- Researchers from around the world spent 10 years compiling a database that now includes 20 million observational records of plant species occurrence, which they say is the largest dataset on botanical biodiversity ever created.
- They found that there are about 435,000 unique land plant species on planet Earth, and that a large fraction of them, 36.5% or some 158,535 species, can be considered “exceedingly rare,” meaning that they have only been observed and recorded anywhere in the world up to five times. In fact, 28.3% of the world’s plants, or 123,149 species, have been observed just three times or less, per the study.
- The research team found that rare species are clustered in a handful of rarity hotspots, and that global warming and the impacts of human land use are already disproportionately impacting the regions that harbor most of these rare plant species.
Rare plant species are far more likely to go extinct than common species, yet we know surprisingly little about global species abundance.
Most efforts to quantify species abundance focus on local communities, according to the authors of a study published late last year in the journal Science Advances, which limits our ability to accurately assess plant rarity.
“Fortunately, with the rapid development of biodiversity databases and networks in the past decade, it is becoming increasingly possible to quantify continental and global patterns of biodiversity and test competing models for the origin and maintenance of these patterns at a global scale,” according to the authors of the study, a research team led by Brian Enquist, a professor of ecology and evolutionary biology at the University of Arizona.
The study was published to coincide with the UN climate negotiations that took place in Madrid, Spain last month.
Enquist and co-authors from around the world spent 10 years compiling a database that now includes 20 million observational records of plant species occurrence, which they say is the largest dataset on botanical biodiversity ever created. Their goal is for that information to be used to inform conservation strategies that take the effects of climate change into account and help reduce global biodiversity loss.
The researchers found that there are about 435,000 unique land plant species on planet Earth, and that a large fraction of them, 36.5% or some 158,535 species, can be considered “exceedingly rare,” meaning that they have only been observed and recorded anywhere in the world up to five times. In fact, 28.3% of the world’s plants, or 123,149 species, have been observed just three times or less, per the study.
“According to ecological and evolutionary theory, we’d expect many species to be rare, but the actual observed number we found was actually pretty startling,” Enquist said in a statement. “There are many more rare species than we expected.”
The research team found that rare species are clustered in a handful of rarity hotspots, including Costa Rica, Madagascar, the Northern Andes in South America, South Africa, and Southeast Asia. From a climatological perspective, these regions remained relatively stable as Earth’s last ice age ended, the researchers found, which is what allowed rare species to survive in those locations.
However, a stable climate past is no guarantee of a stable climate future. Enquist and team discovered that global warming and the impacts of human land use are already disproportionately impacting the regions that harbor most of these rare plant species. Thus, their estimates of global species abundance distributions have important implications for assessing extinction risks and planning conservation interventions.
“Ultimately, rare species, by definition, are more prone to reductions in population size and extinction and should be high priorities for conservation,” the researchers write in the study. “Our results suggest that redoubling global efforts to conserve rare species is needed and that we have a closing window to do so. The tools to ensure that these rare species are maintained are area-based conservation and solutions to climate change.”
Specifically, the researchers suggest that the Convention on Biological Diversity should recognize these areas as critical to conserving all life on Earth and target rarity hotspots for conservation as protected areas are expanded post-2020. They add that, because the UN climate convention “seeks to avoid extinctions due to the exceedance of species’ natural ability to adapt to climate change,” and regions with high numbers of rare species also appear to have “very high future-to-historic velocities of climate change,” conserving rarity hotspots is “yet another reason” we need to aggressively rein in global greenhouse gas emissions.
The researchers conclude: “Joint climate and biodiversity efforts should be made to ensure that these numerous but little-known species, living in unusual climatic circumstances, persist into the future.”
CITATION
• Enquist, B. J., Feng, X., Boyle, B., Maitner, B., Newman, E. A., Jørgensen, P. M., … & Couvreur, T. L. (2019). The commonness of rarity: Global and future distribution of rarity across land plants. Science Advances, 5(11), eaaz0414. doi:10.1126/sciadv.aaz0414
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