Hidden risk: Mercury pollution’s costs to wildlife and people
Cross-posted from Cool Green Science.
Mercury pollution — nothing to worry about if I don’t live in the rural Northeast and don’t eat tons of fish, right?
Guess again, says a new report done by the Biodiversity Research Institute (BRI) in conjunction with The Nature Conservancy. The report, “Hidden Risk,” details the widespread and deep impacts of mercury pollution in terrestrial nature — particularly on animals such as songbirds and bats. Researchers are discovering how mercury is causing big declines in reproductive success among these species, as well as physiological oddities — like developmental asymmetries and an inability of some birds to hit high notes.
And the same rain that brings mercury pollution down from the sky falls on us, too. So are these species a kind of canary in the coal mine for mercury’s effects on other vertebrates, including people? And will strict new federal standards limiting U.S. power plant pollution be enough in a world where mercury pollution is on the rise from China and other nations? I talked with two co-authors of “Hidden Risk” — BRI’s executive director, Dave Evers, and Tim Tear, the Conservancy’s director of science for New York — to find out more. (Download the report here.)
Q. Some are going to be surprised that mercury pollution is still a problem — didn’t various agencies and industries take steps to reduce mercury emissions over the last decade in the United States? So why are high levels of mercury still a problem in many wildlife species?
Dave Evers: Yes, a lot of mercury has been taken out of air pollution over the past few decades — but our understanding is growing of how just a little mercury can adversely affect wildlife, and how many species have been affected. More species are being impacted than we had thought, and the toxicity of methylmercury to those species is at lower threshold levels than we ever realized.
Tim Tear: Many of these species and many of the places affected are in people’s backyards. People used to think that mercury pollution was a problem isolated to remote areas of the Northeast. No more.
Q. So, would someone see a bird or a bat acting strangely because of mercury pollution? Or is this something that data is telling you?
Evers: The effects are difficult to see in the field for the average observer. Mercury doesn’t create physical mutations, and an individual animal with mercury will probably die from predation first. But mercury is a neurotoxin that does impact wildlife behavior, and that behavior impacts their survival and reproduction. We focus on data to really quantify the impacts of mercury on the reproductive success of species.
For example, we quantified mercury impacts on the common loon. Common loons need to spend about 98 percent of their time on a nest incubating their eggs to have those eggs successfully hatch. We’ve quantified with over 5,000 hours of observation that loons with high mercury levels spend only 85 percent of their time incubating those eggs. So they spend less time in an incubation posture, and because of that, eggs do not hatch, and because of that, the species’ reproductive success goes down.
Q. Where is the mercury pollution still coming from? And what U.S. regions are of most concern?
Tear: Most of the research has really focused on the Northeast United States — an area that’s been really hard hit by acid rain, which makes mercury a bigger problem. But mercury pollution is happening all over the world. It comes globally from Asia, as well as nationally from power plants in the Midwest, to locally from waste incinerators. We’re going to need to address all sources of mercury to be successful in stopping these impacts.
Q. And in different habitats, right? Most people in the United States who know about mercury in nature know about it through warnings about the fish they eat.
Evers: Yes, there’s been a paradigm shift in new findings. In the past, most of the scientists assessing risk from mercury in an ecosystem would be looking at fish-eating birds and fish-