In summer, the plants grow quickly (one plant every 25-78 days) during the midnight sun. Svalbard is a breeding ground for many seabirds. There are also polar bears, reindeer, and mammals that live in the sea. Seven national parks and 23 nature reserves cover two-thirds of Svalbard. This protects the fragile natural environment. Sixty percent of land is covered by glaciers, and the islands have many mountains and fjords.