A landscape is considered connected when it has few impediments that restrict the ability of animals to move about, particularly between core areas of habitat. Although natural features such as steep canyons can also restrict animal movement, scientists are increasingly concerned about the rapid expansion of human-related features and activities such as highways, roads, agricultural fields, and urban areas that impede movement between patches of habitat. Habitat fragmentation is commonly cited as one of the leading causes of the loss of biodiversity because it leads to smaller, more isolated populations that have less genetic diversity and are more likely to become extinct.