Western Toads are on the provincial Yellow List, and are considered a species of conservation concern. The cause for such declines is still uncertain, but a combination of threats is suspected. One of the greatest impacts on Western Toad populations in B.C. is habitat destruction. Development in and around wetlands can destroy or isolate populations. Migrating toads are killed by traffic on roads. Pollution, the introduction of aquatic predators (e.g., stocking lakes with fish), and the spread of diseases are also harmful. Large-scale concerns such as global warming and ozone depletion can affect Western Toads by changing temperatures, affecting water levels, and increasing ultraviolet radiation.