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All of the known plants in the Americas, for now

Brazil, with 33,161 species, and Colombia, with 23,104, are top of a recently published survey on the diversity of vascular plants in the Americas, which includes flowering plants and ferns (Science, December 22, 2017). Coordinated by Carmen Ulloa Ulloa, from the Missouri Botanical Garden, USA, the study found that the Americas are home to 124,933 distinct vascular plant species, spread across 6,227 genera and 355 families. The total corresponds to roughly one-third of all known vascular plants worldwide. There are more vascular plant species in South America (82,052 species, of which 73,552 are endemic) than in North America (51,241 species, of which 42,941 are endemic); only 8,300 species are found on both continents. The flora of South America is 6% larger than that of Africa, which is twice the size in terms of land area, and China’s flora is twice as diverse as that of the United States and Canada. The most diverse group in the Americas is the orchid family, with 12,983 species. According to the study, an average of 744 new species are identified per year and there are another 3,500–7,000 in Brazil still to be described. The vast diversity in Brazil can be explained by the varied relief, climate, and altitude, according to botanist Rafaela Campostrini Forzza, a researcher at the Rio de Janeiro Botanical Garden and coauthor of the study. “This survey is the result of a long and collaborative process involving the development of lists for each country, which began 30 years ago, and international commitments such as the Convention on Biological Diversity (CBD), which helped motivate and bring together research teams,” she says.