44,000 Average distance, in miles, traveled each year by Arctic terns as they make the round-trip between their summer breeding grounds in Greenland and Iceland and their winter home in Antarctica. It is the longest recorded migration of any animal. Humpback whales, which can travel more than 5,100 miles annually, hold the record for mammals.
35 Average northward range shift, in miles, of 305 North American bird species, according to a 2009 National Audubon Society analysis of 40 years of observations by bird-watchers. Sixty species had moved 100 miles or more, probably due to climate change.
2 Number of butterfly species transplanted northward in 2001 to help them survive the changing climate in the U.K. A six-year follow-up study declared the relocations a success. In 2008, 31 seedlings of the conifer Torreya taxifolia—a Florida native on the brink of extinction—were planted in North Carolina, where botanists and naturalists continue to monitor their progress.
$120 Billion Approximate annual damage and control costs associated with invasive species in the United States, according to ecologists at Cornell University. The researchers estimate that more than 50,000 nonnative plant, animal, and microbe species inhabit the country. Most invaders arrive with the assistance—intentional or accidental—of humans.
19Number of cities worldwide with a million or more foreign-born residents. Eight are in the United States, led by Miami, where 36.5 percent of residents are from outside the country. Among nations, the United Arab Emirates has the greatest percentage of immigrants, at 71.4 percent. About 12.4 percent of U.S. residents are foreign-born.