Dramatic moth population decline in cities

Insect research reveals that moth decline in urban environments is decimating populations across American cities. These essential nighttime pollinators face unprecedented challenges from rising temperatures and habitat loss.

Urban heat overwhelms

Cities transform into dangerous heat zones that threaten moth survival. Urban areas create what scientists call “heat islands,” where concrete and asphalt absorb sunlight and convert it to heat, This makes cities up to seven degrees Fahrenheit warmer than surrounding areas.

The fastest rates of urbanization in the world are occurring in subtropical and tropical areas, which are also the most affected by this trend. These urban heat islands represent one of the most significant environmental modifications humans impose on urban landscapes.

Research reveals surprising patterns

Researchers from the Florida Museum of Natural History developed innovative techniques to study both adult moths and their caterpillar life stages. Lead researcher Michael Belitz and his team spent a year collecting over 35,000 moths across Alachua County, Florida, examining locations with varying levels of urban development.

The team used an inventive approach, placing funnels under trees to collect caterpillar droppings and estimate population sizes. “Caterpillars are an important food source for breeding birds,” explained Belitz. “Even if birds are seed eaters as adults, they feed their young caterpillars.”

The research challenged conventional assumptions about the survival of urban wildlife. Larger moths, once thought better equipped to navigate urban challenges, actually fared worse than smaller species in urban environments. In warmer climates, these bigger moths expend more energy trying to cool down, putting them at a disadvantage.

Even protected areas affected

Even conservation areas within cities failed to protect moth populations. The team observed significant population declines even in protected areas, such as city parks.

“You might think that you’re looking at a natural environment when you walk into a city park, because it looks intact,” noted co-researcher Robert Guralnick. “The truth is, what you see is a completely different community than those that exist in places like wildlife management areas.”

This finding demonstrates that urban effects extend beyond obvious development zones. Bird communities also struggle when moth populations decline, creating cascading effects through urban food webs.

Solutions offer hope

Urban and suburban communities can take concrete actions to support recovering moth populations. Planting native vegetation represents a crucial strategy for increasing biodiversity and providing essential host plants for moths.

Reducing light pollution also provides significant benefits, as artificial lighting disrupts moth navigation systems. “Turning out lights at night is a truly actionable thing people can do that has a large, positive effect for insects and other animals,” emphasized Belitz.

Creating pollinator-friendly urban environments requires coordinated efforts from homeowners, urban planners, and municipal governments. These actions benefit not only moths but entire urban ecosystems that depend on these nighttime pollinators.

The study was published in the journal Global Change Biology.

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