hey everyone this is your unit five land and water use test review video for AP environmental science we're gonna start with discussing the tragedy of the Commons to it which directly relates to quite a few topics within this unit so what tragedy the Commons is is a common resource that's available for all humans to use so for example the ocean the atmosphere rangelands that are considered public land that often for example cattle are grazed on these are often exploited at unsustainable rates and because of this we often have people using them unsustainably to make a profit the problem is they may get their profit but ultimately they're going to deplete the resource the ocean is often the target of overfishing and dead zones so if you look at the nets that are found on the boat up top those not only damaged fishing populations numbers but also the ocean floor and then you can see the picture down in the bottom right the red is showing the depleted oxygen close to Louisiana where the Mississippi River dumps out into the Gulf of Mexico due to fertilizer use that area has become a oxygen depleted dead zone groundwater depletion is another example as it's often used publicly without any real regulation and is more often than not overdrafted meaning we take more water out than is actually available to us so now that we're talking about water let's take a look at water resources so first of all you should be familiar with the Ogallala Aquifer which is found kind of in the middle of the United States so the graph I'm sorry the map up in the top right is showing us the location so running from Texas up kind of through the Midwest area this is our largest aquifer in the US and one of the biggest ones in the world and this particular aquifer has been largely overdrafted and is nearing depletion due to human use only a small percentage of the water we have on earth is actually accessible as freshwater and because of that we need to be very careful that we don't either pollute misuse or deplete our freshwater resources so groundwater is often referred to as aquifers and they can be confined or unkind find meaning the confined aquifers are actually under pressure where the unkind are up at basically air pressure and these aquifers as they are over drafted it means that they are not able to recharge fast enough to keep up with the amount of water being taken out so other impacts that can be included due to aquifer overdraft or things like subsidence where the land level sinks down and what this looks like let's say this is the land right here our aquifers underneath it and we are using some kind of pipe to draw water out well over time as we are pulling that water up and out of the ground we may see the land actually sink down around where we're drawing water out and so notice the land level has dropped so it's no longer up here it's sunk and we end up with that again it's called subsidence so saltwater intrusion can also occur if an aquifer is near a coastline so notice we got fresh water right here and this is underground so this is your aquifer saltwater out here well as we pull water out of the aquifer we can often have pressure put on saltwater nearby which can pull it in and if the saltwater is mixed in with that freshwater it can actually make it unusable at that point so let's move on to a few ways that we use these resources water resources are heavily used for irrigation about 70% of the water that we have available to us fresh water on Earth is used mainly for agricultural and law and irrigation there's a couple different types of irrigation you can see listed on the left the most evaporation is going to take place with furrow irrigation which you can see in the picture to your right it's the left picture there with the rows of plants you can see the water kind of reflecting the sky in between them so that's going to cause about 40 percent evaporation flood irrigation where it's just flooded out onto a field causes almost as much irrigate or irrigation water loss due to evaporation spray irrigation would be more like what you see your lawn being watered with where you just kind of spraying water over it and then drip irrigation usually uses a line and you can see on the picture on the far right that is going to have like holes for example punctured in it and those holes will slowly drip water this will be the least amount of evaporation and one of the better ways to avoid complications such as salinization from irrigation so salinization we'll talk about in just a minute but again drip irrigation will be your best way to avoid it and then we can try to fix salinization and if it occurs with flushing but the problem with that is you are applying more water to a field and that could potentially leave minerals behind on its own as well other issues that can come up with agriculture include tillage biggest problem being erosion if you look at the bottom left picture what we see is ground that has been tilled oh they take equipment out the kind of claws at the dirt digs it up and turns it over to help aerate it and in doing so is gonna leave it very loose topsoil is what could be lost due to erosion with things like tillage and topsoil is important for holding on to nutrients and water if we have topsoil lost or depleted we are not going to be able to very easily grow plants so one of our solutions to avoiding erosion where soils washing out you can see that in the upper picture there is using things like cover crops which are seen in that bottom right picture notice there's trees and there would normally be bare land between them they were using cover crops in that example to keep that soil in place the roots of the plant help hold it down other types of agricultural impacts include desertification where we have pretty much used the soil to the point where it's losing nutrients rapidly and it's no longer able to support plant life this can also be caused by the way--by over grazing on rangelands so when the grass is constantly removed by cattle and does not have time to grow back you will lose your nutrients in your topsoil as well erosion can also result from over grazing too so salinization is being shown in that picture at the right where you can see the white to kind of crust on top of the land so as water was irrigated on to it it evaporates leaving those salts and minerals behind which as we learned in class prevents plants from being able to grow very easily due to us potential or basically the dissolved materials in the water do not let the plants take up enough water that they need to survive integrated pest