05
May
First Report of Environmental Pollutant Risk Among Tropical Mammals Across the Globe
(Beyond Pesticides, May 5, 2022) A report published in Biological Conservation finds environmental pollutants, including pesticides, pharmaceuticals, plastics, and particulate matter, adversely affect tropical terrestrial wildlife. Specifically, these contaminants can interact with one another, altering the chemical landscape of the ecosystem, and causing changes in the endocrine and microbiome systems of mammals.
Since the publication of Rachel Carson’s Silent Spring (1962), global attention to the danger of pesticides has increased, with environmental agencies banning the use of legacy pesticides like organochlorines for their devastating toxic—sometimes lethal—effects. However, these chemicals can remain in the environment for decades and interact with various current-use pesticides, including organophosphates, neonicotinoids, and pyrethroids. Although many studies demonstrate that environmental pollution plays a significant role in premature deaths among humans, there is a lack of research on how environmental pollution directly affects tropical species mortality. Considering human and wildlife habitats tend to overlap, and chemical pollutants can drift from chemically treated areas, wildlife populations are more likely to experience similar health effects.
With the number of chemicals in the ecosystem growing, studies like these highlight the need for pesticide policies that protect human health in addition to the integrity of the chemical landscapes accommodating wildlife. The researchers note, “Using this [study] background and building on past conservation success, such as mending the ozone layer and decreasing acid rain, we tackle the difficult issue of how to construct meaningful policies and conservation plans that include a consideration of the chemical landscape. We document that policy solutions to improving the chemical landscape are already known and the path of how to construct a healthier planet is discernible.”
The researchers assess how severe the effects of environmental contaminant exposure are among terrestrial mammals in the tropics. To evaluate severity, researchers consider how environmental pollutants interact with one another, the bodily function of mammals (i.e., endocrine and microbiome systems), and the environment itself to produce unanticipated negative impacts. Lastly, researchers determine how to improve policies and conservation efforts when considering the chemical landscape with a catalog of safety data on 10,000 chemicals that predict the toxicity of the range of substances in consumer products for which information is lacking.
With a specific focus on pesticides, the report reinforces that exposure to these toxic chemicals affects wildlife mortality, with sublethal effects weakening species fitness and reproductive rate. Pesticide pollution is increasing in tropical regions, especially in low- and mid-income countries that are home to a high diversity of species. Although countries with higher incomes, like the European Union and the U.S., restrict these environmentally toxic chemicals, mid-and low-income countries import and manufacture these same chemicals without similar restrictions. For instance, DDT is a legacy pesticide that can persist in the environment for decades. Although many high-income countries ban the use and manufacturing of DDT, low- and mid-income countries many still use the product, leading to further environmental contamination and loss of tropical mammal species like the Brazilian Free-Tail Bat. Moreover, there is a lack of research on how chemical pollution from sources like pesticides harms human and wildlife health. Various chemical pollutants are endocrine and microbiome disruptors, ubiquitously dispersed in the tropic and commonly present in mammalian tissue. Exposure can result in changes in sexual reproduction, masculinization and feminization of sex organs, aggressive temperament, and neurological and developmental delays. The researchers note, “The true contribution of chemical pollution, including pesticides, to health outcomes in both humans and wildlife, is likely underestimated because the adverse effects of many environmental contaminants are poorly understood, and interactions among chemicals are rarely investigated.”
Chemical pollution’s detrimental effects on wildlife are not a new phenomenon and can disrupt wildlife productivity via direct or indirect impacts. Insects, other terrestrial and aquatic organisms, and marine and terrestrial mammals can all experience weakened immune function upon pesticide exposure. For instance, studies find pesticide exposure can limit immune response in honey bees, causing early onset of infection or increased probability of mortality from infection. Reports demonstrate that neonicotinoid insecticide exposure impairs honey bees’ ability to groom Varroa mites, responsible for a disease known as deformed wing virus (DWV). Additionally, California sea lions are experiencing high rates of urogenital carcinoma (UGC) cancer from the combined effect of toxic “legacy” pesticides like DDT and the viral infection Otarine herpesvirus-1 (OtHV1). According to multiple studies, exposure to the weed killer glyphosate (patented as an antibiotic) changes the bacterial composition of the gut microbiome in cattle, rodents, and honey bees. Like glyphosate, atrazine can cause gut microbiome disruption, resulting in sex-specific shifts in microbiota. Atrazine is notoriously associated with endocrine disruption among amphibians and reptiles, resulting in reproductive and behavioral changes. Even among humans, exposure to endocrine-disrupting pesticides impacts hormone regulation promoting metabolic diseases like diabetes.
This report is the first to evaluate the severity of environmental pollutant exposure among tropical terrestrial mammals. However, current research likely underestimates the harms of pollutants as of the over 140,000 synthetic chemicals within the ecosystem, less than 5,000 have proper testing for toxicity and safety. Animals and individuals can encounter these chemicals through products (e.g., cosmetics, disinfectants), food, soil, other animal tissue, and the air itself. However, tropical regions contain more threatened and endangered species that are more sensitive to rapid changes in ecosystem structure and chemical bioavailability than temperate regions. For instance, between 2002 and 2019, ~60 million hectares (ha) of tropical forest were lost, resulting in habitat fragmentation that puts wildlife at risk. The researchers highlight that forest edges can contain 56 percent higher concentrations of pollutants, and with fragmented areas, wildlife is more likely to encounter pesticides in chemically treated areas that were once forest habitats. The researchers caution, “Society is not effectively adopting a precautionary principle, rather it is allowing new chemicals and forms of environmental contaminants to be generated in huge quantities and only responding well after the negative consequences of these actions are made apparent, if even then.”
The researcher suggests solutions to generate a path toward a healthier planet and equitable future for people and wildlife:
- Provide credible scientific information to the public and policymakers.
- Create and coordinate teams and networks for monitoring wildlife health.
- Develop a long-lasting foundation that continuously monitors the impacts of environmental contamination and generates science-based policy options.
- Adequate training and mobilizing scientists in developing countries to gather local community information.
- Produce and communicate information that will effectively inform policy decisions and motivate action through salient, credible, and legitimate resources.
The globe is currently going through the Holocene Extinction, Earth’s 6th mass extinction, with one million species of plants and animals at risk and an increasing rate of biodiversity loss. Environmental advocates say it is essential for government agencies to research how previous and ongoing use of chemical pollutants can impact present-day species. Likewise, collaborative, global monitoring of chemical pollutants can help leaders identify the effect on vulnerable species and the most effective unified global strategy. Animals and humans occupy the same space, so both will experience similar declines in general health, fitness, and well-being. Therefore, pesticide use should be phased out and ultimately eliminated to protect the global wildlife and reduce the number of dangerous pesticides exposed to threatened species, such as tropical mammals. Advocating for local and state pesticide reform policies can protect wildlife from pesticide contamination. For more information on pesticide impacts on wildlife, visit Beyond Pesticides’ wildlife page.
Furthermore, buying, growing, and supporting organic can help eliminate the extensive use of pesticides on crops located in wildlife refuges. Organic agriculture has many health and environmental benefits that eliminate the need for chemical-intensive agricultural practices in these sanctuaries. For more information on why organic the right choice, see Beyond Pesticides webpage, Health Benefits of Organic Agriculture.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Mongabay, Biological Conservation
