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Ocean Debris And the Search for the Malaysia Airlines Plane

Two objects spotted by satellite in the Southern Indian Ocean on Thursday might be the “best lead we have right now” in finding missing Malaysia Airlines Flight 370. But are those objects a good lead?

On Monday, my colleague Carl Bialik wrote about the use of statistics to focus on the probable and rule out the implausible. So, to understand how significant these satellite images are, it’s important to understand how many objects a satellite could spot in an ocean. If there is a vast amount of observable debris, this lead could be a lot less helpful in finding that plane.

Created in 1972, the Ocean Conservancy aims to keep the ocean clean. As part of its efforts, the group produces an Ocean Trash Index that “presents state-by-state and country-by-country data about ocean trash collected and tallied by volunteers around the world on one day.”

We looked at the latest data from the organization’s 2013 report. The possible plane debris was spotted by Australian authorities about 1,500 miles southwest of Perth, the capital of Western Australia. The first object spotted was approximately 79 feet long, the second about 16 feet. So, to understand the significance of those images, we will focus on how much ocean trash is found near Australia and is of a similar size.

Volunteers found a total of 11.2 million items of trash on or near the 98 coastlines they looked at. Only 632 of those items were found in or near Australia. The fact that the country accounts for only 0.006 percent of all found trash could make the discovery more significant. But that’s only if you assume that the Ocean Conservancy is working just as hard to find trash in Australian oceans as it is elsewhere. Luckily, the organization is transparent about the distribution of its research.

An impressive 561,633 volunteers helped collect ocean trash for the most recent report. But Australia only had 58 volunteers — 44 of them searching for trash on land and 14 searching either on or under the water. Those individuals accounted for only 0.01 percent of the global search. What’s more, they only covered an area of about 28 miles. That makes it less surprising that so few items were found there relative to other places.

What about the size of the objects discovered? Like in other countries, most trash discovered in Australia’s oceans could not be confused with debris from an airplane. Over half of the found items were the remnants of plastic bags, drink bottles, food wrappers and other consumer products. But volunteers also discovered three objects they labeled as “cars/car parts” and 19 objects they classified as “building materials.” Those items could be as large as those spotted by the satellite.

Here are the types of trash found worldwide:

Waste type Number of items
Consumer debris (e.g. plastic bags, toys) 7,250,257
Smoking products (e.g. cigarette filters) 2,475,996
Fishing-related trash (e.g. fishing lines, boats) 1,003,737
Larger dumping activities (e.g. building materials) 242,461
Medical/personal hygiene (e.g. diapers) 225,828

Keep in mind, the Ocean Conservancy’s methods might be affecting what kind of objects volunteers find. Some people “walk, while others set out on boats. Thousands more don scuba gear to seek trash below the water’s surface.” But most of the scouring stays relatively close to coastlines. Trash washed ashore is more likely to be found (which helps explain why the most common finds are cigarettes and cigarette filters — 2,117,931 of them), and basic hydrodynamics will affect the speed and likelihood that certain objects will reach the coastline (again, cigarette filters are buoyant and thus less likely to sink).

The data gives some context to the recent discovery. The 10,149,988 pounds of trash found in only one day shows just how much waste is in our oceans. Australia might not account for a significant amount of that trash, but finding objects as long as 16 and 79 feet there is surprising. If you assume that the half-million volunteers provided an indication of ocean waste — how much, how big and where it is — then the recent discovery could seem significant.

Mona Chalabi is data editor at the Guardian US, and a columnist at New York Magazine. She was previously a lead news writer for FiveThirtyEight.