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Human impacts on the environment

Human activities—such as land use, water use, and deforestation—often have negative impacts on the environment. These impacts worsen as the human population grows and consumes more resources. Science can help identify ways to reduce our impacts, but it is ultimately up to us to take action. Created by Khan Academy.

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Video transcript

- [Narrator] Everything we do has an impact on the world around us. That can be a good thing, or a bad one. For most of us, that impact can seem pretty small. If you throw an empty can on the ground instead of in the recycling bin, your local park will still be pretty clean. Those actions can add up though. What if everyone you know decides to start throwing their trash on the ground too? Or a nearby factory decides to dump all of their trash there? As the human population of Earth grows, we tend to consume and throw away more and more natural resources. This trash bile is a simple example of pollution, which can also refer to toxic particles in our air or waterways. Human activities are also contributing to more complex problems, like overfishing or deforestation, which can drive wildlife to extinction and disrupt the natural processes that keep our planet running smoothly. Let's take a look at a real place that's facing some of these complex environmental problems. This is Lake Urmia in Iran, once the largest lake in the Middle East and the sixth largest saltwater lake on Earth. The lake was a popular destination for people who wanted to visit its uniquely salty shores, as well as for migratory birds, like flamingos and pelicans, who had stopped to rest during their long journeys. This satellite image of Lake Urmia is from 1984. Now, compare it to another image taken in 2018. In just a few decades, the lake has shrunk dramatically. What happened? Well, around the 1980s, Iran needed to create new jobs and sources of food for its growing population. More people began moving near Lake Urmia, converting large portions of the landscape into agricultural fields. They tried growing profitable new crops like apples, watermelon, and sugar beets, but many of these plants require a lot more water than the dry climate could provide. So people built dams across many of the rivers that float into the region so they could more easily transport fresh water to their fields and communities. Iran has always experienced droughts, but with people using up so much water, the impact of these droughts became much worse. Lake Urmia began to shrink. The remaining water became so salty that many aquatic fish and other small critters couldn't survive, leaving migratory birds and other wildlife without a source of food. Sandstorms blew salt from the dry lake bed over agricultural fields, making it even harder for people to grow food during droughts. Farmers were forced to move away, and many others from the tourist towns followed since few wanted to visit a vanishing lake where people could get sick from breathing the salty air. At one point, lake Imia lost nearly 90% of its historical volume, and many of its once thriving communities turned into ghost towns. There's no question that human activities, from unsustainable farming practices to diverting water flow, cause this environmental catastrophe. Human activities aren't always negative though. We can work together to design technologies that monitor and minimize our harmful impacts. Since environmental problems are often so complex, we need to consider a lot of different things to create sustainable solutions. What does scientific research tell us about this place and how it's changing? What are the needs, desires, and values of the people affected by this problem, both as individuals and as a society? Are there any constraints or challenges that could prevent us from taking action? Despite economic and political constraints, many Iranians support efforts to save Lake Urmia, which has encouraged leaders to provide more funding and other restoration resources. Key parts of the ecosystem are now protected by reserves or national parks. Researchers have introduced new farming practices to the region, such as planting less thirsty pomegranate trees or watering crops at night to prevent evaporation. This has allowed farmers to save water while still producing enough food. Finally, engineers have been building new technologies that transfer water from surrounding areas into the lake. Even with all of these changes, the problems plaguing Lake Urmia aren't completely fixed yet. Wildlife habitats still need to be restored so aquatic species can survive and migratory birds can fuel up for their long journeys. Water levels are still too low to attract many tourists. And salt from the exposed lake bed can still harm people's health when kicked up during sandstorms. People are worried that transferring water into Lake Urmia from nearby regions may cause even more widespread water shortages. Their needs and concerns need to be addressed for decisions to work properly in the long term. While there's still plenty left to do, these efforts, combined with a few good rain years, have allowed Lake Urmia to return to about half of its historical size. Check out this Google Earth image from 2022. It's not back to the way it was, but it's looking a bit better. Lake Urmia isn't the only lake on Earth that's under threat from human activities. For example, the Great Salt Lake in the United States is also shrinking for very similar reasons. Shared challenges can provide opportunities for people to share solutions. People can learn from what others are doing to fix similar problems or even brainstorm new ideas. For example, researchers from Iran and the United States have started working together to compare conservation activities on both of their salt lakes even though they're half a world apart. While human action often has a negative impact on the planet, we have the power to spark positive change too. If you feel like your actions alone are too small to make a difference against a big problem, whether it's a shrinking lake or a giant pile of garbage in your neighborhood, there's usually a few other concerned citizens that would be happy to help find a solution.