A press release dated September 20, 2010, published on the IUCN website states that over one-fifth of the world’s plant species are threatened with extinction. Natural causes such as forest fires, competition from non-native species, and pests are among the causes of the threat. According to Professor Stephen Hopper, though, loss of habitat due to human activities is the main threat to over 20 percent of the plant species on Earth.
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There are 16 known species of Rafflesia that grow in the rainforests of Southeast Asia, and all of them are threatened or endangered. Rafflesia is a parasitic plant that does not have leaves, stem, roots, or chlorophyll. It grows on the root of a vine called Tetrastigma, from which it sucks nutrients with the help of thread-like structures that it sends into the body of its host. The plant is visible only during its reproductive phase when the flowers--which grow almost a meter wide in diameter--sit directly on the forest floor. Over-collection of buds of this plant, which is used as medicine, has contributed considerably to its endangered status. Also, the fact that this plant can grow only in very specific regions of the world is a big challenge for its conservation.
Wollemi pine or Wollemia nobilis was recently discovered in 1994 in a narrow canyon in the Wollemi National Park in Australia. The tree rises to about 40 meters in height, with a trunk that can grow as big as a meter in diameter. It belongs to the family Araucariaceae, and today less than 100 of these plants are left on the planet. The Wollemi pine has upright branches that grow from buds on the trunk. Leaves are borne on branches that grow sideways, from the upright branches. The younger leaves are bright lime-green in color whereas the older ones are deep bluish in color. Leaves are broad, unlike the pines of the northern hemisphere.
American globeflower is a perennial that grows 12 to 20 inches in height and bears pale yellow flowers that bloom between April and June. The leaves are lobed and 3 to 5 inches wide. Once the plant bears flowers, the leaves increase in size. This plant is found in 40 different populations spread across eastern North America. None of the populations contains more than 100 of these plants. Besides threat from human activities, competition from invasive species, slugs eating up flowers, and changes in watersheds by beavers are some other factors that threaten the survival of this plant.
Dwarf bearclaw-poppy or Arctomecon humilis is endemic to Washington County, Utah. It is a perennial herb that belongs to the poppy family. It produces white flowers that bloom during mid April to May. The area in which this plant thrives is undergoing rapid human population growth. Development to support this expansion and off-road vehicle use are shrinking the plant's habitat further.