Final answer:
Introduced species and pests can decrease biodiversity by displacing native species and disrupting ecosystem productivity. Pests can also negatively impact biodiversity by reducing the diversity of food sources.
Step-by-step explanation:
Introduced species and pests can have negative effects on clearing and can lead to a reduction in biodiversity. When invasive species are introduced, they can outcompete and displace native species, resulting in a decrease in biodiversity. Additionally, invasive species can negatively impact ecosystem productivity by disrupting the natural balance of the ecosystem. Pests, such as crop pests, can also negatively affect biodiversity by reducing the diversity of food sources available to other species in the ecosystem.