[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.00,0:00:04.71,Default,,0000,0000,0000,,On the island of Madagascar, there’s a kind\Nof moth that drinks tears from the eyes of
Dialogue: 0,0:00:04.71,0:00:06.29,Default,,0000,0000,0000,,sleeping birds.
Dialogue: 0,0:00:06.29,0:00:10.16,Default,,0000,0000,0000,,When I first heard this, I just sat with that\Nweird idea: there’s a moth that gets most
Dialogue: 0,0:00:10.16,0:00:13.82,Default,,0000,0000,0000,,of the nutrients it needs to survive by drinking\Nbird tears!
Dialogue: 0,0:00:13.82,0:00:17.76,Default,,0000,0000,0000,,Welcome to the biosphere -- the sphere of\Nlife that extends from the depths of the ocean
Dialogue: 0,0:00:17.76,0:00:19.88,Default,,0000,0000,0000,,all the way up to 8 kilometers above Earth.
Dialogue: 0,0:00:19.88,0:00:24.05,Default,,0000,0000,0000,,A lot of incredible things live here, so of\Ncourse, as geographers, we want to know why
Dialogue: 0,0:00:24.05,0:00:28.64,Default,,0000,0000,0000,,bananas and bacteria and tear-drinking moths\Nshow up in some spaces but not others.
Dialogue: 0,0:00:28.64,0:00:30.86,Default,,0000,0000,0000,,And to do that, we have to zoom out a little.
Dialogue: 0,0:00:30.86,0:00:34.86,Default,,0000,0000,0000,,For example, that moth gets its nutrients\Nfrom birds, while birds rely on seeds and
Dialogue: 0,0:00:34.86,0:00:38.10,Default,,0000,0000,0000,,berries from the surrounding plants, which\Ngrow with the help of the Sun.
Dialogue: 0,0:00:38.10,0:00:42.45,Default,,0000,0000,0000,,So the moth and the birds and the plants and\Nthe Sun are all part of an ecosystem -- a
Dialogue: 0,0:00:42.45,0:00:46.86,Default,,0000,0000,0000,,community of living organisms in an area interacting\Nwith their environment.
Dialogue: 0,0:00:46.86,0:00:50.84,Default,,0000,0000,0000,,Ecosystems are built on relationships -- even\Nstrange ones that involve tear-theft.
Dialogue: 0,0:00:50.84,0:00:53.90,Default,,0000,0000,0000,,And the relationship between the amount of\Nenergy a place receives and the movement of
Dialogue: 0,0:00:53.90,0:00:57.10,Default,,0000,0000,0000,,nutrients is what makes the incredible diversity\Nof life possible.
Dialogue: 0,0:00:57.10,0:01:00.28,Default,,0000,0000,0000,,I’m Alizé Carrère and this is Crash Course\NGeography.
Dialogue: 0,0:01:00.28,0:01:08.23,Default,,0000,0000,0000,,INTRO
Dialogue: 0,0:01:08.23,0:01:11.69,Default,,0000,0000,0000,,The biosphere is a complex web of interconnected\Necosystems.
Dialogue: 0,0:01:11.69,0:01:16.87,Default,,0000,0000,0000,,And all ecosystems depend on two key things:\Nthe one-way movement of energy and the cyclic
Dialogue: 0,0:01:16.87,0:01:18.55,Default,,0000,0000,0000,,movement of nutrients.
Dialogue: 0,0:01:18.55,0:01:21.80,Default,,0000,0000,0000,,Energy flows are the paths energy can take\Nthrough an ecosystem.
Dialogue: 0,0:01:21.80,0:01:25.81,Default,,0000,0000,0000,,Energy generally enters ecosystems from the\NSun but doesn’t return to the Sun -- so
Dialogue: 0,0:01:25.81,0:01:28.16,Default,,0000,0000,0000,,energy flows are one-way relationships.
Dialogue: 0,0:01:28.16,0:01:32.86,Default,,0000,0000,0000,,Plants absorb the Sun's energy during photosynthesis,\Nadding carbon dioxide and water to make carbohydrates
Dialogue: 0,0:01:32.86,0:01:34.05,Default,,0000,0000,0000,,and grow bigger.
