Global Insect Decline Linked to Light Pollution

Artificial light may be devastating populations of insects, including species that provide crucial support for human agricultural systems. In a recent article published in the Annals of Applied Biology, researchers examined the effects of light pollution on insects. Artificial light increases environmental pressures faced by insects, the study concluded, and these stresses can contribute to significant and sustained population declines.

Dozens of fruit, vegetable and cereal crops rely directly on insect pollination. Insects also serve crop ecosystems through natural pest control, soil quality improvement and nutrient cycling. These services are especially vital for industrial farming, which requires the careful control of agricultural inputs to maximize productivity. In a future with less insect biodiversity, lower yields and outright crop failures are a distinct possibility.

Previously, studies have shown that light pollution is harmful for a variety of large animals. Artificial light can send migrating birds off course, interfere with hormone production in amphibians, and prevent newly hatched sea turtles from finding their way to the ocean. The new research draws attention to similarly harmful effects of light on insects. Light from both ambient and direct sources can be detrimental. Skyglow—light from populated areas that scatters through the atmosphere and can be seen from miles away—reduces many insect species’ ability to orient themselves, find food, avoid predation and reproduce. Dung beetles, for instance, use the arc of the Milky Way to orient themselves at night and may become lost in areas where light pollution obscures the galaxy.

Many insects are attracted to direct light sources such as street lamps, where they may be killed on contact by heat, electrocution or the force of impact; they may also get trapped and exhausted or preyed upon. Moreover, the study notes that artificial light can impede communication among insects, diminish their average lifespans, and even change their physiology.

Nocturnal insects are particularly vulnerable to the effects of light pollution. The researchers pointed to a recent survey of 63 sites across Germany that experienced more than 75 percent reduction in recorded insect biomass over the past 27 years. The vast majority of these sites, the new study observes, were located near densely populated urban areas where light pollution is widespread. The study acknowledged that climate change, pesticide use and habitat fragmentation likely contributed to the decline; however, the authors also argued that artificial light could have been an important piece of the puzzle. This would make light pollution a critical consideration for environmental policymakers aiming to boost insect populations.

The study alluded to the fact that experimental research on the long-term effects of light pollution on insects is still lacking. Without such empirical evidence, it is difficult to determine the extent to which light pollution may contribute to insect decline. Still, smaller-scale studies on insects and light have revealed a worrying trend—one that, according to the authors, could affordably be reversed through effective policy, along with the deployment of existing technologies such as shielded street lamps and low-scatter LED or sodium-vapor lighting.

Currently, artificial nighttime light coverage is increasing globally at an estimated annual rate of between two and six percent. Slowing and eventually reversing this pattern will require new policies that limit light pollution and incentivize replacing wasteful lighting systems with more efficient alternatives. Regulations limiting light emissions have the potential to improve survival outcomes not only for insects, but also for thousands of other nocturnal species. In the U.S., at least 18 states have adopted laws that restrict light pollution, and many towns and cities have adopted local ordinances imposing additional regulations. In 2002, the Czech Republic became the first country in the world to place limits on light pollution at a federal level, but few other nations have followed its example. Light pollution remains a prominent and growing international concern in both urban and rural areas, particularly as more research illuminates the harmful effects of light on ecosystems.

Article Source: Grubisic, Maja et al., “Insect Declines and Agroecosystems: Does Light Pollution Matter?” Annals of Applied Biology 173(2). (2018): 180-189.

Featured photo: cc/(justme_yo, photo ID: 683667738, from iStock by Getty Images)