According to a new study published on 10 June in Nature Ecology & Evolution, nearly 600 plant species have become extinct over the past two and a half centuries (1). That equates to a rate of around two plant species extinctions per year since 1900, which is around 500 times faster than what is naturally expected.
The previous best guess was based on figures held by the International Union for the Conservation of Nature Red List suggested that around 150 plants have gone extinct. But the true number is closer to 570 — that’s four times higher. The recent project is the most comprehensive effort to chart worldwide plant extinctions to date.
The team of researchers from the Royal Botanic Gardens in the UK and Stockholm University in Sweden analysed a previously unpublished database — based on published literature and the International Union for Conservation of Nature (IUCN) Red List of Threatened Species — of seed plants. From this data, they determined which plants have already become extinct, where they disappeared from, and how quickly.
They discovered that a total of 571 plants species have gone extinct in the past 250 years and the rate of loss is 500 times higher than what it would be without human interference. And although humans are responsible — at least in part — for the rapid demise of many plant species, few people can name a plant that has recently become extinct while most people can name an extinct mammal or bird.
Island species, as well as those living in regions with a tropical or Mediterranean climate, are particularly vulnerable. One notable example is the Chile sandalwood, a tree that grew on the Juan Fernández Islands between Chile and Easter Island and was exploited for its essential oil.
Part of the reason the numbers are so much higher for plants than animals is that there are so many plant species. But that doesn’t mean the consequences are any less significant. And interestingly, the geographical pattern of extinctions is similar for plants and animals — the main areas are high-diversity regions with a tropical or Mediterranean climate.
Bad news for everyone
Biodiversity is crucial to the planet, providing ecosystem services such as pollination, pest control, soil formation and maintenance, carbon sequestration, purification and regulation of water supplies, as well as reducing the threat of natural disasters and providing habitats for beneficial species.
As the authors write, “Plant extinctions endanger other organisms, ecosystems and human well-being, and must be understood for effective conservation planning.” In fact, another recent study found that extinctions lead to co-extinction cascades owing to the independence of many species — both plants and animals.
Furthermore, biodiversity is vital to meeting the Sustainable Development Goals, a list of 17 goals covering social and economic development issues from poverty, clean water, and sanitation to global warming.
We depend on plants. So, understanding how, where, and why these extinctions are occurring could help to stem further excessive losses.
(1) Humphreys, A.M. et al. Global dataset shows geography and life form predict modern plant extinction and rediscovery. Nature Ecology & Evolution (2019). DOI: 10.1038/s41559-019-0906-2