Dialogue: 0,0:01:34.05,0:01:38.06,Default,,0000,0000,0000,,So the Sun's energy is converted into chemical\Nenergy, which is stored in biomass -- any
Dialogue: 0,0:01:38.06,0:01:40.00,Default,,0000,0000,0000,,plant or other living thing.
Dialogue: 0,0:01:40.00,0:01:44.16,Default,,0000,0000,0000,,If a bit of biomass is eaten, it passes on\Nits chemical energy to continue the energy flow.
Dialogue: 0,0:01:44.16,0:01:49.23,Default,,0000,0000,0000,,The rate photosynthesis makes energy across\Nan entire ecosystem, minus the rate that energy
Dialogue: 0,0:01:49.23,0:01:53.68,Default,,0000,0000,0000,,is used is its net primary production -- or\Nthe amount of stored chemical energy in an
Dialogue: 0,0:01:53.68,0:01:55.91,Default,,0000,0000,0000,,ecosystem over a certain amount of time.
Dialogue: 0,0:01:55.91,0:01:59.70,Default,,0000,0000,0000,,For example, on a really small scale, think\Nof a fish tank ecosystem that you can hold
Dialogue: 0,0:01:59.70,0:02:00.94,Default,,0000,0000,0000,,in your hands.
Dialogue: 0,0:02:00.94,0:02:06.88,Default,,0000,0000,0000,,There's water, a fish, soil, rocks, air, light,\Nfood, and one little plant all in a glass bowl.
Dialogue: 0,0:02:06.88,0:02:10.95,Default,,0000,0000,0000,,In this fish tank ecosystem, the net primary\Nproduction is pretty low because only that
Dialogue: 0,0:02:10.95,0:02:14.94,Default,,0000,0000,0000,,one little plant is absorbing energy from\Nthe Sun (along with any photosynthetic bacteria
Dialogue: 0,0:02:14.94,0:02:17.59,Default,,0000,0000,0000,,or algae that grows when I forget to clean\Nthe bowl).
Dialogue: 0,0:02:17.59,0:02:21.96,Default,,0000,0000,0000,,Globally, net primary production on land generally\Nchanges with latitude.
Dialogue: 0,0:02:21.96,0:02:25.97,Default,,0000,0000,0000,,Productivity is highest between the tropics\Nand decreases towards higher latitudes and elevations.
Dialogue: 0,0:02:25.97,0:02:30.02,Default,,0000,0000,0000,,Biogeographers and ecologists who study how\Nlife is distributed on Earth probably figured
Dialogue: 0,0:02:30.02,0:02:34.94,Default,,0000,0000,0000,,that calling regions of the world "very productive\Necosystem" or "extremely not productive ecosystem"
Dialogue: 0,0:02:34.94,0:02:36.41,Default,,0000,0000,0000,,would be boring.
Dialogue: 0,0:02:36.41,0:02:40.79,Default,,0000,0000,0000,,Instead, we classify ecosystems into biomes,\Nor habitats with similar characteristics,
Dialogue: 0,0:02:40.79,0:02:42.45,Default,,0000,0000,0000,,including productivity!
Dialogue: 0,0:02:42.45,0:02:44.73,Default,,0000,0000,0000,,The names are much more descriptive and fun.
Dialogue: 0,0:02:44.73,0:02:48.04,Default,,0000,0000,0000,,The equator gets the most direct sunlight\Nand a lot of precipitation, so there’s a
Dialogue: 0,0:02:48.04,0:02:50.45,Default,,0000,0000,0000,,lot of photosynthesis happening here.
Dialogue: 0,0:02:50.45,0:02:54.22,Default,,0000,0000,0000,,These highly productive ecosystems are all\Ntropical rainforest biomes, which are some
Dialogue: 0,0:02:54.22,0:02:58.57,Default,,0000,0000,0000,,of the most diverse and complex areas of the\Nplanet -- so it's no wonder the tear-drinking
Dialogue: 0,0:02:58.57,0:02:59.66,Default,,0000,0000,0000,,moth lives here.
