White storks face DNA damage and health risks from landfill foraging
Research reveals that while landfill foraging increases body mass in white storks, it triggers early-onset cellular damage and disrupts traditional migration patterns.
White storks across Europe are increasingly supplementing their diets with "junk food" from landfill sites, a behavioral shift that provides a short-term energy boost while potentially causing long-term physiological damage. Recent research indicates that this reliance on human waste is altering the biology of the species, leading to unexpected DNA damage in young birds and the collapse of traditional migratory patterns.
The phenomenon is most pronounced in the Iberian Peninsula, where the availability of landfill food subsidies combined with warmer weather has led some populations to shift from being wholly migratory to partially migratory or even sedentary. In Spain, some storks have abandoned the arduous journey to Africa entirely to live near rubbish dumps. In the town of Alcala de Henares, the number of stork nests grew from 10 in 1970 to 109 in 2021, housing up to 300 birds. According to veterinarian Almudena Soriano, about 70 percent of storks in that area no longer migrate, allowing them to avoid the dangerous crossing of the Strait of Gibraltar.
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The Genetic Cost of Convenience
While landfills offer an "all-you-can-eat buffet" that is energetically cheap to forage, the nutritional quality is poor. Storks ingest a mix of meat scraps, insects, rodents, and earthworms, but they also swallow hazardous materials including plastics, wires, glass, and heavy metals.
Research presented at the Society for Experimental Biology conference in Florence by Anustup Bandyopadhyay, a PhD student at the University of Veterinary Medicine Vienna, suggests a dangerous trade-off. Preliminary results from collaborators in Poland show that landfill-foragers typically possess greater body mass and higher energy stores than those relying on natural prey. However, this weight gain is accompanied by early-onset cellular damage.
Bandyopadhyay noted that researchers detected evidence of DNA damage linked to landfill diets much sooner than anticipated. We expected to see DNA damage linked to diet at the end of their nestling stage, but instead we observe that these differences appear at a very early age, when the birds are only about a week old,
he said via Miragenews.
Population Growth vs. Individual Health
Experts are divided on whether this trend is a net positive for the species. Prof Aldina Franco, an ecologist at the University of East Anglia, describes landfill food as rotting, poor-quality "junk food" that can expose individual birds to diseases and contaminants. But from a population perspective, she argues the benefit may outweigh the cost.
According to The Guardian, Franco suggests that while a few individual storks may die from eating contaminated items, the majority benefit from the extra food. This may be critical given that white stork populations were declining until the 1980s and had disappeared from several European countries before recent reintroductions in the UK and Sweden.
In Poland, the behavior is more recent than in Western Europe.
Altered Movement and Habitats
The guaranteed availability of waste has not only stopped migration but has changed how storks interact with their environment. A study of 17 resident storks using GPS/GSM data loggers found that these birds used landfills more during the non-breeding season (20.1 percent of foraging fixes) than during the breeding season (14.9 percent). This artificial food source has facilitated year-round nest use, with some storks traveling up to 48.2 km to visit landfills during the non-breeding period.
Storks nesting nearest to landfill sites showed a higher reliance on these sites and had smaller foraging ranges in natural habitats.
Summary of Landfill Impact
| Factor | Short-Term Benefit | Long-Term Risk |
|---|---|---|
| Energy & Weight | Increased body mass and higher energy stores | Poor nutritional quality; "junk food" diet |
| Behavior | Less time spent foraging; more energy for breeding | Loss of migratory instincts; sedentary populations |
| Physiology | Easier access to calories during peak nestling demand | DNA damage appearing at one week of age |
| Environmental | Population recovery in previously extinct regions | Ingestion of plastics, glass, wires, and heavy metals |
What to Watch Next
The future of these populations may depend on human waste policy. EU Landfill Directives require the closure or covering of open landfills, a move that could either force storks back to natural prey or cause a dramatic population decline for those that have become dependent on waste.
- Policy Shifts: The municipality of Pinto in Spain is considering covering its landfill to protect storks from swallowing plastic, which may force the birds to leave.
- Alternative Feeding: Alcala de Henares has already closed its landfill but implemented giant feeding stations to maintain its stork population.
- Ongoing Monitoring: Researchers continue to use enzyme immunoassays and high-resolution respirometry to track how contrasting nutritional conditions affect the fitness of young storks.
