but overall we see an upward trend the reason you see that red line zigzagging up and down is that plants are going to be more productive during certain times of the year and they will be taking more carbon dioxide out of the atmosphere that's why we see that zigzag drop but then other times of the year plants are a little more dormant and so we see that line go back up and that means that they are not taking as much carbon dioxide out but if you notice that graph that showing atmospheric co2 at mauna loa observatory in hawaii has a general trend of still increasing over time we see that increase directly correlate to the human use of fossil fuels and then also our net destruction of vegetation or plants meaning basically we're cutting and burning more plants than we're actually replanting as a result of that co2 in the atmosphere we are also seeing global temperatures show a constant increase as well so look at the graph in the bottom right of the slide you can see that the temperatures are zigzagging kind of all over the place but again we see that upward trend so that tells us that global temperatures are increasing though worldwide they're not increasing evenly some parts of the world are actually warming faster than others for example our extreme northern latitudes such as around the north pole are experiencing temperature changes from one to four degrees celsius where other parts of the world the temperature change might be a little milder part of the reason we see those northern regions of the planet experience those more severe changes is something called a feedback loop and there are two positive feedback loops you should be familiar with for the exam that are specifically affecting our northern latitudes like the north pole positive feedback loops are loops of activity that basically encourages further warming so it's not positive as in like good it's positive as in encouraging the warming effect to continue or increase over time so let's look at our first example increasing temperatures are causing thawing of tundra permafrost and what this is is permanently frozen ground because it's so cold in tender regions but as that permafrost thaws what's being released is a lot of methane methane is a very strong greenhouse gas so as we release that methane into the atmosphere it's just encouraging further warming which is encouraging further thaw which is encouraging more methane to be released and that whole cycle just continues that's where the positive aspect of this feedback loop comes in is the loop is encouraging more and more warming over time what we're also seeing is that ice and snow are melting in these polar regions and ice has something called a high albedo what this means is it's very reflective of the heat that is coming in from the sun so normally what we would see is lots of ice and snow help reflect heat back out to space but as ice and snow melt we're actually seeing more water exposed in the polar oceans water actually has a lower albedo meaning it's less reflective it has a tendency to actually absorb heat so what we're seeing is ice is melting as that ice melts we are getting more exposure of water water is going to have a lower albedo or absorb more heat from the sun and as that continues to absorb we're going to see more ice melting and overall temperatures are going to continue to increase over time so both of these are examples again that positive feedback loop that helps kind of perpetuate climate change and temperature increase so let's go ahead and look at a summary of different effects of climate change one of the big things we're going to see is loss of habitat so for example ice melting is going to lead to certain species such as polar bears not having their primary hunting ground we will also see species move into different locations so you may have talked about with biomes back from unit 1 that as the planet warms the biomes that we see in warmer regions such as tropical rainforests or savannahs are kind of starting to spread north and south as we see warmer temperatures further north and further south away from the equator this allows species to move into those areas in addition to that certain species may actually be trying to escape increasing temperatures and may try to move further north to get away from the hotter weather unfortunately we will also see things like diseases spread further north and south a lot of our really severe diseases that affect a lot of our tropical areas are starting to spread as species like mosquitoes also spread north and south due to the same temperature increases we may see things such as soil productivity changes ocean and wind currents can shift we will continue to see increases in ice melting which can also raise sea level and in addition to ice melting and glacier melting raising sea level we are also seeing thermal expansion of the ocean what that means is that the particles of water so the actual h2o molecules are getting more energetic as they get warmer and they're starting to move faster so just think about what you would have learned in chemistry is that particles when they're cold are very slow moving particles that are liquids get moving faster and faster and that's what allows the liquid to basically melt from the solid and then as particles continue to move faster and faster and faster they start to become a gaseous state well as those particles in the ocean are warming it allows them to have more energy and be further apart so we're actually seeing the ocean expand in volume as it gets warmer and then the change we're going to discuss on our next slide is actually ocean acidification and warming that is being caused due to climate change effects the increase in co2 in the atmosphere though is also causing something called ocean acidification that we're going to look at next so let's go a little deeper into the effects on the ocean that occur with climate change and global warming so ocean warming is occurring as the earth's surface warms as well we are seeing greenhouse gases trap more heat water has a high heat capacity it's taking in a lot of that heat as well and the ocean temperature is going up over time what we are seeing as a result of that is two major effects one is that ocean species may start to experience metabolic and reproductive changes very similar to what happens with thermal pollution we are also seeing coral bleaching occurring and this is directly tied to the warming of the oceans basically the algae that lives in the coral leaves the coral and dies and that is causing the coral to turn white as a result and this is why we call it coral bleaching because it literally is turning white another effect of these climate change issues we're seeing specifically due to carbon dioxide is ocean acidification so what we're seeing happen with ocean acidification is that the ocean is absorbing carbon dioxide as it absorbs carbon dioxide it mixes with ocean water and this is the bottom middle box on the slide you see co2 plus h2o what results from that chemical reaction is actually carbonic acid so enough carbonic acid in the ocean due to high levels of carbon dioxide absorption will lead to the ocean becoming slowly more acidic over time our problem with this is that carbonic acid actually steals carbonate from the organisms that need it to build their shells they take it out of the water to grow if carbonic acid is in high quantities those shelled organisms are not able to take that carbonate out of the water the second half of unit 9 addresses biodiversity concerns and basically this is kind of wrapping up all of what we've discussed throughout the year is how does human action affect the diversity of the planet one way to remember the major factors and how humans affect biodiversity is called hypgo it's h-i-p-p-c-o if you look at the boxes on the right that is the words that are associated with the hip-go abbreviation so hypco's not a real word it is a way of remembering the major factors that cause biodiversity loss so things such as habitat destruction which can include fragmentation invasive species which often push out native species from their habitats population growth of people pollution such as air and water pollution climate change and then also over exploitation of species where a lot of species are either over fished or taken out of their habitats and sold or we have things such as poaching occurring which over time can lead to a reduction in that species population the factors that make up hip go often lead to things like threaten an endangered species and in the united states we have the endangered species act that helps protect these species so threatened and endangered species are at high risk of extinction in the immediate future factors that can lead to species becoming threatened and endangered include things like over-exploitation or extensive hunting and trade often these species are specialists meaning they're very picky about where they live and what they eat they often are out competed by invasive species that have been often introduced by people and they also have very specific habitat requirements again which is part of what makes a lot of them specialist species so as i mentioned on the last slide one of the laws we have in the united states is the endangered species act which is a list that helps protect these species from losing their habitat and from further harm there's also the cities trade agreement which is something that's done internationally and it's designed to help countries work together to regulate the trade of animals and plants to ensure that trade is not actually detrimental to their populations the final part of this unit review that i'd like to discuss is a couple methods that can be used for protecting biodiversity so let's take a look at the list on the left one of the most important things to do is to make sure you have strong legislation in a country that is going to help protect species that need to be protected such as the endangered species act you can make sure that poaching is criminalized to help discourage it you would want to protect habitat of species you could also install habitat corridors which are methods of allowing species to travel from one area to another that may be fragmented by things such as neighborhoods and roadways reintroduction is sometimes part of the plan as well one example of this is the reintroduction of gray wolves in the yellowstone national park we would want to make sure that we are monitoring land use to try to make it more sustainable we may institute breeding programs which is often done through zoos we may work to restore compromise ecosystems in lost habitats or we may work to reduce non-native and invasive species which are often generalists that compete with specialist species thank you for choosing science panda to help you review for the ap environmental science exam we hope you found this video helpful don't forget to like and subscribe and also check out our channel for other unit reviews from the ap environmental science course