Over the last three centuries, certain plants are going extinct up to 350 times faster than the historical average, with some of the world’s most biodiverse ecosystems seeing the largest threats to endemic species, according to new research.
Plant extinctions hit an all-time high in 1921 following the Industrial Revolution due to an accelerated demand for land and timber, write study authors in the journal Cell Biology. Nearly half of all plant extinctions since 1700 in South Africa have been due to agriculture, followed by urbanization (38 percent) and invasive species (22 percent). Extinctions have not increased linearly but have instead declined until about 1980 and then since remained relatively constant due in part to modern conservation efforts. Beginning in the 1990s, extinction rates settled in at about 1.26 plant species each year and has remained relatively stable ever since.
“While it is difficult to explain these fluctuations, it is conceivable that a combination of global socio-economic trends and, to some extent, conservation-related policies may partially be responsible for the patterns,” write the authors, noting that the turn of the 20th century was characterized by more demands on land, which leveled out in the 1950s and have since followed conservation movements.
Researchers analyzed a dataset of 291 plant extinctions in 10 biodiversity hotspots from California to the Mediterranean and the South Pacific, as well as six cold spots in Eurasia, all of which encompass about 45 percent of all known plant extinctions. At current levels, the researchers estimate that in the areas studied, 21 more plants will go extinct by 2030, 47 by 2050, and 110 by 2100. However, a similar study published earlier this year found different numbers – as many as two plant species are going extinct each year.
The authors explain this discrepancy by datasets. Simply put, many of the regions in the world measured do not have updated information or protected statuses for endangered plant species, so at-risk regions like Hawaii and Madagascar were excluded from the study. This prohibits researchers from “gaining a more complete and precise picture of what we are losing and at exactly what rate,” said study author Heidi Hirsch, affiliated with the Centre for Invasion Biology at Stellenbosch University, in a statement.
In short, it is difficult to claim that a plant species is extinct without adequate information. To combat this, researchers say an increase in regional datasets will allow scientists to collect more exact data, which will in turn allow them to generalize projections for other areas, including drivers of plant extinctions.
"While our study suggests that modern plant extinctions are relatively low, it is important to keep in mind that plants are exceptionally good at 'hanging in there'. Some of them are among the longest living organisms on earth today and many can persist in low densities, even under prolonged periods of unfavorable environmental conditions,” said study author Johannes Le Roux, adding that a recent report indicated that 431 plant species previously thought to be extinct have been rediscovered.
“This means that many plant species may technically not be extinct, even though they only have one or a few living individuals remaining in the wild,” he said.
The authors conclude that their work leaves more questions than answers; biodiversity assessments are essential to updating existing data and standardizing methodologies, particularly in the Anthropocene as humans play such an influential role on the climate and global ecosystems.