Dialogue: 0,0:02:59.66,0:03:02.77,Default,,0000,0000,0000,,Similar patterns happen on either side of\Nthe equator, but we’re going to turn north
Dialogue: 0,0:03:02.77,0:03:04.69,Default,,0000,0000,0000,,because there’s more land in the northern\Nhemisphere.
Dialogue: 0,0:03:04.69,0:03:08.63,Default,,0000,0000,0000,,There’s also less and less precipitation\Nas we move out from the equator, and less
Dialogue: 0,0:03:08.63,0:03:12.65,Default,,0000,0000,0000,,and less productivity because photosynthesis\Ncan't happen without water.
Dialogue: 0,0:03:12.65,0:03:17.00,Default,,0000,0000,0000,,The biomes gradually shift from tropical rainforests\Nto tropical savanna to desert.
Dialogue: 0,0:03:17.00,0:03:21.82,Default,,0000,0000,0000,,Further north, in temperate and high latitudes,\Nthe net primary production varies seasonally.
Dialogue: 0,0:03:21.82,0:03:26.45,Default,,0000,0000,0000,,Like one biome is the broadleaf deciduous\Nforests with oak, beech, hickory, maple, elm
Dialogue: 0,0:03:26.45,0:03:27.99,Default,,0000,0000,0000,,and chestnut trees.
Dialogue: 0,0:03:27.99,0:03:31.52,Default,,0000,0000,0000,,These trees have increased productivity in\Nthe sunny spring and summer, and shed their
Dialogue: 0,0:03:31.52,0:03:33.79,Default,,0000,0000,0000,,leaves in the cooler fall and winter seasons.
Dialogue: 0,0:03:33.79,0:03:37.50,Default,,0000,0000,0000,,Up here in the middle of continents, there\Nare temperate grassland biomes with rich soils
Dialogue: 0,0:03:37.50,0:03:40.96,Default,,0000,0000,0000,,that produce the tall grass of prairies and\Nthe shortgrass of steppe climates.
Dialogue: 0,0:03:40.96,0:03:45.07,Default,,0000,0000,0000,,Further north where there are poorer soils\Nand colder climates, we meet the boreal forest
Dialogue: 0,0:03:45.07,0:03:49.03,Default,,0000,0000,0000,,biomes, which have mainly evergreen pine,\Nspruce, fir and larch trees.
Dialogue: 0,0:03:49.03,0:03:53.72,Default,,0000,0000,0000,,At even higher latitudes, the decreasing temperatures\Ngive us the icy tundra biome with no trees
Dialogue: 0,0:03:53.72,0:03:55.34,Default,,0000,0000,0000,,and very little productivity.
Dialogue: 0,0:03:55.34,0:03:59.12,Default,,0000,0000,0000,,So the amount of energy flow through different\Necosystems varies wildly, which limits which
Dialogue: 0,0:03:59.12,0:04:00.99,Default,,0000,0000,0000,,type of plants can thrive there.
Dialogue: 0,0:04:00.99,0:04:05.34,Default,,0000,0000,0000,,And because plants feed more consumers than\Nany other food source, more plants means more
Dialogue: 0,0:04:05.34,0:04:08.72,Default,,0000,0000,0000,,biodiversity, or the number of different plants\Nand animals in an ecosystem.
Dialogue: 0,0:04:08.72,0:04:14.36,Default,,0000,0000,0000,,And we can't talk about biodiversity without\Nthe other key component of all ecosystems: nutrients.
Dialogue: 0,0:04:14.36,0:04:19.46,Default,,0000,0000,0000,,Nutrients are chemical elements like carbon,\Noxygen, nitrogen, sulfur, and phosphorus -- stored
Dialogue: 0,0:04:19.46,0:04:22.21,Default,,0000,0000,0000,,in both the living and nonliving parts of\Nan ecosystem.
Dialogue: 0,0:04:22.21,0:04:24.69,Default,,0000,0000,0000,,And we actually have technical terms for those\Ntoo.
