A plant species is considered extinct when there is no reasonable doubt that its last individual has died, signifying a permanent loss from the planet’s biodiversity. A distinction exists for plants that disappear from their native environments but persist elsewhere. These are categorized as “extinct in the wild” (EW), surviving only in settings like botanical gardens or seed banks. This status means they no longer contribute to their natural ecosystem.
Causes of Plant Extinction
The primary drivers of plant extinction are linked to human activity. The most significant cause is habitat destruction, where land is cleared for agriculture, urban development, and logging. This process removes plants and fragments the remaining habitats into patches too small to support viable populations.
Climate change is another major pressure, altering temperature and precipitation regimes that plants are adapted to. Some plants are unable to migrate to new, suitable areas quickly enough, leading to population decline. The introduction of invasive species also disrupts ecosystems, as non-native plants can outcompete endemic species or introduce diseases. Finally, overcollection for horticultural or medicinal use can decimate populations of rare plants.
Notable Examples of Extinct Plants
One well-known extinct plant is Silphium, a species that grew in a coastal region of North Africa. Believed to be a member of the fennel family, it was highly prized in antiquity as a seasoning, a cure-all medicine, and a contraceptive. Its resin was so valuable it was stored in Rome’s treasury and depicted on Cyrenian coins. Intense demand led to overharvesting, and combined with land-use changes, the plant vanished, with the last stalk reportedly given to the Roman Emperor Nero.
A more recent extinction is that of the Saint Helena olive (Nesiota elliptica). This small tree was endemic to the island of its name and was part of the buckthorn family, not a true olive. Deforestation and grazing by introduced goats made the species exceedingly rare by the 19th century. In 1977, a single surviving tree was discovered, sparking conservation efforts, but the plant was largely self-incompatible. The last wild individual died in 1994, and a cultivated cutting survived until 2003 before succumbing to a fungal infection.
Ecological Impact of Plant Extinction
The loss of a plant species can destabilize an entire ecosystem. Plants form the foundation of most food webs, and their removal means a direct loss of food for insects, birds, and mammals that depend on them. This can lead to a decline in animal populations, a phenomenon known as a trophic cascade, where the impact ripples up the food chain.
Beyond providing food, plants create physical habitats, and their extinction can lead to the loss of shelter for many organisms. The disappearance of a plant can also disrupt symbiotic relationships, such as those with specific pollinators or with mycorrhizal fungi in the soil. Without their plant partners, these associated species may also face extinction. On a larger scale, the loss of plant cover can lead to increased soil erosion and alter local water cycles, affecting the health of the entire landscape.
The Science of Plant De-extinction
The concept of reversing extinction, while complex, is being explored through several scientific avenues. For plants classified as extinct in the wild, the path to recovery is more straightforward, relying on preserved materials. Viable seeds stored in seed banks can be germinated, and the resulting plants cultivated to build a new population for eventual reintroduction into a restored habitat. This method offers a direct way to bring a species back to its natural environment.
For species that are completely extinct, the process is far more theoretical and technologically demanding. One approach involves using DNA extracted from preserved herbarium specimens. Using advanced genome-editing techniques like CRISPR, scientists could potentially reconstruct the extinct plant’s genetic code and insert it into the cells of a closely related living species. This would not create a perfect replica but rather a hybrid proxy of the extinct plant. While still largely in the experimental stages for plants, these methods represent a potential, albeit challenging, future for recovering lost biodiversity.