Which human activities are the main causes of endangered species declines?

Human activities are the primary drivers of biodiversity loss, accounting for approximately 99 percent of threatened species. The principal human-induced threats to species in the wild include:1

• Habitat loss and degradation: This is the leading cause of global biodiversity decline. It occurs through the conversion of natural areas for agriculture, deforestation, mining, and urban development, which destroys, fragments, or degrades the environments species need to survive.2
• Unsustainable hunting: Exploiting natural resources—such as plants, animals, and fish—faster than they can reproduce leads to population collapses and extinction.3
• Pollution: Chemical runoff, such as nitrogen fertilizers, can disrupt ecosystems, while other pollutants increase stress on native species.12
• Introduced species: Non-native species can outcompete or prey upon native populations, often leading to their decline.12
• Global warming: Human-driven climate change alters habitats and seasonal patterns, forcing species to adapt at rates that often exceed their natural capacity.14

These factors frequently act in combination, creating a cumulative stress that significantly increases the risk of extinction for many species.4