Dialogue: 0,0:04:24.69,0:04:28.20,Default,,0000,0000,0000,,The living things like plants and animals\Nand bacteria (or their dead bodies) are the
Dialogue: 0,0:04:28.20,0:04:30.47,Default,,0000,0000,0000,,biotic parts of an ecosystem.
Dialogue: 0,0:04:30.47,0:04:34.53,Default,,0000,0000,0000,,And the nonliving things like the soil, atmosphere,\Nand groundwater are the abiotic parts.
Dialogue: 0,0:04:34.53,0:04:38.33,Default,,0000,0000,0000,,Unlike how energy flows in one direction,\Nthe paths that nutrients take through the
Dialogue: 0,0:04:38.33,0:04:43.08,Default,,0000,0000,0000,,ecosystem are nutrient cycles between the\Nbiotic and abiotic parts.
Dialogue: 0,0:04:43.08,0:04:48.26,Default,,0000,0000,0000,,And unlike energy from the Sun, all the nutrients\Nwe have right now on Earth are all we’ll ever have.
Dialogue: 0,0:04:48.26,0:04:52.24,Default,,0000,0000,0000,,It's like how nitrogen moves from being a\Ngas in the atmosphere to a solid in the soil.
Dialogue: 0,0:04:52.24,0:04:56.64,Default,,0000,0000,0000,,[Instead of a one-way system like...aliens\Ndropping gift-wrapped boxes of nitrogen from
Dialogue: 0,0:04:56.64,0:04:58.41,Default,,0000,0000,0000,,space… or at least not that we know of].
Dialogue: 0,0:04:58.41,0:05:01.96,Default,,0000,0000,0000,,The biotic parts of ecosystems really help\Nfacilitate these nutrient cycles.
Dialogue: 0,0:05:01.96,0:05:04.94,Default,,0000,0000,0000,,Like, let's look at our fish tank ecosystem\Nagain!
Dialogue: 0,0:05:04.94,0:05:09.08,Default,,0000,0000,0000,,Producers like our little plant capture nutrients\Nfrom the abiotic parts, turning carbon dioxide
Dialogue: 0,0:05:09.08,0:05:13.60,Default,,0000,0000,0000,,into carbohydrates through photosynthesis\Nor absorbing nitrogen compounds through its roots.
Dialogue: 0,0:05:13.60,0:05:17.34,Default,,0000,0000,0000,,Consumers like the fish take nutrients from\Nother organisms, munching on fish food or
Dialogue: 0,0:05:17.34,0:05:18.34,Default,,0000,0000,0000,,the plant's leaves.
Dialogue: 0,0:05:18.34,0:05:23.06,Default,,0000,0000,0000,,And decomposers break down dead plant leaves…\Nor our fish eventually... and return the nutrients,
Dialogue: 0,0:05:23.06,0:05:26.05,Default,,0000,0000,0000,,like nitrogen gas, to the abiotic parts of\Nthe tank.
Dialogue: 0,0:05:26.05,0:05:30.49,Default,,0000,0000,0000,,Ultimately, nutrients cycling through ecosystems\Ndepend on biological, geological, and chemical
Dialogue: 0,0:05:30.49,0:05:35.19,Default,,0000,0000,0000,,processes operating within the atmosphere,\Nhydrosphere and lithosphere, and make up Earth’s
Dialogue: 0,0:05:35.19,0:05:36.42,Default,,0000,0000,0000,,biogeochemical cycles.
Dialogue: 0,0:05:36.42,0:05:39.92,Default,,0000,0000,0000,,We can compare nutrients across the Earth's\Nbiosphere just like we compared net primary
Dialogue: 0,0:05:39.92,0:05:42.50,Default,,0000,0000,0000,,production across different latitudes and\Nbiomes.
Dialogue: 0,0:05:42.50,0:05:47.13,Default,,0000,0000,0000,,Like let's look at three biomes we met before:\Nthe tropical rainforest, deciduous forest,
Dialogue: 0,0:05:47.13,0:05:48.60,Default,,0000,0000,0000,,and boreal forests.
