How do human activities cause species to become endangered?

Human activities are the primary drivers of biodiversity loss, with approximately 99 percent of threatened species at risk due to human influence. These activities disrupt ecosystems and threaten the survival of countless organisms through several key mechanisms:1

• Habitat Loss and Degradation: This is the most pervasive threat. It involves the destruction or fragmentation of natural areas for agriculture, logging, and urban development. When habitats are destroyed or subdivided, species lose essential food and shelter, often leading to population declines or extinction.23
• Overexploitation: The unsustainable hunting, fishing, and collection of plants and animals deplete populations faster than they can reproduce. This includes practices like poaching and industrial overfishing, which can trigger trophic cascades that destabilize entire food chains.142
• Invasive Species: Humans often introduce non-native species to new environments, whether intentionally or accidentally. These species can outcompete native organisms for resources or act as aggressive predators, leading to the decline of local populations.23
• Pollution and Global Warming: Chemical pollution, such as fertilizer runoff, creates eutrophic "dead zones" where aquatic life cannot survive. Simultaneously, climate change driven by greenhouse gas emissions poses an existential threat, altering habitats and forcing species to adapt or face extinction.3542
• Disease: While diseases occur naturally, human activities—such as global trade in food and pets—have accelerated the spread of pathogens, such as the fungus responsible for amphibian chytridiomycosis, to vulnerable populations worldwide.12