American biologists have identified the cause of intense mercury pollution of many tropical bird species. It turned out that the problem was related to gold mining. The study was published in the scientific journal magazine Ecotoxicology.
Scientists analyzed 2,316 blood and feather samples from 322 bird species collected from nine countries in Central America, South America and the Caribbean. They found some of the highest mercury concentrations ever observed in songbirds. For example, one green kingfisher had 30 times more toxic metals in its body compared to safe levels.
According to researchers, the cause of mercury poisoning of the environment and its inhabitants is in most cases associated with the development of gold deposits. Mercury concentrations near gold mining sites were almost four times higher than in other areas.
Artisanal and small-scale gold mining remains the largest source of mercury pollution in the world, accounting for approximately 38% of human-caused mercury pollution. These operations use mercury to access tiny gold particles in soil and sediment. Mercury binds to gold, forming an amalgam, and the resulting nuggets evaporate when heated, leaving gold behind. In this case, the liquid metal mixes with both soil and water, and also mixes with the atmosphere as vapor.
Agricultural deforestation through burning of vegetation also releases mercury into the environment.
Biologists have also found high levels of mercury in birds of prey and aquatic species. Carnivorous birds are more sensitive to the toxin because they ingest the poison from the flesh of their prey.
Scientists have warned that mercury pollution poses a threat not only to birds but also to humans. The toxic substance weakens the immunity of animals, making them more vulnerable to pathogens of various diseases, some of which can be transmitted to humans.
Previous scientists I learnedthat spiders can poison other animals with mercury.