management is one possible solution to trying to reduce our amount of pesticide use so what we can do instead is just using chemical pesticides is use things like crop rotation so that the insects if they're preferential to one plant over another will not stick around for very long why don't you swap the plants out using natural predators to help control them so for example ladybugs eat aphids a Fitzie plants so if we have ladybugs around to help eat the aphids that can help protect our plants genetically modified organisms or GMOs are another option if they are more resistant to pests then hopefully they won't result in an infestation in their plot that they're on or even mulch which can help weeds from growing in all right let's move on to mining so for mining we need to know types of mining which we'll cover in just a minute and also a few vocab terms so ore is going to be our rock that contains a profitable amount of minerals so like iron ore for example is going to contain iron within whatever it is that we pull out of the ground reserves are a source that we know is available to mine and then depletion time for reserves refers to approximately 80% of reserves thought to have been used up overburden is the soil that we remove when mining so I feel good the picture in the bottom right you can see they're digging down so anything that was soil covering where that kind of ditch has been created by mining would have been overburden and they've removed that spoils is our waste created by mining so as we process or waste is often created and is left behind and then tailings is referring to the mining residue from water use during mining processes so we can see that in the upper right picture where they have created dams or pools to hold that tailings fluid impacts of mining include things like disruption of land and habitats so you can see on those pictures at the right where we have a strip mining occurring in the top picture and an open pit mine in the bottom picture that the land is basically bare there's no plants they're all gone the trees are gone topsoil is gone and we're digging down into the layers of rock that's left there and in the case of that we're leaving behind spoils banks which can cover up good topsoil that hasn't been disturbed by the mine itself we end up using liquids again that can leave tailings behind we've read about the Samarco dam collapse in Brazil where once that tailings dam collapsed the town that was kind of down stream from it ended up flooded by a lot of that liquid and that liquid can contain toxic chemicals as well and then water quality impacts all that loose dirt created from mining can end up moving into waterways due to erosion and washout and sediments and waterways can block sunlight can clog fish gills and cause other problems with the health of the aquatic habitat and then the major one that we keep hearing over and over again with these impacts from agriculture from mining from deforestation as we'll see in just a minute is erosion which is when soil is moved from one place to another due to wind or water often picked up and runoff after rain and removing of that soil if enough topsoil is lost that soil may no longer be fertile and allow plants to grow in it so let's move on to fishing impacts bycatch is considered organisms that you're not meaning to catch in your nets so if you're trying to catch tuna and you end up catching either juvenile tuna which usually there's certain size or age limits on fish you're allowed to catch dolphins or turtles or other marine organisms that are unintentional those are considered bycatch often they can be killed in the nets and then fishery collapsed is considered to decline in a known fish population in a certain region by more than 90% so those collapses are make it very difficult for the fish populations to recover afterwards due to the limit on the size as it's currently is in that collapsed state and the genetic limitations of fish trying to come back from that kind of genetic bottleneck as well so some of the fishing impacts that are a real problem other than bycatch are ocean pollution a lot of fishing equipment gets dumped into the ocean either intentionally or unintentionally and also damage to the seafloor and coral reefs and other delicate ecosystems that are in the benthic part of the ocean or the ocean floor so nets that are contained weights or if nets or drive over coral reefs those can tear them up quite a bit so ways that we can fix some of our issues particularly with fishery collapse and overfishing is laws and regulations that can help limit the catch that we have or that can limit the particular time of year that we're allowed to go fishing community based management which works with largely fishing based communities to try to have them kind of do a little more of the management themselves creating marine reserves monitoring a fish populations so that if we need to put regulations in place we can earlier rather than after fishery collapses occurred consumer choice so choosing as an individual purchaser of fish to not buy fish that are already known to be over harvested to try to discourage their continued harvest and also reducing government subsidies which is basically where the government puts funds into a particular industry to try to encourage it for economic growth aquaculture is also one particular solution to overfishing of wild fish and this occurs where we grow fish in tanks you can see on the right the picture of those rings are contained netting areas in the ocean where fish are contained within them the problem is it's done at very high density and so we get a lot of waste contamination issues due to the fish poop all being right next to that aquaculture tank and there's a lot of fish there way more than would normally be crammed into that kind of area disease can also be a problem so if disease gets started among fish within the aquaculture a kind of cage that they have it can run rampant because of the fish are all very close together escaped fish especially if they're larger due to the food being used or are genetically modified I can enough impacting the wild fish in the ecosystem they're basically stronger and bigger and so they will out-compete them and there often is a lot of antibiotic use in aquaculture as well to try to keep the fish healthy so the good things though are they are cost-effective and it's not a very large area of land to get a lot of fish so there's less environmental impact then maybe fishing in different areas all the time and having the nets and weights damage them could be