Atlantic Ocean Gatun Locks Embera Village ADVANCES Gamboa Gatun Lake Rainforest Resort Cruise Top 10 Polluters Canal Cruise Gaillard Cut Pedro Miguel Locks Circle area shows Total in ocean Mira ores Locks amount of plastic Panama City Yellow Beach Resort Hai Paci c Ocean Indus Daystop Overnight Two Nights Nile Join the smart shoppers & experienced travelers 100,000 All other who have chosen Caravan since 1952 metric tons rivers Plastic from Meghna, Asian rivers Brahmaputra, Panama Plastic from Ganges $ African rivers 8-Days 1295 Pearl Panama Canal Cruise, Beaches, Yangtze and Rainforests Amur Fully guided tour w/ all hotels, all meals, Niger all activities, and a great itinerary. The numbers used in the graphic are based on a model that uses high-end Mekong Your Panama Tour Itinerary estimates of the plastic in each river. Day 1. Welcome to Panama City, Panama. Day 2. Visit the ruins ENVIRONMENT of Panama Viejo. Keel-billed Toucan Day 3. Gatun Lake and Rivers of Plastic VOL. 51, NO. 21; NOVEMBER 2017 7, Panama Canal Cruise. A signifi cant amount of the waste in oceans comes from just 10 rivers Day 4. Cruise more of the Panama Canal. Our seas are choking on plastic. A stag- of all that waste could be pouring in from Day 5. Visit an Embera gering eight million metric tons wind up in just 10 rivers, eight of them in Asia. Pollera Dancer Village in the jungle. oceans every year, and unraveling “Rivers carry trash over long distances Day 6. Free time today exactly how it gets there is critical. A recent and connect nearly all land surfaces with ENVIRONMENTAL SCIENCE & TECHNOLOGY, IN at your beach resort. study estimates that more than a quarter the oceans,” making them a major battle- SOURCE: “EXPORT OF PLASTIC DEBRIS BY RIVERS INTO THE SEA,” BY CHRISTIAN SCHMIDT ET AL., Day 7. Explore a Kuna Tribal Marketplace. Panama Canal Day 8. You return with great memories! BIOPHYSICS Detailed Itinerary at Caravan∙com Porpoise- Your Panama Tour Hotels—Listed by Day 1, 2 Panama City Marriott Courtyard 3, 4 Gamboa Gamboa Rainforest Resort Driven Life 5, 6 Playa Bonita Westin Playa Bonita Resort The marine mammals have 7 Panama City InterContinental Miramar their own natural sonar Choose Your Guided Tour plus tax, fees Guatemala with Tikal 10 days $1395 The best military sonar technology pales Costa Rica 9 days $1295 in comparison with the echolocation por- Panama Canal Tour 8 days $1295 poises use to track prey, predators and ob- Yangtze fi nless porpoise Nova Scotia & P.E.I. 10 days $1495 stacles. The marine mammals can fi nd ob- Canadian Rockies 9 days $1795 jects a few centimeters wide from 100 me- Sonar works by bouncing sound waves Grand Canyon & Zion 8 days $1495 ters away—akin to spotting a walnut from off objects and detecting the signals’ return California Coast 8 days $1595 across a football fi eld—by releasing clicks time. Normally if the source of a sonar Mount Rushmore 8 days $1395 from their blowholes. Sonar-equipped pulse is smaller than the wavelength of the New England, Fall Colors 8 days $1395 ships, in contrast, must emit sound waves sound, it releases sound signals in all direc- from multiple sources spread out over at tions, like light scattering from a disco ball. Brilliant, Affordable Pricing “—Arthur Frommer, Travel Editor ” least a few meters. A recent study suggests To send a targeted beam in a specifi c direc- porpoises’ ultraeffi cient echolocation is tion, the source must be much larger than Order Your FREE Brochure made possible by adjustable structures in the wavelength. But porpoises manage to Call 1-800-CARAVAN their heads—a fi nding that may help hu- evade this requirement. Visit Caravan.com The #1 In Value mans improve our own sonar technology. To fi nd out how, scientists used CT GETTY IMAGES ® Graphic by Amanda Montañez sad0218Adva3p.inddUntitled-6 1 16 12/18/1712/15/17 11:11 5:27 PMAM Untitled-11 1 12/18/17 11:01 AM ground in the fight against sea pollution, New Version! explains Christian Schmidt, a hydrogeologist at the Helmholtz Center for Environmental Research in Leipzig, Germany. Schmidt and his colleagues dug up pub- lished data on the plastic concentration in 57 rivers of various sizes around the world. These measurements included bottles and bags, as well as microscopic fibers and beads. The re- searchers multiplied these concentrations by the rivers’ water discharge to calculate the total weight of plastic flowing into the sea. They then fed these data into a model that compared them with the estimated weight of plastic litter generated per person per day along each river. The results, published last November in En - vironmental Science & Technology, show that riv- ers collectively dump anywhere from 0.47 mil- lion to 2.75 million metric tons of plastic into the seas every year, depending on the data used in the models. The 10 rivers that carry 93 percent of that trash are the Yangtze, Yellow, Hai, Pearl, Amur, Mekong, Indus and Ganges Delta in Asia, and the Niger and Nile in Africa. The Yangtze alone dumps up to an estimated 1.5 million met- ric tons of plastic waste into the Yellow Sea. Better waste collection and management practices in the most polluted regions would help stem the tide, Schmidt says, but raising public awareness is also crucial. —Prachi Patel scans to study the heads of finless porpoises (Neophocaena phocaenoides ). They learned the creatures’ foreheads contain complicated structures involving air sacs, soft tissues and skull bones. These components make up layers that let sound pass through at different veloci- ties, enabling the animals to control their beams’ focus. “If we can understand these structures, then we can redesign our sonar sys- tems and put them into [smaller] boats,” says Wenwu Cao, a physicist at Pennsylvania State University and co-author of the study, pub- lished last December in Physical Review Applied. The work suggests that porpoises share Over 75 New Features & Apps in Origin 2018! some tricks with another mammal famous for For a FREE 60-day echolocation: bats. “I am intrigued that there Over 500,000 registered users worldwide in: evaluation, go to ◾ 6,000+ Companies including 20+ Fortune Global 500 could be a way for the porpoises to change OriginLab.Com/demo ◾ 6,500+ Colleges & Universities and enter code: 9246 their emission pattern by compressing the fore- ◾ 3,000+ Government Agencies & Research Labs head complex,” says Rolf Müller, a professor of mechanical engineering at Virginia Tech, who has studied bat sonar but was not involved in the porpoise study. Next to human technolo- 25+ years serving the scientific & engineering community gy, it seems bats and porpoises really are a few flaps or laps ahead. —Clara Moskowitz February 2018, ScientificAmerican.com 17 Untitled-1 1 9/20/17 4:49 PM sad0218Adva3p.inddUntitled-6 1 17 12/18/1712/15/17 11:52 5:27 PMAM.