The Industrial Revolution had a significant impact on the population of peppered moths (Biston betularia) in Britain, particularly in the context of natural selection and color variation. Before the Industrial Revolution, the majority of peppered moths had a light, speckled coloration that provided camouflage against the lichen-covered trees in their natural habitats.
However, during the Industrial Revolution, which began in the late 18th century and progressed into the 19th century, increased industrial activities led to widespread pollution. Factories released large amounts of soot and other pollutants into the environment, which killed off the lichens on trees and darkened the bark. As a result, the lighter-colored moths became more visible to predators, while darker-colored moths (a genetic variant known as the melanic form) became better camouflaged against the soot-darkened trees.
This change in the environment led to a shift in the population dynamics of the two color variants. The darker moths had a survival advantage in the polluted industrial areas, and their numbers increased significantly, while the lighter moths faced higher predation rates and decreased in population. This phenomenon is a classic example of "industrial melanism," which illustrates how environmental changes can drive natural selection and modify species populations.
As pollution control measures were implemented in the later 20th century, the environment began to recover. Lichens returned, and the populations of lighter-colored moths began to increase again. This adaptation cycle demonstrates how species can respond to changing environmental pressures over time.