Why are fireworks harmful and what can replace them?

First, the intensity of the noise generated by firework explosions is extremely high. In general, it exceeds the threshold at which humans risk hearing loss, and it often exceeds the pain threshold. But this intense noise doesn’t just affect humans. The ones who suffer the most from this are the animals around. Studies on this subject are not very numerous and focus on birds and companion animals, but they are still sufficient to determine the negative effects of fireworks at distances of up to 10 km from the explosion site¹.

For companion animals, the sound of fireworks can causes considerable panic and fear, directly observable by the people who take care of them². Whether dogs, cats, horses, birds, or small mammals, the reactions are similar and the animals may scream, flee, hide and, to a lesser extent, urinate and defecate. These behaviors, observed in a wide range of species, suggest that fireworks cause panic and fear in most animals who can hear them, not just a few isolated species.

The reason for this fear is simple: the noise of fireworks, which is unusually loud and unpredictable for animals, is perceived as a threat³. Their fears and related behaviors are responses built up to protect their lives, which they normally do in the presence of predators. Unfortunately, animals can’t follow the human holiday calendar and thus can’t predict nor understand the nature of fireworks, so they can’t even become habituated to them over time.

Although stress and anxiety are already a major source of suffering, the negative consequences don’t stop there, as shown by studies conducted on birds, which to some extent can be generalized to other animals.

First, it is possible that the shock wave produced by the explosion of fireworks directly causes pain in birds⁴.

Then, after the detonation, the panicked birds fly away in unusual large numbers⁷ and altitudes^{5, 6, 7}. Some birds flee as far as 500 km away from the fireworks before finding a new roost⁶. Obviously, birds with poor flying skills, such as juveniles, are at increased risk of fatal accidents, getting lost, and predation⁴.

In the days following a fireworks display, some bird species increase the amount of time they spend foraging, for a period that can exceed 10 days. This increased foraging is necessary to compensate for the fatigue and loss of energy caused by their sudden flight, usually in the middle of the night when they are resting⁶. This fatigue, coupled with stress, anxiety, and other negative reactions, also has the detrimental effect of temporarily reducing their immunocompetence⁵, which is their immune system’s ability to function properly and protect them from pathogens.

Fireworks can’t normally kill birds directly⁷, unless they are fired directly at them. The possibility of animal having heart attacks due to the rapid and intense increase in heart rate is sometimes raised in newspaper coverage⁸, but no studies seem to confirm or refute this hypothesis. On the other hand, in some cases, flying birds may collide with obstacles or other birds, which can be fatal. Therefore, from time to time, the use of fireworks results in a veritable mass slaughter of birds. Documented cases — with many cases likely undocumented — include the thousands of dead passerines in Arkansas in 2011⁹, the hundreds who died the following year in the same state¹⁰, and more recently the hundreds who died in Rome in 2021¹¹. The frequency of these mass deaths is unknown, and the risk factors are not fully understood due to a lack of studies on the subject. However, it seems likely that panic and poor visibility at night increase the risk of collisions.