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  • This video was made in collaboration with the National Center for Science Education.

  • The Central Valley of California is one of the United States' breadbaskets, or, more

  • accurately, “producebaskets. For folks who live here, common-sense water conservation

  • is second nature. Linda, an agricultural laborer, has lived here all her life, and she carefully

  • teaches her children to be conscious of their water usage. They use shorter showers and

  • are careful with their tooth-brushing routines. They know to give their unfinished drinking

  • water to the house plants, and the family yard outside reflects an awareness of California's

  • increasingly dry climate: it's an appealing rock garden, lined with cacti and succulents.

  • Yet the surrounding tomato and almond farms where Linda has worked for the last 15 years

  • are thirsty industries. During the last several decades, as California has experienced an

  • extended drought, the Central Valley has been forced to rely on groundwater, steadily drawing

  • down the level of the water in the underlying aquifer. The drawdown has been so extreme,

  • in fact, that the land above the aquifer is noticeably sinking.

  • Climate change is expected to make freshwater scarcity worse, both in the water-stressed

  • Central Valley and around the world. Because when greenhouse gases accumulate and the atmosphere

  • warms, the water cycle changes. With the rise of global temperatures comes the accelerated

  • melting of sea ice and glaciers, which returns water that's been locked up for thousands

  • of years back into the dynamic water cycle. Warmer temperatures lead both to greater evaporation

  • of that newly introduced water and an atmosphere that can hold more of that water as vapor.

  • Because water vapor is a potent greenhouse gas, increased evaporation leads to increased

  • warming, and so on: a phenomenon known as a positive feedback loop. And ultimately,

  • as evaporation increases, so too does water scarcity. On the other hand, increased amounts

  • of atmospheric water vapor and heat energy can also combine to fuel events like hurricanes.

  • It may seem counterintuitive, but big storms can actually intensify water scarcity. When

  • too much water arrives all at once, much of it will simply run off leaving aquifers unreplenished.

  • On top of all of that, a big hurricane can also cause extensive infrastructure damage

  • and contamination that further worsens water scarcity.

  • These global scale phenomena have local consequences. In California's Central Valley, residents

  • like Linda have seen firsthand how sustained drought has pitted individuals against industry

  • in the struggle for a finite and critical resourcewater. The Central Valley grows

  • the bulk of California's produce and accounts for an estimated 12% of overall agricultural

  • production in the US. When the industry began to develop, California's climate was much

  • wetter. Through years of drought, however, the Central Valley has sustained its agriculture

  • by drawing heavily on its aquifers and reservoirs But, this diminishing water reserve is increasingly

  • contaminated with agricultural byproducts like nitrate and arsenic, which concentrate

  • into a potent concoction as the water level drops. Linda is well aware that her well-water

  • is undrinkable. Even showering in the water gives her youngest daughter, Sara, a rash,

  • and she currently relies on donations of potable water from a local non-profit. But that water

  • never seems to be enough, which is one of the reasons she teaches her children to be

  • so careful with water. And Linda and her family are not alone; California's current Governor

  • estimates that 1 million Californians have unsafe drinking water. But this is just the

  • beginning. Scientists expect climate change to exacerbate California's droughts along

  • with its fire seasons, which means it's likely that the state's water woes will

  • only get worse.

  • But California isn't alone in experiencing water scarcity. The Amazon rainforest has

  • experienced unprecedented droughts in the last few years and the fires that roared through

  • the system in 2019 are indicative of that dryness. The Amazon is important for many

  • reasonsbiodiversity, carbon storage, and culturebut the sheer volume of the

  • forest and its component trees means that it drives its own weather system. About half

  • of the rainwater that falls on the Amazon is generated from transpiration by the trees

  • themselves. Recent research has shown that large, mature trees withstand dry conditions

  • better than the shorter agricultural vegetation that often replaces it following deforestation.

  • However, when exposed to sustained drought, even big trees die. Because trees play such

  • an important role in the local water cycle, their loss is expected to fundamentally transform

  • the Amazon ecosystem, with jungle eventually transforming into savannah. And the more trees

  • lost, the worse the drought, which in turn stresses and kills more trees. It's another

  • positive feedback loop. And unfortunately, there is also a third loop: when the bodies

  • of the dead trees are decomposed, stored carbon is released back to the atmosphere, strengthening

  • the greenhouse effect and further driving climate change.

  • This problem isn't limited to the Central Valley and Amazon rainforest, however. Approximately

  • 70% of the world's population faces water scarcity at least one month a year, with 500

  • million peopleabout 6% of the populationexposed to severe water scarcity all year

  • round. Most often this scarcity is exacerbated by poor distribution, management, and political

  • practices more so than by an overall global shortage of freshwater. Humans have become

  • larger consumers of water as our population has boomed over the last several decades,

  • but consumption is not equitable. The agricultural industry is responsible for consuming almost

  • 70% of the world's freshwater, with large corporations that enjoy political and economic

  • clout consuming heavily, as in the case of the produce companies who employ Linda in

  • the California Central Valley. There Linda and her community suffer the consequences

  • of environmental and water mismanagement, while the agricultural industry continues

  • to drain local aquifers.

  • But there are alternatives to our current practices: water-efficient solutions such

  • as improved irrigation, cover cropping, and agroforestry can help reduce agriculture's

  • drain on freshwater. In addition, to protect the limited amount of freshwat

  • er we do have access to, we must regulate water pollution and improve wastewater treatment.

  • all the while employing water recycling techniques with proper filtration and purification to

  • conserve as much water as possible.

  • Addressing freshwater scarcity globallymuch like addressing climate changehowever,

  • requires a multifaceted approach. And because the two issues are intricately connected,

  • addressing freshwater scarcity will require a concerted effort to mitigate climate change.

  • With just 2 degrees Celsius of warming it's estimated that 40% of the global population

  • might be exposed to extreme water scarcity. Climate change solutions then, like combining

  • strategies to sequester carbon with those to reduce emissions, are water scarcity solutions.

  • These strategies, though, must require systemic socio-economic change to address the increasing

  • demand for freshwater. They must tackle the problem at its source with policies to protect

  • the rights of the people from industrial overuse.

  • Water scarcity is a recurring reality for the majority of the world's population,

  • and as climate change alters the water cycle and exacerbates extreme weather, it's likely

  • that more people will suffer. Without transformative action, the water-saving techniques that Linda

  • uses today will become the new normal for more and more people worldwide. For Linda

  • and especially for her daughter, Sara, water shortages and contaminated water are all they

  • know. Yet, there are ways forward. Addressing climate change and alleviating water scarcity

  • will require immense political action, as will assuring that their consequences do not

  • fall disproportionately on those who are most vulnerable. But for such a vital resource

  • as water, the effort will be well worth it.

  • Hey everyone, Charlie here. If you've been watching Our Changing Climate for a while

  • or just stumbled across this video and are wondering how you can help me make more videos,

  • then consider supporting the show on Patreon. As an OCC patron, you'll gain early access

  • to videos, special behind the scenes updates, as well as a members only group chat. In addition,

  • each month my supporters vote on an environmental group that I then donate a portion of my monthly

  • revenue to. So if you want to support the channel or are feeling generous, head over

  • to patreon.com/ourchangingclimate and become an OCC patron. The script for this video was

  • written by Annie, a graduate student research fellow at the National Center for Science

  • Education. She did an amazing job and it was a lot of fun to work with her. Thanks for

  • watching and I'll see you next time!

This video was made in collaboration with the National Center for Science Education.

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我们的全球水危机(Our Global Water Crisis, Explained.)

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    joey joey 發佈於 2021 年 06 月 13 日
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