When thinking about extinct species, many people think about extinct animals like dinosaurs, woolly mammoths or the dodo. There are, however, many plants that have also become extinct for various reasons.
How do plants become extinct?
The reasons why a plant may become extinct are very similar to the reasons any other organism, such as an animal, may become extinct. Plant extinction can happen due to natural causes, such as climate change or mass extinction (refer Topic 1, Chapter 1). Plants can also become extinct due to man-made causes, such as habitat destruction or introduced species (refer Topic 1, Chapter 2).
Like other organisms, plants have an important part in the ecosystem. If a plant species is destroyed, other species in the ecosystem that depend on it can be harmed. As a result, it is important to prevent the extinction of any species to protect the entire ecosystem.
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An ancient extinct plant: Araucaria mirabilis
Although some plants have become extinct, their extinction is rarely a result of natural causes. Some plants that existed millions of years ago, such as tree ferns and gingko trees, have survived and remain largely unchanged. That does not mean that plants never become extinct due to natural causes, however. The tree Araucaria mirabilis is an example of an ancient plant that became extinct.
Araucaria mirabilis was a coniferous tree that grew in a forest once located in Arizona in the south-western United States. This tree was related to the modern-day monkey puzzle tree, which is found in South America, and the Norfolk Island pine, which is found on Norfolk Island between Australia and New Zealand. Araucaria mirabilis most likely became extinct due to climate change. Today, the forest in which Araucaria mirabilis was found is located in a desert. Conditions would have needed to be much more moist for a coniferous forest to grow.
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Habitat destruction: Macoun's shining moss
In the 19th century, a Canadian scientist named John Macoun discovered a large, brownish-green moss with shiny stems growing in Ontario, a Canadian province. This moss was only found in a small area around the town of Belleville. Between 1862 and 1864, Macoun collected at least two samples of the moss.
The only area where this unique plant was found, however, was cleared, probably to make way for a new farm. When the area was cleared, the plant's habitat disappeared, and along with it, Macoun's shining moss. Efforts to find other specimens of the moss were unsuccessful, and the plant is presumed extinct.
Introduced species: the flora of St. Helena
St. Helena is an island located between Africa and South America. Since its discovery by a Portuguese sailor in 1502, the island and its plant life have declined significantly. One of the main reasons for this decline was the introduction of non-native species.
When the first sailors arrived at St. Helena, it was uninhabited. There were no native plant-eating mammals, and the island was covered in lush vegetation. The island was home to 49 endemic (found only in one place) plant species, of which six are now extinct, four are extinct in the wild but still cultivated, and four have wild populations of less than 50 individuals. The extinct plants on St. Helena include the stringwood tree, the St. Helena heliotrope, the St. Helena olive, the dwarf ebony and the dwarf cabbage tree.
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The plant species on St. Helena began to decline once settlers introduced livestock, particularly goats. These animals fed upon the native vegetation, which was not equipped to deal with grazing as the vegetation had not evolved with plant-eating mammals. The settlers also used native trees for wood and tannin, depleting the forests. Once the forests were nearly gone, the settlers imported plants from other places to fill the gaps, but these plants choked out the native flora (plants).
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Today, St. Helena looks barren. The parts of the island that are still forested have been heavily invaded by non-native species. A large-scale conservation effort is taking place, however, and many native plants are being cultivated in the hope of re-introducing them to the wild.