Appreciating nature through his lens

A 12-day-old harp seal with cream-colored fur lies prone on an ice floe. A school of yellowfin tuna pulse inside a commercial fishing boat’s net. Divers swim with a gigantic whale shark in Australian waters. Leatherneck turtles lay eggs where surf meets yellow sand.

For the cover story for National Geographic last May on leatherback turtles - which have survived 100 million years in part by using the whole of the world’s oceans as their “pond’’ - Skerry traveled from the cold northern waters off Canada to breeding grounds in the Caribbean.

He has photographed whales, manta rays, shrimp, and the humbler creatures lower down on the food chain that keep the oceans alive. For a story on the ocean’s depletion, he photographed dead “by-catch,’’ or unwanted fish, raining down through the sea after being dumped as trash. Some 60 billion pounds of by-catch are caught and disposed of annually.

The high-profile photojournalist typically spends eight months a year in the field on assignment for a range of publications. He speaks widely on environmental issues, is a frequent guest on TV shows such as “20/20,’’ and has authored three books.

This weekend, Skerry comes to Duxbury for a presentation based on his recent feature stories for National Geographic. Titled “Crucial Waters - Reporting on the World’s Oceans,’’ the program will focus on photographic journalism that both celebrates the sea and raises awareness of threats.

The program’s sponsor is Sustainable Duxbury, a local group whose mission is public education on the threat posed by global warming and the benefits of practical energy-saving measures.

Human resource exploitation and waste is taking a heavy toll on the health of the oceans, said Judi Vose, cochairwoman of the group.

“We’re killing the oceans,’’ said Vose, citing the plastic trash that ends up in the ocean, covering vast stretches of the ocean floor, killing plankton and other small creatures that larger ones feed on.

Earlier this year, Sustainable Duxbury carried out an education project on plastic waste by collecting five days’ worth of plastic bags from the local transfer station - an estimated 24,150 bags in total, according to the group’s Anne Baird.

“Tying them together would have resulted in a chain of bags over 5 miles long,’’ Baird said. The collection of bags was gathered at the town beach and recycling station for people to see - an eye-opener effective in pointing out how many bags the average Duxbury home uses in a week, she said.

The group is also spreading the message on the effect of global warming on both land and sea by backing the “350.org’’ call to action, members said. Because the amount of carbon in the atmosphere is over 350 parts per million - the safe level, according to climate scientists - Arctic sea ice is melting, glaciers are thawing, and ocean water is turning steadily more acidic. Sustainable Duxbury persuaded local churches to ring their bells last Saturday at 3:50 p.m. to take part in the international action.

Skerry’s work has helped show that global warming has further stressed an already degraded maritime environment. In the last 50 years, 90 percent of the big fish in the ocean have disappeared, according to National Geographic reports his photos have illustrated. More than 100 million sharks are taken annually, and some species of whales and sea turtles are on the brink of extinction.

But his photos also illustrate the ocean’s vitality and the range of life it supports. The images capture rare species and exotic locations from beneath the Arctic ice to remote tropical coral reefs.

“The oceans are in trouble,’’ Skerry said. “My hope is to continually find new ways of creating images and stories that both celebrate the sea, yet also highlight environmental problems. Photography can be a powerful instrument for change.’’

Robert Knox can be reached at rc.knox2@gmail.com.