Dialogue: 0,0:05:48.60,0:05:52.05,Default,,0000,0000,0000,,We know that there's less and less productivity\Nas we move up in latitude, so there's less
Dialogue: 0,0:05:52.05,0:05:54.63,Default,,0000,0000,0000,,and less biomass, and there's also less and\Nless nutrients.
Dialogue: 0,0:05:54.63,0:05:58.01,Default,,0000,0000,0000,,Fewer nutrients isn't necessarily a death\Nsentence for the trees, though.
Dialogue: 0,0:05:58.01,0:06:01.05,Default,,0000,0000,0000,,It just means that the ecosystem is structured\Ndifferently.
Dialogue: 0,0:06:01.05,0:06:04.65,Default,,0000,0000,0000,,Like boreal forests have a lot of nutrient\Nfilled litter because the cold keeps material
Dialogue: 0,0:06:04.65,0:06:06.11,Default,,0000,0000,0000,,from decomposing.
Dialogue: 0,0:06:06.11,0:06:09.61,Default,,0000,0000,0000,,But deciduous forests have a lot of nutrient-rich\Nsoil because it’s warm enough for material
Dialogue: 0,0:06:09.61,0:06:12.76,Default,,0000,0000,0000,,to decompose, but not warm enough for a lot\Nof biomass to grow.
Dialogue: 0,0:06:12.76,0:06:17.22,Default,,0000,0000,0000,,So a tree that’s adapted to life in a cold\Nboreal forest might not make it in a tropical
Dialogue: 0,0:06:17.22,0:06:20.19,Default,,0000,0000,0000,,rainforest because of the different energy\Navailability and nutrient stores.
Dialogue: 0,0:06:20.19,0:06:23.69,Default,,0000,0000,0000,,Let’s consider the tropical rainforests,\Nwhich are the most diverse biomes with lush
Dialogue: 0,0:06:23.69,0:06:26.28,Default,,0000,0000,0000,,vegetation and a lot of biodiversity.
Dialogue: 0,0:06:26.28,0:06:31.16,Default,,0000,0000,0000,,But that decadence hides the fragile balance\Nof all the complex energy flows and nutrient cycles.
Dialogue: 0,0:06:31.16,0:06:32.54,Default,,0000,0000,0000,,Let's go to the Thought Bubble!
Dialogue: 0,0:06:32.54,0:06:36.39,Default,,0000,0000,0000,,Within the tropical rainforests, broadleaf\Nevergreen trees form a canopy at different
Dialogue: 0,0:06:36.39,0:06:39.96,Default,,0000,0000,0000,,heights, and little or no sunlight reaches\Nthe shady forest floor.
Dialogue: 0,0:06:39.96,0:06:44.18,Default,,0000,0000,0000,,These huge trees absorb most of the soil nutrients,\Nwhich doesn't leave a lot for other organisms.
Dialogue: 0,0:06:44.18,0:06:48.72,Default,,0000,0000,0000,,And they have a shallow root system to grab\Nas many of the minerals as possible from biogeochemical
Dialogue: 0,0:06:48.72,0:06:50.54,Default,,0000,0000,0000,,processes near the surface.
Dialogue: 0,0:06:50.54,0:06:54.09,Default,,0000,0000,0000,,And as the large amounts of rain filter down\Nthrough the soil, the minerals that dissolve
Dialogue: 0,0:06:54.09,0:06:57.17,Default,,0000,0000,0000,,in water are leached away to inaccessible\Ndeeper levels.
Dialogue: 0,0:06:57.17,0:07:00.40,Default,,0000,0000,0000,,To survive, the rainforest has to rapidly\Ncycle nutrients.
Dialogue: 0,0:07:00.40,0:07:04.18,Default,,0000,0000,0000,,The canopy trees are producers, along with\Nunderstory plants that work together to keep
Dialogue: 0,0:07:04.18,0:07:06.13,Default,,0000,0000,0000,,vital nutrients moving through the ecosystem.
