What's the biggest threat to freshwater habitats?

Such a pretty sight -- a school of sockeye salmon return in the Adams River in British Columbia, Canada.
Such a pretty sight -- a school of sockeye salmon return in the Adams River in British Columbia, Canada.
Chris Cheadle/Getty Images

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There are two types­ of water in all the world -- freshwater and saltwater. Oceans, or saltwater, cover about 70 percent of the Earth's surface and account for 97 percent of our water. That means that only 3 percent of the Earth's water is freshwater, and nearly three-quarters of that freshwater is locked away in glaciers and ice caps [source: WWF].

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For humans, saltwater isn't drinking water -- our bodies can't metabolize the saline and m­inerals. It's possible to desalinize saltwater to make it safe for drinking, but the price tag on that process is high -- five times the cost of processing water from ordinary sources. So we're pretty much dependent on freshwater to quench our thirst. And that's not the only reason we need freshwater -- we need it to grow food and we even use it to fuel electricity.

All of this is to say that freshwater sources are vital. And it's bad news that they're under threat. The statistics are alarming. Since 1970, freshwater species have seen a 50 percent decline. More than a billion people lack access to clean water, and 2.6 billion people don't have access to clean sanitation. No clean sanitation means a polluted water supply and tainted freshwater sources. An average of 4,500 children die per day due to unsafe water and inadequate hygiene [source: WWF].

Freshwater sources range from streams, rivers, lakes and ponds to groundwater, cave water, springs, floodplains, and wetlands like bogs, marshes and swamps. These freshwater havens are home to many plant and animal species -- in fact, scientists have documented over 45,000 freshwater species. There are dozens of reasons why freshwater is in danger. But what is the biggest threat to its survival?

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No. 1 Threat to Freshwater Habitats: Agriculture

A water jet sprays onto fields of potatoes.
A water jet sprays onto fields of potatoes.
Fernand Ivaldi/Getty Images

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The biggest threat today to freshwater ecosys­tems is agricult­ure. Agriculture is the raising of crops and livestock for food. Obviously, we can't stop farming -- we have to farm to eat and we have to eat to survive. But unfortunately this vital institution hurts our freshwater systems. How?

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Freshwater is a renewable resource -- through precipitation -- but it's not unlimited. If human consumption outpaces natural restoration, the quality and quantity of remaining freshwater sources suffers. Agriculture accounts for a whopping 70 percent of our freshwater use. Crops like rice, cotton and sugar are particularly thirsty and need a lot of water to grow. For example, it can take up to 1,300 gallons (5,000 liters) of water to grow just 2.2 pounds (1 kilo) of rice. To give you a sense of how much water that requires worldwide, the 2008 forecast for world rice production was 434.3 million tons (394 million metric tons) [source: USDA].

Water is indispensable for farming. But many countries grow crops that are unsuitable for the local climate and soil, often because government subsidies make growing those crops profitable. When overproduction occurs, the soil salinity (saltiness) increases and it becomes more difficult to grow hardy crops and raise cattle. In turn, farmers start using pesticides and chemicals to help their crops grow. The pesticide chemicals then wash into the remaining water sources, destroying freshwater habitats and the species that live there. In fact, the polluted runoff can wash all the way to the coast and even begin to affect the marine ecosystem.

Another major threat to freshwater ecosystems is the construction of dams, which are used in part for irrigating crops. Dams allow us to store water in a reservoir during a wet season and then release it as needed during a dry season. However, dams also divert water flow patterns, which affects the habitats of local birds and fish and can obstruct fish migration, reducing spawning. Dams and flow diversion disrupt natural flooding cycles, reduce water flow, drain wetlands, increase flood risk and threaten species.

The agriculture industry's poor drainage and irrigation systems also squander precious water. The World Wildlife Fund estimates that only 20 to 50 percent of water extracted for farming actually reaches the crops [source: WWF]. With traditional flood irrigation systems, farmers pump or manually bring water to the fields where it simply flows through the crop area. If the fields aren't flat, water ends up pooling in the lower areas and misses the higher areas altogether. Switching to a more efficient method of irrigation could save water -- a good thing for freshwater habitats that are being sucked dry. For example, drip irrigation is a much more controlled method of watering, where water slowly trickles from feeder hoses to very specific areas.

There are other ways to minimize impact as well. Planting trees for shade and windbreak can help increase water retention in soil. In addition, adding plant waste to the soil increases its organic content and helps it use water more efficiently. Growing crops that are better suited to the soil and climate of a specific location is also critically important. For example, the Niger River basin in Africa grows rice during the dry season. This results in increased water needs. Growing wheat in the same area requires 20 to 40 percent less water.

With the right strategies, perhaps freshwater habitats and their species can be preserved. For more information on green topics, visit the links on the next page.

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Sources

  • Clover, Charles. "Food shortages: How will we feed the world?" Telegraph.co.uk. April 24, 2008. (Nov. 17, 2008) http://www.telegraph.co.uk/scienceandtechnology/science/sciencenews/3340417/Food-shortages-how-will-we-feed-the-world.html
  • "Freshwater Conservation: The Role of Freshwater Ecosystems." The Nature Conservancy. 2008. (Nov. 12, 2008) http://www.nature.org/initiatives/freshwater/about/art25836.html
  • "Freshwater Conservation: What We Do: Promoting Sustainable Agricultural Practices." The Nature Conservancy. 2008. (Nov. 12, 2008) http://www.nature.org/initiatives/freshwater/strategies/agriculture.html
  • "Freshwater: what's at stake, what we're missing, what we're losing, what it's worth." WWF-World Wide Fund For Nature. April 8, 2007. (Nov. 12, 2008) http://www.panda.org/about_wwf/what_we_do/freshwater/about_freshwater/importance_value/index.cfm
  • "Overproduced, oversubsidised and very thirsty." WWF-World Wide Fund For Nature. Feb. 7, 2007. (Nov. 12, 2008) http://www.panda.org/about_wwf/what_we_do/freshwater/problems/thirsty_crops/sugar/index.cfm
  • "People and Freshwater." WWF-World Wide Fund For Nature. May 24, 2007. (Nov. 12, 2008) http://www.panda.org/about_wwf/what_we_do/freshwater/about_freshwater/people_freshwater/index.cfm
  • "Thirsty Crops." WWF-World Wide Fund For Nature. July 20, 2007. (Nov. 12, 2008) http://assets.panda.org/downloads/wwfbookletthirstycrops.pdf
  • "Thirsty crops cause water shortages and pollution." WWF-World Wide Fund For Nature. July 20, 2007. (Nov. 12, 2008) http://www.panda.org/about_wwf/what_we_do/freshwater/problems/thirsty_crops/index.cfm
  • United Nations Environment Program (UNEP). "Challenges to International Waters: Regional Assessments in a Global Perspective: Freshwater Shortage." Feb. 28, 2006. (Nov. 12, 2008)http://www.unep.org/dewa/giwa/publications/finalreport/freshwater_shortage.pdf

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