The sunflower sea star has been listed as a critically endangered species following a groundbreaking population study led by Oregon State University (OSU) and The Nature Conservancy.

“These giant sea stars used to be easy to find and were a hit with divers. Unfortunately, your chances of finding one now are next to nothing in most of the areas near the United States—this listing is one step to extinction—and I don’t think they’re coming back without help,” said OSU’s Sarah Gravem, a research associate in the College of Science and the lead author of the study.

Populations of the sunflower sea star suffered dramatic crashes because of a marine (海洋的) wildlife epidemic event, which began in 2013. Scientists used more than 61,000 population surveys from 31 data sets to calculate a 90.6% decline in the sunflower sea stars and estimated that as many as 5.75 billion animals died from the disease, whose cause has not been determined. Moreover, the research showed no sign of population recovery in any region in the five to seven years since the event.

Sunflower sea stars are a key catcher of purple sea urchins (海胆) and the sea star decline has helped the increase in the urchin population in many regions. Too many urchins are linked to a decline in kelp forests（海藻林) already facing pressure from marine heat wave events, making the future uncertain for ecosystems that provide habitat for thousands of marine animals and help support coastal economies.

“Because most people are not out in the ocean every day, we don’t realize how much it’s being changed and impacted by humans. We need to think about how to keep our ocean healthy. While reducing the release of carbon dioxide is the most pressing need, rebuilding key catcher populations, like the sunflower sea star, can be an important piece of the puzzle too,” said study co-author Sara Hamilton, a Ph. D. candidate in the OSU College of Science.

In a partnership with the 5 Gyres Institute, Trash Free Maryland took to the Chesapeake Bay in November to study the presence of micropiastics in the water. Setting out from Deale, Md., the research team collected seven samples by dragging a trawl (拖网) for an hour at a time. The trawl was fitted with a cone-shaped (锥形的) net, whose holes measure 330 microns (微米) wide, about the width of two to three strands of human hair. Water flows through the main opening and the fine mesh (网眼) of net ensures anything suspended in the water is trapped behind.

In seven samples, the net picked up algae (海藻) trash, foam and plastic. According to the 5 Gyres Institute representative, the first sample collected contained almost 10 times the amount of plastic than would be collected in a typical ocean sample. The plastic found in the Chesapeake Bay samples included bits of bags, sheeting, fishing line and microbeads, which are small plastic scrubbers found in face wash, toothpaste and cleaning products. Microbeads in particular are a major source of microplastics pollution worldwide. They are small enough to bypass water treatment systems’ filters (过滤器) and end up in waterways. Scientists warn that chemicals and toxins (毒素) absorbed by microbeads and other microplastics could be passed on to organisms who mistake them for food and eat them, and could then be passed up higher and higher on the food chain, eventually reaching humans.

From a distance, the grey cement bridge looks unremarkable. Two tunnels on either side of the Trans-Canada Highway are in semi-circles that end bluntly on the pavement below. But on top, away from passing motorists’ eyes, lies a grassy oasis. Against the odds, pine trees and wildflowers have taken root here, giving the overpass a fringe of greenery. On the edges, wire fencing provides safe passage for wandering animals.

Tony Clevenger has dedicated much of his life to studying the performance of Banff’s wildlife crossing structures. When the first wildlife bridges went up, Clevenger, a researcher with the Western Transportation Institute, was living in Canmore, and recalls the distinctly negative atmosphere that surrounded what many saw as a hair-brained scheme by Parks Canada. Save for a few small crossings in the eastern United States, no one had ever attempted something like this before — and no one believed it would work. Editorials in the local paper scoffed at the “waste of taxpayers’ money” and confidently stated animals would never use the $2 million to $3 million man-made bridges. Others believed wolves would herd their prey into the fence, violently killing them before shocked tourists. 

“This project started in a bad spot. There was a lot of opposition and criticism,” Clevenger says. “It took several years of good data, publishing in scientific peer-reviewed journals, to change people’s minds.” 

Clevenger now has 17 years-worth of data proving the efficacy of the crossings. Among large carnivores, mortality (死亡) rates are 50 to 100 per cent lower along sections of the highway where overpasses and underpasses exist. In those same sections, mortality rates for elk are almost zero, compared to 100 elk-vehicle collisions per year in the mid-1990s. Clevenger’s research has shown that 11 species of large mammals in Banff have used the structures more than 200,000 times, including unexpected species such as red fox, hoary marmot, boreal toads, wolverines, lynx, garter snakes and beavers. 

In 2014, a Montana State University study found that not only are grizzly bears using the crossing structures, but the structures are also helping to maintain genetically healthy populations among the bears that use them. Grizzlies were crossing with enough frequency to ensure populations on either side of the highway weren’t genetically isolated from each other. 

“This is Canada’s biggest conservation success story — it’s the largest highway mitigation complex in the world,” says Clevenger. “You won’t find anything anywhere else in the world close to what we have. We have the most overpasses in one localized area and almost half of all the overpasses in North America.”