Dialogue: 0,0:07:06.13,0:07:10.08,Default,,0000,0000,0000,,Herbivores like gorillas and caterpillars\Ntake in those nutrients and move them around
Dialogue: 0,0:07:10.08,0:07:14.27,Default,,0000,0000,0000,,through their excrement and by being eaten\Nthemselves, like by jaguars or geckos.
Dialogue: 0,0:07:14.27,0:07:18.80,Default,,0000,0000,0000,,And the warmth and humidity helps decomposers\Nand their chemical reactions, so any dead
Dialogue: 0,0:07:18.80,0:07:20.55,Default,,0000,0000,0000,,plants or animals decay quickly.
Dialogue: 0,0:07:20.55,0:07:24.30,Default,,0000,0000,0000,,Because nutrients get sucked from the soils\Nso quickly, when those huge trees are cut
Dialogue: 0,0:07:24.30,0:07:27.16,Default,,0000,0000,0000,,down, the energy flows and nutrient cycles\Nbreak.
Dialogue: 0,0:07:27.16,0:07:31.73,Default,,0000,0000,0000,,Those big producers aren't there to sustain\Nconsumers or shed leaves to recycle nutrients.
Dialogue: 0,0:07:31.73,0:07:36.05,Default,,0000,0000,0000,,So deforestation, or removing trees to use\Nthe land for something else, can be especially
Dialogue: 0,0:07:36.05,0:07:40.15,Default,,0000,0000,0000,,destructive in tropical regions if you don't\Nconsider the biogeochemical cycles.
Dialogue: 0,0:07:40.15,0:07:41.57,Default,,0000,0000,0000,,Thanks, Thought Bubble.
Dialogue: 0,0:07:41.57,0:07:45.65,Default,,0000,0000,0000,,We have negative associations with the word\N"deforestation" for good reason -- a lot of
Dialogue: 0,0:07:45.65,0:07:48.86,Default,,0000,0000,0000,,tree removal has caused immense damage to\Necosystems.
Dialogue: 0,0:07:48.86,0:07:52.42,Default,,0000,0000,0000,,But indigenous communities have figured out\Na type of calculated clearing that allows
Dialogue: 0,0:07:52.42,0:07:56.14,Default,,0000,0000,0000,,them to work with the rapid nutrient recycling\Nof tropical rainforest biomes.
Dialogue: 0,0:07:56.14,0:08:00.57,Default,,0000,0000,0000,,In parts of Asia, Africa, and South America\Nwith dense tropical forests, many farmers
Dialogue: 0,0:08:00.57,0:08:05.12,Default,,0000,0000,0000,,have to rely on a kind of subsistence agricultural\Npractice, which means they only grow enough
Dialogue: 0,0:08:05.12,0:08:06.62,Default,,0000,0000,0000,,food for their families.
Dialogue: 0,0:08:06.62,0:08:11.84,Default,,0000,0000,0000,,Staples like rice are grown in southeast Asia,\Nmaize and cassava in South America, and sorghum in Africa.
Dialogue: 0,0:08:11.84,0:08:16.23,Default,,0000,0000,0000,,Yams, sugarcane, plantains, and vegetables\Nare also planted to supplement staples and
Dialogue: 0,0:08:16.23,0:08:18.27,Default,,0000,0000,0000,,to provide fuel and fodder for animals.
Dialogue: 0,0:08:18.27,0:08:23.18,Default,,0000,0000,0000,,This practice goes by many names, like swidden,\Nshifting cultivation, and slash-and-burn agriculture.
Dialogue: 0,0:08:23.18,0:08:27.71,Default,,0000,0000,0000,,The farmers begin by cutting small areas of\Ntropical forests into slash, or cut vegetation,
Dialogue: 0,0:08:27.71,0:08:29.61,Default,,0000,0000,0000,,that’s then dried and burned.
Dialogue: 0,0:08:29.61,0:08:33.45,Default,,0000,0000,0000,,The ash gets mixed with the poor soil to provide\Nneeded minerals and nutrients -- basically
Dialogue: 0,0:08:33.45,0:08:37.47,Default,,0000,0000,0000,,using all the good stuff stored up in the\Nvegetation biomass to help new crop plants grow.
