Since the dawn of the plastic era in the 1950s, humanity has manufactured a staggering 8.3 billion tons of plastic, with an additional 380 million tons produced annually. Despite recycling efforts, only 9% of this plastic is repurposed, leaving the remainder to infiltrate our environment.
Plastic pollution has pervaded every corner of the earth, from the deepest ocean trenches to the peak of Mount Everest, and alarmingly, it has made its way into the tissues of humans and other organisms.
The long-term effects of ingested plastic on human health remain uncertain. However, studies on rodents have demonstrated that ingested microplastics can adversely affect the liver, intestines, exocrine and reproductive organs.
Among the wildlife most vulnerable to plastic ingestion are scavenging birds, particularly New World vultures. These creatures frequently forage at landfills and have been observed to consume synthetic materials like boat seats, rubber seals, and roofs.
In a groundbreaking study published in the journal Frontiers in Ecology and Evolution, a team of researchers from the United States has discovered a correlation between the amount of plastic ingested by black and turkey vultures (Coragyps atratus and Cathartes aura) and their location on suburban and exurban maps.
According to the study, the amount of plastic ingested by these vultures is not simply a matter of urban versus rural habitats; rather, it is influenced by the local density of human commerce within urbanized landscapes.
Hannah Partridge, a doctoral student at the Department of Geography and Earth Sciences of the University of North Carolina at Charlotte and the study’s first author, elaborated on the findings: “Here we show that black vultures and turkey vultures in areas with more urban development and a greater density of commercial food providers ingest more plastic.”
Partridge also proposed a surprising hypothesis: “It’s possible that they eat some of this plastic on purpose rather than exclusively by accident, as is typically believed.”
Between 2021 and 2022, Partridge et al. examined eight communal roosts shared by black and turkey vultures in the Charlotte Metropolitan Area, a region with a growing human population of 2.8 million. These roosts typically host between 20 and 500 vultures. To better understand the vultures’ plastic consumption, the researchers collected a total of 1,087 pellets of undigested material, which the birds had regurgitated.
Upon analysis, it was discovered that a staggering 60% of these pellets contained plastic, which accounted for an average of 2.7% of the total mass. In addition to plastic, the pellets also contained various other materials such as vegetation, dirt, rocks, animal remains, metal, fabric, paper, wood, and glass.
The researchers utilized Fourier transform infrared (FTIR) spectroscopy to identify the specific types of plastic material present in the samples. The most common plastics found were silicone rubber (7.5% of samples analyzed), high-density polyethylene (7.0%), polyethylene (6.4%), and silicate bio-polyethylene (5.3%).
To further investigate the relationship between plastic consumption and human development, the researchers assessed the amount of plastic within the pellets in relation to four measures of human development. These measures were analyzed within increasing distances, ranging from 400 meters to 20 kilometers as the vulture flies, from the roost.
The four measures included the density of commercial food providers (encompassing everything from small stores and food trucks to large supermarkets and restaurants), the density of livestock and game producers, the extent of developed land cover, and the proximity to the nearest landfill.
Exploratory statistical analyses demonstrated a strong correlation between the proportion of pellet mass composed of plastic and increasing urban land cover, as well as the density of food providers within a 20-kilometer radius. The authors concluded that black vultures in the Charlotte Metropolitan Area, in particular, may primarily ingest plastics directly from dumpsters belonging to food providers.
Hannah Partridge offered her observations, stating, “Black vultures will often roost overnight on a transmission tower next to a fast-food restaurant and fly straight to the dumpster first thing in the morning.”
Conversely, turkey vultures display this behavior less frequently, as they tend to prefer more rural areas and natural food sources.
The researchers sought to understand whether vultures consume plastic intentionally or accidentally. They hypothesized that vultures might frequently mistake plastic for nutritious bone fragments, which are typically found in carrion.
Partridge commented, “Vultures are curious and always looking for new food sources, so they may ingest plastic thinking it’s food. But they may also sometimes ingest plastic intentionally, to collect bulk to help vomit up indigestible parts of carrion like hair.”
To address the issue of plastic ingestion by vultures and other vulnerable animals, the study’s senior author, Dr. Sara Gagné, an associate professor in the same department, provided some recommendations. “Food providers such as restaurants and grocery stores can ensure that their garbage is properly bagged, that trash makes it to the dumpster, and that the dumpster is closed and secured. We can also work towards banning single-use plastics to protect vultures and other species from harm,” Dr. Gagné advised.
This research highlights the urgent need to address plastic pollution and its far-reaching impacts on both wildlife and human populations. As the extent of plastic ingestion by animals becomes more evident, further investigation is required to understand the full scope of its consequences on ecosystems and public health. The study’s findings underscore the importance of mitigating plastic waste and developing more sustainable waste management strategies, particularly in densely populated urban areas.
Plastic pollution has become a global environmental crisis, with a profound impact on wildlife around the world. The production, use, and improper disposal of plastic products have led to large-scale contamination of terrestrial and aquatic habitats, affecting numerous species in various ways:
Addressing plastic pollution and its impacts on wildlife requires a comprehensive approach, including reducing plastic production and consumption, improving waste management practices, promoting recycling and reusable alternatives, and raising public awareness about the harmful effects of plastic on the environment and its inhabitants.
Image Credit: Hannah Partridge