Twothirds of the worlds longest rivers no longer run free

first_img Sign up for our daily newsletter Get more great content like this delivered right to you! Country Two-thirds of the world’s longest rivers no longer run free Click to view the privacy policy. Required fields are indicated by an asterisk (*) Email About two-thirds of the world’s longest rivers are no longer free flowing, compromising their ability to move sediment, facilitate fish migration, and perform other vital ecosystem services, according to a new study. And with more than 3700 large dams in the works, the future of free-flowing waterways looks even bleaker, researchers say.To get a global perspective on river conditions, Bernhard Lehner, a hydrologist at McGill University in Montreal, Canada, who for years has studied the effects of dams on entire watersheds, teamed up with researchers from the World Wildlife Fund (WWF), based in Washington, D.C., and elsewhere. Using aerial, satellite, and other data, the team examined 12 million kilometers of waterways, evaluating their flows in 4.5-kilometer segments.Traditionally, researchers focused on dams when assessing a river’s free flow. But in this assessment, the team also considered the impacts on flow created by riverbank levees, other flood control structures, and water diversions for power, irrigation, or drinking supplies. “It’s a more comprehensive analysis of global hydrology than we have had before,” says N. LeRoy Poff, a hydroecologist at Colorado State University in Fort Collins who was not part of the project. By Elizabeth PennisiMay. 8, 2019 , 1:00 PMcenter_img © Antonio Busiello/WWF-U.S. Free-flowing rivers are increasingly threatened by dams, levees, and water diversions, such as for these shrimp farms in Ecuador. Country * Afghanistan Aland Islands Albania Algeria Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia, Plurinational State of Bonaire, Sint Eustatius and Saba Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory Brunei Darussalam Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, the Democratic Republic of the Cook Islands Costa Rica Cote d’Ivoire Croatia Cuba Curaçao Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands (Malvinas) Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard Island and McDonald Islands Holy See (Vatican City State) Honduras Hungary Iceland India Indonesia Iran, Islamic Republic of Iraq Ireland Isle of Man Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, Democratic People’s Republic of Korea, Republic of Kuwait Kyrgyzstan Lao People’s Democratic Republic Latvia Lebanon Lesotho Liberia Libyan Arab Jamahiriya Liechtenstein Lithuania Luxembourg Macao Macedonia, the former Yugoslav Republic of Madagascar Malawi Malaysia Maldives Mali Malta Martinique Mauritania Mauritius Mayotte Mexico Moldova, Republic of Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Norway Oman Pakistan Palestine Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Qatar Reunion Romania Russian Federation Rwanda Saint Barthélemy Saint Helena, Ascension and Tristan da Cunha Saint Kitts and Nevis Saint Lucia Saint Martin (French part) Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Sint Maarten (Dutch part) Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and the South Sandwich Islands South Sudan Spain Sri Lanka Sudan Suriname Svalbard and Jan Mayen Swaziland Sweden Switzerland Syrian Arab Republic Taiwan Tajikistan Tanzania, United Republic of Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Venezuela, Bolivarian Republic of Vietnam Virgin Islands, British Wallis and Futuna Western Sahara Yemen Zambia Zimbabwe In particular, the researchers focused on the 246 longest rivers encompassing more than 1000 kilometers of flowing water—think the Nile and Mississippi rivers—because of their huge ecological impact. Just 90 of those big rivers are still unencumbered, they report today in Nature. Most of the remaining unblocked rivers are in the Amazon, the Arctic, and Africa’s Congo basin.“In the U.S., Europe, and more developed areas, these longer, free-flowing rivers don’t really exist,” Poff says. And those free rivers that remain “are some of the most important places for freshwater species,” says Michele Thieme, a WWF freshwater ecologist. Freshwater plants and animals are declining twice as fast as terrestrial and marine populations, WWF has found. And rivers in general have a lot of hidden value not fully appreciated by policymakers, Thieme notes.Thieme and Bernhard hope this assessment will have an effect on both global and local policymaking. It provides a ready source of data for countries working to meet international sustainable management goals, which include protection for freshwater systems. And the study’s methodology can be applied more locally with finer scale data to help guide where to site—or remove—dams to maintain or restore free flows.WWF, for example, is advocating increased use of solar or wind power to cut down on the need for more hydroelectric dams, which could help protect areas such as Asia’s Mekong delta. The group has also worked with Myanmar and the World Bank’s International Finance Corporation to try to keep dams off the Irrawaddy and the Salween river, two of that country’s major free-flowing waterways. And it’s helping establish baseline monitoring of the water quality of Canada’s Liard River, which runs from the Yukon into the Northwest Territories and is one of that country’s last long free-flowing rivers.Already, the increased awareness of the value of free-flowing rivers is leading to policy changes, WWF notes. In February, Slovenia agreed to stop hydropower development on that country’s Mura River, one of the last refuges with otters and the Danube salmon. Last year, Mexico established water reserves in about 300 river basins—water reserved for nature and not stored behind dams.Bernhard would like to see more such decisions. “We hope that our data can be used to find smarter and more sustainable solutions in how we manage rivers,” he says.last_img

Leave a Reply

Your email address will not be published. Required fields are marked *