Dialogue: 0,0:08:37.47,0:08:41.43,Default,,0000,0000,0000,,Of course, these crop plants use minerals\Nand nutrients from the soil as they grow,
Dialogue: 0,0:08:41.43,0:08:44.19,Default,,0000,0000,0000,,and we eat them to get those minerals and\Nnutrients in our bodies.
Dialogue: 0,0:08:44.19,0:08:48.01,Default,,0000,0000,0000,,So after a few years, and before the soil\Nis completely exhausted, the farmers move
Dialogue: 0,0:08:48.01,0:08:51.86,Default,,0000,0000,0000,,on to another part of land and repeat the\Nclearing, burning, and planting process.
Dialogue: 0,0:08:51.86,0:08:55.96,Default,,0000,0000,0000,,The previous plot is left unplanted, and eventually\Nthe forest will naturally expand to start
Dialogue: 0,0:08:55.96,0:08:59.50,Default,,0000,0000,0000,,using that soil as part of its carefully balanced\Nnutrient cycling.
Dialogue: 0,0:08:59.50,0:09:02.86,Default,,0000,0000,0000,,This land rotation is a key part of why humans\Nhave been able to keep farming like this for
Dialogue: 0,0:09:02.86,0:09:04.58,Default,,0000,0000,0000,,thousands of years.
Dialogue: 0,0:09:04.58,0:09:07.93,Default,,0000,0000,0000,,But when widespread clear-cutting happens,\Necosystems can collapse.
Dialogue: 0,0:09:07.93,0:09:11.99,Default,,0000,0000,0000,,For example, we've seen this destruction in\Nthe Amazon when rice, soy, and corn have been
Dialogue: 0,0:09:11.99,0:09:15.65,Default,,0000,0000,0000,,commercially cultivated and sold in domestic\Nand international markets.
Dialogue: 0,0:09:15.65,0:09:19.66,Default,,0000,0000,0000,,The soil is exhausted after 3-5 years, so\Ncrops can't really grow anymore, and then
Dialogue: 0,0:09:19.66,0:09:21.34,Default,,0000,0000,0000,,large cattle operations move in.
Dialogue: 0,0:09:21.34,0:09:25.57,Default,,0000,0000,0000,,As cattle feed and trample the ground, the\Nsoils are exposed to plenty of UV radiation
Dialogue: 0,0:09:25.57,0:09:29.45,Default,,0000,0000,0000,,from sunlight, as well as cycles of wetting\Nand drying from precipitation.
Dialogue: 0,0:09:29.45,0:09:33.43,Default,,0000,0000,0000,,The soils become a brick-like substance called\Nlaterite, which isn’t great for growing…
Dialogue: 0,0:09:33.43,0:09:38.11,Default,,0000,0000,0000,,so the once-lively rainforest basically becomes\Nhard, barren, and lifeless.
Dialogue: 0,0:09:38.11,0:09:42.38,Default,,0000,0000,0000,,Tropical rainforests cover 6 percent of Earth’s\Nlandmass, but contain 50 percent of the world’s
Dialogue: 0,0:09:42.38,0:09:46.70,Default,,0000,0000,0000,,species, many of which haven’t been described\Nby science and are critical to the world’s biodiversity.
Dialogue: 0,0:09:46.70,0:09:51.79,Default,,0000,0000,0000,,But since the 1980s, 1/5 of the Amazon has\Nbeen deforested as we build more towns, roads,
Dialogue: 0,0:09:51.79,0:09:54.07,Default,,0000,0000,0000,,dams, farms, and mines.
Dialogue: 0,0:09:54.07,0:09:57.100,Default,,0000,0000,0000,,Across the Atlantic, deforestation in Ituri\Nin the Congo Basin, the world’s second largest
Dialogue: 0,0:09:57.100,0:10:01.74,Default,,0000,0000,0000,,expanse of equatorial rainforest, is endangering\Nthe mountain gorilla.
