Canada is divided into fifteen terrestrial and five marine ecozones. These ecozones encompass over 80,000 classified species of Canadian wildlife, with an equal number yet to be formally recognized or discovered. Due to human activities, invasive species and environmental issues in the country, there are currently more than 800 species at risk of being lost. Over half of Canada's landscape is intact and relatively free of human development. The boreal forest of Canada is considered to be the largest intact forest on Earth, with approximately  undisturbed by roads, cities or industry. Since the end of the last glacial period, Canada has consisted of eight distinct forest regions, with 42 percent of its land area covered by forests (approximately 8 percent of the world's forested land).