Mercury is a toxic substance released in large quantities into the environment due to numerous human activities, such as artisanal small scale gold mining, fossil fuel combustion, and waste incineration. Recognised by the World Health Organisation (WHO) as one of the ten most dangerous chemicals for public health, mercury’s harmful effects extend beyond humans, wreaking havoc on wildlife ecosystems. This chemical can travel through the air, reaching remote areas as far as the Arctic.
Last year, during COP-5 of the Minamata Convention on Mercury, the Parties acknowledged mercury pollution as a direct driver of global biodiversity loss and highlighted the opportunities for the implementation of both the Minamata Convention and the Kunming-Montreal Global Biodiversity Framework (GBF) in a mutually supportive way. Further insights of the co-benefits are detailed in this report.
As a follow up to its relevant work, the Minamata Convention Executive Secretary emphasised the harmful effects of mercury pollution on biodiversity during COP-16 on Biological Diversity (21 October – 1 November) in Cali, Colombia. Two side events were further organised by the Minamata Secretariat, discussing the use of mercury in artisanal small scale gold mining, and its impact on people and ecosystems, for example in the Amazon Basin, encouraging responsible sourcing.
Mercury and nature
Mercury is a chemical element, a toxic heavy metal that does not break down in the environment, which means it is indestructible. Once mercury is released into the atmosphere, it begins to move in the environment, accumulating in soil, water and sediments.
Human industrial activities have significantly increased mercury levels in nature. The European Environment Agency (EEA) states that human industrial activities have led to hundreds of thousands of tonnes of mercury being released into the environment. As of 2021, levels of mercury in the atmosphere were recorded to be 500% over the natural levels. In the oceans, concentrations of mercury were as much as 200% above the natural levels.
Mercury contamination therefore affects ecosystems on numerous levels, destroying natural habitats and harming various animal species. It can interfere with natural behaviors of animals, disrupt food systems in the environment, as well as cause major population decline among various species.
Devastating impact on bird populations
Birds are among the primary victims of mercury dispersion. Researchers often consider birds to be “excellent bio-indicators of environmental mercury contamination,” using them as models to inform regulatory measures. A recent study by Han et al. (2023) highlights the major threats mercury poses to bird populations, underscoring the serious ecological implications of this toxic substance, discussed in detail at COP16 on Biodiversity.
Some of the bird species dangerously exposed to mercury contamination are those nesting near bodies of water. Though higher concentrations of mercury may be lethal to birds, sub-lethal levels can also have adverse effects associated with changes in behavior, lower reproduction and immune suppression.
Mercury can either suppress or overstimulate birds’ immune systems by altering blood cell proportions, specifically lowering lymphocytes and weakening T-cells that ensure immunity. Immune suppression leads to higher pathogen exposure and poses risks of disease outbreaks. On the other hand, overstimulation of the immune system can affect migratory birds’ energy levels required for long-distance seasonal migration.
A study in the high-Arctic archipelago Svalbard, which had a coal mining history dating back to the early 20th century, found that birds in that area experienced mercury-induced immune suppression. These changes occurred in spite of the fact that the levels of mercury in the area were lower than in most European cities, suggesting that even low levels of mercury can significantly impair birds’ health. In another recent study in the US, conducted near Waynesboro’s South River in Virginia, mercury exposure was found to alter birds’ behaviour, changing the way they learned their songs. Philippe Grandjean, Adjunct Professor of environmental health at Harvard School of Public Health, compared such effects to speech impairment in humans that can occur as a result of ingestion of methylmercury, one of the forms of mercury occurring in nature.
More studies have documented symptoms including ataxia, lethargy, reduced appetite, poor hatching success and changes in parental habits of birds as a result of exposure to mercury, revealing the true scale of this toxic substance’s influence on the major group of animals.
Urgent need to act
While the Minamata Convention is in place, together with several national regulations, there is clearly a need to continue addressing the issues of mercury contamination in the environment to ensure the wellbeing of natural ecosystems, survival of species as well as human health. The example of birds clearly illustrates the long-term effects of this dangerous chemical on living organisms beyond human existence, presenting yet another man-made threat to the planet.
Action taken by states globally should as a minimum, implement and enforce the Minamata Convention on mercury and incorporate joint efforts to reduce and where feasible eliminate mercury from anthropogenic sources. Such initiatives should take place at national, regional and local levels to ensure a more sustainable approach to resources and drastically reduce the amount of mercury in the environment to protect all life forms.
We thank Shivani Ronanki, a PhD candidate at the Wageningen Research Institute and intern at the EEB, for her participation in this article.