Dialogue: 0,0:10:01.74,0:10:06.41,Default,,0000,0000,0000,,And in southeast Asia clearcutting for palm\Noil plantations endanger orangutans, Sumatran
Dialogue: 0,0:10:06.41,0:10:08.35,Default,,0000,0000,0000,,tigers, and Sumatran elephants.
Dialogue: 0,0:10:08.35,0:10:12.73,Default,,0000,0000,0000,,When humans disturb the biosphere, we alter\Nhow energy flows and how nutrients cycle,
Dialogue: 0,0:10:12.73,0:10:16.02,Default,,0000,0000,0000,,which can throw off entire ecosystems in unexpected\Nways.
Dialogue: 0,0:10:16.02,0:10:20.14,Default,,0000,0000,0000,,And if we're not careful, that moth that drinks\Nthe tears of sleeping birds -- or plenty of
Dialogue: 0,0:10:20.14,0:10:23.45,Default,,0000,0000,0000,,other remarkable living organisms -- may no\Nlonger exist.
Dialogue: 0,0:10:23.45,0:10:26.83,Default,,0000,0000,0000,,But just like we can be good stewards of our\Nlittle fish tank, we can take care of the
Dialogue: 0,0:10:26.83,0:10:29.79,Default,,0000,0000,0000,,world around us and the much bigger ecosystems\Nwe're a part of.
Dialogue: 0,0:10:29.79,0:10:33.83,Default,,0000,0000,0000,,Learning where our food comes from and how\Nit’s produced is a good first step, like
Dialogue: 0,0:10:33.83,0:10:37.13,Default,,0000,0000,0000,,by supporting farmers who try to grow food\Nsustainably.
Dialogue: 0,0:10:37.13,0:10:41.07,Default,,0000,0000,0000,,And we’ll keep talking about our role in\Necosystems, energy, and food and how geography
Dialogue: 0,0:10:41.07,0:10:45.07,Default,,0000,0000,0000,,and spatial thinking can help address some\Nof the critical issues we’re facing, like
Dialogue: 0,0:10:45.07,0:10:49.46,Default,,0000,0000,0000,,how we can have enough food and water to sustain\Nourselves and our environment.
Dialogue: 0,0:10:49.46,0:10:53.54,Default,,0000,0000,0000,,Many maps and borders represent modern geopolitical\Ndivisions that have often been decided without
Dialogue: 0,0:10:53.54,0:10:58.20,Default,,0000,0000,0000,,the consultation, permission, or recognition\Nof the land's original inhabitants.
Dialogue: 0,0:10:58.20,0:11:02.86,Default,,0000,0000,0000,,Many geographical place names also don't reflect\Nthe Indigenous or Aboriginal peoples languages.
Dialogue: 0,0:11:02.86,0:11:06.64,Default,,0000,0000,0000,,So we at Crash Course want to acknowledge\Nthese peoples’ traditional and ongoing relationship
Dialogue: 0,0:11:06.64,0:11:10.28,Default,,0000,0000,0000,,with that land and all the physical and human\Ngeographical elements of it.
Dialogue: 0,0:11:10.28,0:11:13.80,Default,,0000,0000,0000,,We encourage you to learn about the history\Nof the place you call home through resources
Dialogue: 0,0:11:13.80,0:11:18.40,Default,,0000,0000,0000,,like native-land.ca and by engaging with your\Nlocal Indigenous and Aboriginal nations through
Dialogue: 0,0:11:18.40,0:11:21.03,Default,,0000,0000,0000,,the websites and resources they provide.
Dialogue: 0,0:11:21.03,0:11:24.34,Default,,0000,0000,0000,,Thanks for watching this episode of Crash\NCourse Geography which is filmed at the Team
Dialogue: 0,0:11:24.34,0:11:28.12,Default,,0000,0000,0000,,Sandoval Pierce Studio and was made with the\Nhelp of all these nice people.
Dialogue: 0,0:11:28.12,0:11:31.100,Default,,0000,0000,0000,,If you want to help keep all Crash Course\Nfree for everyone, forever, you can join our
Dialogue: 0,0:11:31.100,0:11:34.60,Default,,0000,0000,0000,,community on Patreon.