With the human population fast approaching 8 billion, human beings are leveling forests, clearing savannas, and transforming entire landscapes to make way for industrial-scale agriculture, highways, and an increasingly expansive urban footprint. As a result, one in five plant species worldwide is at risk of extinction. Agriculture alone is responsible for about a third of the risk.
The sobering statistics are among the findings in "State of the World's Plants," a report by the Royal Botanic Gardens, Kew, in London (RBG), which compiled the work of more than 80 scientists who delved into the impacts of human activities, invasive species, and climate change on the world's flora.
More than 10 percent of Earth's vegetated surface is highly sensitive to variations in the climate, according to the report, and widespread extinctions due to climate change are expected by mid-century. However important it may be to understand the impacts of climate change on plants, it hasn't been well documented to date, said Steve Bachman, a species conservation researcher for the botanic gardens.
"Although climate change dominates the headlines, the main threats to plants are still the conversion of land for agriculture and livestock farming," Bachman said.
Researchers found that an estimated 21 percent of global plant species are currently threatened with extinction using criteria from the International Union for Conservation of Nature, which evaluates the conservation status of plant and animal species around the world and keeps a "Red List" of threatened species. However, according to the RBG, the current Red List covers only about 20,600 plant species, or 5 percent of all plants.
Orchid, mint, and heather families are under-represented on the list, according to the report, which finds that better and broader assessments of threats to different plants are needed to fight against disappearing species. With a more thorough understanding of which plants are threatened and where, the report argues, countries can try to conserve them before they reach the precipice of extinction.
Some countries have designated important plant areas (IPAs) to safeguard sites with threatened species, threatened habitats, and exceptional botanical richness. In Guinea, which has the highest plant species diversity in West Africa, many rare species are increasingly threatened by habitat loss and degradation, according to the report. The RBC and UGAN-Herbier National de Guinée, a plant research center, started the first IPA program in tropical West Africa last year in hopes of expanding protected areas and conserving vulnerable species such as Pitcairnia feliciana, the only member of the pineapple family native outside of the Americas.
Humans and animals consume at least 31,128 plant species, such as for food, medicine, or fuel, according to the report. Researchers also found that 2,034 new vascular plant species were discovered last year.
"An uncomfortable number of plant species are threatened in the wild and slipping toward extinction," Bachman said. "We could be losing species before they are even formally described. We can see from the report that plants have over 30,000 documented uses, but if they are gone we will never know. And extinction is a one-way road. We can't bring them back."
Kierán Suckling, executive director of the Center for Biological Diversity based in Tucson, Arizona, said some threatened extinctions are sure to happen but that it's not inevitable that all 20 percent of endangered plant species will die off, especially if nations enact conservation measures.
He pointed to the US Endangered Species Act as an example, which has helped to improve the conditions of about 85 percent of species protected by the law. Meanwhile, the populations of about 70 percent of so-called "common species" — species with large enough population sizes that they are not considered endangered — are declining. That's because common species aren't receiving the attention that endangered species attract, he said.
"We sometimes forget that it's the daily activity of building roads, buildings, and housing complexes that is destroying the planet most rapidly," he said. "And we need to be reminded of that."
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