Which threat is causing the fastest species declines?

The fastest species declines today are driven by habitat destruction and fragmentation, largely due to human activity. When forests are cleared for agriculture, cities, or roads, animals lose the resources they depend on food, shelter, and breeding areas. This makes survival and reproduction difficult, causing rapid population drops. Other major threats include overexploitation (hunting and fishing), pollution, and climate change. 

However, habitat loss remains the primary and fastest-acting factor because it instantly destroys entire ecosystems. Tropical rainforests and wetlands have suffered especially severe losses. Species that are highly specialized or endemic to one region are most at risk. For example, many amphibians and pollinators are declining because their habitats are being converted into farmlands and urban areas. 

According to the UN and IUCN, the rate of extinction today is 100 to 1,000 times higher than natural background levels—mostly due to our alteration of landscapes. Protecting habitats through reserves and sustainable development is key to slowing these declines.