For millions of years, a variety of large herbivores, or megafauna, influenced terrestrial ecosystems. Among many others, these included elephants in Europe, giant wombats in Australia, and ground sloths in South America. However, these animals experienced a wave of extinctions coinciding with the worldwide expansion of humans, leading to dramatic but still not fully understood changes in ecosystems. Even the survivors of these extinctions strongly declined, and many are currently threatened with extinction.