like what we see with the other types of fishing all right let's take a look at benefits of forests and also drawbacks of deforestation and so with forests they can help stabilize soil and prevent erosion because their roots help hold the soil in place they can slow runoff for us in trees and for us actually help water infiltrate into the ground better so it also lessens flooding because of that the infiltration into the ground encouraging that helps to purify water as well as it percolates into groundwater forests are excellent carbon sinks because of the photosynthesis and respiration processes that take place because they take so much carbon out of the atmosphere and store it within their tissues they are considered a very good carbon sink so cutting forests down put carbon into the atmosphere and then again like we said it does help improve infiltration of water into the ground so drawbacks that occur when we DeForest are it not only alters landscapes and habitats but removing trees and their roots can degrade soil so we lose topsoil erosion can take place and then as we cut trees down we are likely adding carbon to the atmosphere or taking away something that helps take carbon out so we'll have that increase overall generally - because trees help water infiltrate into the ground runoff is more common and with that runoff you could be carrying quite a bit of dirt along with it or sediments into nearby waterways due to erosion for quite a while the Forestry Service tried to suppress fires in the United States and this could be kind of considered a failure because a lot of fire suppression leads to woody accumulation so leaves and twigs and other dead and decaying matter on the forest floor building up over time in the forests that are meant to burn on a regular basis it's just kind of the way that habitat or that ecosystem is that helps get rid of that accumulation and so fires tend to be more minor and more easy to control once they get started with fire suppression that builds up to the point where those fires can easily get out of control so one of the things that we do now instead is controlled or prescribed burning where our firefighters and ecologists and foresters will burn certain chunks of forests to try to prevent out-of-control fire later on you should also know about clear cutting and clear cutting is going to be something that's definitely going to destroy forest communities because it does cut down every tree that's in the community it's very effective and very efficient but it's also extremely destructive with deforestation especially in rain forest soil erosion is a huge problem because nothing is holding the soil in place so one potential solution is using something like selective cutting where some trees are left behind to help maintain the actual forest itself some trees are left to help repopulate the forest and then only certain trees are cut down for logging and timber production purposes with rangeland this is another tragedy of the Commons issue that can easily crop up because rangeland lands are often public or federal lands that people can get permits to graze their own cattle on so over grazing of cattle is going to continue to eat away at the grass and eventually damage the soil in the location on top of the risk the risk of the over grazing and potentially desertification or nutrient lost from the soil we can have a rosin take place due to lack of plants like grass holding the soil in place and also cattle waste and waterways within the rangeland is a big problem too because cattle waste can lead to eutrophication and then they trample the edges of stream beds a lot of the times causing even further erosion so the way we can fix this is make sure streams are fenced or protected in some way supplement the cows feed to prevent them from eating all of the grafts in the area and also moving the cattle from range area to range area on a regular basis you can also help prevent them from over feeding on the grass with urbanization the biggest thing you need to know is what the problem with impervious surfaces is and impervious surfaces are areas that do not allow water to seep through the surface so it concrete and asphalt and rooftops even into the ground and so we end up with more runoff you'll have significantly more water running off into sewer drains and then out into waterways when there is a highly urbanized area so problems of runoff when all that goes into a sewer drain anytime there's rain it goes into a stream starts to pick up the velocity and the volume of that stream which can lead to big damage along the sides habitat damage erosion and potentially flooding as well so when the water is not naturally seeping into the ground as much as it is running off the ground into waterways flooding is definitely a possible thing and then with these impervious areas things like car oil pesticides fertilizers even animal feces and bacteria can get picked up and that runoff and can move into waterways as well leading to eutrophication and remember eutrophication occurs when nutrients like nitrogen and phosphorous which is why the animal feces is a problem gets into waterways causes algae to over grow because it's a limiting factor in the growth of not only algae but plants as well they grow too much they end up dying and decaying and as they decay they eat up oxygen causing hypoxia or a dead zone to form then one of the last things we talked about was meat production and this is often done in industrialized countries and concentrated animal feeding operations or ke foes and K foes are very very high density growth of animals like cow pigs and chickens for food purposes so these animals are kept in very small confined areas throughout their life until they are large enough to be sent in for slaughter for production of meat that's in sold to grocery stores so it's very efficient and does minimize the land needed to grow a lot of meat generally meat requires way more land than growing plants does but we can end up with problems such as antibiotic resistance because these animals are often given by antibiotics to stay healthy being in such close quarters in such high density disease spreads rampantly so antibiotics end up necessary concentrated waste when you have a hundred thousand chickens in a very small area that's a lot of chicken waste and a lot of nitrogen so that can lead to eutrophication and then also just the ethical issues of that many animals that densely packed into a particular space thank you for watching the unit 5 test review video I hope this helps and good luck on your test